Garmin Radius to Fix Leg Project Report -...

Garmin Document 005-00586-21 Rev. 1

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For Public Distribution – Garmin International, Inc.

Garmin Radius to Fix Leg Project Report

In support of

FAA Memorandum of Agreement Number DTFAWA-11-A-80009

January 15, 2013

Document Number: 005-00586-21 Rev. 1

Garmin International, Inc. 1200 E. 151st Street

Olathe, Kansas 66062 U.S.A.

FOR PUBLIC DISTRIBUTION

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The contents of this report reflects the views of Garmin International, Inc., and do not necessarily reflect the views of the Federal Aviation Administration (FAA) or the Department of Transportation (DOT). Neither the FAA nor the DOT makes any warranty or guarantee, or promise, expressed or implied, concerning the content or accuracy of the views expressed herein. This is the copyright work of Garmin International, Inc., and was developed in the performance of Memorandum of Agreement Number DTFAWA-11-A-80009, as amended (the "MOU", "Other Transaction Authority" or "OTA"), and any use, modification, reproduction, release, performance, display or disclosure of this work, in whole or in part, is subject to the license grant set forth in Article 6 of Modification 2 to the Memorandum of Agreement DTFAWA-11-A-80009, dated August 6, 2012. Copyright © 2013 Garmin International, Inc. Garmin®, G1000®, and G2000® are registered trademarks of Garmin. Microsoft® and Excel® are registered trademarks of Microsoft Corporation. MathWorks® and MATLAB® are registered trademarks of The MathWorks, Inc.

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EXECUTIVE SUMMARY Required Navigation Performance (RNP) 1 with Curved Path is a key NextGen Performance Based Navigation capability enabling precise departure, arrival and approach procedures. Repeatable curved paths provide benefits such as avoiding obstacles and terrain features to lower approach procedure minimum altitudes, de-conflicting traffic flows from multiple airports in high density airspace, optimizing paths for reduced fuel consumption and reduced carbon emissions, and avoiding noise sensitive areas. The curved path capability is accomplished through Radius-to-Fix (RF) legs. The Federal Aviation Administration (FAA) has design criteria for public use area navigation (RNAV) global positioning system (GPS) procedures with RF legs and has begun publishing these procedures, which have the potential to provide additional NextGen benefits to Part 23 aircraft general aviation (GA) operations. However, current FAA installation and operational guidance, which is based on consensus standard flight technical error (FTE) assumptions and MLS curved path studies, states that an aircraft should be equipped with a flight director (FD) and/or roll-steering autopilot (AP) and an electronic map display depicting the RF leg to fly a RF leg procedure with acceptable curved path 95% FTE. The FD and/or roll-steering AP capabilities are burdensome to RF leg adoption by Part 23 GA due to lack of equipage in many aircraft and certification overhead for aircraft that have equipage. FAA and Garmin International, Inc., with procedure design support from Hughes Aerospace Corporation, collaborated on a project to collect data to determine whether instrument-rated GA pilots could hand fly RF legs while meeting a 0.5 nm 95% FTE target and RF leg altitude restrictions without the aid of a FD or AP in Part 23 Category A and B aircraft equipped with Garmin® GPS/SBAS (satellite based augmentation system) panel mount and integrated flight deck equipment. Two special RNAV (GPS) approach procedures with complex RF legs designed to stress avionics hardware/software and subject pilot capabilities were created at Paola/Miami County, Kansas airport (K81) near Garmin’s flight operations home airport. Data collection profiles were jointly developed with the FAA and data collection flights were flown from June through August 2012 with twelve subject pilots in two aircraft, a minimally equipped Piper Cherokee 6 and a technically advanced Cessna 400. Data post-processing and analysis was performed throughout the data collection flights and preliminary results were briefed regularly to FAA to ensure the project was achieving objectives and so that the project could be responsive to issues resulting from the briefings. This report describes the project including Purpose, Data Collection Overview, Data Analysis Results, Human Factors Discussion, and Conclusions and Recommendations. The primary conclusions and recommendations of this report are:

• Ability to Hand Fly RF Legs: Instrument-rated general aviation pilots are able to hand fly RF legs and meet the 0.5 nm 95% FTE target and RF leg altitude restrictions without the aid of a flight director or autopilot in Part 23 Category A and B aircraft that are either minimally equipped or technically advanced (see Section 2.2 for a detailed discussion of equipage aspects). All pilots demonstrated acceptable proficiency on both straight legs and RF legs. The increase in RF leg FTE over straight leg FTE can be expected to be about the same magnitude from a minimally equipped aircraft to a technically advanced aircraft. In support of these conclusions, Table 29 shows there was more than 50% margin when comparing the calculated 95% FTE for all RF legs with the 95% FTE 0.5 nm target. Table 30 shows there was still margin when comparing the calculated 99.99% FTE for all RF legs with the 95% FTE 0.5 nm target. Additionally, while speed is a contributing factor to FTE, it is not the major contributing factor to FTE. Given the significant Cherokee FTE margins, it has been shown that it is reasonable to extrapolate FTE for a minimally equipped aircraft up to speeds as high as 200 KTAS and still maintain 95% FTE below the 0.5 nm FTE target with sufficient margin for safe operation. Subject pilot comments were in harmony with this conclusion. In support of this conclusion, Table 31 shows there should be more than 40% margin at 200 KTAS when comparing the extrapolated minimally equipped aircraft 95% FTE for all legs with the 95% FTE 0.5 nm target.

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Recommendation 1: Garmin recommends FAA revise its installation and operational guidance for RF legs to make clear that applicants may obtain airworthiness approval for installations without flight director/autopilot. To preclude the need to demonstrate adequate FTE margin for aircraft flying RF legs at greater than 200 knots without flight director/autopilot, Garmin recommends FAA revise its installation and operational guidance for RF legs to allow applicants to utilize an Aircraft Flight Manual limitation that restricts flying RF legs to 200 knots or less.

• Moving Map: As this project has shown, FTE is decreased when a moving map is available and is thus consistent with the MLS curved path study conclusion that led to the FAA installation and operational guidance that “an aircraft must have an electronic map display depicting … RF legs”. However, this project has also clearly shown that a moving map is not required to maintain acceptable RF leg FTE, even during complex procedures and missed approaches. This conclusion is supported by Table 32, which shows there was greater than 46% margin over the 95% FTE 0.5 nm target when pilots flew RF legs in the minimally equipped aircraft with the no map configuration. While FAA installation and operational approval guidance provides display installation field of view guidance for several types of information associated with equipment supporting RNAV (GPS) approaches, the guidance is ambiguous with respect to the purpose of the moving map for RF legs and its acceptable display location. This ambiguity may lead to varying interpretations for acceptable equipment installations supporting RF leg procedures. This ambiguity is a particular concern for existing approved aircraft installations where the equipment that provides the RNAV (GPS) primary guidance and annunciations also incorporates a moving map where the moving map has marginal display placement but other displayed information complies with FAA and manufacturer installation field of view guidance. Consequently, to remove these ambiguities: Recommendation 2: Garmin recommends FAA revise its installation and operational guidance for RF legs to make clear that the main purpose of the moving map is to enhance situational awareness, and that it is acceptable for the moving map to be located either in the pilot’s primary field of view or on a readily accessible display page outside the primary field of view.

• Equipment Contribution to Pilot Workload: Subject pilots stated workload could be lowered substantially if frequent message prompts and associated course setting tasks could be eliminated or reduced. Recommendation 3: Garmin recommends FAA consider revisions to its installation and operational guidance for RF legs to indicate that, to the extent practical, applicants seeking airworthiness approval of equipment capable of RF legs should minimize frequent recurring and unnecessary avionics operational tasks while RF legs are active.

• Pilot Training and Experience: Pilots of all experience classifications, low, medium and high time, were able to fly RF legs with 95% FTE less than the 0.5 nm target without training specific to RF legs. Recommendation 4: Garmin recommends FAA update the Instrument Flying Handbook and Instrument Procedures Handbook to include a description of RF legs and the suggested techniques to successfully fly them. Garmin also recommends FAA update the Aeronautical Information Manual to add the “RF” abbreviation to the Abbreviations/Acronyms Appendix and other appropriate information regarding RF legs related to RNP procedures such as RNAV (GPS) approaches.

• RF Leg Procedure Design: Pilots were able to hand fly complex RF leg procedures, including those with RF legs not explicitly allowed or even non-conforming according to current procedure design criteria, with 95% FTE lower than the 0.5 nm target. Table 33 shows there was almost 30% margin when comparing the calculated 95% FTE on the highest FTE non-conforming RF leg (K8105-K8106) terminating at the FAF with the 95% FTE 0.5 nm target. Recommendation 5: Given the FTE margins demonstrated with the complex RF leg prototype procedures, Garmin recommends FAA consider revisions to the Order 8260.58 RF leg procedure design criteria to: 1) Explicitly allow “S” RF legs and,


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2) Allow RF legs terminating at the FAF “wherever airspace is critical to maximizing the benefit for terminal area operations.” Recommendation 6: Garmin recommends FAA consider providing a copy of this report to the ICAO Instrument Flight Procedure Panel (IFPP) to support international harmonization of RF leg procedure design criteria via the RF Design Criteria working paper, particularly with respect to proposed intermediate approach segment design criteria for RF legs.

Additional rationale supporting these conclusions and recommendations is included in Section 5. Implementation of these recommendations will broaden NextGen benefits and provide additional incentive for GPS/SBAS equipage while retaining consistency with the Performance Based Navigation philosophy as the project results have clearly shown that total system error targets during RF legs can be met without autopilot, flight director, and moving map equipment or RF leg-specific pilot training.


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TABLE OF CONTENTS

1. PURPOSE ........................................................................................................................................... 11

1.1 BACKGROUND ................................................................................................................................. 11 1.2 GOALS AND OBJECTIVES ................................................................................................................. 14 1.3 REPORT STRUCTURE ...................................................................................................................... 15

2. DATA COLLECTION OVERVIEW ...................................................................................................... 16

2.1 RF LEG PROTOTYPE PROCEDURES ................................................................................................. 16 2.2 AIRCRAFT/EQUIPMENT OVERVIEW ................................................................................................... 18 2.3 SUBJECT PILOTS ............................................................................................................................. 26 2.4 OTHER CREW ................................................................................................................................. 27 2.5 TRAINING ........................................................................................................................................ 27 2.6 FLIGHT PROFILES ............................................................................................................................ 27 2.7 FLIGHT PROCESS ............................................................................................................................ 29 2.8 FTE CALCULATION ......................................................................................................................... 30

3. DATA ANALYSIS RESULTS .............................................................................................................. 32

3.1 FLIGHT STATISTICS ......................................................................................................................... 33 3.2 AGGREGATE RF LEG FTE ............................................................................................................... 33 3.3 INDIVIDUAL RF LEG FTE ................................................................................................................. 36 3.4 EFFECTS OF AIRCRAFT SPEED......................................................................................................... 40 3.5 STRAIGHT LEG FTE VS. RF LEG FTE COMPARISON ......................................................................... 46 3.6 MAP VS. NO MAP RF LEG FTE COMPARISON ................................................................................... 50 3.7 PILOT EXPERIENCE VS. RF LEG FTE COMPARISON .......................................................................... 52 3.8 RF LEG ALTITUDE MANAGEMENT ..................................................................................................... 55

4. HUMAN FACTORS DISCUSSION ...................................................................................................... 57

4.1 PILOT FACTORS .............................................................................................................................. 57 4.2 ENVIRONMENTAL FACTORS ............................................................................................................. 58 4.3 AIRCRAFT/EQUIPMENT FACTORS ..................................................................................................... 59 4.4 CHART DESIGN FACTORS ................................................................................................................ 64 4.5 FTE EXCEEDANCE ASSESSMENT SUMMARY ..................................................................................... 65

5. CONCLUSIONS AND RECOMMENDATIONS ................................................................................... 67

5.1 EQUIPMENT/INSTALLATION .............................................................................................................. 69 5.2 TRAINING ........................................................................................................................................ 74 5.3 RF LEG PROCEDURE DESIGN .......................................................................................................... 74

APPENDIX A – DETAILED DATA ANALYSIS RESULTS .................................................................. 76

A.1 INDIVIDUAL RF LEG FTE ............................................................................................................... 76

A.2 PILOT RF LEG FTE ......................................................................................................................... 77

A.3 AGGREGATE RF LEG GROUND TRACK PLOTS ........................................................................ 78

A.4 AGGREGATE RF LEG VERTICAL PROFILE PLOTS ................................................................... 92


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A.5 EXTRAPOLATING FTE TO HIGHER SPEEDS ............................................................................ 104

A.6 INDIVIDUAL STRAIGHT LEG FTE ............................................................................................... 109

A.7 PILOT STRAIGHT LEG FTE ......................................................................................................... 110

A.8 AGGREGATE STRAIGHT LEG PLOTS ....................................................................................... 111

APPENDIX B – DETAILED HUMAN FACTORS DISCUSSION ........................................................ 119

B.1 CHEROKEE WORKLOAD RATING SUMMARY .......................................................................... 119

B.2 FTE EXCEEDANCE ASSESSMENT DETAILS ............................................................................ 122

APPENDIX C – DATA POST-PROCESSING .................................................................................... 130

APPENDIX D – ABBREVIATIONS .................................................................................................... 132

APPENDIX E – REFERENCED DOCUMENTS ................................................................................. 134

TABLE OF FIGURES FIGURE 1. K81 RNAV (GPS) X RWY 3 (SPECIAL) APPROACH ....................................................................... 17 FIGURE 2. K81 RNAV (GPS) X RWY 21 (SPECIAL) APPROACH ..................................................................... 18 FIGURE 3. PIPER CHEROKEE 6 AIRCRAFT ...................................................................................................... 19 FIGURE 4. PIPER CHEROKEE 6 COCKPIT ........................................................................................................ 19 FIGURE 5. PIPER CHEROKEE 6 COCKPIT #2 CDI ............................................................................................ 20 FIGURE 6. CHEROKEE GNS 430W INSTALLATION LOCATION .......................................................................... 21 FIGURE 7. GNS 430W MAP PAGE WITH WIND VECTOR .................................................................................. 21 FIGURE 8. GNS 430W DEFAULT NAVIGATION PAGE ...................................................................................... 22 FIGURE 9. GNS 430W SET COURSE MESSAGE ............................................................................................. 22 FIGURE 10. CESSNA 400 AIRCRAFT............................................................................................................... 23 FIGURE 11. CESSNA 400 G2000® PROTOTYPE COCKPIT ............................................................................... 23 FIGURE 12. G2000 PFD ARRANGEMENT ....................................................................................................... 24 FIGURE 13. PFD STATUS WINDOW – RF LEG ACTIVE LEG ............................................................................. 25 FIGURE 14. G2000 MFD ARRANGEMENT ....................................................................................................... 26 FIGURE 15. PROFILE 1 .................................................................................................................................. 28 FIGURE 16. PROFILE 2 .................................................................................................................................. 29 FIGURE 17. PILOT LINE COLOR LEGEND ........................................................................................................ 32 FIGURE 18. AGGREGATE FTE: ALL RF LEGS FOR BOTH AIRCRAFT ................................................................ 34 FIGURE 19. AGGREGATE FTE: ALL RF LEGS FOR CHEROKEE ........................................................................ 35 FIGURE 20. AGGREGATE FTE: ALL RF LEGS FOR C400 ................................................................................ 36 FIGURE 21. LOWEST 95% FTE RF LEG AGGREGATE GROUND TRACKS .......................................................... 38 FIGURE 22. HIGHEST 95% FTE RF LEG AGGREGATE GROUND TRACKS ......................................................... 39 FIGURE 23. CHEROKEE 95% FTE VS. TAS TREND ........................................................................................ 42 FIGURE 24. C400 95% FTE VS. TAS TREND ................................................................................................ 42 FIGURE 25. CHEROKEE ALL LEGS FTE VS. 10 KT TAS RANGES ..................................................................... 45 FIGURE 26. CHEROKEE ALL LEGS DISTRIBUTION OVER TAS RANGE ................................................................ 45 FIGURE 27. AGGREGATE FTE: ALL STRAIGHT LEGS FOR BOTH AIRCRAFT ...................................................... 47 FIGURE 28. AGGREGATE FTE: ALL STRAIGHT LEGS FOR CHEROKEE ............................................................. 48


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FIGURE 29. AGGREGATE FTE: ALL STRAIGHT LEGS FOR C400 ...................................................................... 49 FIGURE 30. GNS 430W DEFAULT NAVIGATION PAGE .................................................................................... 51 FIGURE 31. TEST CARD RATING SCALE ......................................................................................................... 58 FIGURE 32. PILOT 007 INTERCEPTING K8107-K8108 .................................................................................... 63 FIGURE 33. MLS CURVED PATH STUDY EFIS ND FIGURE .............................................................................. 72 FIGURE 34. PILOT LINE COLOR LEGEND ........................................................................................................ 78 FIGURE 35. K8102-K8103 RF LEG AGGREGATE GROUND TRACKS ................................................................ 79 FIGURE 36. K8104-K8105 AND K8105-K8106 RF LEGS AGGREGATE GROUND TRACKS ................................ 80 FIGURE 37. K8104-K8105 RF LEG AGGREGATE GROUND TRACKS ................................................................ 81 FIGURE 38. K8105-K8106 RF LEG AGGREGATE GROUND TRACKS ................................................................ 82 FIGURE 39. K8107-K8108 RF LEG AGGREGATE GROUND TRACKS ................................................................ 83 FIGURE 40. K8121-K8122, K8122-K8123, K8123-K8124, AND K8124-K8125 RF LEGS AGGREGATE GROUND

TRACKS ................................................................................................................................................. 84 FIGURE 41. K8121-K8122 RF LEG AGGREGATE GROUND TRACKS ................................................................ 85 FIGURE 42. K8122-K8123 RF LEG AGGREGATE GROUND TRACKS ................................................................ 86 FIGURE 43. K8123-K8124 RF LEG AGGREGATE GROUND TRACKS ................................................................ 87 FIGURE 44. K8124-K8125 RF LEG AGGREGATE GROUND TRACKS ................................................................ 88 FIGURE 45. K8127-K8128 RF LEG AGGREGATE GROUND TRACKS ................................................................ 89 FIGURE 46. K8129-K8132 RF LEG AGGREGATE GROUND TRACKS ................................................................ 90 FIGURE 47. K8134-K8135 RF LEG AGGREGATE GROUND TRACKS ................................................................ 91 FIGURE 48. K8102-K8103 RF LEG AGGREGATE VERTICAL PROFILES ............................................................ 93 FIGURE 49. K8104-K8105 RF LEG AGGREGATE VERTICAL PROFILES ............................................................ 94 FIGURE 50. K8105-K8106 RF LEG AGGREGATE VERTICAL PROFILES ............................................................ 95 FIGURE 51. K8107-K8108 RF LEG AGGREGATE VERTICAL PROFILES ............................................................ 96 FIGURE 52. K8121-K8122 RF LEG AGGREGATE VERTICAL PROFILES ............................................................ 97 FIGURE 53. K8122-K8123 RF LEG AGGREGATE VERTICAL PROFILES ............................................................ 98 FIGURE 54. K8123-K8124 RF LEG AGGREGATE VERTICAL PROFILES ............................................................ 99 FIGURE 55. K8124-K8125 RF LEG AGGREGATE VERTICAL PROFILES .......................................................... 100 FIGURE 56. K8127-K8128 RF LEG AGGREGATE VERTICAL PROFILES .......................................................... 101 FIGURE 57. K8129-K8132 RF LEG AGGREGATE VERTICAL PROFILES .......................................................... 102 FIGURE 58. K8134-K8135 RF LEG AGGREGATE VERTICAL PROFILES .......................................................... 103 FIGURE 59. CHEROKEE DESCENDING LEGS FTE VS. 10 KT TAS RANGES ..................................................... 104 FIGURE 60. CHEROKEE DESCENDING LEGS DISTRIBUTION OVER TAS RANGE ............................................... 105 FIGURE 61. CHEROKEE CLIMBING LEGS FTE VS. 10 KT TAS RANGES ........................................................... 106 FIGURE 62. CHEROKEE CLIMBING LEGS DISTRIBUTION OVER TAS RANGE ..................................................... 106 FIGURE 63. CHEROKEE LEVEL LEGS FTE VS. 10 KT TAS RANGES ................................................................ 107 FIGURE 64. CHEROKEE LEVEL LEGS DISTRIBUTION OVER TAS RANGE .......................................................... 108 FIGURE 65. K8103-K8104 STRAIGHT LEG AGGREGATE GROUND TRACKS .................................................... 111 FIGURE 66. K8108-K8109 STRAIGHT LEG AGGREGATE GROUND TRACKS .................................................... 112 FIGURE 67. DODSN-K8120 STRAIGHT LEG AGGREGATE GROUND TRACKS ................................................. 113 FIGURE 68. K8120-K8121 STRAIGHT LEG AGGREGATE GROUND TRACKS .................................................... 114 FIGURE 69. K8128-K8129 STRAIGHT LEG AGGREGATE GROUND TRACKS .................................................... 115


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FIGURE 70. K8133-K8134 STRAIGHT LEG AGGREGATE GROUND TRACKS .................................................... 116 FIGURE 71. K8135-K8136 STRAIGHT LEG AGGREGATE GROUND TRACKS .................................................... 117 FIGURE 72. K8136-DODSN STRAIGHT LEG AGGREGATE GROUND TRACKS ................................................. 118 FIGURE 73. PILOT 001 FTE EXCEEDANCE, K8127-K8128 ............................................................................ 123 FIGURE 74. PILOT 008 FTE EXCEEDANCE, K8104-K8105-K8106 ................................................................ 123 FIGURE 75. PILOT 008 FTE EXCEEDANCE, K8107-K8108 ........................................................................... 125 FIGURE 76. PILOT 009 FTE EXCEEDANCE, K8104-K8105-K8106 ............................................................... 126 FIGURE 77. PILOT 010 FTE EXCEEDANCE, K8104-K8105-K8106 ............................................................... 127 FIGURE 78. PILOT 011 FTE EXCEEDANCE, K8134-K8135 ........................................................................... 128 FIGURE 79. PILOT 011 FTE EXCEEDANCE, K8104-K8105-K8106 ............................................................... 129 FIGURE 80. PILOT 011 FTE EXCEEDANCE, K8107-K8108 ........................................................................... 129 FIGURE 81. DETECTING AN RF LEG FOR CALCULATING FTE ......................................................................... 130 FIGURE 82. DETECTING A STRAIGHT LEG AND RF LEG VERTICAL PROFILE .................................................... 131

TABLE OF TABLES TABLE 1. DATA COLLECTION ERROR CONTRIBUTIONS .................................................................................... 30 TABLE 2. FLIGHT STATISTICS SUMMARY ........................................................................................................ 33 TABLE 3. AGGREGATE FTE FOR ALL RF LEGS ............................................................................................... 36 TABLE 4. RF LEG KEY CHARACTERISTICS AND FTE RANK .............................................................................. 37 TABLE 5. AGGREGATE RF LEG FTE EXCLUDING HIGHEST FTE LEGS ............................................................. 39 TABLE 6. ALL RF LEG VS. EXCLUDED RF LEG TO FAF AGGREGATE FTE COMPARISON ................................... 39 TABLE 7. ALL RF LEG VS. EXCLUDED “S” RF LEGS AGGREGATE FTE COMPARISON ........................................ 40 TABLE 8. RF LEG SPEEDS FLOWN AND WIND SPEEDS .................................................................................... 40 TABLE 9. RF LEG OVERLAPPING AVERAGE TAS AGGREGATE FTE ................................................................. 41 TABLE 10. RF LEG OVERLAPPING TAS AGGREGATE FTE COMPARISON ......................................................... 41 TABLE 11. CHEROKEE RF LEG TAS RANGE AGGREGATE FTE ....................................................................... 42 TABLE 12. C400 RF LEG TAS RANGE AGGREGATE FTE ............................................................................... 42 TABLE 13. CHEROKEE NO MAP RF LEGS PER TAS RANGE ............................................................................ 43 TABLE 14. CHEROKEE LEG GROUPS .............................................................................................................. 43 TABLE 15. CHEROKEE ALL LEGS FTE VS. 10 KT TAS RANGE ......................................................................... 44 TABLE 16. STRAIGHT LEG FLIGHT STATISTICS SUMMARY................................................................................ 46 TABLE 17. AGGREGATE FTE FOR ALL STRAIGHT LEGS ................................................................................... 49 TABLE 18. RF LEG VS. STRAIGHT LEG AGGREGATE FTE COMPARISON BY LEG TYPE ..................................... 50 TABLE 19. STRAIGHT LEG FTE VS. RF LEG AGGREGATE FTE COMPARISON BY AIRCRAFT .............................. 50 TABLE 20. CHEROKEE NO MAP VS. MAP RF LEG AGGREGATE FTE COMPARISON ........................................... 51 TABLE 21. RF LEG AGGREGATE FTE COMPARISON BETWEEN CHEROKEE GNS 430W CONFIGURATIONS AND

C400 ..................................................................................................................................................... 51 TABLE 22. PILOT AGGREGATE RF LEG FTE ................................................................................................... 52 TABLE 23. PILOT EQUIPMENT EXPERIENCE COMPARISON WITH RF LEG FTE .................................................. 53 TABLE 24. PILOT AGGREGATE STRAIGHT LEG FTE ........................................................................................ 54 TABLE 25. CHEROKEE PILOT AGGREGATE RF LEG VS. STRAIGHT LEG AGGREGATE FTE COMPARISON ............ 54 TABLE 26. C400 PILOT AGGREGATE RF LEG VS. STRAIGHT LEG AGGREGATE FTE COMPARISON .................... 55


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TABLE 27. RF LEG SET COURSE MESSAGE FREQUENCY ................................................................................ 61 TABLE 28. RF LEG 0.5 NM FTE EXCEEDANCE SUMMARY ............................................................................... 66 TABLE 29. RF LEG AGGREGATE 95% FTE MARGIN – ALL LEGS ..................................................................... 67 TABLE 30. RF LEG AGGREGATE 99.99% FTE MARGIN – ALL LEGS ................................................................ 67 TABLE 31. CHEROKEE EXTRAPOLATED 200 KTAS 95% FTE MARGIN ............................................................ 67 TABLE 32. CHEROKEE RF LEG AGGREGATE 95% FTE MARGIN – MAP VS. NO MAP FTE LEGS ....................... 68 TABLE 33. RF LEG AGGREGATE 95% FTE MARGIN – HIGHEST FTE LEG ....................................................... 69 TABLE 34. AGGREGATE FTE FOR EACH RF LEG ............................................................................................ 76 TABLE 35. CALCULATED FTE RANGE FOR EACH RF LEG ............................................................................... 76 TABLE 36. PILOT AGGREGATE RF LEG FTE ................................................................................................... 77 TABLE 37. PILOT AGGREGATE RF LEG CALCULATED FTE RANGE .................................................................. 77 TABLE 38. CHEROKEE DESCENDING LEGS FTE VS. 10 KT TAS RANGE .......................................................... 104 TABLE 39. CHEROKEE CLIMBING LEGS FTE VS. 10 KT TAS RANGE ............................................................... 105 TABLE 40. CHEROKEE LEVEL LEGS FTE VS. 10 KT TAS RANGE ................................................................... 107 TABLE 41. AGGREGATE FTE FOR EACH STRAIGHT LEG ................................................................................ 109 TABLE 42. RECORDED FTE RANGE FOR EACH STRAIGHT LEG ...................................................................... 109 TABLE 43. PILOT AGGREGATE STRAIGHT LEG FTE ...................................................................................... 110 TABLE 44. PILOT AGGREGATE STRAIGHT LEG RECORDED FTE RANGE ......................................................... 110 TABLE 45. CHEROKEE WORKLOAD RATING SUMMARY .................................................................................. 119


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1. PURPOSE On September 14, 2011 the Federal Aviation Administration (FAA) and Garmin International, Inc. signed a Memorandum of Agreement, (MOA) DTFAWA-11-A-80009. DTFAWA-11-A-80009 was amended by Modification 2 signed August 6, 2012. Per DTFAWA-11-A-80009 Mod 2 Article 2.A:

“The purpose of this agreement between the Federal Aviation Administration (FAA) and Garmin International Inc. (“Garmin”) is to support the FAA in determining whether the AC 90-105 and AC 20-138B installation guidance can be revised to allow hand flown Radius-to-Fix (RF) Turns to existing criteria on required navigation performance (RNP) for public use RNAV wide area augmentation system (WAAS) approaches. … This Agreement will require Garmin (a WAAS General Aviation Equipment manufacturer) to lead a collaborative effort to obtain flight test data of hand flown RF turns to RNAV (GPS) approach procedures for fixed wing aircraft. This data will support the FAA in its effort to determine whether AC 90-105 and AC20-138B installation guidance can be revised to allow hand-flown RF turns to existing terminal procedure criteria.”1

This Project Report summarizes the project and the resulting conclusions and recommendations in a publicly distributable document.

1.1 Background

1.1.1 Radius-to-Fix Procedure Design Background Required Navigation Performance (RNP) 1 with Curved Path is a key NextGen Performance Based Navigation (PBN) capability enabling precise departure, arrival and approach procedures, including repeatable curved paths.2 The curved path capability is accomplished through Radius-to-Fix (RF) legs that enable procedure designers to adapt Standard Instrument Departures (SIDs), Standard Terminal Arrival Routes (STARs), and approach segments in ways not possible with straight segments including:

• Avoiding obstacles and terrain features to lower approach procedure minimum altitudes • De-conflicting traffic flows from multiple airports in high density airspace • Optimizing paths for reduced fuel consumption and reduced carbon emissions • Avoiding noise sensitive areas

Particularly important to general aviation (GA) operations are de-conflicting and improving traffic flows to general aviation and reliever airports near air transport hub airports and lowering approach procedure minimum altitudes at any airport. The FAA introduced the RF leg on RNP authorization required (AR) approach procedures based on FAA Order 8260.52, United States Standard for Required Navigation Performance (RNP) Approach Procedures with Special Aircraft and Aircrew Authorization Required (SAAAR). Order 8260.52:

• Allows RF legs in all segments including the final approach. • Defines the primary obstacle evaluation area (OEA) as 2×RNP on either side of the segment

centerline3.

1 The quoted text references FAA AC 20-138B; FAA AC 20-138C is the current revision. The underlying issues associated with the installation requirements are still pertinent to the DTFAWA-11-A-80009 Mod 2 Article 2.A Purpose. 2 FAA, NextGen Implementation Plan, page 43. 3 FAA Order 8260.52 1.7.


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Due to these advanced attributes, use of RNP AR procedures is limited to aircraft and aircrew with special authorization. RNP AR procedures with RF legs have been demonstrated to provide the aforementioned increased capabilities and improved minima on Part 25 aircraft. However, RNP AR procedures do not benefit Part 23 aircraft more typical of GA operations because of the special authorization requirements. Furthermore, limiting RF legs to RNP AR procedures also limits the NextGen benefits potential. Public use area navigation (RNAV) global positioning system (GPS) approaches also can be designed with RF legs based on FAA Order 8260.58, United States Standard for Performance Based Navigation (PBN) Instrument Procedure Design.4 Order 8260.58:

• Allows RF legs only in the initial, intermediate, and missed approach segments. • Obstacle evaluations are performed using:

o 2×RNP primary plus 1×RNP secondary areas on either side of the segment centerline within 30 nautical miles (nm) of the airport reference point (ARP).

o 4×RNP primary plus 2×RNP secondary beyond 30 nm of the ARP. While the procedure design criteria in Order 8260.58 and its predecessor, Order 8260.54A, The United States Standard for Area Navigation (RNAV), have allowed procedures to be designed with RF legs since December 2007, procedure designers have only recently begun to include RF legs on RNAV (GPS) procedures, such as the Carlsbad/McClellan-Palomar, California RNAV (GPS) Y RWY 24 (July 2012), and non-RNP AR procedures, such as the Ketchikan, Alaska ILS Z RWY 11 (circa 2009). Procedures with RF legs have the potential to provide additional NextGen benefits to Part 23 aircraft GA operations.

1.1.2 Radius-to-Fix Equipment Background Current FAA guidance provided in Advisory Circular (AC) 90-105, Approval Guidance for RNP Operations and Barometric Vertical Navigation in the U.S. National Airspace System, and AC 20-138C, Airworthiness Approval of Positioning and Navigation Systems, states that an aircraft should be equipped with a flight director (FD) and/or roll-steering autopilot (AP) and an electronic map display depicting the RF leg to fly a RF leg procedure with acceptable curved path 95% flight technical error (FTE).5 The FAA guidance for manual and coupled straight path segment 95% FTE values originated with consensus standard6 assumptions included in RTCA/DO-208, Minimum Operational Performance Standards for Airborne Supplemental Navigation Equipment Using Global Positioning System (GPS).7 Subsequent microwave landing system (MLS) curved path studies were also used as input to the FAA RF leg equipment guidance; the MLS studies found the workload and flight technical error (FTE) too high when using only horizontal situation indicator (HSI)-type lateral guidance for curved path segments.8 Consensus standard RTCA/DO-283A, Minimum Operational Performance Standards for Required

4 FAA Order 8260.58 was published after this project began. The Order 8260.58 Volume 6 criteria for designing RNAV (GPS) approaches with RF legs are nearly identical to the Order 8260.54A criteria used to design the special RNAV (GPS) approaches used by this project. 5 FAA AC 90-105 Appendix 5 2.b.(1) and 2.b.(2); FAA AC 20-138C Appendix 3 A3-2.b.(1) and A3-2.b.(3). 6 RTCA develops consensus-based recommendations with input from government, industry and academic organizations from the United States and around the world. 7 RTCA/DO-208 Appendix E 2.5 indicates:

• The manual FTE values were based on 1978 FAA tests using VOR/DME • The autopilot coupled FTE values were based on the June 1988 EUROCONTROL Experimental Centre

Report No. 216, Navigation Accuracy of Aircraft Equipped with Advanced Navigation Systems, and a review of manufacturer’s specifications

• The flight director coupled FTE values were based on MLS RNAV flight tests and flight simulations 8 NASA TP 3255, Concluding Remarks, “Pilot comments indicated the need for flight director guidance when flying the curved approaches.” (page 20) NLR TP 91446 L, 11.5 Conclusions on instrumentational provisions, “Situation awareness is improved by a moving map display. This improvement is most beneficial and may be required to provide necessary situational awareness for complex procedures or in situations where a missed approach is required.” (page 78)


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Navigation Performance for Area Navigation, subsequently extended the straight path segment coupled 95% FTE values to curved path segments while indicating “manual flight operation on curved path segments will require separate evaluation”.9 The MLS curved path studies used aircraft with Category C and Category D approach speed limits; aircraft approach speed limits are defined by 14 Code of Federal Regulations (CFR) 97.3 as follows:

“As used in the standard instrument procedures prescribed in this part-- Aircraft approach category means a grouping of aircraft based on a speed of VREF, if specified, or if VREF is not specified, 1.3 Vso at the maximum certificated landing weight. VREF, Vso, and the maximum certificated landing weight are those values as established for the aircraft by the certification authority of the country of registry. The categories are as follows-- (1) Category A: Speed less than 91 knots. (2) Category B: Speed 91 knots or more but less than 121 knots. (3) Category C: Speed 121 knots or more but less than 141 knots. (4) Category D: Speed 141 knots or more but less than 166 knots. …”

Since no other data existed, the MLS study results and consensus standard FTE assumptions were also applied to aircraft with Category A and Category B approach speed limits that are normally associated with Part 23 GA aircraft. The flight guidance system (FGS) flight director (FD) and/or roll-steering autopilot (AP) capabilities are burdensome to RF leg adoption by Part 23 GA for a variety of reasons including:

• Few GA aircraft have a flight director. • Only 50% of IFR-capable US GA aircraft have an autopilot.10 • Most GA aircraft FGS use conventional course deviation and heading error inputs not roll-

steering: o Pilots must manually update selected heading for each leg unless the aircraft is equipped

with an automatically slewed (auto-slew) HSI or an adapter to auto-slew the autopilot heading error input to be consistent with a RF leg’s continuously changing desired track.

o Most GA aircraft do not have auto-slew HSI or autopilot heading error adapter and thus would be subject to additional equipment expense.

• For GA aircraft with FGS, FAA requires manufacturers to demonstrate RF leg capability with each navigation system/FGS combination via Type Certificate (TC) or Supplemental Type Certificate (STC):

o Obtaining a TC or STC is often impractical due to the expense and overhead associated with such certification projects.

Unlike Part 25 aircraft, Part 23 GA aircraft are primarily equipped with TSO-C146() GPS/SBAS (satellite based augmentation system) equipment. RF legs are an optional capability for TSO-C146() equipment.11

9 Per RTCA/DO-283A 2.2.5.1:

“The required PEE [Position Estimation Error] accuracy performance can be determined based on fixed allocations for PSE [Path Steering Error] based on the following assumptions: • FTE analysis provided in RTCA/DO-208, Appendix E … for straight line path segments. • The RTCA/DO-208 values for FTE capability for flight director or autopilot operation are also applicable to

curved paths. • Approval for manual flight operation on curved path segments will require separate evaluation of PSE.”

10 FAA, General Aviation and Part 135 Activity Surveys - CY 2010, http://www.faa.gov/data_research/aviation_data_statistics/general_aviation/CY2010/, Chapter VIII. Avionics. 11 Per RTCA/DO-229C and RTCA/DO-229D 2.2.1.3.3 “If the equipment is designed to perform RF legs, …”


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TSO-C146() equipment must prohibit selection of unsupported procedures.12 But AC 90-105 is more restrictive in that even if the TSO-C146() equipment supports RF legs:

“The [RNP] system must restrict pilot access to procedures requiring RF leg capability if the system can select the procedure, but the aircraft is not otherwise equipped (e.g., the aircraft does not have the required roll steering autopilot or flight director installed).”13

The lack of these FGS equipment capabilities in many Part 23 GA aircraft prevents them from being able to fly RF legs, and also results in a potential lack of deployment of public use RNAV (GPS) approaches with Radius-to-Fix (RF) legs.

1.2 Goals and Objectives

1.2.1 Contractual Goals and Objectives DTFAWA-11-A-80009 Mod 2 Article 2.B established the following goals and objectives for the project:

“The primary goal of this project is to enhance the safety and efficiency capabilities of the fielded Garmin equipment with a new public use RF Turn operational application and to expand that new capability through the revised installation guidance to other aircraft operators/users. … The second goal is to utilize the Garmin technical expertise in the development of revised installation guidance into aircraft avionics because of their previous experience and understanding of the certification processes. … Another goal of this effort is for Garmin to help the FAA address one significant aspect of WAAS-enabled flight operations, which is deployment of public use RNAV (GPS) approaches with Radius-to-Fix (RF) turns. … In support of these objectives, two sets of data will be collected, one for GNS 430W/530W and one for G2000. Specific objectives of this project include: 1) Provide data to determine if Category A and B aircraft can hand fly RF turns within the

bounds of established Flight Technical Error (FTE) during RNAV (GPS) procedures and, 2) Recertify existing GPS/WAAS equipment with RF turn capability.”

1.2.2 Hypothesis To support the aforementioned goals and objectives, the following hypothesis was developed:

• Given that: o Part 23 GA pilots flew distance measuring equipment (DME) arcs for years with

rudimentary information: - No positive course guidance. - Only a small DME distance readout.

o TSO-C146() equipment: - Has adequate moving map capability to display curved path legs. - Has positive course guidance via course deviation indicator (CDI) and/or HSI

depending on installation. - Is certified for hand flown DME arc procedures.

• It follows that these TSO-C146() equipment capabilities are adequate for pilots in Part 23 aircraft to hand-fly RF legs within the RNP performance standard.

12 Per RTCA/DO-229C and RTCA/DO-229D 2.2.1.3 “The equipment shall not permit the flight crew to select a procedure or route that is not supported by the equipment, either manually or automatically (e.g., a procedure is not supported if it incorporates an RF leg and the equipment does not provide RF leg capability).” 13 FAA AC 90-105 9.h.(2).


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1.2.3 Flight Technical Error (FTE) Target AC 20-138C 16-2 and Table 9 include the following discussion of RNP FTE with respect to straight and curved path segments:14

“The aircraft manufacturer should verify maintenance of FTE (95% of the flying time) during straight path segments per Table 9 below. The FTE should be demonstrated in each phase of flight, both with and without autopilot and/or FD as applicable. The FTE values below are also acceptable for curved path segments only with an autopilot and/or FD. Manual flight operation on curved path segments will require a separate FTE evaluation.

RNP (nm) FTE (nm) FTE Basis

0.3 0.125 Autopilot 0.25 Flight Director or Manual Operation

1.0 0.5 Flight Director or Autopilot 0.8 Manual Operation

2.0 1.0 Manual Operation 4.0 2.0 Manual Operation

Table 9. RNP FTE Performance” Order 8260.58, and its predecessor Order 8260.54A, limit RF legs on RNAV (GPS) approach procedures to initial, intermediate, and missed approach segments; these segments correspond to RNP 1 in AC 20-138C Table 9. Consequently, to support the goal of revising the AC 90-105 and AC 20-138C installation guidance to allow instrument-rated pilots operating typical Part 23 GA aircraft without the aid of a flight director or autopilot, the 95% FTE target was chosen to be 0.5 nm. In other words, the 0.5 nm (95%) FTE target for instrument-rated pilots to hand-fly RNAV (GPS) approach procedures with RF legs is identical to that which AC 20-138C and RTCA/DO-283A credit for RNP 1 curved path segments with flight director or autopilot. In keeping with the contractual data collection objectives, the scope of this project was limited to aircraft which fall within Category A and Category B approach speed limits.

1.3 Report Structure This report describes the activities undertaken by Garmin and the FAA to show that instrument-rated pilots operating typical Part 23 GA aircraft without the aid of a flight director or autopilot can hand fly RF legs with acceptable FTE. This report is structured as follows:

Section 2. Data Collection Overview – Describes activities and methods used to collect and post-process FTE data in support of project goals Section 3. Data Analysis Results – Describes results of the data analysis performed on the collected FTE data Section 4. Human Factors Discussion – Describes human factors and subjective pilot comments Section 5. Conclusions and Recommendations – Presents project conclusions and recommendations

14 The AC 20-138C Table 9 FTE values are identical to the RTCA/DO-283A Table 2-6 Path Steering Error (PSE) Allocation (95%).


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2. DATA COLLECTION OVERVIEW This section describes the activities and methods used to collect FTE data in support of project goals.

2.1 RF Leg Prototype Procedures FAA’s Global Navigation Satellite System (GNSS) Program Office contracted with Hughes Aerospace Corporation (Hughes) to develop two special RNAV (GPS) approach procedures with RF legs at Paola/Miami County, Kansas airport (K81). The baseline for designing the K81 approach procedures was to use the then current Order 8260.54A15 criteria including:

• RF legs are not applicable to the final segment or section 1 of the missed approach segment (section 2.5.3).

• OEA construction limits leg radius to a minimum value equal-to or greater-than the OEA (primary and secondary) half-width (section 2.5.3).

Note: Given the restriction from using RF legs in the final segment, this effectively means the minimum RF leg radius is 3 nm

• RF legs in the intermediate segment must terminate at least 2 nm prior to the final approach fix (FAF) (section 2.5.3).

• The maximum allowable bank angle on an RF is 20 degrees (15 degrees if only categories A and B are published) (section 2.5.3).

• The first missed approach leg may be followed by an RF leg when the initial straight leg has reached full width (section 6.2).

As a starting point for the K81 procedures, FAA requested Garmin and Hughes to review several RF leg prototype instrument procedures designed to stress avionics hardware/software and subject pilot abilities. These prototype “FOR TEST ONLY” procedures were designed by The MITRE Corporation in response to a request by AFS-470 and AIR-130.16 One difference between the MITRE prototype procedures and the Order 8260.54A RF leg criteria was that the MITRE prototype procedures included an RF leg ending at the FAF. It was decided to include an RF leg ending at the FAF on one of the K81 procedures with the intent that it might help inform an International Civil Aviation Organization (ICAO) Instrument Flight Procedure Panel (IFPP) working paper17 that includes proposed intermediate approach segment design criteria for RF legs as well as support a future extension to the Order 8260.54A, now Order 8260.58, RF leg criteria. It was also of interest to determine whether there is a relationship between aircraft speed and RF leg FTE. In particular, it was desirable to determine whether RF leg FTE is influenced to a greater degree by slow speed flight or by high speed flight. Consequently, FAA requested the procedures be designed to service Category A through D aircraft per FAA Order 8260.54A, where possible. Given the aforementioned considerations, the resulting procedures incorporate the following attributes:

• Eleven RF legs on two procedures • Smallest radius: 2.986 nm; slightly less than 3 nm minimum allowed by Order 8260.54A and

Order 8260.58 • Largest radius: 13.034 nm • Two 180 degree legs and one 305 degree leg • One “S” turn; i.e., consecutive RF legs with opposite turn direction

15 FAA Order 8260.58 was published after the special RNAV (GPS) approaches used by this project were designed. The Order 8260.58 Volume 6 criteria for designing RNAV (GPS) approaches with RF legs are nearly identical to the Order 8260.54A criteria. 16 MITRE, Document No. MP120612 17 ICAO, IFPP/10 WGWHL Working Paper 28 rev. 12


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• Sequence of RF legs with decreasing radii • Vertical profiles including step-down and continuous descent • Support various aircraft speed categories (Cat A/B vs. Cat A/B/C/D)

Figure 1 and Figure 2 depict the K81 procedure charts. The one change Garmin made to the charts Hughes provided was to include an LNAV approach Minimum Descent Altitude (MDA). This change was made to provide a more realistic flight profile that included climbing missed approach RF legs.

Figure 1. K81 RNAV (GPS) X RWY 3 (Special) Approach


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Figure 2. K81 RNAV (GPS) X RWY 21 (Special) Approach

Hughes also provided ARINC 424 data for the K81 RF leg procedures that Garmin used as input to its database processing software to created special avionics databases for the equipment described below.

2.2 Aircraft/Equipment Overview The focus of this project was General Aviation aircraft with two types of TSO-C146() equipment:

• The popular Garmin GNS 430W/530W-series panel mount navigator connected to an external CDI representing a minimally equipped IFR aircraft.

• The Garmin G2000 integrated flight deck representing a Technically Advanced Aircraft (TAA).


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The objective was to collect data on already fielded avionics systems with the intent that the follow-on certification process could be performed more quickly and to provide an equipage path for a significant number of existing GA aircraft. To meet these needs, two Garmin company-owned aircraft with differing performance capabilities and avionics equipment were selected for this project. Garmin’s GNS 430W and G2000 software included uncertified RF leg capability that had been previously used on FAA demonstration flights and during bench trials.18 While the primary project goal was to measure RF leg FTE, the FAA agreed that a secondary goal during the data collection flights was to conduct preliminary evaluations of the RF leg presentation via subjective feedback from FAA Aircraft Certification Office (ACO) and Aircraft Evaluation Group (AEG) pilots as well as from subject pilots.

2.2.1 Piper Cherokee & GNS 430W Garmin’s Piper Cherokee 6 (N4878S, PA32-260) was selected to represent a “worst case” IFR aircraft with minimal equipage as defined by 14 CFR 91.205(d). The Cherokee is capable of approach speeds between 85 – 154 KTAS (based on average KTAS logged during RF legs; actual logged data ranged between 76 and 170 KTAS; see Section 3.4 for more details).

Figure 3. Piper Cherokee 6 Aircraft

Figure 4. Piper Cherokee 6 Cockpit

18 MITRE, F083-L08-047-001


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The Cherokee was equipped with Garmin GNS 530W and GNS 430W GPS/SBAS navigators along with a traditional instrument arrangement. The GNS 530W was connected to the center #1 HSI and the GNS 430W (circled on left-hand side of Figure 4) was connected to the #2 CDI with manual course select resolver and integrated vertical deviation indicator (VDI) in the lower-right corner of the instrument arrangement (circled at center of Figure 4; Figure 5 provides a detailed depiction of the #2 CDI whose actual size is 3.25”W x 3.25”H).

Figure 5. Piper Cherokee 6 Cockpit #2 CDI

To best represent a minimally equipped IFR aircraft, the avionics setup was intentionally limited. Pilots were only able to use the GNS 430W and the #2 CDI during data collection flights. The GNS 530W was set to a date/time page preventing the moving map from being used. Pilots were able to use the #1 HSI only as a directional gyro (DG) with heading bug. The autopilot in the Cherokee was not engaged during any data collection flights.

2.2.1.1 GNS 430W Display Installation Location

The Cherokee #2 CDI provides a source select annunciation in the primary field of view, consistent with the requirements of AC 20-138C.19 However, the left edge of the GNS 430W is located approximately 16.75 inches to the right of the pilot’s field-of-view centerline (center of the attitude direction indicator, ADI). This places the GNS 430W’s GPS mode annunciation field outside the STC installation location limits. Figure 6 compares the GNS 430W STC installation location limits with the actual Cherokee GNS 430W location.

19 FAA AC 20-138C 14-6.6.a.


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Figure 6. Cherokee GNS 430W Installation Location To be STC compliant in this location, an external GPS status annunciator is required. However, this annunciator was not installed for the data collection flights because the GNS 430W is normally the backup navigator in the Cherokee. After an initial evaluation flight jointly conducted by Garmin and the FAA, the Cherokee installation was considered acceptable for data collection flights as it was deemed more stressing to pilots than what normally would be encountered in a real-world conforming installation.

2.2.1.2 GNS 430W Display Factors

Relevant GNS 430W display aspects utilized while flying RF legs are described below.

Moving Map As noted in Section 1.1.2, current FAA guidance requires that an aircraft be equipped with an electronic map display depicting the RF leg. The GNS 430W is capable of displaying a moving map depicting the RF leg. The moving map can also display a wind vector in the lower right corner that provides wind velocity and direction information to the pilot. Note the wind vector can be displayed only when True Airspeed (TAS) and heading data are supplied to the GNS 430W by external sources; many GA installations will not display the wind vector. Figure 7 shows the Map page with wind vector.

Figure 7. GNS 430W Map Page with Wind Vector

Default NAV Page To test whether an electronic map display is truly a minimum capability, some flight profile segments intentionally required the pilot to fly the RF legs using the GNS 430W Default Navigation (Default NAV) page where only numeric information is provided. This configuration also allowed data collection without the Map page wind vector, which is not available in many GA installations. Figure 8 shows a typical Default NAV page.


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Figure 8. GNS 430W Default Navigation Page

The Default NAV page displays a graphic CDI, the active leg of the active flight plan, and six pilot-selectable data fields. The default settings for these fields are distance to waypoint (DIS), desired track (DTK), bearing to waypoint (BRG), ground speed (GS), ground track (TRK) and estimated time en route (ETE). The active leg indication uses a curved path segment drawn between the preceding and active waypoints to indicate the leg is an RF leg. The curved arrow is readily distinguishable from traditional straight leg segments, helping to cue the pilot that an RF leg is active. Pilots were briefed that they could configure these data fields as they desired. The training material the pilots were provided recommended that track angle error (TKE) and cross-track error (XTK) configuration be selected in lieu of the BRG and ETE fields to allow for specific navigation techniques on RF legs (see Section 3.6 for further discussion).

Existing Message Features When interfaced with an HSI or CDI with manual course select resolver, as in the Cherokee 6 installation, the GNS 430W annunciates a flashing amber “MSG” annunciation any time the selected course value differs from desired track (DTK) by 10 degrees. Figure 9 shows a typical “Set course” message displayed on the Messages page after the pilot presses the MSG key.

Figure 9. GNS 430W Set Course Message

For straight leg segments, the desired track only changes if two consecutive straight leg segments do not have the same course; consequently, pilot interaction to adjust the selected course is minimized. However, on a curved path, such as an RF leg or DME arc, desired track is continually changing, which results in repeated flashing “MSG” annunciations and pilot interaction to adjust the selected course. “Set course” messages and the need to manually update the selected course are not pilot workload factors in installations with an auto-slew HSI. While such installations are becoming more common, most GA aircraft do not have an auto-slew HSI.

2.2.2 Cessna 400 & G2000 Garmin’s Cessna model LC41-550FG, hereafter referred to as Cessna 400 or C400 (N999GL) was selected to represent a TAA aircraft with higher performance and advanced avionics. The C400 is capable of approach speeds between 120 – 196 KTAS (based on average KTAS logged during RF legs; actual logged data ranged between 104 and 212 KTAS; see Section 3.4 for more details).


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Figure 10. Cessna 400 Aircraft

Figure 11. Cessna 400 G2000® Prototype Cockpit

This Cessna 400 was equipped with a prototype Garmin G2000 integrated flight deck, including dual-touch screen controllers and 14-inch widescreen displays. The G2000 is Garmin’s next-generation integrated flight deck intended for Part 23 high performance aircraft and is an evolution of the successful G1000® integrated flight deck. While the G2000 provides an enhanced user experience through the incorporation of touch screen control technology; the G2000 primary flight instrument displays used to navigate the RF legs are virtually identical to those that would be available to the pilot in currently fielded G1000 installations. The G2000 consists of multiple LRUs which provide various functions. Relevant to this project are the following LRUs:

• GDU 1400W – The GDU 1400W is a wide-aspect ratio high resolution color display that provides flight information to the pilot. For G2000 systems, there are typically two side-by-side GDU 1400Ws serving as Primary Flight Display (PFD) and Multi-Function Display (MFD).

• GTC 570 – The GTC 570 touch screen controller is the primary controller that the pilot uses to interact with the avionics system. Communication and navigation radio tuning, audio system


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control, MFD page navigation, and Flight Management System (FMS) functions are provided by the GTC 570.

• GIA 63W – The GIA 63W is a remote-mounted integrated avionics unit that provides multiple functions to the system, including GPS/SBAS sensor, communication and navigation radios, flight director, and various sensor inputs/outputs. Typical G2000 systems have two GIA 63Ws installed.

The following advanced features of the G2000 were intentionally disabled for testing: • Synthetic vision • Pathways (also known as highway-in-the-sky) • Flight path marker

Additionally, the flight director and autopilot were not engaged.

Primary Flight Display (PFD) Relevant aspects of the G2000 PFD arrangement that were utilized while flying RF legs are described below. Figure 12 illustrates the PFD arrangement.

Figure 12. G2000 PFD Arrangement

The following descriptions are keyed to the Figure 12 numbered annotations. 1) Auto-Slew HSI

An auto-slewing HSI is displayed in the lower center of the PFD, and is driven by the G2000’s FMS desired track computations. On an RF leg, the HSI course is automatically rotated as desired track changes, providing real-time course deviation guidance to the pilot.

2) HSI GPS Ground Track (TRK) Indication The G2000 provides a ground track “bug” on the HSI in the form of a magenta caret. In low cross-wind conditions, the magenta caret is generally not visible as it is rendered one layer below the magenta course needle, the heading bug, and the compass heading index. However, in higher cross-wind conditions where larger wind correction angles occur, the magenta ground track caret is readily visible and aids pilots in maintaining course (i.e. pilots can maneuver the aircraft such that the caret is above the course needle to maintain course).

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3) Wind Vector G2000 provides a wind vector indication to the pilot to the left of the HSI. There are three pilot-selectable formats for the indication, including varying methods of displaying the same vector sums. A G2000 system includes all necessary inputs to compute wind vector information and this feature is available in all Garmin integrated flight decks.

4) PFD Inset Map / Traffic Inset The PFD inset map is a pilot-selectable inset window on the PFD that displays moving map data and various map overlays including the active flight plan. RF leg segments are displayed as part of the active flight plan, within the pilot’s optimum primary field of view. A traffic inset window is selectable in lieu of the inset map, displaying a traditional traffic page with concentric range rings.

5) PFD Status Window The PFD status window depicts the active FMS leg along with distance and ETE to the next waypoint. The active leg indication uses a curved path segment drawn between the preceding and active waypoints to indicate the leg is an RF leg, as shown in Figure 13. The curved arrow is readily distinguishable from traditional straight leg segments, helping to cue the pilot that an RF leg is active, similar to the indication used for the GNS 430W active leg field on the Default NAV page.

Figure 13. PFD Status Window – RF Leg Active Leg

Multi-Function Display (MFD) Figure 14 illustrates the MFD arrangement, including two side-by-side Multi-Function Windows (MFW), and relevant aspects of the G2000 MFD arrangement that were utilized while flying RF legs:

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Figure 14. G2000 MFD Arrangement The following descriptions are keyed to the Figure 14 numbered annotations.

1. Engine Data (not shown) The left-most portion of the MFD display is devoted to displaying engine and airframe sensor data to the pilot.

2. MFD Datafields Eight pilot-selectable data fields are displayed above the MFW panes. Pilots were given the opportunity to configure the data fields as they desired prior to each flight.

3. MFD Moving Map / Track Vector The left MFW pane was configured to be the Navigation Map for this project. The Navigation Map displays a large format view of the surrounding environment relative to ownship position with display features such as active flight plan, landmarks, aviation data, obstacles, terrain, and traffic data. Pilot preference was also allowed with respect to map orientation; nearly all pilots used the “Heading Up” format. A map track vector was available to depict the aircraft’s predicted turn rate based on GPS ground track in the form of a cyan vector line originating from the ownship icon. As the aircraft is banked, the track vector begins to curve, showing the predicted turn rate of the aircraft, projected out to a pilot-selectable time period (selectable times are 30 seconds or 60 seconds and 2, 5, 10, or 20 minutes). On RF legs, a possible pilot technique is to use the track vector as a reference while establishing initial bank angle by aligning the vector with the curved segment of the RF leg and periodically checking the vector/map depiction during the turn. Note that subject pilots were not trained or briefed on any of the map features prior to data collection flights.

4. Traffic Map The right MFW pane was set to the Traffic Map page for all flights to serve as a traffic avoidance aid to the safety pilot. Flight plan data was also overlaid on this pane as shown in Figure 14.

2.3 Subject Pilots A total of twelve pilots participated in data collection flights for this project. Six subject pilots were recruited by Garmin; of these pilots, two were not Garmin employees. Six FAA pilots also flew data collection flights. A wide range of experience levels from low time instrument-rated pilots to highly experienced former airline and/or military pilots was represented in the pilot pool. A summary of pilot experience follows.

Garmin-Recruited Pilots • Two high time pilots (30,000+ flight hours)

o Former airline/military large aircraft experience o Minimal to moderate experience with Garmin equipment o First time flying LPV approach for one subject

• Two medium time pilots (between 1,400 to 5,000 flight hours) o High performance GA aircraft experience (multi-engine piston and turboprop) o Highly experienced with Garmin equipment

• Two low time pilots (between 240 to 500 flight hours) o Experience with Garmin equipment

FAA Pilots • Three ACO test pilots • One AEG test pilot • One Small Aircraft Directorate (SAD) test pilot • Flight Deck Chief Scientific and Technical Advisor (CSTA)


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2.4 Other Crew A Garmin test pilot served as safety pilot and pilot in command (PIC) for all flights. The safety pilot was responsible for ensuring the overall safety and conduct of the flight in accordance with Garmin operating procedures. A FAA flight test engineer and Human Factors Specialist performed the test director/observer duties on 16 flights (44%). Two Garmin associates shared the test director/observer duties on the remaining flights. The test director/observer recorded notes on overall airmanship, scan, workload, altitude/course deviations, and subject pilot feedback comments.

2.5 Training A training syllabus was developed to ensure a consistent level of familiarity across all subject pilots before they began data collection flights. The intent was to provide only the minimum training information necessary; equivalent to that typically available to instrument-rated pilots. Garmin created the draft training material and adjusted it based on feedback from FAA review. The training material centered on the GNS 430W and included a draft GNS 430W Pilot’s Guide Addendum describing the RF leg implementation. Draft addendums to the Instrument Flying Handbook and Instrument Procedures Handbook describing RF legs were also created. The training material was provided to the subject pilots in advance of their data collection flights. The actual training materials provided to subject pilots have been delivered separately to FAA.

2.6 Flight Profiles Garmin and the FAA worked jointly to develop a series of flight profiles and flight test plan that were used during the data collection flights. The flight profiles were created with the following objectives:

• Flights would take off from and land at New Century Aircenter, Gardner, Kansas airport (KIXD) where Garmin’s aircraft hangar is located.

• Include standard RNAV (GPS) LPV practice approaches early during the first flight to establish overall Garmin-recruited subject pilot competency and to give pilots an opportunity to become familiar with the handling characteristics of the unfamiliar aircraft under IFR conditions. FAA subject pilots did not fly these practice approaches.

• Maximize “on RF leg” time by breaking up the flight such that multiple segments of each approach could be flown repeatedly. 20

• Fly RF legs at a variety of speeds, including pilot discretion and assigned speeds. Garmin-recruited pilots flew both Profiles 1 and 2 in both aircraft starting with the Cherokee; Pilot 002 also flew Profile 3 once in the Cherokee. For the Cherokee flights, Garmin-recruited pilots flew Profile 1 first and then flew Profile 2. On the C400 flights, Garmin-recruited pilots flew Profile 2 first (morning) and then flew Profile 1 (afternoon); this decision was made to provide turbulence / heat relief for the subject pilots since the Profile 2 flight has longer duration. FAA pilots flew Profile 2 in both aircraft with the exception of Pilot 012, who only flew the C400.

20 Maximizing “on RF leg” time was deemed important due to the longer than usual prototype approach designs. The entire K81 RNAV (GPS) X RWY 21 approach distance is over 110 nm.


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2.6.1 Profile 1

Figure 15. Profile 1

For Cherokee flights, profile 1, shown in Figure 15, included two RNAV (GPS) LPV practice approaches into Coffey County, Burlington, Kansas airport (KUKL) and one RF leg approach. This profile was slightly modified during flights in the C400 to only fly one practice LPV approach, the KUKL RNAV (GPS) RWY 18, and to include an extra RF leg, the K8134-K8135 RF leg, before returning to KIXD. All speeds during Profile 1 were at the subject pilot’s discretion.


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2.6.2 Profile 2

Figure 16. Profile 2

Profile 2, shown in Figure 16, included three RF leg approaches. All speeds were at the subject pilot’s discretion; however, for C400 flights, the project focus narrowed to evaluate hand flown FTE in the higher speed regime. Consequently, after the first RWY 21 approach, the subject pilot was instructed to fly best forward speed throughout the remainder of the profile including the low approach to the airport and the missed approach segment.

2.6.3 Profile 3 Profile 3 is a subset of Profile 2, utilizing the two RWY 21 approaches but excluding the RWY 3 approach (i.e., the Figure 16 red Approach #1 and blue Approach #2 but not the green Approach #3). Profile 3 was intended to determine the effect of slow speed flight on RF leg FTE and the subject pilot was instructed to fly at 90 knots. A post-flight assessment determined flying additional slow speed profiles was unnecessary because preliminary FTE results indicated slow speed was not a significant enough factor to justify further flights.

2.7 Flight Process Prior to initiating each data collection flight, all participants were required to attend a pre-flight briefing. The test director and safety pilot jointly conducted the briefing. The K81 RF leg procedure approach charts, flight test profile, weather forecast, aircraft operating limitations, emergency procedures, crew


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responsibilities, and any other relevant topics were reviewed for each flight. Subject pilots were encouraged to verbalize feedback and comments throughout the flight. All flight profiles were hand-flown during daytime Visual Meteorological Conditions (VMC); the autopilot and flight director were disengaged for the entire flight. Subject pilots wore a vision limiting device to simulate an IFR environment. In the Cherokee, Profile 1 duration was typically 2 hours; the Profile 2 duration was longer, usually lasting between 2.6 to 2.8 hours. C400 flights were generally shorter due to higher average KTAS. During each flight, subject pilots were evaluated for their performance by the test director. Observations and pilot comments were recorded on test cards. The test director made every effort to question the subject pilot on a non-interference basis. The test director and safety pilot shared in the duties of acting as ATC, giving clearances and instructions in a realistic manner to the subject pilots. When operating in the terminal vicinity of the K81 airport, the safety pilot handled radio communication duties to assure coordinated communications between ATC and aircraft on CTAF. There were several instances where the safety pilot was required to take the controls and deviate from the flight path due to traffic conflicts; these instances are annotated on the ground track plots. After completing each data collection flight, subject pilots were debriefed, including a review of the test director notes, a discussion of problematic aspects of the flight, as well as collection of feedback and recommended enhancements.

2.8 FTE Calculation Logged binary ARINC 429 data was post-processed into data points for each GPS position and associated navigation data (e.g., cross-track error). For navigation data output at a rate less frequent than the 5 Hz GPS position data, the data point used the most recent value. The data points were separated into individual files for each RF leg and straight leg of interest with identification by flight, pilot, etc. Additional details about the data post-processing and the detection of RF legs and straight legs are included in Appendix C.

2.8.1 Error Sources Table 1 summarizes the data collection error contributions from sources other than FTE for this project.21

Table 1. Data Collection Error Contributions

Source Error (m) Cherokee C400

Path Steering Display Error – Note 122 26-30 (left) 0.0 Path Definition Error 4.7 4.7 Position Estimation Error – Note 2 3.1 3.1 Note 1: The other component of path steering error, FTE, is the purpose

of this study and is discussed below. The Cherokee 25-30 meter error is the approximate left offset based on CDI display width, CDI needle width, 1 nm full scale, and one-fourth needle width offset left of center with the GNS 430W outputting a static centered electrical signal. This is within

21 RTCA/DO-283A 1.9.2 discusses error terms associated with various lateral navigation components. 22 The GNS 430W electrical output used to drive the Cherokee lateral deviation display complies with RTCA/DO-229D Table 2-8, whose requirements are identical to those in RTCA/DO-283A Table 2-4. The G2000 PFD lateral deviation display complies with RTCA/DO-229D Table 2-9, whose requirements are identical to those in RTCA/DO-283A Table 2-3.


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the RTCA/DO-229D Table 2-8 requirement for 3% accuracy of centered display, which is 56 m at 1 nm full scale.

Note 2: Based on average GPS/WAAS position horizontal figure of merit (HFOM) over all RF legs recorded during data collection; HFOM overbounds the actual position error.

2.8.2 RF Leg FTE Calculation For the purpose of this project, RF leg FTE is calculated as follows:

• Per RTCA/DO-229D 2.2.1.3.3 (and RTCA/DO-283A D.3), the Desired Path for an RF leg is the RF leg radius calculated as the distance from the RF leg center position to the RF leg end waypoint position. The Desired Path radius for each RF leg was calculated using the waypoint positions extracted from the ARINC 424 data provided by Hughes.

• For each RF leg data point, aircraft distance from the RF leg center was calculated as the distance from the ARINC 424 RF leg center position to the recorded data point position.

• FTE for each RF leg data point was calculated as the aircraft distance from the RF leg center minus the Desired Path RF leg radius.

Effectively, the calculated FTE is the same as Total System Error. While this is a conservative approach, it is practical because, as can be seen from the values in Table 1, error contributions from sources other than FTE are minimal. A small number of RF legs were partially included in the FTE analysis due to the leg being aborted or broken off and restarted for traffic avoidance. The data point files for these legs were hand modified after the automated processing to remove extraneous FTE that would skew the results. The leg was terminated when it became apparent that a deviation was occurring. A leg was considered intercepted when the pilot’s intentions were apparent. Two RF legs were entirely excluded from the FTE analysis because the leg was intercepted beyond the point where the automated post-processing detected an RF leg starting point.

2.8.3 Straight Leg FTE Calculation When briefing preliminary results to FAA, questions arose as to how the RF leg FTE compared to straight leg FTE. While a comparison of straight leg FTE to RF leg FTE wasn’t one of the original project goals, the data collection equipment logged avionics data during the entire flight so such a comparison was considered technically feasible. Since the error contributions discussed in Section 2.8.1 and summarized in Table 1 are small and since the questions about how RF leg FTE compared to straight leg FTE were not part of the original project goals, logged cross-track error (XTK) was considered to be an acceptable substitute for calculating FTE based on logged aircraft position distance to the straight leg desired path. Consequently, in the Section 3.5 discussion, XTK and FTE are used interchangeably when referring to straight leg FTE. Some straight legs were entirely excluded from the FTE analysis due to pilot maneuvers.


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3. DATA ANALYSIS RESULTS This section describes the results of the data analysis performed on the collected FTE data. The following explanations are relevant to the plots and tables included in this section:

• For RF leg plots and tables, negative FTE values are inside the leg centerline and positive FTE values are outside the leg centerline. On right-hand RF legs, a left of course (negative) cross-track is outside the leg centerline while on left-hand RF legs, a left of course (negative) cross-track is inside the leg centerline.

• For straight leg plots and tables, negative FTE values are left of course and positive FTE values are right of course.

• On the ground track plots, solid lines indicate tracks included in the FTE calculation while dashed lines indicate tracks that are not included in the FTE calculation. Figure 17 shows the pilot line color legend for the aggregate ground track plots.

Figure 17. Pilot Line Color Legend

The calculated FTE statistical plots include graphical depictions of: • Normal (Gaussian) distribution probability density • Histogram • Density estimate23 • Mean (µ) • Standard deviation (σ), 95% (2σ), 99% (2.6σ), 99.7% (3σ), 99.9% (3.3σ), and 99.99% (4σ)

23 The density estimate is determined with MATLAB’s ksdensity function, “which produces an empirical version of a probability density function. That is, instead of selecting a density with a particular parametric form and estimating the parameters, it produces a nonparametric density estimate that adapts itself to the data.” “[f,xi] = ksdensity(x) computes a probability density estimate of the sample in the vector x. f is the vector of density values evaluated at the points in xi. The estimate is based on a normal kernel function, using a window parameter (width) that is a function of the number of points in x. The density is evaluated at 100 equally spaced points that cover the range of the data in x.”


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3.1 Flight Statistics Table 2 summarizes the flight statistics for the data collection flights:

Table 2. Flight Statistics Summary

Total Cherokee flight hours: 43.4Total Cherokee RF legs logged: 224Total C400 flight hours: 30.9Total C400 RF legs logged: 239Total flight hours: 74.3Total RF legs logged: 463

Of the 463 RF legs logged: 454 RF legs were entirely included in the FTE analysis 7 RF legs were partially included in the FTE analysis due to the leg being aborted or broken off

and restarted for traffic avoidance. 2 RF legs were excluded from the FTE analysis because the leg was intercepted beyond the

point where the automated processing detects an RF leg starting point. Excluding these legs resulted in a loss of less than 0.5% of the legs (2 of 463) in the FTE calculation, so their exclusion had minimal impact on the results.

With 5 Hz GPS position logging, over 524,000 data points were attributed to RF legs and used in the FTE analysis; this represents over 29 hours of data logged during RF legs.

3.2 Aggregate RF Leg FTE Figure 18 shows the aggregate FTE for all RF legs for both the Cherokee and C400 aircraft. Similar aggregated plots were created for:

• All RF legs for the Cherokee as shown in Figure 19 • All RF legs for the C400 as shown in Figure 20

The lateral deviation full-scale for all RF legs included in the FTE analysis was 1 nm with the exception of the K81 RNAV (GPS) X RWY 3 approach K8105-K8106 RF leg terminating at the FAF (see Figure 22 for more details on the K8105-K8106 RF leg lateral full-scale).


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Figure 18. Aggregate FTE: All RF Legs for Both Aircraft

Note: The calculated FTE range for both aircraft was -0.616 to 0.680 nm.


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Figure 19. Aggregate FTE: All RF Legs for Cherokee

Note: The calculated FTE range for the Cherokee was -0.616 to 0.680 nm.


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Figure 20. Aggregate FTE: All RF Legs for C400

Note: The calculated FTE range for the C400 was -0.380 to 0.495 nm. Table 3 summarizes the aggregate FTE for all RF legs for both aircraft and for each aircraft.

Table 3. Aggregate FTE for All RF Legs Mean FTE (nm)

ConfidenceFTE (nm)

Both Aircraft Cherokee C400 Both

Aircraft Cherokee C400 AircraftDiff % Diff

0.018 0.010 0.029 95% 2σ 0.218 0.239 0.183 -0.056 -23.4

99.7% 3σ 0.327 0.359 0.275 -0.084 -23.499.99% 4σ 0.437 0.479 0.367 -0.112 -23.4

Note 1: Aircraft Diff was computed as: C400 FTE - Cherokee FTE

Note 2: % Diff was computed as: ( ( C400 FTE - Cherokee FTE ) / Cherokee FTE ) * 100

While 95% FTE was approximately 25% lower on the C400, both Cherokee and C400 95% FTE are less than half the 0.5 nm target. Further, 99.99% FTE is less than the 0.5 nm target for both aircraft and for each aircraft.

3.3 Individual RF Leg FTE Table 4 summarizes key characteristics of each RF leg and, by aircraft, 95% FTE, and the rank of the RF leg by 95% FTE. Additional data result details for each RF leg are included in Appendix A.


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Table 4. RF Leg Key Characteristics and FTE Rank

Leg Radius (nm)

Turn Direction Segment Vertical

Characteristic

Cherokee 95% 2σ

C40095% 2σ

FTE (nm) Rank FTE

(nm) Rank

K8102-K8103 13.034 Left Intermediate Pilot discretion 0.211 4 0.155 4

K8104-K8105 3.000 Right Intermediate Descend 600’ in 4.4 nm 0.332 10 0.235 10

K8105-K8106 3.000 Left Intermediate Descend 600’ in 4.6 nm 0.354 11 0.256 11

K8107-K8108 4.320 Left Missed approach Climbing 0.268 9 0.159 5

K8121-K8122 7.612 Left Intermediate Level 0.180 1 0.134 1

K8122-K8123 4.698 Left Intermediate Level 0.188 2 0.164 6

K8123-K8124 2.986 Left Intermediate Descend 2000’ in 9.6 nm

0.219 7 0.198 8

K8124-K8125 3.140 Left Intermediate 0.212 5 0.204 9

K8127-K8128 3.000 Right Missed approach Climbing 0.236 8 0.143 2

K8129-K8132 6.000 Left Missed approach Level 0.208 3 0.167 7

K8134-K8135 3.000 Right Missed approach Level 0.214 6 0.145 3

Note 1: The classification of an RF leg as being in the Intermediate segment is based solely on the ARINC 424 data provided by Hughes. The actual RF leg classification might be in the Initial segment per Order 8260.54A and Order 8260.58.

Note 2: Rank is based on lowest to highest 95% FTE where 1 is the lowest FTE.

For each aircraft, 95% FTE for each RF leg is less than half the 0.5 nm target. The mean 95% FTE (see Table 3) shows the Cherokee has a slight bias to the outside of the RF legs, possibly due to the wide pilot scan and associated right-turning tendency, while the C400 shows a more pronounced bias to the outside of the RF legs, likely due to higher airspeed combined with more difficult handling qualities. Section 3.3.1 and Section 3.3.2 provide discussion and aggregate ground track plots of the RF legs with the lowest and highest FTE. Additional RF leg aggregate ground track plots are included in Appendix A.

3.3.1 Lowest FTE RF Leg K81 RNAV (GPS) X RWY 21 approach K8121-K8122 RF leg had the lowest FTE in both the Cherokee and C400 aircraft. Figure 21 shows the aggregate ground tracks for both aircraft. Characteristics that are believed to have contributed to the low FTE are:

• Long straight and level legs preceded it: Profile 2 Approach 1 had over 10 nm of straight and level flight and Profile 2 Approach 2 had over 15 nm of straight and level flight.

• The relatively large radius of 7.612 nm. • The RF leg was flown at a level altitude.


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Figure 21. Lowest 95% FTE RF Leg Aggregate Ground Tracks

Note: Outer gray lines are 0.5 nm from the RF leg centerline. Inner gray lines are 0.25 nm from the RF leg centerline.

3.3.2 Highest FTE RF Legs The K81 RNAV (GPS) X RWY 3 approach RF legs K8104-K8105 and K8105-K8106 had the two highest FTE ranks for both the Cherokee and C400 aircraft. Figure 22 shows the aggregate ground tracks for both aircraft for both legs. Characteristics that are believed to have contributed to the high FTE are:

• The two legs form an “S” turn; consecutive RF legs with opposite turn direction. • The K8105-K8106 RF leg does not conform to Order 8260.54A or Order 8260.58 procedure

design criteria because it terminates at the FAF; Order 8260.54A and Order 8260.58 require RF legs in the intermediate segment to terminate at least 2 nm prior to the FAF.

• Both RF legs had the minimum 3.0 nm radius allowed by Order 8260.54A and Order 8260.58. • Both RF legs had descending vertical paths.

Traffic avoidance maneuver


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Figure 22. Highest 95% FTE RF Leg Aggregate Ground Tracks

Note 1: On the K8104-K8105 RF leg: • Outer gray lines are 0.5 nm from the RF leg centerline. • Inner gray lines are 0.25 nm from the RF leg centerline.

Note 2: On the K8105-K8106 RF leg: • Outer black lines represent CDI full scale. CDI full scale is 1

nm until 2 nm before the FAF then narrows to 0.236 nm at the FAF.

• Inner black lines represent CDI half scale. • Gray lines are 0.25 nm from the RF leg centerline.

To determine whether the RF leg terminating at the FAF or the “S” RF legs contributed significantly to higher FTE, aggregate RF leg FTE was computed when:

• Excluding just the K8105-K8106 RF leg to the FAF and, • Excluding both the K8104-K8105 and K8105-K8106 “S” RF legs.

Table 5 summarizes the calculated FTE. Table 5. Aggregate RF Leg FTE Excluding Highest FTE Legs

Excluded RF Legs

Mean FTE (nm) 95% 2σ FTE (nm) Both

Aircraft Cherokee C400 Both Aircraft Cherokee C400 Aircraft

Diff % Diff

RF Leg to FAF 0.017 0.009 0.029 0.213 0.232 0.180 -0.052 -22.4 "S” RF Legs 0.017 0.009 0.027 0.208 0.227 0.176 -0.051 -22.5



Table 6 compares the 95% FTE calculated for all RF legs against the 95% FTE calculated excluding just the K8105-K8106 RF leg to the FAF.

Table 6. All RF Leg vs. Excluded RF Leg to FAF Aggregate FTE Comparison

Aircraft Type

95% 2σ FTE (nm)

All RF Legs Excluded RF Leg to

FAFDifference % Diff

Both Aircraft 0.218 0.213 -0.005 -2.3 Cherokee 0.239 0.232 -0.007 -2.9

C400 0.183 0.180 -0.003 -1.6


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Note 1: Difference was computed as: excluded leg FTE – all RF leg FTE

Note: % Diff was computed as: ( ( excluded leg FTE – all RF leg FTE ) / all RF leg FTE ) * 100

Table 7 compares the 95% FTE calculated for all RF legs against the 95% FTE calculated excluding both the K8104-K8105 and K8105-K8106 “S” RF legs.

Table 7. All RF Leg vs. Excluded “S” RF Legs Aggregate FTE Comparison

Aircraft Type

95% 2σ FTE (nm) All RF Legs Excluded

“S” RF Legs Difference % Diff Both Aircraft 0.218 0.208 -0.010 -4.6

Cherokee 0.239 0.227 -0.012 -5.0 C400 0.183 0.176 -0.007 -3.8

Note 1: Difference was computed as: excluded leg FTE – all RF leg FTE

Note 2: % Diff was computed as: ( ( excluded leg FTE – all RF leg FTE ) / all RF leg FTE ) * 100

The following observations can be made from these comparisons: • Despite several stressing factors (consecutive RF legs with opposite leg direction, non-

conforming RF leg terminating at FAF, minimum allowed radius, and descending vertical paths), these factors contributed only slightly (between 1.6% and 5.0%) to increasing RF leg FTE.

The following conclusions can be made from the observations in this section: • Order 8260.58 RF leg procedure design criteria could be expanded to allow “S” RF legs where

necessary. • Order 8260.58 RF leg procedure design criteria could be expanded to allow RF legs terminating

at the FAF when necessary.

3.4 Effects of Aircraft Speed Table 8 summarizes the range of true airspeeds and ground speeds flown during RF legs as well as winds aloft speeds encountered during RF legs for each aircraft as determined from the collected data.

Table 8. RF Leg Speeds Flown and Wind Speeds

TAS (kt) GS (kt) Winds Aloft (kt)

Cherokee C400 Cherokee C400 Cherokee C400 Average 122 166 115 169 ----- ----- Minimum 76 104 58 100 1 1 Maximum 170 212 165 225 44 35

Note Average winds aloft speeds and direction were computed from the collected data but the variation in wind speed and wind direction across the set of RF legs resulted in values that were not meaningful.

As shown in Table 3, the faster, better equipped C400 had lower aggregate FTE than the slower, minimally equipped Cherokee. To determine whether the lower C400 FTE was entirely due to better equipment, aggregate FTE for RF legs where average TAS overlapped between the Cherokee and C400 aircraft was calculated. The initial average TAS overlap range of 130 to 147 kt was selected for the following reasons:


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• The 130 kts average TAS lower bound was 10 kt higher than the Cherokee average TAS during RF legs at the time (120 kt)24 and thus was considered representative of RF legs flown at faster speeds in the Cherokee.

• The 147 kt average TAS upper bound represented the fastest average TAS for any RF leg flown at the time in the Cherokee.

• The number of C400 RF legs in the same average TAS range was considered sufficient to provide a meaningful comparison.

The additional average TAS overlap range of 135 to 147 kt was selected to determine if there was a significant change in FTE when using a narrower faster TAS range. Table 9 summarizes the calculated FTE.

Table 9. RF Leg Overlapping Average TAS Aggregate FTE

Average TAS Overlap (kts)

Number of Legs Mean FTE (nm) 95% 2σ FTE (nm) Cherokee C400 Cherokee C400 Cherokee C400 Aircraft Diff % Diff

130-147 85 43 -0.004 0.028 0.228 0.168 -0.060 -26.3 135-147 56 28 0.011 0.031 0.245 0.180 -0.065 -26.5

Note 1: Average TAS was computed by averaging the logged TAS for all data points attributed to a particular RF leg.



Table 10 compares the 95% FTE calculated for RF legs where average TAS overlaps (Table 9) with the 95% FTE for all RF legs (Table 3) over the entire TAS range (Table 8).

Table 10. RF Leg Overlapping TAS Aggregate FTE Comparison Average

TAS Overlap

(kts)

95% 2σ FTE (nm)

Cherokee C400 Aircraft Diff % Diff

130-147 0.228 0.168 -0.060 -26.3 135-147 0.245 0.180 -0.065 -26.5 Note 1 0.239 0.183 -0.056 -23.4

Note 1: See Table 8 for TAS ranges applicable to each aircraft. Note 2: Aircraft Diff was computed as:

C400 FTE - Cherokee FTE Note 3: % Diff was computed as:

( ( C400 FTE - Cherokee FTE ) / Cherokee FTE ) * 100 The following observations can be made from these comparisons:

• The 95% FTE and percentage difference between aircraft where average TAS overlaps are comparable to the corresponding values for all RF legs over the entire TAS range.

To eliminate equipment differences and determine whether faster speeds contributed to higher FTE, aggregate FTE for RF legs for three TAS ranges for each aircraft was calculated. The TAS ranges were selected by taking the number of RF legs for each aircraft and dividing by three and then splitting the set of RF legs for each aircraft into average TAS ranges that have approximately the same number of RF legs in each range. Table 11 and Table 12 summarize the calculated FTE.

24 Pilot 011 flew after this decision was made and the Cherokee average TAS during RF legs increased to 122 kt.


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Table 11. Cherokee RF Leg TAS Range Aggregate FTE

Average TAS Range

(kts) Number of Legs

Mean FTE (nm)

95% 2σ FTE (nm)

85-113 75 0.022 0.261 114-132 70 0.005 0.218 133-154 77 0.004 0.237

Table 12. C400 RF Leg TAS Range Aggregate FTE

Average TAS Range

(kts) Number of Legs

Mean FTE (nm)

95% 2σ FTE (nm)

120-162 80 0.039 0.178 163-175 74 0.014 0.182 176-196 85 0.038 0.186

Figure 23 illustrates the Cherokee 95% FTE trend over the three TAS ranges using Table 11 data:

Figure 23. Cherokee 95% FTE vs. TAS Trend

NOTE: The 95% FTE Trend for the Cherokee is shown over finer resolution TAS ranges in Section 3.4.1.

Figure 24 illustrates the C400 95% FTE trend over the three TAS ranges using Table 12 data:

Figure 24. C400 95% FTE vs. TAS Trend

NOTE: Given the higher speeds achieved in the C400 and the smooth 95% FTE trend, determining the 95% FTE trend over finer resolution TAS ranges was deemed unnecessary.

The following observations can be made from these comparisons:

0.18

0.2

0.22

0.24

0.26

0.28

85‐113 114‐132 133‐154

Cherokee 95% FTE vs. TAS

FTE (nm)

0.17

0.175

0.18

0.185

0.19

120‐162 163‐175 176‐196

Corvalis 95% FTE vs. TAS

FTE (nm)


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• The slowest Cherokee average TAS range had the highest FTE. • There is a much higher variation in FTE within the Cherokee average TAS ranges than within the

C400 average TAS ranges. • When excluding the slowest Cherokee average TAS range, FTE did increase as speed

increased. The rate of FTE increase may have some correlation to the aircraft equipment. While examining the Section 3.6 map vs. no map RF leg results, it was noted that the no map 95% FTE (0.268 nm) was nearly identical to the slowest Cherokee average TAS range FTE (0.261 nm). To determine whether there was a correlation between the variation in the Cherokee average TAS range FTE results and the no map configuration, Table 13 compares the number of no map legs performed in each average TAS range with the total number of RF legs performed in the same average TAS range.

Table 13. Cherokee No Map RF Legs Per TAS Range

Average TAS Range

(kts) 95% 2σ

FTE (nm) No Map RF

Legs in TAS Range

Total RF Legs in

TAS Range% No Map

Legs

85-113 0.261 33 75 44.0 114-132 0.218 18 70 25.7 133-154 0.237 27 77 35.1

Note: % No Map Legs was computed as: ( no map RF legs / total RF legs ) * 100

The following observations can be made from these comparisons: • Both the highest FTE in the slowest Cherokee average TAS range and the higher variation in

FTE within the Cherokee average TAS ranges can be attributed to the proportion of RF legs flown with the no map configuration in each average TAS range.

3.4.1 Extrapolating FTE to Higher Speeds The minimally equipped Cherokee was not able to be flown at the higher speeds achieved in the technically advanced C400. One of the early project concerns was whether Cherokee FTE results could be extrapolated to higher speeds in order to understand whether minimally equipped aircraft flying at higher speeds could be expected to maintain 95% FTE lower than the 0.5 nm FTE target. To support the concept of extrapolation, an evaluation of FTE over a finer resolution speed range was determined necessary to be able to plot, detect, and analyze trends. In order to accomplish this, all Cherokee RF legs were divided into 10 kt groups using the average TAS value for each leg. Then 95% FTE was calculated as an aggregate for all of the legs in each speed range. While accomplishing these activities, it was observed that depending on RF leg vertical characteristics, certain leg groups were biased toward a certain portion of the speed spread. To understand the relationship between speed and FTE, leg groups were further divided by vertical characteristics. The leg groups used for this analysis are as follows:

Table 14. Cherokee Leg Groups

Leg Group Number of Legs

Descending 97 Climbing 39 Level 86 All 222

FTE extrapolation for the All leg group is discussed below. Discussion of the FTE extrapolation for the other Descending, Climbing, and Level leg groups is included in Appendix A.


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95% FTE was calculated for each of the leg groups and then plotted using a simple plotting utility available in Microsoft Excel. These plots and analysis are presented in the following sections. Although the recorded average TAS range was between 85 and 154 kts, FTE is extrapolated out to 200 kts in these plots since 200 kts was near the peak average TAS range for the C400. Using Excel’s Trendline capability, several predicted FTE trend lines were generated for each plot. Excel uses mathematical regression analysis to determine a “least squares” (best fit) curve which corresponds to the sampled TAS ranges. Several different calculation methods were used, including logarithmic, linear, and power functions25. For logarithmic and power Trendlines, Excel uses a transformed regression model. The equation for each Trendline is provided on each plot.

Note: Trendlines are not intended to represent an exact relationship between predicted FTE and TAS, as they do not account for real world variables like pilot workload, meteorological conditions, aircraft operational requirements, etc. Trendlines are merely intended to provide a representation of what FTE could be expected based on the detected trends in the collected data.

All Leg FTE vs. TAS Extrapolation

Table 15 presents the calculated 95% FTE in 10 kt increments for all legs. A plot of the Table 15 data is shown in Figure 25.

Table 15. Cherokee All Legs FTE vs. 10 kt TAS Range

Average TAS Range

(kts) Number of

Legs 95% 2σ

FTE (nm)

85-90 11 0.129 91-100 17 0.280

101-110 36 0.287 111-120 40 0.229 121-130 33 0.205 131-140 75 0.232 141-150 9 0.256 151-160 1 0.257 161-170 - 0.273 171-180 - 0.279 181-190 - 0.285 191-200 - 0.290

Note: Entries in bold blue text represent the most conservative case extrapolated data derived from the power Trendline depicted in Figure 25.

25 Microsoft Excel Trendline employs the following equations:

Linear Trendline calculates the least squares fit of a line using Logarithmic Trendline calculates the least squares fit through points using ln Power Trendline calculates the least squares fit through points using b


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Figure 25. Cherokee All Legs FTE vs. 10 kt TAS Ranges

The following observations were made from Table 15 and Figure 25 and the data upon which they were based:

• All but 2 of the 11 legs flown between the 85-90 kt TAS range were flown by the subject pilot who had the lowest Cherokee 95% FTE. Almost all 85-90 kt TAS legs were flown during the Flight 3 profile, where the pilot was given a target 90 kt speed to maintain. This explains the significantly lower FTE in this range when compared to FTE in the other ranges.

o Eliminating the 85-90 and 91-100 kt TAS ranges results in Trendline computations with a negative slope, which is regarded as unreasonable.

o Eliminating the lowest three TAS ranges results in a curve similar to the curves with all TAS ranges, and thus was considered unnecessary.

• All legs flown between the 141-160 kt TAS ranges were flown by the subject pilot who had the highest Cherokee 95% FTE who was directed to fly “best forward speed”. This FTE value maintains parity with the other TAS ranges.

• Each of the predicted FTE Trendlines are very similar, despite the different regression computations employed, suggesting that the trends are appropriate for this data set.

Figure 26. Cherokee All Legs Distribution over TAS Range

The following additional observations were made from Figure 26 and the data upon which it was based: • The majority of the legs were flown between the 131-140 kt TAS range.

0.000

0.050

0.100

0.150

0.200

0.250

0.300

0.350

All Turns 95% FTE (nm)

95% (2σ) FTE (nm)

Logarithmic Trend y=0.0345ln(x)+0.1886

Linear Trend y=0.007x+0.2029

Power Trend y=0.1739x^0.2059

0

20

40

60

80

Number of Turns (All)

Number of Turns


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o Of these 75 legs, 46 occurred during level flight, and 27 occurred in descending flight. • Only one leg was recorded in the 151-160 kt TAS range.

3.4.2 Speed Conclusions The following conclusions can be made from the observations in this section:

• The 95% FTE differences between the C400 and the Cherokee were solely due to equipment. Even so, when using the Cherokee’s equipment, 95% FTE was less than half the 0.5 nm FTE target.

• A concern at the beginning of the project was whether slow speed flight would influence RF leg FTE due to pilots relaxing or becoming bored. While the Cherokee slowest average TAS range FTE is larger than the FTE for the Cherokee middle and highest speed average TAS ranges, it is not true that all pilots had higher RF leg FTE when flying at slow speeds because, as observed in Section 3.7, Pilot 002 was the only pilot to fly Profile 3 at 90 knots and Pilot 002 had the lowest Cherokee 95% FTE.

• While speed is a contributing factor to FTE, it is not the major contributing factor to FTE. While the minimally equipped Cherokee was not able to be flown at the higher speeds achieved in the technically advanced C400, given the significant Cherokee FTE margins, it has been shown that it is reasonable to extrapolate FTE for a minimally equipped aircraft up to speeds as high as 200 KTAS and still maintain 95% FTE below the 0.5 nm FTE target with sufficient margin for safe operation. The extrapolation results are considered conservative for the following reasons:

o The most conservative case trend was used for the extrapolation. o Speed is not expected to be a significant factor for level or climbing legs (see Appendix A

discussion of the FTE extrapolation for the level and climbing leg groups). o Although speed becomes a more relevant factor during descending legs due to:

An expected pilot workload increase during descents while on an approach, and Aircraft exhibiting a natural tendency to increase speed during descents

The descending leg group had the widest speed spread per recorded leg yet also had the flattest FTE trend. (See Appendix A discussion of the FTE extrapolation for the descending leg group.)

3.5 Straight Leg FTE vs. RF Leg FTE Comparison Table 16 summarizes the flight statistics for these straight legs:

Table 16. Straight Leg Flight Statistics Summary Total Cherokee straight legs logged: 128Total C400 straight legs logged: 152Total straight legs logged: 280

With 5 Hz GPS position logging, over 179,000 data points were attributed to straight legs and used in the FTE analysis; this represents over 9.9 hours of data logged during straight legs. Figure 27 shows the aggregate FTE for all straight legs for both the Cherokee and C400 aircraft. Similar aggregated plots were created for:

• All straight legs for the Cherokee as shown in Figure 28 • All straight legs for the C400 as shown in Figure 29

The lateral deviation full-scale was 1 nm for all straight legs included in the FTE analysis.


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Figure 27. Aggregate FTE: All Straight Legs for Both Aircraft

Note: The recorded FTE range for both aircraft was -0.475 to 0.454 nm.


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Figure 28. Aggregate FTE: All Straight Legs for Cherokee

Note: The recorded FTE range for the Cherokee was -0.475 to 0.454 nm.


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Figure 29. Aggregate FTE: All Straight Legs for C400

Note: The recorded FTE range for the C400 was -0.334 to 0.293 nm. Table 17 summarizes the aggregate FTE for all straight legs for both aircraft and for each aircraft.

Table 17. Aggregate FTE for All Straight Legs Mean FTE (nm)

ConfidenceFTE (nm)

Both Aircraft Cherokee C400 Both

Aircraft Cherokee C400 Aircraft Diff % Diff

0.005 0.025 -0.020 95% 2σ 0.167 0.186 0.122 -0.064 -34.4

99.7% 3σ 0.250 0.280 0.183 -0.097 -34.699.99% 4σ 0.334 0.373 0.244 -0.129 -34.6



Additional data result details for each straight leg are included in Appendix A. Table 18 compares the 95% FTE calculated for all straight legs against the 95% FTE calculated for all RF legs by leg type.


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Table 18. RF Leg vs. Straight Leg Aggregate FTE Comparison By Leg Type

Aircraft Type

95% 2σ FTE (nm)

RF Leg Straight Leg Leg Type Diff % Diff

Both Aircraft 0.218 0.167 -0.051 -23.4 Cherokee 0.239 0.186 -0.053 -22.2

C400 0.183 0.122 -0.061 -33.3 Note 1: Leg Type Diff was computed as:

straight leg FTE – RF leg FTE Note 2: % Diff was computed as:

( ( straight leg FTE – RF leg FTE ) / RF leg FTE ) * 100 The following observations can be made from these comparisons:

• While the RF leg 95% FTE is larger than the straight leg 95% FTE, in absolute terms the larger RF leg FTE is approximately the same for the Cherokee as for the C400, increasing 0.053 nm for the Cherokee and 0.061 nm for the C400, despite the differences in aircraft and equipment.

Table 19 compares the 95% FTE calculated for all straight legs against the 95% FTE calculated for all RF legs by aircraft.

Table 19. Straight Leg FTE vs. RF Leg Aggregate FTE Comparison By Aircraft

Leg Type 95% 2σ FTE (nm)


Straight Leg 0.186 0.122 -0.064 -34.4 RF Leg 0.239 0.183 -0.056 -23.4



The following observations can be made from these comparisons: • As was observed in the Section 3.4 discussion of aircraft speed effects on RF leg FTE, straight

leg FTE also improved in the faster, better equipped C400. However, it is worth noting that in absolute terms the higher Cherokee FTE is approximately the same for straight legs as for RF legs, increasing 0.064 nm for straight legs and 0.056 nm for RF legs, despite the differences in aircraft and equipment.

The following conclusions can be made from the observations in this section: • All pilots demonstrated acceptable proficiency on both straight legs and RF legs. • The increase in RF leg FTE over straight leg FTE can be expected to be about the same

magnitude from a minimally equipped aircraft to a Technically Advanced Aircraft. • Considering that pilots have significantly more experience flying straight legs, and that workload

is higher on RF legs than it is on straight legs, the larger RF leg FTE is expected.

3.6 Map vs. No Map RF Leg FTE Comparison Throughout the Cherokee test flights, the test director periodically required each subject pilot (11 of the 12 total subject pilots) to fly the RF legs using the GNS 430W Default NAV page where only numeric information is provided. Figure 30 shows the Default NAV page configured with digital track angle error (TKE) and cross-track error (XTK) fields.


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Figure 30. GNS 430W Default Navigation Page

The purpose of changing between map and Default NAV pages was multi-fold: • To explore the effects of flying RF legs with and without a moving map. • Switching display configurations during flights helped ensure pilot learning and familiarity were

not unduly biasing the FTE data being collected. • To investigate whether pilots were relying on the map for navigation.

Pilots were briefed on the use of the TKE and XTK fields to guide the pilot to the RF leg centerline. The technique is to minimize cross track error (XTK) by using track angle error (TKE) as a reference while making course corrections. Pilots were briefed that when the TKE and XTK arrows were displayed in opposite directions, the pilot was guiding the aircraft closer to the RF leg centerline; when the arrows were displayed in the same direction, the pilot was guiding the aircraft away from the RF leg centerline. The magnitude of the TKE field gave pilots an indication of the intercept or divergence angle. No similar exercise was conducted on the C400 since the moving map is such an integral part of the G2000 avionics and was not easily eliminated (although on some flights toward the end of the project, pilots were asked to fly without the PFD inset map). Table 20 summarizes and compares the aggregate FTE calculated for RF legs using the no map and map GNS 430W configurations in the Cherokee.

Table 20. Cherokee No Map vs. Map RF Leg Aggregate FTE Comparison Number of Legs Mean FTE (nm) 95% 2σ FTE (nm)

No Map Map No Map Map No Map Map No Map vs. Map

Diff % Diff

78 144 0.029 0.000 0.268 0.219 -0.049 -18.3 Note 1: No Map vs. Map Diff was computed as:

map FTE – no map FTE Note 2: % Diff was computed as:

( ( map FTE – no map FTE ) / no map FTE ) * 100 The following observations can be made from these comparisons:

• While the no map configuration produced 95% FTE that was just over half (54%) the 0.5 nm target, the map configuration produced 95% FTE that was nearly 20% smaller.

Table 21 compares the 95% FTE calculated for the various Cherokee GNS 430W configurations used on RF legs against the 95% FTE calculated for all RF legs on the C400. Table 21. RF Leg Aggregate FTE Comparison Between Cherokee GNS 430W Configurations and C400

Configuration 95% 2σ FTE (nm)


No Map 0.268 0.183 -0.085 -31.7 Map 0.219 0.183 -0.036 -16.4 All 0.239 0.183 -0.056 -23.4



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The following observations can be made from these comparisons: • When the moving map was used, the difference between FTE for the better equipped C400 and

the minimally equipped Cherokee narrowed significantly. The following conclusions can be made from the observations in this section:

• The availability of the moving map improved FTE and lack of the moving map was a significant contributing factor to the Cherokee FTE being larger than the C400 FTE.

3.7 Pilot Experience vs. RF Leg FTE Comparison Table 22 summarizes the pilot aggregate RF leg FTE for each aircraft.

Table 22. Pilot Aggregate RF Leg FTE

Pilot Class- ifica- tion

Number of Legs Mean FTE (nm) 95% 2σ FTE (nm)

Cherokee C400 Cherokee C400 Cherokee C400 Aircraft Diff

% Diff

001 FAA 17 17 0.029 0.064 0.257 0.187 -0.070 -27.2 002 Med 34 23 0.002 0.019 0.108 0.151 +0.043 +39.8 003 FAA 17 17 -0.023 -0.029 0.289 0.211 -0.078 -27.0 004 FAA 17 17 0.003 0.023 0.159 0.099 -0.060 -37.7 005 Low 22 23 -0.004 0.001 0.238 0.137 -0.101 -42.4 006 Med 22 34 0.001 0.042 0.160 0.203 +0.043 +26.9 007 Low 21 17 -0.007 -0.022 0.150 0.168 +0.018 +12.0 008 High 22 22 0.046 0.064 0.346 0.184 -0.162 -46.8 009 High 22 23 0.022 0.048 0.268 0.190 -0.078 -29.1 010 FAA 17 17 -0.004 0.044 0.178 0.196 +0.018 +10.1 011 FAA 11 11 0.053 0.040 0.393 0.203 -0.190 -48.3 012 FAA 0 18 n/a 0.049 n/a 0.111 n/a n/a



Note 3: Pilot 002 flew Profile 3 once in the Cherokee; thus, having more RF legs than other Garmin-recruited pilots.

Note 4: Pilot 012 only flew the C400. Additional data result details for each pilot are included in Appendix A. The following observations can be made from the pilot RF leg data:

• All pilots demonstrated the ability to meet the 95% FTE 0.5 nm target in both aircraft. • Both Low time pilots had lower FTE than the aggregate FTE for all RF legs in both aircraft. • Both High time pilots had higher FTE than the aggregate FTE for all RF legs in both aircraft,

although only slightly higher in the C400. • While RF leg FTE was lower for most pilots in the better equipped C400, 36% of the pilots that

flew both aircraft (4 of 11) had lower RF leg FTE in the minimally equipped Cherokee. • Pilot 002 had the lowest Cherokee 95% FTE at 0.108 nm or approximately 22% of the 0.5 nm

target. Pilot 002 was the only pilot to fly Profile 3 at 90 knots; this FTE result is inconsistent with the Section 3.4 observation that the slowest Cherokee average TAS range had the highest FTE.

• Pilot 011 had the highest Cherokee 95% FTE at 0.393 nm or approximately 79% of the 0.5 nm target. This may have been due to flying the entire RWY 3 approach, which includes the “S” turn to the FAF, without the moving map.

• Pilot 004 had the lowest C400 95% FTE at 0.099 nm or approximately 20% of the 0.5 nm target.


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• Pilot 003 had the highest C400 95% FTE at 0.211 nm or approximately 42% of the 0.5 nm target. As part of the pilot demographic questionnaire associated with the project, each pilot was asked to rate their experience with the GNS 430W equipment that was used in the Cherokee and the Garmin G1000 integrated flight deck, the G2000’s predecessor used in the C400. Table 23 compares the pilot’s equipment experience self-rating with the RF leg FTE to determine whether there was a correlation between pilot equipment experience and RF leg FTE.

Table 23. Pilot Equipment Experience Comparison with RF Leg FTE

Pilot Class-ifica-tion

Cherokee C400

GNS 430W Experience

95% 2σ FTE (nm)

% Diff with Aggregate

95% 2σ FTE (nm)

G1000 Experience

95% 2σ FTE (nm)

% Diff with Aggregate

95% 2σ FTE (nm)

001 FAA Regular User 0.257 +7.5 Regular

User 0.187 +2.2

002 Med Expert 0.108 -54.8 Expert 0.151 -17.5

003 FAA Some Familiarity 0.289 +20.9 Regular

User 0.211 +15.3

004 FAA Some Familiarity 0.159 -33.5 Some

Familiarity 0.099 -45.9

005 Low Regular User 0.238 -0.4 Expert 0.137 -25.1

006 Med Expert 0.160 -33.1 Expert 0.203 +10.9

007 Low Some Familiarity 0.150 -37.2 Regular

User 0.168 -8.2

008 High Regular User 0.346 +44.8 Regular

User 0.184 +0.5

009 High Some Familiarity 0.268 +12.1 Some

Familiarity 0.190 +3.8

010 FAA Some Familiarity 0.178 -25.5 Some

Familiarity 0.196 +7.1

011 FAA Some Familiarity 0.393 +64.4 Regular

User 0.203 +10.9

012 FAA n/a n/a n/a Regular User 0.111 -39.3

Note 1: Cherokee Diff with aggregate 95% 2σ FTE was computed as: ( ( Cherokee FTE - 0.239 ) / 0.239 ) * 100 where 0.239 nm was the aggregate FTE for all RF legs in the Cherokee

Note 2: C400 Diff with aggregate 95% 2σ FTE was computed as: ( ( Cherokee FTE - 0.183 ) / 0.183 ) * 100 where 0.183 nm was the aggregate FTE for all RF legs in the C400

The following observations can be made from this comparison: • In 4 of 5 cases that pilots rated themselves as Expert with the equipment, their FTE was lower

than the aggregate FTE for all RF legs in the respective aircraft; the last case was approximately 11% larger.

• Pilots that rated themselves as a Regular User with the equipment had FTE that ranged from nearly 40% lower to nearly 45% higher than the aggregate FTE for all RF legs in the respective aircraft. When the extremes were removed from this comparison, FTE was within the range of 8% lower to 15% higher.

• Pilots that rated themselves as having Some Familiarity with the equipment had much greater FTE variability ranging from nearly 46% lower to over 64% larger than the aggregate FTE for all


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RF legs in the respective aircraft. When the extremes were removed from this comparison, FTE was within the range of 37% lower to 21% higher.

Table 24 summarizes the pilot aggregate straight leg FTE for each aircraft. Table 24. Pilot Aggregate Straight Leg FTE

Pilot Class- ifica- tion



% Diff

001 FAA 11 11 -0.024 -0.033 0.189 0.108 -0.081 -42.9 002 Med 20 15 0.018 -0.003 0.090 0.083 -0.007 -7.8 003 FAA 9 12 0.060 0.003 0.303 0.157 -0.146 -48.2 004 FAA 10 11 -0.024 0.005 0.120 0.100 -0.020 -16.7 005 Low 12 16 0.075 -0.007 0.222 0.099 -0.123 -55.4 006 Med 12 20 0.017 -0.030 0.098 0.108 +0.010 +10.2 007 Low 12 10 0.026 -0.040 0.115 0.121 +0.006 +5.2 008 High 13 12 0.054 -0.011 0.275 0.103 -0.172 -62.5 009 High 12 16 0.034 -0.056 0.120 0.141 +0.021 +17.5 010 FAA 10 12 0.009 -0.001 0.121 0.102 -0.019 -15.7 011 FAA 7 5 0.028 -0.012 0.184 0.129 -0.055 -29.9 012 FAA 0 12 n/a -0.039 n/a 0.126 n/a n/a



Note 3: Pilot 002 flew Profile 3 once in the Cherokee; thus, having more straight legs than other Garmin-recruited pilots.

Note 4: Pilot 012 only flew the C400. Additional data result details for each pilot are included in Appendix A. Table 25 compares pilot aggregate RF leg vs. straight leg FTE in the Cherokee. Table 26 compares pilot aggregate RF leg vs. straight leg FTE in the C400.

Table 25. Cherokee Pilot Aggregate RF Leg vs. Straight Leg Aggregate FTE Comparison


Cherokee 95% 2σ FTE (nm)

RF Leg Straight Leg Diff % Diff

1 FAA 0.257 0.189 -0.068 -26.5 2 Med 0.108 0.090 -0.018 -16.7 3 FAA 0.289 0.303 +0.014 +4.8 4 FAA 0.159 0.120 -0.039 -24.5 5 Low 0.238 0.222 -0.016 -6.7 6 Med 0.160 0.098 -0.062 -38.8 7 Low 0.150 0.115 -0.035 -23.3 8 High 0.346 0.275 -0.071 -20.5 9 High 0.268 0.120 -0.148 -55.2 10 FAA 0.178 0.121 -0.057 -32.0 11 FAA 0.393 0.184 -0.209 -53.2 12 FAA n/a n/a n/a n/a

Note 1: Leg Diff was computed as: straight leg FTE – RF leg FTE

Note 2: % Diff was computed as: ( ( straight leg FTE – RF leg FTE ) / RF leg FTE ) * 100


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Table 26. C400 Pilot Aggregate RF Leg vs. Straight Leg Aggregate FTE Comparison


C400 95% 2σ FTE (nm)

RF Leg Straight Leg Diff % Diff

1 FAA 0.187 0.108 -0.079 -42.2 2 Med 0.151 0.083 -0.068 -45.0 3 FAA 0.211 0.157 -0.054 -25.6 4 FAA 0.099 0.100 +0.001 +1.0 5 Low 0.137 0.099 -0.038 -27.7 6 Med 0.203 0.108 -0.095 -46.8 7 Low 0.168 0.121 -0.047 -28.0 8 High 0.184 0.103 -0.081 -44.0 9 High 0.190 0.141 -0.049 -25.8 10 FAA 0.196 0.102 -0.094 -48.0 11 FAA 0.203 0.129 -0.074 -36.5 12 FAA 0.111 0.126 +0.015 +13.5

Note 1: Leg Diff was computed as: straight leg FTE – RF leg FTE

Note: % Diff was computed as: ( ( straight leg FTE – RF leg FTE ) / RF leg FTE ) * 100

The following observations can be made from these comparisons: • Individual pilot RF leg FTE ranged from 5% lower to 55% higher than their straight leg FTE on the

Cherokee. • Individual pilot RF leg FTE ranged from over 13% lower to 48% higher than their straight leg FTE

on the C400. • While pilots generally had lower straight leg FTE with a particular aircraft/equipment combination,

just over 13% (3 of 23 pilot/aircraft combinations) had lower RF leg FTE than straight leg FTE. The following conclusions can be made from the observations in this section:

• Pilots of all experience classifications, low, medium and high time, were able to fly RF legs with 95% FTE less than the 0.5 nm target without training specific to RF legs.

• Pilots with more equipment experience generally had lower RF leg FTE. • Pilots will not always have higher RF leg FTE in minimally equipped aircraft than in better

equipped aircraft. • Pilots will not always have higher RF leg FTE than straight leg FTE.

3.8 RF Leg Altitude Management The test directors used the Instrument Rating Practical Test Standards for Airplane, Helicopter, and Powered Lift (PTS) as a reference while observing subject pilots. During debriefings, the subject pilots commented that there was confusion about the altitudes on the charts vertical profiles (Section 4.4 provides more details about the chart design issues). It was determined that the chart vertical profiles were not compliant with FAA charting standards that require a waypoint shown on the vertical profile to include a crossing altitude. Some waypoints shown on the vertical profile did not have altitudes but implied a descent. This caused confusion with some pilots. Additionally, when briefing preliminary results to FAA, questions arose as to pilot compliance with meeting waypoint altitudes during the RF legs.


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The only altitude data logged during data collection was geometric altitude relative to mean sea level (GSL)26 while pilots must fly to charted altitudes, which are based on barometrically derived altitudes corrected for local barometric pressure. Consequently, a quantitative evaluation of pilot compliance with charted altitudes was not possible. The average GPS/WAAS vertical figure of merit (VFOM), which overbounds the actual vertical error, for all RF legs recorded during data collection was 26 ft (8.0 m) for both the Cherokee and the C400. Thus, the logged GSL altitude was considered sufficient to perform a qualitative evaluation using plots of the logged GSL altitude; the vertical profile plots are included in Appendix A. In all but a few cases, the subject pilots met the RF leg altitude restrictions. Explanations are provided for those plots where vertical profile tracks did not meet RF leg altitude restrictions. These explanations are sufficient to conclude that all subject pilots met the RF leg altitude restrictions in accordance with the PTS (±100 ft).

26 Per AC 20-163 3.a “We define geometric altitude relative to MSL in this AC as the height above MSL, derived primarily from geometric sources. Those sources are systems (like global positioning systems [GPS]) not affected by local barometric pressure. Geometric altitude relative to MSL is therefore distinct from barometrically-derived altitude, and from height above reference surfaces other than MSL.”


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4. HUMAN FACTORS DISCUSSION This section presents some of the human factors observations that were collected throughout the course of the data collection effort. The intent is to provide “real world” insight into the evaluation environment in order to help better characterize the collected quantitative FTE data. The Human Factors related aspects to be presented are as follows:

• Pilot Factors • Environmental Factors • Aircraft/Equipment Factors • Charting Factors

4.1 Pilot Factors Prior Flight Experience Based on the pilot feedback received, in combination with the data presented in Section 3.7, pilot experience was judged as not a significant factor during this project. The low time pilots were able to learn the techniques to fly RF legs just as quickly as the high time pilots and demonstrated satisfactory FTE results. In some cases higher time pilots tended to overanalyze the navigation problem, or struggled to “unlearn” habits formed over their past experiences. As an example, one high time pilot flying the Cherokee for the first time began the descent toward the first LPV practice approach 32 nm from the IAF. This same pilot mentioned several times the difficulty in breaking old disciplines, such as flying to a constant heading or treating waypoints as “fly over” instead of “fly by”. Another high time pilot frequently mentioned having difficulty in adjusting his scan to the mechanical ADI in the Cherokee (he was used to an electronic sky pointer-style ADI). This same pilot, who exhibited highly disciplined airmanship commensurate with his flight experience, had never flown an LPV approach until this project.

Learning As the pilots flew successive approaches they demonstrated an expected increase in familiarity during the flights. Most pilots flew two flights back-to-back on the same day. However, the familiarity accrued by the third or fourth approach was generally offset to some degree by fatigue (see discussion in Section 4.2). The afternoon flights were generally longer, hotter, and required greater mental concentration. For some pilots, the second flight in the Cherokee was delayed by several weeks due to weather or schedule issues, so learning and prior experience became less of an issue. It is also worth noting that delays between 2 to 8 weeks occurred between Cherokee and C400 flights. The breakdown in waiting time between each aircraft for each pilot is shown below:

• 001 – 8 wks 007 – 3 wks • 002 – 5 wks 008 – 3 wks • 003 – 5 wks 009 – 2 wks • 004 – 6 wks 010 – 3 wks • 005 – 5 wks 011 – 0 wks • 006 – 5 wks 012 – n/a

Although the approach profiles were generally the same between both aircraft, the time delay between flights as well as the introduction of a completely different aircraft and avionics configuration ensured that the FTE data was not unduly biased for pilot learning or familiarity factors.

Workload Pilots were questioned on workload after completing major segments of a flight profile. The test cards carried a three point rating scale as shown in Figure 31.


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Figure 31. Test Card Rating Scale

Due to the methodology of flying the same approach profiles repeatedly, these rating questions were not applied consistently to each approach or to each flight; instead the test directors solicited feedback from the subject pilots at opportune moments during flight so as not to become intrusive or distracting. The intent was to evaluate differences in workload during various RF legs while using different avionics configurations, as well as to measure changes in pilot perception over time, pilot learning and fatigue. Since the Cherokee was intended to be a more stressing installation, more attention was devoted to evaluating workload; accordingly, a set of test card workload ratings and comments has been provided in Appendix B. When asked to rank mental effort and concentration required for an approach, workload was typically ranked between Medium and High for approaches flown in the Cherokee. Especially stressing were the RWY 3 K8104-K8105-K8106 “S” turn RF legs. In several cases pilots appeared to be task saturated during this portion of the approach (Section 4.5 and Appendix B document some of these instances). Out of 25 explicit ratings recorded for approach workload, 14 were ranked High (56%) and 11 were ranked Medium (44%). Of the 11 Medium rankings, three pilots expressed their workload was actually between Medium and High (labeled Medium+ in Appendix B). Pilots flying the RWY 21 K8129-K8132 and K8134-K8134 missed approach legs generally ranked workload as Low to Medium, as these legs were less stressing, being made during level flight with shallow bank angles. Of six explicit ratings recorded for these missed approach legs, there were three instances where workload was rated Low, two instances rated as Medium, and only one instance where workload was rated High. In several instances, pilots rated workload lower on their second flight and/or approach than they did on their first flight and/or approach, congruent with the observations made regarding pilot learning and familiarization. Several pilots made comparisons to their previous experiences indicating that workload was similar to flying other approaches such as DME arc, ADF or ILS. The AEG pilot evaluated workload as no worse than an average instrument approach, with precision approach radar (PAR) approaches being used as the pilot’s high workload baseline. Since all pilots that flew the Cherokee (11 of the 12 total) flew it first, workload in the C400 was evaluated on the basis of indirect comparisons to the Cherokee. Workload in the C400 was generally regarded as much lower than the Cherokee (see pilot comments in Section 4.3.2). Similar to the Cherokee, workload on the RWY 21 K8129-K8132 and K8134-K8135 missed approach legs was generally lower than on the intermediate segments of the approach.

4.2 Environmental Factors Test Environment It is recognized that test environments may introduce abnormal or additional stresses on some pilots. Contributors to the abnormal stresses included the simulated instrument conditions that the test subjects were required to fly under. For example, pilots had to wear a vision restricting device, cope with simulated ATC clearances, and were also required to fly certain approaches at abnormally high speeds. In addition, the presence of test personnel was recognized as a potential contributor to increased pilot


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stress levels due to perceptions of scrutiny being directed at a pilot’s flying abilities. Every effort was made to put the subject pilots at ease and to make the test environment as realistic as possible in order to minimize the effects of test environment abnormalities in the collected data. Another possibility that was carefully guarded against was the potential tendency for a subject pilot to relax excessively, devote less than full attention to flying, and rely on the safety pilot for help. The test director and safety pilot provided basic coaching only if deemed required so as not to compromise safety or the evaluation; pilots were always given the opportunity to detect and correct errors before the safety pilot or test director intervened.

Fatigue Flights were very fatiguing due to the evaluation environment. Heat and turbulence played a significant role and continuous light to moderate turbulence was typical at lower altitudes throughout the evaluation period between June and August, 2012. The length of the approaches and associated workload further contributed to high fatigue levels with flights typically lasting between 1.5 to 3 hours. Between the second and third approaches of the Flight 2 profile, subject pilots were allowed to remove the vision restricting device while the safety pilot took over flying duties for approximately 10 minutes, to simulate VFR “on top” conditions. The fatigue experienced during this project would not be unlike that occasionally encountered in a real world environment. The heat, turbulence, and extended flight durations were all considered beneficial to the evaluations and produced a highly stressing environment for pilots to cope with.

Aircraft Familiarity Several pilots commented that (un)familiarity with an aircraft could be just as prominent a factor contributing to higher workload as other variables such as airspeed, approach complexity, avionics implementation, etc. The safety pilot took steps to attempt to minimize the effects of pilot unfamiliarity by providing recommended power settings, approach speeds, and occasional coaching. Subject pilots flew the aircraft for the entirety of each flight, including takeoffs and landings, except instances where safety pilot intervention was required due to traffic avoidance or to provide scheduled breaks to the pilots. The relationship between pilot familiarity with an aircraft and the question of hand flying RF legs at higher airspeeds was discussed with several pilots. Several pilots, including two FAA pilots, felt that flying at higher airspeeds in a familiar aircraft would not be a significant factor as a pilot would be accustomed to flying and staying ahead of the aircraft throughout its performance envelope. This corresponds with the assessments made in Section 3.4, where increased airspeed was shown to not detrimentally impact FTE.

4.3 Aircraft/Equipment Factors

4.3.1 Cherokee

Display Placement One of the most significant Cherokee installation factors was the GNS 430W display placement. As described in Section 2.2.1.1, the GNS 430W was located on the far right extent of the pilot’s field of view in a sub-optimum location appropriate only for a backup panel-mount navigator. Nearly all pilots commented on the very wide scan between primary instruments and the GNS 430W. The following observations were made during this project:

• The wider abnormal scan had the effect of creating significant head and eye movement and, as a consequence, increased pilot workload.

o The wide scan had the affect of creating a subtle right-turning tendency for some pilots • The display placement was generally disliked by pilots; however, several pilots rated placement

between Adequate and Marginal o Two pilots commented that the location was suitable as a secondary or backup

instrument but not ideal for primary field-of-view o At first some pilots felt the display location was adequate; however, as the flight

progressed, placement was not rated as highly due to increased fatigue • The wide scan revealed which instruments and indications pilots tended to rely upon during

stressing conditions:


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o The more experienced pilots tended to fixate on the primary instruments in a traditional scan, with only periodic glances at the GNS 430W, sometimes detrimentally impacting FTE

o Other pilots, especially those with low time, tended to concentrate more on the GNS 430W, to the occasional detriment of attitude and altitude management

• Display placement caused some pilots to occasionally miss some of the GNS 430W prompts described later in this section (MSG annunciation, SUSP annunciation, etc.) Note that if the GNS 430W installation was equipped with external GPS navigation annunciator(s), as would be required for a conforming installation, MSG and WPT annunciations would have been presented to the crew under these conditions within the primary field-of-view. Consequently, these annunciations might not have been easily missed by pilots although it is recognized the annunciations may have increased pilot workload if the annunciation led to a task, as in the case of the “Set course” messages.

Nevertheless, the flight evaluations demonstrated that acceptable FTE is achievable in such a configuration. The placement, although less than ideal, is not unlike some fielded installations today in older aircraft where physical limitations prevent the equipment being positioned closer to the pilot.

CDI Resolution Several pilots commented on the mechanical CDI’s low resolution; however, the instrument was assessed to be within TSO-C146() requirements (see discussion in Section 2.8.1). As pilots developed their scan, they tended to try different techniques to see which was most suitable for the task at hand. Those who focused on flying to numerical data on the GNS 430W often found that the CDI did not present the same resolution and precision as the GNS 430W Default NAV page numeric data. Those who flew to the CDI tended to react slower to off course conditions. One FAA pilot remarked the CDI was “almost a too late indication”; he noted once he was able to detect movement in the needle, the aircraft appeared to be significantly off course when viewing the map. Another FAA pilot mentioned the potential need for greater emphasis on training for CDI scaling. When CDI scaling narrowed and sensitivity increased on the final approach course, the problem was somewhat reversed; pilots who tended to fly to the GNS 430W’s numeric data could not react quickly enough to numeric deviation data due to the increased workload. One medium time pilot conceded that for the final approach, his problem was an excessive focus on numeric data, where it should have been on the CDI/VDI indications. In summary, pilots felt the numeric data was most useful for flying with greater precision in lower workload conditions. When workload increased, the ability to mentally interpret numeric data was reduced, reaction times slowed, and the possibility of significant course deviations increased.

“Set course” Message Prompts As described in Section 2.2.1.2, for installations where a manual course HSI/CDI is interfaced to the GNS 430W system, any time the unit detects that selected course is greater than desired track (DTK) by more than 10 degrees, the pilot receives a “Set course” message prompt. The intent of the prompt is to remind the pilot to set the CDI course to the current DTK value: For straight leg segments this is a one-time task while on RF legs, as with a DME arcs, DTK continually changes so there are multiple prompts. When the project began, RF legs were viewed as similar enough to DME arcs that the “Set course” message implementation was left unchanged. This “Set course” implementation had worked well on DME arcs and had been in place since 1998 with the initial certification of the GNS 430W’s predecessor, the TSO-C129a GNS 430. During flight evaluations, pilots received frequent MSG annunciations on the GNS 430W, with an observed frequency as high as every 10 to 20 seconds. A typical sequence of initial pilot / equipment interactions is summarized as follows:

• The pilot first had to notice the flashing MSG annunciation. Due to GNS 430W placement this did not always occur right away (likely due to the absence of an external annunciation, which would be required in the Cherokee to be an STC conforming installation).

• The pilot then had to press the MSG key to view the “Set course” message on the Message page.


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• The pilot had to read the message, understand its meaning, and then correlate it with a task. • With attention turned to the CDI, the pilot used the CDI course setting knob to adjust the selected

course. In several instances, pilots initially set the wrong course selector (HSI) or set the heading bug instead of the required #2 CDI course.

• The pilot then had to press the MSG key to remove the Messages page. With the time duration required to accomplish the above series of interactions while maintaining course on an approach, workload was significantly affected. The frequency of these messages was regarded almost universally by pilots as a nuisance. Under duress, some pilots completely ignored the message annunciation, choosing instead to “fly the airplane first” (based on their training), where others were completely task saturated to the point where they failed to recognize the flashing MSG annunciation. One test subject did not change the CDI course at all after completing the first approach. With some coaching during flight or in debriefs, pilots soon realized they could “stay ahead” of the prompt by routinely setting the CDI course ahead of DTK by 10 degrees; this is still a frequent task, but similar in nature to the technique employed for DME arcs. Similarly, if the flashing MSG annunciation appeared, some pilots determined they could first review and update the CDI course without viewing the message; if the MSG annunciation extinguished based on this action, the pilot could conclude the “Set course” message was the trigger. One FAA pilot felt that workload could be reduced by an order of magnitude if he did not have to manage the “Set course” messaging during RF legs. Installations equipped with an auto-slewing HSI will not experience this behavior as the course deviation indictor is driven by the GNS 430W and will always be in agreement with the DTK. However, as stated previously, many GA aircraft are not equipped with auto-slewing HSI. The subject pilot feedback and observations by the test director led to analysis into what drove the increased workload. The analysis reveals the primary cause to be the smaller minimum radius for RF legs when compared to typical DME arcs. Table 27 shows the “Set course” message frequency for each RF leg assuming the aircraft is flying at 150 KTAS, which was at the high end of the speeds flown in the Cherokee.

Table 27. RF Leg Set Course Message Frequency

Leg Radius (nm)

Arc Distance

(nm)

Arc Start

(°)

Arc End (°)

Arc Change

(°) Messages Per Leg

Distance Between

Messages (nm)

Time Between

Messages (sec)

K8102-K8103 13.0 13.1 190 133 58 5 2.6 63

K8104-K8105 3.0 4.4 313 036 84 8 0.6 13

K8105-K8106 3.0 4.6 216 128 88 8 0.6 14

K8107-K8108 4.3 13.7 128 308 180 18 0.8 18

K8121-K8122 7.6 4.8 230 194 36 3 1.6 38

K8122-K8123 4.7 5.4 194 128 67 6 0.9 22

K8123-K8124 3.0 5.1 128 029 99 9 0.6 14

K8124-K8125 3.1 4.4 029 308 81 8 0.6 13

K8127-K8128 3.0 4.7 128 218 90 8 0.6 14

K8129-K8132 6.0 31.9 038 093 305 30 1.1 26

K8134-K8135 3.0 9.4 233 053 180 18 0.5 13

Note 1: Messages Per Leg was computed as: floor( Arc Change / 10 ), 1 ) where 10 is the degrees of difference between the selected course and DTK that would generate a “Set course” message and “floor” rounds a number down to the nearest multiple of significance, in this case 1


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Note 2: Distance Between Messages was computed as: Arc Distance / Messages Per Leg

Note 3: Time Between Messages was computed as: ( Distance Between Messages / 150 ) * 3600 where 150 is the speed in knots and 3600 is the number of seconds / hour

The K8102-K8103 and K8121-K8122 RF legs have radii similar to those typical of DME arcs with times between “Set course” messages of 63 and 38 seconds, respectively. This is significantly less frequent than the 13 to 14 second time between “Set course” messages on RF legs with minimum radius of 3 nm. The K8102-K8103 and K8121-K8122 RF legs also have fewer messages per leg because the arc spans fewer degrees. On the K8134-K8135 arc, a pilot could experience 18 “Set course” messages with only 13 seconds between messages when flying at 150 KTAS. Using 200 KTAS, which was at the high end of the speeds flown in the C400, a pilot could experience “Set course” messages as frequently as 9-10 seconds on minimum radius RF legs.

Moving Map vs. Default NAV Page As previously discussed in Section 3.6, pilots were asked to fly approaches with and without the GNS 430W moving map. In lieu of the moving map, the Default NAV page was selected, providing a graphical CDI, numeric data fields, and active leg information. Pilot feedback was generally mixed on the ability to fly without the moving map. Nearly all pilots regarded the no map configuration as being more difficult going into the evaluations. At least two pilots purposely chose to fly without the map for their practice LPV approaches and their first RF leg approaches without being prompted to do so by the test director. The logic they communicated was that “if I can fly without the map, then adding the map will only make things easier”. Most pilots indicated higher workload and reduced situational awareness without the map, although several pilots acknowledged that flying the Default NAV page was surprisingly possible. Some pilot comments are summarized as follows:

• Pilot 002 stated that it was “difficult to infer aircraft position along arc without map; it’s not intuitive where you are”.

• Pilot 003 (FAA) remarked that “mental workload was much higher with Default NAV page”. • Pilot 005 felt as long as a paper chart was available “flying the Default NAV page is not more

difficult than with the map” and noted he had finer course control with numeric data. However, the same pilot also admitted situational awareness was better with the moving map.

• Pilot 008 remarked that the approach was “still a challenge, map or no map”. • Pilot 011 (FAA) stated the moving map was a “big anxiety reducer”.

As pilots began flying without the moving map, they adapted very quickly to the GNS 430W’s Default NAV page. Pilots were given the opportunity to configure the data fields as they desired. After acclimating to the numeric navigation data, several pilots reflected that they actually liked the data presentation. Some pilots clearly exhibited a preference for using numeric data due to their flying backgrounds. As mentioned previously, several pilots noted that although the numeric data allowed for greater precision and finer course control, it was more difficult to read and interpret under higher workload situations, such as while on final approach. The temptation for pilots flying in this environment was to control the cross-track error (XTK) value and make it as perfect as possible. Another significant factor in the no map configuration was the greater potential for a loss of situational awareness. Even without the moving map, the GNS 430W continued to show active leg information to the pilot. Most pilots were able to make use of this information and maintain situational awareness on the approach by cross-checking with the paper chart. However, in several instances pilots became disoriented. High time Pilot 008 admitted “I’m lost” on the RWY 21 approach; under duress he was not able to easily correlate the aircraft position on the approach with the active leg displayed to him on the GNS 430W. Chart clutter, wide scan, and fatigue were also factors during these instances. Without prompting from the test director, one low time pilot exhibited a tendency to quickly switch back to the moving map page on the GNS 430W, just to keep the “big picture” view fresh in his mind.


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Recovering back to course after experiencing significant deviations was one of the more challenging conditions where the moving map proved essential. When faced with the task of having to intercept an RF leg ahead of him after deviating significantly off course to avoid traffic, Pilot 007 quickly and intuitively selected the moving map to determine aircraft location relative to the active leg. He was able to visualize the RF leg ahead and successfully completed the intercept 1/3rd of the way along the leg. The initial intercept angle was nearly 82°, and pilot was able to reduce the intercept to a more manageable ~25° as shown in Figure 32.

Figure 32. Pilot 007 Intercepting K8107-K8108

In conclusion, the collected FTE data presented in Section 3.6 supports the idea that an RF leg could be flown without a moving map displayed. However, the slightly worse no map results also appear to correlate with the higher workload conditions experienced by pilots. Thus, a moving map is recognized as an important component in maintaining pilot situational awareness on complex approaches, especially those with multiple RF legs.

Wind Vector The wind vector indication on the GNS 430W map display was regarded as a valuable indication by most of the pilots flying RF legs. Many were able to integrate the vector into their scan, and several used the vector to make mental wind correction computations. Several pilots remarked that flying RF legs without the wind vector would have been more difficult. A High time pilot felt the wind vector was his most valuable indication; when asked to fly with the Default NAV page, he really missed the wind vector. Low time pilots did not mention the wind vector as much, although this does not imply they were not using it. Ultimately, FTE was shown to be acceptable without the wind vector during legs where the GNS 430W was configured with the Default NAV page, which is important because, as noted in Section 2.2.1.2, many GNS 430W installations will not display the wind vector (the wind vector can be displayed only when True Airspeed (TAS) and heading data are supplied by external sources).

4.3.2 C400 No specific G2000 training was provided to the subject pilots by Garmin other than a short opportunity to use the equipment on a bench and a briefing on the display arrangement prior to flight. As noted in


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Section 4.1, with the exception of Pilot 011, pilots flew the C400 between two to eight weeks after their last Cherokee flight. Nearly all pilots commented that the C400 with G2000 avionics supported significantly reduced workload when compared to the Cherokee, despite being flown at higher speeds and being a more complex aircraft. Typical of pilot comments were the following:

• System is huge advantage over 430W…easily 1/3rd less workload • G2000 is much nicer, everything is within my field-of-view • G2000 makes it easier to be more accurate • Scan is less labor intensive

These comments are consistent with the FTE data collected, showing approximately 26% lower FTE than in the Cherokee for a given speed range (Section 3.4, Table 9). Specific to flying RF legs, the following avionics aspects were noted as being significant differentiating factors when compared to the minimally equipped aircraft:

• Larger format integrated displays placed directly within the pilot’s primary field-of-view • Reduced scan width • Auto-slewing HSI • No frequent “Set course” nuisance messages

Other G2000 display aspects were utilized to varying degrees while flying approaches. Pilot sentiments are summarized below:

• HSI Ground Track Bug – Not particularly useful for many pilots since it was typically “buried” below the CDI course pointer unless flying in high crosswinds. When in view, some pilots did like the indication and felt it simplified flying the RF leg.

• Baro VNAV – Was not particularly useful since most pilots elected to begin their descents ahead of the vertical path guidance. G2000 stops providing VNAV cues when descending prior to reaching the Top of Descent point, so in most cases, no VNAV descent guidance was presented until the final approach advisory glidepath became active.

• Wind Vector – Similar to the GNS 430W, the G2000 wind vector indication was considered by many as a very useful indication and was used by a majority of pilots to determine appropriate wind corrections while flying RF legs.

• Map track vector – Most pilots did not notice the track vector at all until it was pointed out by the test director. Some pilots felt the track vector was useful while flying RF legs since it was visually intuitive to bank the aircraft until the track vector aligned with the RF leg; however, depending on turbulence, wind, and track vector prediction time settings, pilots also acknowledged it could be distracting.

• PFD Inset Map/Traffic Inset – Some pilots chose to use this exclusively over the MFD due to close proximity to their primary instrument scan. Others preferred the larger size and resolution of the MFD moving map.

4.4 Chart Design Factors In several instances, chart design became a contributing factor to pilot confusion and situational awareness issues. It was understood going into the evaluation that the approach charts were prototype copies which had not undergone the typical review process during design. During the pre-flight briefings, the charts were reviewed in some detail and initial pilot questions were answered. Copies of the prototype approach charts were printed out using identical dimensions to that of official paper charts for realism. Some pilots opted to print the charts in a larger format, per their standard routine. Most subject pilots placed the charts on the control yoke clip for viewing during the approaches but some used a kneeboard. There were many comments received, some during flight and others during debriefs. The following aspects were among the issues most prominently discussed with subject pilots:

• The missed approach plan view inset window for RWY 3 was mistaken several times for a right turn. On at least two occasions, pilots initiated right turns after crossing K8107. The arrow indicating direction of flight, leading to K8109, was not large enough to be noticed by pilots during


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flight. Several pilots mistook K8109 for the next waypoint after the missed approach, and did not cross-check with the GNS 430W (which was providing active navigation to K8107). Pilots felt the missed segment could be drawn more intuitively to clearly indicate a left turn requirement.

• Pilots noted the final approach courses had no charted course in the plan view. • Some pilots commented that the numeric waypoint naming convention made it difficult to

remember waypoints, or to pick out a specific waypoint on the chart. • One pilot commented that the missed approach sequence block on the RWY 21 chart read from

left to right but the profile view was from right to left, which was perplexing to him. Also, the missed approach procedure for this runway spans the entire length of the approach plate, which is unusual for a typical approach.

• The profile view on the RWY 3 approach chart lead to confusion on descent requirements, specifically at the K8103 waypoint. The descent path at K8103 changes glidepath angles for no apparent reason; however, no altitude constraint is listed at the K8103 waypoint. Technically, since no altitude constraint was assigned, descent to 3800 ft was acceptable immediately after crossing K8102. However, some pilots did not begin the descent to 3800 ft until after K8103 due to confusion with the profile appearance. It was determined that the chart vertical profiles were not compliant with FAA charting standards that require a waypoint shown on the vertical profile to include a crossing altitude.

• One pilot wondered why the RWY 21 profile view shows a continuous descent but only shows altitudes on some waypoints rather than all waypoints, once again leading to confusion on descent requirements, specifically at the K8124 waypoint. Technically, since no altitude constraint was assigned, descent to 3000 ft was acceptable immediately after crossing K8123. However, some pilots did not begin descents to 3000 ft until after K8124. Similar to the RWY 3 chart vertical profile, it was determined that the chart vertical profiles were not compliant with FAA charting standards.

• A number of comments received were related to the topic of clutter. In turbulence, the sheer number of waypoints and font sizes made reading the chart difficult. Several pilots lost situational awareness in varying degrees, and voiced questions such as “Which leg am I on?” or “What is the next waypoint?” In cases where the moving map was not used, some pilots seemed to have greater difficulty maintaining situational awareness and could not easily correlate aircraft position on the approach (even though without the moving map, the GNS 430W clearly indicated the active leg).

4.5 FTE Exceedance Assessment Summary Of the 461 RF legs entirely or partially included in the FTE assessment, there were nine instances where pilots exceeded the 0.5 nm FTE target. All excessive deviations occurred only during Cherokee flights, all of which were the pilot’s first data collection flight (with the exception of FAA Pilot 001 who had previously flown an evaluation flight). Table 28 summarizes the instances where pilots exceeded the 0.5 nm FTE target.


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Table 28. RF Leg 0.5 nm FTE Exceedance Summary Aircraft Flight

Number Pilot

ID Flight

Scenario RF Leg Identifier

(Sequence #) Contributing Factors to Exceedance

633 001 2 K8127-K8128 (11) • Pressed SUSP key prior to missed approach,

inadvertently activating OBS mode • Loss of situational awareness

645 008 1

K8104-K8105 (2) • Strong crosswind • High workload – “Set course” message frequency • Using Default NAV page

K8105-K8106 (3) • Brief continuation of K8104-K8105 (2) exceedance

K8107-K8108 (4)

• Misinterpreted charted missed approach as right turn

• Pressed SUSP key prior to missed approach, inadvertently activating OBS mode

• Using Default NAV page

647 009 1 K8105-K8106 (3) • High workload – Significant weather deviation and

abnormally steep descent • Loss of situational awareness

649 010 2 K8105-K8106 (15) • High workload – Cockpit tasks • Using Default NAV page

652 011 2

K8134-K8135 (1) • Learning RF leg flying technique

K8105-K8106 (10) • High workload • Using Default NAV page

K8107-K8108 (11) • Misinterpreted charted missed approach as right

turn • Using Default NAV page

Appendix B provides further analysis of the factors related to these exceedances.


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5. CONCLUSIONS AND RECOMMENDATIONS The primary conclusions and recommendations of this report are:

• Ability to Hand Fly RF Legs: Instrument-rated general aviation pilots are able to hand fly RF legs and meet the 0.5 nm 95% FTE target and RF leg altitude restrictions without the aid of a flight director or autopilot in Part 23 Category A and B aircraft that are either minimally equipped or technically advanced (see Section 2.2 for a detailed discussion of equipage aspects). All pilots demonstrated acceptable proficiency on both straight legs and RF legs. The increase in RF leg FTE over straight leg FTE can be expected to be about the same magnitude from a minimally equipped aircraft to a technically advanced aircraft. In support of these conclusions, Table 29 shows there was more than 50% margin when comparing the calculated 95% FTE for all RF legs with the 95% FTE 0.5 nm target.

Table 29. RF Leg Aggregate 95% FTE Margin – All Legs

Aircraft Type 95% 2σ FTE (nm) Calculated Target Margin % Margin

Both Aircraft 0.218 0.500 +0.282 +56.4 Cherokee 0.239 0.500 +0.261 +52.2

C400 0.183 0.500 +0.317 +63.4 Note 1: In Table 29 and Table 30, margin was computed as:

target FTE - calculated FTE Note 2: In Table 29 and Table 30, % margin was computed as:

( ( target FTE - calculated FTE ) / target FTE ) * 100 Table 30 shows there was still margin when comparing the calculated 99.99% FTE for all RF legs with the 95% FTE 0.5 nm target.

Table 30. RF Leg Aggregate 99.99% FTE Margin – All Legs

Aircraft Type 99.99% 4σ FTE (nm) Calculated Target Margin % Margin


C400 0.367 0.500 +0.133 +26.6 Additionally, while speed is a contributing factor to FTE, it is not the major contributing factor to FTE. Given the significant Cherokee FTE margins, it has been shown that it is reasonable to extrapolate FTE for a minimally equipped aircraft up to speeds as high as 200 KTAS and still maintain 95% FTE below the 0.5 nm FTE target with sufficient margin for safe operation. Subject pilot comments were in harmony with this conclusion. In support of this conclusion, Table 31 shows there should be more than 40% margin at 200 KTAS when comparing the extrapolated minimally equipped aircraft 95% FTE for all legs with the 95% FTE 0.5 nm target.

Table 31. Cherokee Extrapolated 200 KTAS 95% FTE Margin

Leg Group 95% 2σ FTE (nm) Extrapolated Target Margin % Margin

Descending 0.276 0.500 +0.224 +44.8 Climbing 0.306 0.500 +0.194 +38.8

Level 0.346 0.500 +0.154 +30.8 All 0.290 0.500 +0.210 +42.0

Note 1: Margin was computed as: target FTE - extrapolated FTE

Note 2: % margin was computed as: ( ( target FTE - extrapolated FTE ) / target FTE ) * 100


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Recommendation 1: Garmin recommends FAA revise its installation and operational guidance for RF legs to make clear that applicants may obtain airworthiness approval for installations without flight director/autopilot. To preclude the need to demonstrate adequate FTE margin for aircraft flying RF legs at greater than 200 knots without flight director/autopilot, Garmin recommends FAA revise its installation and operational guidance for RF legs to allow applicants to utilize an Aircraft Flight Manual limitation that restricts flying RF legs to 200 knots or less. Section 5.1 includes additional discussion of this recommendation.

• Moving Map: As this project has shown, FTE is decreased when a moving map is available and is thus consistent with the MLS curved path study conclusion that led to the FAA installation and operational guidance that “an aircraft must have an electronic map display depicting … RF legs”. However, this project has also clearly shown that a moving map is not required to maintain acceptable RF leg FTE, even during complex procedures and missed approaches. This conclusion is supported by Table 32, which shows there was greater than 46% margin over the 95% FTE 0.5 nm target when pilots flew RF legs in the minimally equipped aircraft with the no map configuration.

Table 32. Cherokee RF Leg Aggregate 95% FTE Margin – Map vs. No Map FTE Legs

Configuration 95% 2σ FTE (nm) Calculated Target Margin % Margin

No Map 0.268 0.500 +0.232 +46.4 Map 0.219 0.500 +0.281 +56.2 All 0.239 0.500 +0.261 +52.2

Note 1: In Table 32 and Table 33, margin was computed as: target FTE - calculated FTE

Note 2: In Table 32 and Table 33, % margin was computed as: ( ( target FTE - calculated FTE ) / target FTE ) * 100

While FAA installation and operational approval guidance provides display installation field of view guidance for several types of information associated with equipment supporting RNAV (GPS) approaches, the guidance is ambiguous with respect to the purpose of the moving map for RF legs and its acceptable display location. This ambiguity may lead to varying interpretations for acceptable equipment installations supporting RF leg procedures. This ambiguity is a particular concern for existing approved aircraft installations where the equipment that provides the RNAV (GPS) primary guidance and annunciations also incorporates a moving map where the moving map has marginal display placement but other displayed information complies with FAA and manufacturer installation field of view guidance. Consequently, to remove these ambiguities: Recommendation 2: Garmin recommends FAA revise its installation and operational guidance for RF legs to make clear that the main purpose of the moving map is to enhance situational awareness, and that it is acceptable for the moving map to be located either in the pilot’s primary field of view or on a readily accessible display page outside the primary field of view. Section 5.1.2 includes additional discussion of this recommendation.

• Equipment Contribution to Pilot Workload: Subject pilots stated workload could be lowered substantially if frequent message prompts and associated course setting tasks could be eliminated or reduced. Recommendation 3: Garmin recommends FAA consider revisions to its installation and operational guidance for RF legs to indicate that, to the extent practical, applicants seeking airworthiness approval of equipment capable of RF legs should minimize frequent recurring and unnecessary avionics operational tasks while RF legs are active. Section 5.1.3 includes additional discussion of this recommendation.

• Pilot Training and Experience: Pilots of all experience classifications, low, medium and high time, were able to fly RF legs with 95% FTE less than the 0.5 nm target without training specific to RF legs.


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Recommendation 4: Garmin recommends FAA update the Instrument Flying Handbook and Instrument Procedures Handbook to include a description of RF legs and the suggested techniques to successfully fly them. Garmin also recommends FAA update the Aeronautical Information Manual to add the “RF” abbreviation to the Abbreviations/Acronyms Appendix and other appropriate information regarding RF legs related to RNP procedures such as RNAV (GPS) approaches. Section 5.2 includes additional discussion of this recommendation.

• RF Leg Procedure Design: Pilots were able to hand fly complex RF leg procedures, including those with RF legs not explicitly allowed or even non-conforming according to current procedure design criteria, with 95% FTE lower than the 0.5 nm target. Table 33 shows there was almost 30% margin when comparing the calculated 95% FTE on the highest FTE non-conforming RF leg (K8105-K8106) terminating at the FAF with the 95% FTE 0.5 nm target.

Table 33. RF Leg Aggregate 95% FTE Margin – Highest FTE Leg

Aircraft Type 95% 2σ FTE (nm) Calculated Target Margin % Margin


C400 0.256 0.500 +0.244 +48.8 Recommendation 5: Given the FTE margins demonstrated with the complex RF leg prototype procedures, Garmin recommends FAA consider revisions to the Order 8260.58 RF leg procedure design criteria to: 1) Explicitly allow “S” RF legs and 2) Allow RF legs terminating at the FAF

“wherever airspace is critical to maximizing the benefit for terminal area operations.”27 Recommendation 6: Garmin recommends FAA consider providing a copy of this report to the ICAO Instrument Flight Procedure Panel (IFPP) to support international harmonization of RF leg procedure design criteria via the RF Design Criteria working paper,28 particularly with respect to proposed intermediate approach segment design criteria for RF legs. Section 5.3 includes additional discussion of these recommendations.

Implementation of these recommendations will broaden NextGen benefits and provide additional incentive for GPS/SBAS equipage while retaining consistency with the Performance Based Navigation philosophy as the project results have clearly shown that total system error targets during RF legs can be met without autopilot, flight director, and moving map equipment or RF leg-specific pilot training. Note that the preceding recommendations are repeated in the discussion that follows.

5.1 Equipment/Installation As noted in Section 1.1.2, the primary issue preventing wide-spread Part 23 GA aircraft RF leg capability is related to the burdensome AC 90-105 and AC 20-138C flight director and/or roll-steering autopilot equipage statements. The basis for the AC 90-105 and AC 20-138C statements regarding flight director and/or roll-steering autopilot comes from an MLS curved path study for jet transport aircraft29 and from 27 This phrase quoted from MITRE, F03L-L12-013, Recommendations “4. Given the range of systems tested and the excellent performance, the RF should be considered for turning flight wherever airspace is critical to maximizing benefit for terminal area operations.” 28 ICAO, IFPP/10 WGWHL Working Paper 28 rev. 12 29 NASA TP 3255, Concluding Remarks, “Based on these data and comments, it is concluded that flight director guidance is required for manually controlled flight in a jet transport airplane along curved paths to low decision heights (approximately 200 ft above ground level). Without flight director guidance, much greater pilot training and nonprecision-approach landing minima would be required.” (page 20-21)


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consensus standard RTCA/DO-283A assumptions for coupled 95% FTE values on curved path segments.30 However, this project has clearly shown that general aviation pilots are able to hand fly RF legs without the aid of a flight director or autopilot in Part 23 Category A and B aircraft as supported by:

• Table 29, which shows there was more than 50% margin when comparing the calculated 95% FTE for all RF legs with the 95% FTE 0.5 nm target in both the minimally equipped and technically advanced aircraft.

• Table 30, which shows there was still margin when comparing the calculated 99.99% FTE for all RF legs with the 95% FTE 0.5 nm target.

• Table 31, which shows there should be more than 40% margin at 200 KTAS when comparing the extrapolated minimally equipped aircraft 95% FTE for all legs with the 95% FTE 0.5 nm target. Using the extrapolation for all legs is consistent with the Table 29 comparison and is considered conservative for the following reasons:

o The most conservative case trend was used for the extrapolation. o Speed is not expected to be a significant factor for level or climbing legs (see Appendix A

discussion of the FTE extrapolation for the level and climbing leg groups). o Although speed becomes a more relevant factor during descending legs due to:

An expected pilot workload increase during descents while on an approach, and Aircraft exhibiting a natural tendency to increase speed during descents

The descending leg group had the widest speed spread per recorded leg yet also had the flattest FTE trend. (See Appendix A discussion of the FTE extrapolation for the descending leg group.)

o A pilot workload reduction is expected from software modifications that will be made to the “Set course” message prompts as discussed in Section 5.1.3.

Recommendation 1: Garmin recommends FAA revise its installation and operational guidance for RF legs to make clear that applicants may obtain airworthiness approval for installations without flight director/autopilot. To preclude the need to demonstrate adequate FTE margin for aircraft flying RF legs at greater than 200 knots without flight director/autopilot, Garmin recommends FAA revise its installation and operational guidance for RF legs to allow applicants to utilize an Aircraft Flight Manual limitation that restricts flying RF legs to 200 knots or less.

5.1.1 Display Location It is recognized that display location can significantly impact scan rate and pilot workload. However, despite the marginal placement of the GNS 430W, adequate FTE was still maintained during this project. In the case of the Cherokee, the marginal placement was the result of the GNS 430W being installed as a secondary navigation source. This characteristic produced a more stressing evaluation, and therefore was desirable for data collection purposes. Garmin GNS 430W/530W placement is currently controlled by the following STC installation requirements:

• For IFR-approved operations, an external CDI/HSI indicator must be installed in the pilot’s primary field-of-view. This is the pilot’s primary source of lateral and vertical guidance, including RF legs.

• Maximum horizontal and vertical distances from the pilots’ field-of-view centerline must be met with respect to GPS navigation annunciations specified by AC 20-138C (see Figure 6):

o Installations unable to meet these distances are required to be equipped with external annunciators.

o Without external annunciators, it is acceptable for a unit located outside of these distances to serve as a redundant or secondary navigator; however, IFR flights may not originate or be predicated on this unit unless the primary system has failed.

30 RTCA/DO-283A 2.2.5.1 (page 45)


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It is important to note that some older aircraft instrument panels may not allow for installation of panel mount GPS navigators within the “center stack”. Examples include older Cessna aircraft with interfering control cables behind the instrument panel, Beechcraft Barons and Bonanzas with center-mounted control column, Cirrus SR20 and SR22 with pedestal mounting, etc. As long as the required external annunciators are installed, the existing STC requirements are deemed sufficient with respect to RF leg operations for the following reasons:

• Pilots today fly other high workload approaches (RNAV (GPS), ADF, DME arc, etc.) in aircraft equipped similarly to the Cherokee.

• This project has shown that RF legs can be successfully flown even with marginal display placement in a minimally equipped aircraft.

Consequently, except as noted in the Section 5.1.2 moving map discussion, FAA’s AC 20-138C display location installation guidance combined with existing STC installation instructions are sufficient.

5.1.2 Moving Map While the primary issue preventing wide-spread Part 23 GA aircraft RF leg capability is related to the burdensome AC 90-105 and AC 20-138C flight director and/or roll-steering autopilot equipage statements, AC 90-105 and AC 20-138C also indicate that:

“The aircraft must have an electronic map display depicting the RNP computed path of the selected procedure including RF legs.”31

The AC 90-105 and AC 20-138C statement is based on the following conclusion from an MLS curved path study for transport category aircraft with Category C and Category D approach speed limits:

“Situation awareness is improved by a moving map display. This improvement is most beneficial and may be required to provide necessary situational awareness for complex procedures or in situations where a missed approach is required.”32

The MLS curved path study used a map mode presentation of the approach path on an electronic flight information system (EFIS) navigation display (ND) for the captain’s primary guidance while first officers were presented with primary guidance on a HSI.33 Figure 33 shows an example of the EFIS ND map mode used in the MLS curved path study.

31 FAA AC 90-105 Appendix 5 2.b.(2); FAA AC 20-138C Appendix 3 A3-2.b.(3). FAA AC 20-138C 16-3.a also states:

“The map display should be capable of depicting the curved, RF leg segments without discontinuities on both active and inactive leg segments if a moving map display is included with or interfaced to the positioning and navigation equipment.”

32 NLR TP 91446 L, 11.5 Conclusions on instrumentational provisions (page 78) 33 NLR TP 91446 L, 4.3 Cockpit avionics and instrumentation (page 16)


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Figure 33. MLS Curved Path Study EFIS ND Figure34

Unlike many large transport category aircraft, most GA aircraft do not have an EFIS-style moving map display capable of providing primary guidance. Instead, moving maps are intended to enhance situational awareness with primary guidance being displayed on a CDI or HSI. This has the benefit of eliminating path tracking issues noted by the MLS curved path study where:

“Pilots using electro-mechanical instruments (first officers) noticed more often and in an earlier phase, the discrepancies between flight director commands and track deviation indications than the pilots using a moving map display (captains). This may be due to the fact that the track deviation indicator of the HSI yields a much more prominent cue (bar) than the deviation indicators on the MAP display (small pointers).”35

As well as eliminating the associated pilot training issue noted by the MLS curved path study where: “The last training issue concerns the lack of absolute tracking accuracy using a moving map display. With a moving map display, the raw data cues were not prominent enough to ensure quality tracking performance. With the current map scales available, and the raw data cues, it appears that as long as there are no problems requiring a high degree of position awareness, electro-mechanical type instruments provide for the best tracking performance. The best overall solution appears to be: better scaling and adding emphasis to off-track raw data cues with a moving map display.”36

GA aircraft using a CDI or HSI for primary guidance and a moving map to enhance situational awareness have the benefit of both types of path tracking information when flying RF legs. As this project has shown, FTE is decreased when a moving map is available and is thus consistent with the MLS curved path study conclusion that led to the FAA installation and operational guidance that “an aircraft must have an electronic map display depicting … RF legs”.37 However, this project has also

34 NLR TP 91446 L, Figure 4 (page 86) 35 NLR TP 91446 L, 10 TEST RESULTS SUMMARY (page 74) 36 NLR TP 91446 L, 9.14 Training issues (page 71) 37 FAA AC 90-105 Appendix 5 2.b.(2); FAA AC 20-138C Appendix 3 A3-2.b.(3).


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clearly shown that a moving map is not required to maintain acceptable RF leg FTE, even during “complex procedures or in situations where a missed approach is required”.38 This conclusion is supported by Table 32, which shows there was greater than 46% margin over the 95% FTE 0.5 nm target when pilots flew RF legs in the minimally equipped Cherokee with the GNS 430W in the no map configuration.39 As noted in Section 5.1.1, display location was a concern for the minimally equipped Cherokee due to the marginal placement of the GNS 430W; this same concern also applies to many installations of the significant GNS 430W/GNS 530W field population. While FAA installation and operational approval guidance provides display installation field of view guidance for several types of information associated with equipment supporting RNAV (GPS) approaches,40 the guidance is ambiguous with respect to the purpose of the moving map for RF legs and its acceptable display location. The following examples illustrate these concerns:

• The installation guidance for equipment supporting RNAV (GPS) approaches repeatedly mentions a moving map in the context of its use for primary guidance.41 This may lead to varying interpretations as to the purpose of the moving map for RNAV (GPS) approaches with RF legs.

• There is no field of view guidance provided regarding the location of the moving map that the aircraft “must have”42 for RNAV (GPS) approaches with RF legs. This may lead to varying interpretations as to the acceptable location of the moving map for future TC/STC and field approval installations supporting RF legs as well as fielded installations that could support RF legs with a software upgrade and related Aircraft Flight Manual change.

This ambiguity may lead to varying interpretations for acceptable equipment installations supporting RF leg procedures. This ambiguity is a particular concern for existing approved aircraft installations where the equipment that provides the RNAV (GPS) primary guidance and annunciations also incorporates a moving map where the moving map has marginal display placement but other displayed information complies with FAA and manufacturer installation field of view guidance. Consequently, to remove these ambiguities:

Recommendation 2: Garmin recommends FAA revise its installation and operational guidance for RF legs to make clear that the main purpose of the moving map is to enhance situational awareness, and that it is acceptable for the moving map to be located either in the pilot’s primary field of view or on a readily accessible display page outside the primary field of view.43

38 NLR TP 91446 L, 11.5 Conclusions on instrumentational provisions (page 78) 39 A total of 78 RF legs were flown in the no map configuration with each Cherokee subject pilot (11 of the 12 total subject pilots) contributing to the 78 RF legs. Thus, the Table 32 results may be considered statistically significant. 40 FAA AC 90-105 Appendix 1 3.g; FAA AC 20-138C 14-2.b and 14-6.6. 41 FAA AC 90-105 Appendix 1 3.g and 3.g.(6); FAA AC 20-138C 8-3.g.(1), 8-3.g.(3)(e) Note, 8-3.g.(3)(f), 15-2, 15-2.c, and 15-2.2. The referenced AC 20-138C 8-3.g guidance is relevant to this discussion since Chapter 8 is titled “Equipment Performance - RNP Approach” and RNAV (GPS) approaches are categorized as RNP approaches. The referenced AC 20-138C 15-2 guidance is relevant to this discussion since Chapter 15 is titled “Installation Considerations - RNAV Multi-Sensor Equipment” and RNAV multi-sensor equipment may have similar map display location issues (e.g., pedestal mounted location). 42 FAA AC 90-105 Appendix 5 2.b.(2); FAA AC 20-138C Appendix 3 A3-2.b.(3). 43 AC 20-138C 8-3.h.(6) makes use of the phrase “either in the pilot’s primary field of view or on a readily accessible display page” for display of RNP approach information such as distance between flight plan waypoints, active navigation sensor type, etc.


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5.1.3 Messaging/Prompts

“Set course” Message Prompts Aside from display location, one of the primary pilot workload drivers in the Cherokee was the GNS 430W’s “Set course” messaging scheme. Several subject pilots stated workload could be lowered substantially if the frequent “Set course” message prompts and associated course setting tasks could be eliminated or reduced. Analysis in Section 4.3.1 reveals the primary cause of more frequent prompting when compared to typical DME arcs is the smaller minimum radius for RF legs (see Table 27 and the discussion that follows it for details).

Recommendation 3: Garmin recommends FAA consider revisions to its installation and operational guidance for RF legs to indicate that, to the extent practical, applicants seeking airworthiness approval of equipment capable of RF legs should minimize frequent recurring and unnecessary avionics operational tasks while RF legs are active.

To support this recommendation, Garmin will evaluate methods to eliminate or reduce the frequency of the GNS 430W’s “Set course” messages while flying RF legs during TSO/STC activities.

5.2 Training The following conclusions can be made from the observations throughout this project:

• RF legs do not require any unique or specialized training beyond what is already being provided for typical instrument procedures.

• Pilots of all experience classifications, low, medium and high time, were able to fly RF legs with 95% FTE less than the 0.5 nm target without training specific to RF legs.

• Pilots with more equipment experience generally had lower RF leg FTE. To support typical pilot instrument procedure training for procedures with RF legs:

Recommendation 4: Garmin recommends FAA update the Instrument Flying Handbook and Instrument Procedures Handbook to include a description of RF legs and the suggested techniques to successfully fly them. Garmin also recommends FAA update the Aeronautical Information Manual to add the “RF” abbreviation to the Abbreviations/Acronyms Appendix and other appropriate information regarding RF legs related to RNP procedures such as RNAV (GPS) approaches.

To support this recommendation, FAA should consider the following items based on pilot feedback and data analysis: • Pilots should not attempt to fly approaches with RF legs without first gaining familiarity with the

avionics implementation and related RF leg capabilities. Practicing hand-flown RF legs in simulated IFR conditions is highly recommended before attempting in actual IFR.

• Pilots should thoroughly brief the entire approach, paying special attention to the missed approach procedure, prior to flying a RF leg procedure.

• Remembering to un-suspend waypoint sequencing on panel-mount equipment, such as the GNS 430W, is of high importance when flying approaches with an RF leg located on missed approach segment and should be emphasized in training materials (see Section 4.5 and Appendix B for details on instances where this was a factor).

5.3 RF Leg Procedure Design Pilots were able to hand fly complex RF leg procedures, including those with RF legs not explicitly allowed or even non-conforming according to current procedure design criteria.

Recommendation 5: Given the FTE margins demonstrated with the complex RF leg prototype procedures, Garmin recommends FAA consider revisions to the Order 8260.58 RF leg procedure design criteria to: 1) Explicitly allow “S” RF legs and, 2) Allow RF legs terminating at the FAF


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“wherever airspace is critical to maximizing the benefit for terminal area operations”. While this recommendation is well supported by Table 33 showing that even the highest FTE non-conforming RF leg (K8105-K8106) terminating at the FAF had almost 30% margin over the 95% FTE 0.5 nm target, it is tempered by the phrase “wherever airspace is critical to maximizing the benefit for terminal area operations” to recognize that use of “S” RF legs and RF legs terminating at the FAF were the most stressing flown from a pilot workload perspective.44 Consequently, favoring the existing Order 8260.58 requirement for a minimum 2 nm straight leg segment prior to the FAF will alleviate this high workload scenario and allow pilots to get established on the final course prior to reaching the FAF. It also may be appropriate to consider using larger radius RF legs or including a speed constraint in the procedure design, such as is charted on the Ketchikan (Alaska) International (PAKT) ILS or LOC/DME Z RWY 11 approach RF leg, where procedures are designed with an “S” RF leg or RF leg terminating at the FAF. Additionally:

Recommendation 6: Garmin recommends FAA consider providing a copy of this report to the ICAO Instrument Flight Procedure Panel (IFPP) to support international harmonization of RF leg procedure design criteria via the RF Design Criteria working paper,45 particularly with respect to proposed intermediate approach segment design criteria for RF legs.

44 See Section 3.3.2 discussion of the highest FTE RF legs including characteristics that are believed to have contributed to the higher FTE. Also see Section 4.5 and Appendix B where five of the nine instances that pilots exceeded the 0.5 nm FTE target were on the highest FTE RF legs. 45 ICAO, IFPP/10 WGWHL Working Paper 28 rev. 12


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Appendix A – Detailed Data Analysis Results

A.1 Individual RF Leg FTE Table 34 summarizes the aggregate FTE for each RF leg by aircraft.

Table 34. Aggregate FTE for Each RF Leg

Leg Number of Legs Mean FTE (nm) 95% 2σ FTE (nm)


% Diff

K8102-K8103 17 18 0.000 -0.010 0.211 0.155 -0.056 -26.5 K8104-K8105 17 18 -0.003 0.074 0.332 0.235 -0.097 -29.2 K8105-K8106 17 18 0.042 0.027 0.354 0.256 -0.098 -27.7 K8107-K8108 16 18 0.085 0.080 0.268 0.159 -0.109 -40.7 K8121-K8122 23 24 0.022 0.008 0.180 0.134 -0.046 -25.6 K8122-K8123 23 24 0.008 0.028 0.188 0.164 -0.024 -12.8 K8123-K8124 23 24 0.007 0.078 0.219 0.198 -0.021 -9.6 K8124-K8125 23 24 0.007 0.091 0.212 0.204 -0.008 -3.8 K8127-K8128 23 24 -0.005 -0.012 0.236 0.143 -0.093 -39.4 K8129-K8132 18 18 0.001 0.011 0.208 0.167 -0.041 -19.7 K8134-K8135 22 29 -0.040 0.016 0.214 0.145 -0.069 -32.2



Table 35 summarizes the calculated FTE range for each RF leg by aircraft. Table 35. Calculated FTE Range for Each RF Leg

Leg Calculated FTE Range (nm) Cherokee C400 Aircraft Diff

K8102-K8103 -.408 to .394 -.362 to .291 -.046 to .103 K8104-K8105 -.472 to .552 -.141 to .394 -.331 to .158 K8105-K8106 -.552 to .661 -.380 to .298 -.172 to .363 K8107-K8108 -.287 to .680 -.257 to .380 -.030 to .300 K8121-K8122 -.224 to .318 -.198 to .169 -.026 to .149 K8122-K8123 -.325 to .401 -.165 to .278 -.160 to .123 K8123-K8124 -.402 to .467 -.141 to .392 -.261 to .075 K8124-K8125 -.328 to .432 -.140 to .495 -.188 to -.063 K8127-K8128 -.325 to .521 -.303 to .179 -.022 to .342 K8129-K8132 -.464 to .455 -.348 to .426 -.116 to .029 K8134-K8135 -.616 to .224 -.255 to .292 -.361 to -.068


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A.2 Pilot RF Leg FTE Table 36 summarizes the pilot aggregate RF leg FTE for each aircraft.

Table 36. Pilot Aggregate RF Leg FTE

Pilot / Classification



% Diff

001 / FAA 17 17 0.029 0.064 0.257 0.187 -0.070 -27.2 002 / Med 34 23 0.002 0.019 0.108 0.151 +0.043 +39.8 003 / FAA 17 17 -0.023 -0.029 0.289 0.211 -0.078 -27.0 004 / FAA 17 17 0.003 0.023 0.159 0.099 -0.060 -37.7 005 / Low 22 23 -0.004 0.001 0.238 0.137 -0.101 -42.4 006 / Med 22 34 0.001 0.042 0.160 0.203 +0.043 +26.9 007 / Low 21 17 -0.007 -0.022 0.150 0.168 +0.018 +12.0 008 / High 22 22 0.046 0.064 0.346 0.184 -0.162 -46.8 009 / High 22 23 0.022 0.048 0.268 0.190 -0.078 -29.1 010 / FAA 17 17 -0.004 0.044 0.178 0.196 +0.018 +10.1 011 / FAA 11 11 0.053 0.040 0.393 0.203 -0.190 -48.3 012 / FAA 0 18 0.000 0.049 n/a 0.111 n/a n/a



Note 3: Pilot 002 flew Profile 3 once in the Cherokee; thus, having more RF legs than other Garmin-recruited pilots.

Note 4: Pilot 012 only flew the C400. Table 37 summarizes the pilot aggregate RF Leg calculated FTE range for each aircraft.

Table 37. Pilot Aggregate RF Leg Calculated FTE Range Pilot /

Classification Calculated FTE Range (nm)

Cherokee C400 Aircraft Diff 001 / FAA -0.265 to 0.521 -0.151 to 0.405 0.114 to 0.116 002 / Med -0.325 to 0.248 -0.330 to 0.394 0.005 to 0.146 003 / FAA -0.464 to 0.432 -0.362 to 0.394 0.102 to 0.038 004 / FAA -0.190 to 0.377 -0.112 to 0.169 0.078 to 0.208 005 / Low -0.472 to 0.401 -0.348 to 0.278 0.124 to 0.123 006 / Med -0.254 to 0.233 -0.261 to 0.495 0.007 to 0.262 007 / Low -0.283 to 0.286 -0.253 to 0.230 0.030 to 0.056 008 / High -0.552 to 0.680 -0.380 to 0.324 0.172 to 0.356 009 / High -0.428 to 0.660 -0.170 to 0.392 0.258 to 0.268 010 / FAA -0.263 to 0.560 -0.257 to 0.297 0.006 to 0.263 011 / FAA -0.616 to 0.661 -0.213 to 0.426 0.403 to 0.235 012 / FAA n/a -0.070 to 0.278 n/a

Note: Pilot 012 only flew the C400.


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A.3 Aggregate RF Leg Ground Track Plots The following explanations are relevant to the ground track plots included in this section:

• 1 nm of ground track data is included before and after the RF leg. • Solid lines indicate tracks included in the FTE calculation while dashed lines indicate tracks that

are not included in the FTE calculation. Figure 34 shows the pilot line color legend for the aggregate ground track plots.

Figure 34. Pilot Line Color Legend

• Unless otherwise specified: o Outer gray lines are 0.5 nm from the RF leg centerline. o Inner gray lines are 0.25 nm from the RF leg centerline.

• Rank is based on lowest to highest 95% FTE where 1 is the lowest FTE. Additional characteristics of each RF leg not described below are summarized in Section 3.3 Table 4.


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K8102-K8103 RF Leg Figure 35 shows the aggregate ground tracks for both aircraft.

Figure 35. K8102-K8103 RF Leg Aggregate Ground Tracks

Characteristics of the K8102-K8103 RF leg are: • FTE rank (1 to 11): Cherokee: 4, C400: 4 • Preceded by 8.4 nm straight leg at level altitude • 13.034 nm radius; largest radius of all RF legs • 13.1 nm length • Altitude: Pilot discretion but not to descend below the K8104 charted altitude constraint of 3800 ft


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K8104-K8105 and K8105-K8106 RF legs Figure 36 shows the aggregate ground tracks for both aircraft.

Figure 36. K8104-K8105 and K8105-K8106 RF Legs Aggregate Ground Tracks

Note: On the K8105-K8106 RF leg: • Outer black lines represent CDI full scale. CDI full scale is 1


• Inner black lines represent CDI half scale. Individual aggregate ground track plots for these RF legs follow.


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Characteristics of the K8104-K8105 RF leg are: • FTE rank (1 to 11): Cherokee: 10, C400: 10 • Preceded by 5.9 nm straight leg descending to K8104 3800 ft charted altitude constraint • First leg of the “S” turn • 3.000 nm radius; minimum allowed by Order 8260.54A and Order 8260.58 • 4.4 nm length • Altitude: Descending 600 feet to K8105 charted altitude constraint of 3200 ft


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Note: On the K8105-K8106 RF leg: • Outer black lines represent CDI full scale. CDI full scale is 1


• Inner black lines represent CDI half scale. Characteristics of the K8105-K8106 RF leg are:

• FTE rank (1 to 11): Cherokee: 11, C400: 11 • Preceded by K8104-K8105 RF leg • Second leg of the “S” turn • Ends at FAF with narrowing CDI scale; Order 8260.54A and Order 8260.58 require RF legs must

terminate at least 2 nm prior to the FAF • 3.000 nm radius; minimum allowed by Order 8260.54A and Order 8260.58 • 4.6 nm length • Altitude: Descending 600 feet to K8106 charted altitude constraint of 2600 ft


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Characteristics of the K8107-K8108 RF leg are: • FTE rank (1 to 11): Cherokee: 9, C400: 5 • Preceded by 2.0 nm straight climbing missed approach leg • 180 degree arc • 4.320 nm radius • 13.7 nm length (the K81 RWY 3 chart shows 13.1 nm; this value was found to be incorrect after

data collection flights began so the chart was left unchanged) • Altitude: Climbing to assigned altitude of 3100 ft



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K8121-K8122, K8122- K8123, K8123- K8124, and K8124-K8125 RF Legs Figure 40 shows the aggregate ground tracks for both aircraft.

Figure 40. K8121-K8122, K8122-K8123, K8123-K8124, and K8124-K8125 RF Legs Aggregate

Ground Tracks Individual aggregate ground track plots for these RF legs follow.




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Characteristics of the K8121-K8122 RF leg are: • FTE rank (1 to 11): Cherokee: 1, C400: 1 • Preceded by 10 to 15 nm straight legs at level altitude • 7.612 nm radius • 4.8 nm length • Altitude: Level at assigned altitude • One RF leg partially included in FTE analysis due to traffic avoidance maneuver



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Characteristics of the K8122-K8123 RF leg are: • FTE rank (1 to 11): Cherokee: 2, C400: 6 • Preceded by K8121-K8122 RF leg • 4.698 nm radius • 5.4 nm length • Altitude: Level at assigned altitude • One RF leg partially included in FTE analysis due to traffic avoidance maneuver



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Characteristics of the K8123-K8124 RF leg are: • FTE rank (1 to 11): Cherokee: 7, C400: 8 • Preceded by K8122-K8123 RF leg • 2.986 nm radius; smaller than 3.0 nm minimum allowed by Order 8260.54A and Order 8260.58 • 5.1 nm length • Altitude: Descending 2000 feet to K8125 charted altitude constraint of 3000 ft • One RF leg partially included in FTE analysis due to traffic avoidance maneuver



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Characteristics of the K8124-K8125 RF leg are: • FTE rank (1 to 11): Cherokee: 5, C400: 9 • Preceded by K8123-K8124 RF leg • 3.140 nm radius • 4.4 nm length • Altitude: Descending to K8125 charted altitude constraint of 3000 ft • One RF leg partially included in FTE analysis due to traffic avoidance maneuver



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Characteristics of the K8127-K8128 RF leg are: • FTE rank (1 to 11): Cherokee: 8, C400: 2 • Preceded by 2.0 nm straight climbing missed approach leg • 3.000 nm radius • 4.7 nm length • Altitude: Climbing to assigned altitude of 5000 ft


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Characteristics of the K8129-K8132 RF leg are: • FTE rank (1 to 11): Cherokee: 3, C400: 7 • Preceded by 10 nm straight leg at level altitude • 305 degree arc • 6.000 nm radius • 31.9 nm length • Altitude: Level at assigned altitude of 3100 ft, 3700 ft, or 5000 ft • Two RF legs partially included in FTE analysis due to leg being aborted

Turn aborted

Turn aborted


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Characteristics of the K8134-K8135 RF leg are: • FTE rank (1 to 11): Cherokee: 6, C400: 3 • Preceded by 5 nm straight leg at level altitude • 180 degree arc • 3.000 nm radius; minimum allowed by Order 8260.54A and Order 8260.58 • 9.4 nm length • Altitude: Level at assigned altitude of 3100 ft or 5000 ft


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A.4 Aggregate RF Leg Vertical Profile Plots The following explanations are relevant to the vertical profile plots included in this section:

• 1 nm of vertical profile data is included before and after the RF leg. • 0.0 on the charted axis represents the waypoint where the RF leg ends. • Dashed black horizontal lines represent the charted or assigned altitude specified in the chart

title. • Solid colored lines are the vertical profile tracks. Figure 34 shows the pilot line color legend for

the aggregate vertical profile plots. Additional characteristics of each RF leg not described below are summarized in Section 3.3 Table 4 and Section A.3.


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K8102-K8103 RF Leg Figure 48 shows the aggregate vertical profiles for both aircraft.

Figure 48. K8102-K8103 RF Leg Aggregate Vertical Profiles

Characteristics of the K8102-K8103 RF leg are: • Preceded by 8.4 nm straight leg at level altitude • 13.034 nm radius; largest radius of all RF legs • 13.1 nm length • Altitude: Pilot discretion but not to descend below the K8104 charted altitude constraint of 3800 ft

Note some of the pilots did not begin descents to 3800 ft until after K8103. Due to chart design issues, in some instances pilots simply were not aware they could descend. In other instances, the blue and amber lines tracking slightly above 3500 ft show occasions where altitude was intentionally held low due to cloud decks.


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Characteristics of the K8104-K8105 RF leg are: • Preceded by 5.9 nm straight leg descending to K8104 3800 ft charted altitude constraint • First leg of the “S” turn • 3.000 nm radius; minimum allowed by Order 8260.54A and Order 8260.58 • 4.4 nm length • Altitude: Descending 600 feet to K8105 charted altitude constraint of 3200 ft

Note: On his first RF leg approach, Pilot 005 descended below the charted 3200 ft altitude constraint by ~200 ft, approximately 0.75 nm from the K8105 fix, and continued the descent to the next charted altitude of 2600 ft.


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Characteristics of the K8105-K8106 RF leg are: • Preceded by K8104-K8105 RF leg • Second leg of the “S” turn • Ends at FAF with narrowing CDI scale; Order 8260.54A and Order 8260.58 require RF legs must

terminate at least 2 nm prior to the FAF • 3.000 nm radius; minimum allowed by Order 8260.54A and Order 8260.58 • 4.6 nm length • Altitude: Descending 600 feet to K8106 charted altitude constraint of 2600 ft

It is worth noting that within approximately 1 nm of the K8106 waypoint, the altitude plots converge into a tighter group, indicative of advisory vertical guidance becoming active and being followed.


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Characteristics of the K8107-K8108 RF leg are: • Preceded by 2.0 nm straight climbing missed approach leg • 180 degree arc • 4.320 nm radius • 13.7 nm length (the K81 RWY 3 chart shows 13.1 nm; this value was found to be incorrect after

data collection flights began so the chart was left unchanged) • Altitude: Climbing to assigned altitude of 3100 ft (in some instances, at test director’s discretion,

other altitudes were given, for example to avoid heavy turbulence or cloud layers)


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Characteristics of the K8121-K8122 RF leg are: • Preceded by 10 to 15 nm straight legs at level altitude • 7.612 nm radius • 4.8 nm length • Altitude: Level at assigned altitude

Note the blue, amber, and dark red lines are instances where altitude was intentionally held below cloud decks.


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Characteristics of the K8122-K8123 RF leg are: • Preceded by K8121-K8122 RF leg • 4.698 nm radius • 5.4 nm length • Altitude: Level at assigned altitude

Note the blue, amber, and dark red lines are instances where altitude was intentionally held below cloud decks.


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Characteristics of the K8123-K8124 RF leg are: • Preceded by K8122-K8123 RF leg • 2.986 nm radius; smaller than 3.0 nm minimum allowed by Order 8260.54A and Order 8260.58 • 5.1 nm length • Altitude: Descending 2000 feet to K8125 charted altitude constraint of 3000 ft

Note some of the pilots did not begin descents to 3000 ft until after K8124. Due to chart design issues, in some instances pilots simply were not aware they could descend until it was too late on the approach to do so safely. For example, Pilot 008 flew back-to-back RWY 21 approaches and was full-scale deflection high on the advisory vertical glide path on both occasions. In other instances, altitudes were kept high due to local airport traffic conflicts.


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Characteristics of the K8124-K8125 RF leg are: • Preceded by K8123-K8124 RF leg • 3.140 nm radius • 4.4 nm length • Altitude: Descending to K8125 charted altitude constraint of 3000 ft

The following notes are keyed to the Figure 55 numbered annotations: 1) On Flight 188, Pilot 008 had difficulty on the RWY 21 approach in the C400; he was confused

about the altitude select and VNAV descent indications and never started his descent, even though he vocally called out the 3000 ft charted altitude requirement. Pilot ended up flying through the advisory vertical glide path, achieving full scale deflection high on the final approach. Pilot leveled at 2600 ft for the remainder of the final approach.

2) While flying Flight 203 in the C400, local traffic conflicts prevented descent. Pilot 006 was instructed to level off at 4500 ft and held this altitude until past K8126.

3) While flying Flight 642 in the Cherokee, Pilot 006 was instructed to level off at 2,600 due to local airport traffic conflict. Pilot maintained descent prior to reaching K8125 then leveled off.

1

2

3


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The safety pilot’s instructions were likely interpreted in a way that caused Pilot 006 to ignore the previously briefed altitude constraint.



Characteristics of the K8127-K8128 RF leg are: • Preceded by 2.0 nm straight climbing missed approach leg • 3.000 nm radius • 4.7 nm length • Altitude: Climbing to assigned altitude of 5000 ft


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Characteristics of the K8129-K8132 RF leg are: • Preceded by 10 nm straight leg at level altitude • 305 degree arc • 6.000 nm radius • 31.9 nm length • Altitude: Level at assigned altitude of 3100 ft, 3700 ft, or 5000 ft


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Characteristics of the K8134-K8135 RF leg are: • Preceded by 5 nm straight leg level at level altitude • 180 degree arc • 3.000 nm radius; minimum allowed by Order 8260.54A and Order 8260.58 • 9.4 nm length • Altitude: Level at assigned altitude of 3100 ft or 5000 ft

Note the blue and amber lines are instances where altitude was intentionally held below cloud decks.


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A.5 Extrapolating FTE to Higher Speeds

Descending Leg FTE vs. TAS Extrapolation

Table 38 presents the 95% FTE in 10 kt increments for all descending legs. A plot of the Table 38 data is shown in Figure 59.

Table 38. Cherokee Descending Legs FTE vs. 10 kt TAS Range

Average TAS Range

(kts) Number of

Legs 95% 2σ

FTE (nm)

85-90 4 0.183 91-100 2 0.338

101-110 21 0.255 111-120 17 0.231 121-130 18 0.250 131-140 27 0.250 141-150 7 0.270 151-160 1 0.257 161-170 - 0.270 171-180 - 0.272 181-190 - 0.274 191-200 - 0.276


Figure 59. Cherokee Descending Legs FTE vs. 10 kt TAS Ranges


• All three Trendlines are tightly grouped, and suggest a slight increase in FTE with increased speeds.

• The descending leg group presents the flattest FTE curve of all leg groups.

0.000

0.050

0.100

0.150

0.200

0.250

0.300

0.350

0.400

Descending Turns 95% FTE (nm)

95% (2σ) FTE (nm)





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• The 95% FTE value for the 91-100 kt TAS range is higher than the other TAS ranges for the following reasons:

o Only two legs were grouped into this TAS range. o Further research revealed that one leg was flown with very low FTE and one leg was

flown with very high FTE. o The very high FTE leg occurred during Flight 645 Leg #2 (K8104-K8105). This is the

primary contributor to the high 95% FTE value observed above. This leg happens to be one of nine instances where the 0.5 nm FTE target was exceeded and is further analyzed in Appendix B (see Figure 74).

Figure 60. Cherokee Descending Legs Distribution over TAS Range

The following additional observations were made from Figure 60 and the data upon which it was based: • The descending leg group constitutes the majority of legs flown in the Cherokee (97 total legs). • The descending legs are the most evenly distributed across the TAS ranges.

Climbing Leg FTE vs. TAS Extrapolation

Table 39 presents the 95% FTE in 10 kt speed increments for all climbing legs. A plot of the Table 39 data is shown in Figure 61.

Table 39. Cherokee Climbing Legs FTE vs. 10 kt TAS Range

Average TAS Range

(kts) Number of

Legs 95% 2σ

FTE (nm)

85-90 2 0.137 91-100 13 0.267

101-110 10 0.351 111-120 8 0.160 121-130 4 0.206 131-140 2 0.273 141-150 0 151-160 0 161-170 - 0.280 171-180 - 0.289 181-190 - 0.297 191-200 - 0.306

Note: Entries in bold blue text represent the most conservative case extrapolated data derived from the linear Trendline depicted in Figure 61.

051015202530

Number of Turns (Descending)

Number of Turns


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Figure 61. Cherokee Climbing Legs FTE vs. 10 kt TAS Ranges


• The linear trend extrapolation is most conservative. • The 95% FTE value for the 101-110 kt TAS range is higher than the other TAS ranges. Further

research revealed that another Flight 645 leg was a significant contributor to the high 95% FTE value. This leg happens to be one of nine instances where the 0.5 nm FTE target was exceeded and is further analyzed in Appendix B (see Figure 75).

Figure 62. Cherokee Climbing Legs Distribution over TAS Range

The following additional observations were made from Figure 62 and the data upon which it was based: • Climbing legs had a greater number of legs concentrated at low speed ranges, and there were

fewer legs for each incremental speed range. This suggests that speed will not be as prominent a factor on climbing legs when compared to other factors such as pilot workload and situational awareness.

Level Leg FTE vs. TAS Extrapolation

Table 40 presents the 95% FTE in 10 kt speed increments for all level legs. A plot of the Table 40 data is shown in Figure 63.

0.000

0.050

0.100

0.150

0.200

0.250

0.300

0.350

0.400

Climbing Turns 95% FTE (nm)

95% (2σ) FTE (nm)




0

5

10

15

Number of Turns (Climbing)

Number of Turns


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Table 40. Cherokee Level Legs FTE vs. 10 kt TAS Range

Average TAS Range

(kts) Number of

Legs 95% 2σ

FTE (nm)

85-90 5 0.051 91-100 2 0.205

101-110 5 0.251 111-120 15 0.238 121-130 11 0.140 131-140 46 0.213 141-150 2 0.212 151-154 0 - 161-170 - 0.294 171-180 - 0.312 181-190 - 0.330 191-200 - 0.346


Figure 63. Cherokee Level Legs FTE vs. 10 kt TAS Ranges


• All of the legs flown between the 85-90 TAS range were flown by the subject pilot who had the lowest Cherokee 95% FTE. All 85-90 TAS legs were flown during the Flight 3 profile, where the pilot was given a target 90 kt speed to maintain. This explains the significantly lower FTE in this range compared to the other TAS ranges. This also has the effect of artificially increasing the slope of the Trendlines, creating higher extrapolated FTE values than would otherwise be realized.

0.000

0.050

0.100

0.150

0.200

0.250

0.300

0.350

0.400

Level Turns 95% FTE (nm)

95% (2σ) FTE (nm)





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Figure 64. Cherokee Level Legs Distribution over TAS Range

The following additional observations were made from Figure 64 and the data upon which it was based: • The level legs group has an unusually large number legs in the Cherokee’s cruising speed of

131-140 kt. This suggests pilots naturally fly at an aircraft’s design cruise speed during level flight; given an increase in cruise speed, FTE is not expected to be detrimentally effected since:

o Pilots are accustomed to maneuvering at the aircraft’s cruise speed. o Workload during level legs was not found to be excessive during data collection flights

(see further discussion in Section 4.1).

0

10

20

30

40

50

Number of Turns (Level)

Number of Turns


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A.6 Individual Straight Leg FTE Table 41 summarizes the aggregate FTE for each straight leg by aircraft.

Table 41. Aggregate FTE for Each Straight Leg

Leg Number of Legs Mean FTE (nm) 95% 2σ FTE (nm)

Cherokee C400 Cherokee C400 Cherokee C400 Aircraft Diff % Diff

K8103-K8104 17 18 0.026 -0.021 0.190 0.115 -0.075 -39.5 K8108-K8109 16 14 0.021 -0.021 0.192 0.115 -0.077 -40.1

DODSN-K8120 13 20 0.010 -0.008 0.228 0.142 -0.086 -37.7 K8120-K8121 23 23 0.035 -0.015 0.145 0.108 -0.037 -25.5 K8128-K8129 12 13 0.008 -0.034 0.169 0.120 -0.049 -29.0 K8133-K8134 14 23 0.023 -0.030 0.163 0.116 -0.047 -28.8 K8135-K8136 22 29 0.072 -0.001 0.163 0.130 -0.033 -20.2

K8136-DODSN 11 12 0.030 -0.013 0.259 0.066 -0.193 -74.5 Note 1: Aircraft Diff was computed as:

C400 FTE - Cherokee FTE Note 2: % Diff was computed as:

( ( C400 FTE - Cherokee FTE ) / Cherokee FTE ) * 100 Table 42 summarizes the recorded FTE range for each straight leg by aircraft.

Table 42. Recorded FTE Range for Each Straight Leg

Leg Recorded FTE Range (nm) Cherokee C400 Aircraft Diff

K8103-K8104 -0.210 to 0.422 -0.243 to 0.110 0.033 to 0.312 K8108-K8109 -0.405 to 0.266 -0.228 to 0.129 -0.177 to 0.137

DODSN-K8120 -0.475 to 0.400 -0.334 to 0.234 -0.141 to 0.166 K8120-K8121 -0.167 to 0.291 -0.170 to 0.122 0.003 to 0.169 K8128-K8129 -0.219 to 0.369 -0.190 to 0.151 -0.029 to 0.218 K8133-K8134 -0.152 to 0.394 -0.200 to 0.137 0.048 to 0.257 K8135-K8136 -0.161 to 0.368 -0.154 to 0.293 -0.007 to 0.075

K8136-DODSN -0.400 to 0.454 -0.124 to 0.075 -0.276 to 0.379


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A.7 Pilot Straight Leg FTE Table 43 summarizes the pilot aggregate straight leg FTE for each aircraft.

Table 43. Pilot Aggregate Straight Leg FTE

Pilot / Classification



% Diff

001 / FAA 11 11 -0.024 -0.033 0.189 0.108 -0.081 -42.9 002 / Med 20 15 0.018 -0.003 0.090 0.083 -0.007 -7.8 003 / FAA 9 12 0.060 0.003 0.303 0.157 -0.146 -48.2 004 / FAA 10 11 -0.024 0.005 0.120 0.100 -0.020 -16.7 005 / Low 12 16 0.075 -0.007 0.222 0.099 -0.123 -55.4 006 / Med 12 20 0.017 -0.030 0.098 0.108 +0.010 +10.2 007 / Low 12 10 0.026 -0.040 0.115 0.121 +0.006 +5.2 008 / High 13 12 0.054 -0.011 0.275 0.103 -0.172 -62.5 009 / High 12 16 0.034 -0.056 0.120 0.141 +0.021 +17.5 010 / FAA 10 12 0.009 -0.001 0.121 0.102 -0.019 -15.7 011 / FAA 7 5 0.028 -0.012 0.184 0.129 -0.055 -29.9 012 / FAA 0 12 0.000 -0.039 n/a 0.126 n/a n/a



Note 3: Pilot 002 flew Profile 3 once in the Cherokee; thus, having more straight legs than other Garmin-recruited pilots.

Note 4: Pilot 012 only flew the C400. Table 44 summarizes the pilot aggregate straight leg recorded FTE range for each aircraft.

Table 44. Pilot Aggregate Straight Leg Recorded FTE Range Pilot /

Classification Recorded FTE Range (nm)

Cherokee C400 Aircraft Diff 001 / FAA -0.405 to 0.201 -0.171 to 0.101 -0.234 to 0.100 002 / Med -0.142 to 0.136 -0.116 to 0.123 -0.026 to 0.013 003 / FAA -0.475 to 0.369 -0.171 to 0.234 -0.304 to 0.135 004 / FAA -0.158 to 0.167 -0.126 to 0.179 -0.032 to -0.012 005 / Low -0.144 to 0.454 -0.161 to 0.140 0.017 to 0.314 006 / Med -0.092 to 0.216 -0.243 to 0.104 0.151 to 0.112 007 / Low -0.210 to 0.153 -0.190 to 0.077 -0.020 to 0.076 008 / High -0.311 to 0.422 -0.132 to 0.107 -0.179 to 0.315 009 / High -0.079 to 0.210 -0.228 to 0.161 0.149 to 0.049 010 / FAA -0.152 to 0.186 -0.128 to 0.095 -0.024 to 0.091 011 / FAA -0.400 to 0.368 -0.124 to 0.293 -0.276 to 0.075 012 / FAA n/a -0.334 to 0.078 n/a

Note: Pilot 012 only flew the C400.


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A.8 Aggregate Straight Leg Plots Section A.3 provides descriptions of the plot line styles included in the figures below.

K8103-K8104 Straight Leg Figure 65 shows the aggregate ground tracks for both aircraft.

Figure 65. K8103-K8104 Straight Leg Aggregate Ground Tracks


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DODSN-K8120 Straight Leg Figure 67 shows the aggregate ground tracks for both aircraft.

Figure 67. DODSN-K8120 Straight Leg Aggregate Ground Tracks


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K8136-DODSN Straight Leg Figure 72 shows the aggregate ground tracks for both aircraft.

Figure 72. K8136-DODSN Straight Leg Aggregate Ground Tracks


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Appendix B – Detailed Human Factors Discussion

B.1 Cherokee Workload Rating Summary Table 45 summarizes the pilot Cherokee workload rating.

Table 45. Cherokee Workload Rating Summary Pilot / Classi- fication

Flight # Low Med High Comments

001 / FAA 633

X RWY 21 Approach #1 Noted workload was highest on final leg in first RWY 21 approach.

X

RWY 21 Approach #2 Pilot intentionally slowed down to lower workload on second RWY 21 approach. With Default NAV page being used, pilot experienced higher FTE; test conductor noted he was not as smooth without the map.

002 / Med 639

X

RWY 21 Approach #1 Pilot commented that workload was lower since this flight was not as hot or rough as the prior flights. Flying slower (assigned target of 90 kts) also made things easier (although pilot commented that higher levels of concentration were required to be devoted to maintain airspeed). Without the moving map, the pilot rated workload as being similar to that of an ADF approach, with different tasks.

X

RWY 21 Missed Segment – Large Arc Flown without the moving map. Commented that holding altitude and airspeed is just as tasking as maintaining course, but that maintaining course was probably easier. Pilot stated that RF leg approaches would definitely require training, but remarked that so do other approaches like ILSs.

003 / FAA X Noted that mental workload was much higher with Default NAV

page (no map)

004 / FAA X

Pilot noted high workload due to the messaging of the GNS 430W. Flying with Default NAV page, pilot commented that workload is higher in steeper RF legs

005 / Low

638

X RWY 3 Approach #1 Pilot stated flying the approach was ‘like flying multiple DME arcs’ and also that the approach was ‘a bit of work’.

X

RWY 21 Missed Segment – Large Arc On large arc, pilot stated that one ‘could get tired doing that’ relating the size of the arc to the time duration required to navigate it. The pilot actively managed the 430W messaging and CDI course setting around the entire leg. Pilot was clearly fatigued at this point in the flight; pilot later noted that his workload was fairly high, partially due to higher levels of concentration due to this being his first flight.

640

X RWY 21 Approach #1 Pilot commented that his first approach ‘felt pretty good’ compared to the previous flight. Flown with moving map.

X+

RWY 21 Approach #2 Pilot flew second approach without moving map. Rated second approach workload ‘medium +’. Felt that flying without map took getting used to, and with practice, it would not be more difficult than with moving map.

X Third approach flown with pilot using both moving map and Default NAV page; after this approach pilot rated workload high due to fatigue, and getting behind aircraft.


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Pilot / Classi- fication


006 / Med

641

X

RWY 3 Approach #1 On first RWY 3 approach pilot rated workload as High. Commented that the short succession of fixes with altitude changes contribute to higher workload…

X

RWY 21 Missed Segment – Large Arc While flying the large arc, pilot commented it was ‘almost like a DME arc’ and that it ‘wasn’t too bad’ since there were no altitude changes or descents. Pilot felt altitude changes really increase workload.

642

X+

RWY 21 Approach #1 Pilot rated workload as ‘medium +’. Pilot commented that the approach ‘felt better, but was still busy, with a lot going on’. Commented that scan was getting faster.

X+

RWY 21 Approach #2 Approach flown with Default NAV page, pilot rated workload as ‘medium +’ but commented that fatigue was increasing and scan was wearing out. In flight debrief pilot again remarked workload was ‘same as DME arc’.

007 / Low

644

X

RWY 3 Approach #1 Pilot rated workload as High (qualified remark as being 7 or 8 out of 10 numerically). Commented on significant amount of head movement between instruments and 430W. Pilot used Default NAV page for approach, but periodically checked moving map.

X

RWY 21 Missed Segment – Large Arc Pilot remarked workload was ‘Medium’ indicating it was less than the previous approaches, and that he had more time to develop a rhythm. Pilot finally selected moving map after flying both practice approaches and RWY 3 approach and remarked that the map was ‘most helpful’.

650

X

RWY 21 Approach #1 Pilot commented that the overall scan size (width) in Cherokee created more workload. When asked to make assessment on a scale of 1-5 pilot rated workload a 3.

X

RWY 21 Approach #2 Approach flown using the Default NAV page. Pilot commented that workload was higher with the CDI only. When asked to make assessment on a scale of 1-5 pilot rated workload a 4. Pilot noted workload was higher since he had to create a mental picture of the approach (without the map available).


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008 / High

645 X

RWY 3 Approach #1 On RWY 3 approach, flown with the Default NAV page (by pilot’s choice), pilot rated workload High. Pilot commented that he was ‘having a hard time visualizing the turns’ and was also consumed with managing the 430W’s message prompts stating the prompts were ‘busy little guys’. Pilot also remarked that the scan in Cherokee was abnormal and very wide.

646

X

RWY 21 Approach #1 Pilot indicated workload ‘was a lot lower’ from previous flight. Pilot also commented the approach is ‘still a challenge, map or no map’.

X RWY 21 Approach #2 Flown using the Default NAV page, pilot rated workload as ‘Medium’.

X

RWY 3 Approach #2 Pilot rated workload as ‘Medium’ while using moving map. Pilot felt the techniques being applied for RF legs could be learned within ~1 hr in order to become more intuitive.

009 / High

647

X

RWY 3 Approach #1 On first RWY 3 approach, pilot rated workload as ‘High’. Pilot admitted difficulty staying oriented and maintaining situational awareness. Commented on the large number of approach fixes in close succession. Pilot remarked that flying the approach was ‘a chore’. Pilot felt the wind vector indication was very helpful.

X

RWY 21 Missed Segment – Large Arc While flying large arc, pilot commented workload was ‘Medium’ and ‘not as high as the previous approach’. Pilot felt his scan was getting better, and began incorporating bank attitude into scan.

648

X

RWY 21 Approach #1 Using the moving map, pilot ranked workload as ‘Medium’. Pilot remarked he was having difficulty adapting to the ADI display indication, but didn’t understand why it was a significant factor. Pilot background suggests negative transfer from Boeing 767 EFIS display.

X

RWY 21 Approach #2 Using the Default NAV page, pilot still ranked workload as ‘Medium’ but admitted it was more difficult. At one point, pilot lost all situational awareness and stated ‘I’m lost’, as he was now relying mostly on the charting, and couldn’t tell where he was on the approach. Safety pilot provided coaching at this point to point out the active leg indication on 430W. Pilot also commented that the loss of the wind vector was significant.

X

RWY 3 Approach #2 Pilot switched to moving map; commented that he missed the ‘active leg’ indication from the Default NAV page. Pilot exhibited situational awareness lapses again and had difficulty determining if he had yet passed a waypoint. Commented that he was having a difficult time staying oriented with the chart and the map.

010 / FAA 649

Pilot preferred Default NAV page for flight. Pilot commented that workload ‘seems reasonable’ and is within range of other approaches.


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011 / FAA 652

X

RWY 21 Approach #1 Pilot initially commented that too much info being presented to pilot, but stated that the moving map is a significant anxiety reducer. Commented on CDI sensitivity; the CDI shows ‘on course’ while the map shows diverging from course. Thought that the CDI was a ‘too late’ indication. Pilot was absorbed in find/maintain an optimum constant bank angle for the RF leg; consequently tended to not include 430W in scan as much. Pilot admitted he was not cued in to the level of maneuvering aggressiveness required to maintain course on certain legs. Pilot rated workload at least being ‘Medium’, and commented that if he was alone, in actual IFR conditions, then workload would undoubtedly be ‘High’. Pilot felt the 430W messaging was very taxing and increased workload.

X

RWY 21 Missed Segment – Large Arc Pilot switched to Default NAV page on large arc and realized an improvement in FTE. Pilot rated workload low on the arc, compared to the approach.

X

RWY 3 Approach – Max Fwd Speed Pilot chose to use Default NAV page for entire approach. Pilot found himself dropping CDI out of scan and concentrating (excessively) on the numeric data. Pilot momentarily lost situational awareness at K8105, did not know which leg was ahead. Pilot misinterpreted the missed approach turn, believed it was a right turn at K8107-K8108. Pilot workload was very high at the K8104-K8105-K8106 series of legs. Pilot found himself depending on 430W datafields to keep the CDI centered. Pilot admitted later that the approach would be much easier with the moving map, and the pilot would have had a better sense of the leg radius. Pilot felt speed wasn’t more of a factor than any other variables present at the time (wind, altitude changes, etc).

Note: Pilot 012 / FAA only flew the C400.

B.2 FTE Exceedance Assessment Details The following explanations are relevant to the plots included in the following discussions:

• 1 nm of ground track data is included before and after the RF leg. • Solid red lines indicate tracks included in the FTE calculation while dashed red lines indicate

tracks that are not included in the FTE calculation. • Outer gray lines are 0.5 nm from the RF leg centerline. • Inner gray lines are 0.25 nm from the RF leg centerline. • On the K8105-K8106 RF leg:

o Outer black lines represent CDI full scale. CDI full scale is 1 nm until 2 nm before the FAF then narrows to 0.236 nm at the FAF.

o Inner black lines represent CDI half scale.

Flight 633, N4878S, Pilot 001 This flight was FAA Pilot 001’s second flight in the Cherokee (first actual data collection flight). Pilot 001 had previously flown the Cherokee approximately one month prior to evaluate system readiness for data collection; this first flight was flown without the use of a vision restriction device. Flying Profile 2, the pilot experienced momentary FTE exceedance on his second K81 RWY 21 missed approach RF leg at K8127-K8128. The pilot noted an increase in workload over the first flight due to the


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use of a vision restricting device. Prior to flying the missed approach, the pilot reached to press the SUSP key; however, SUSP had not yet been activated and the OBS function was activated instead. The pilot did not notice this as he configured for the missed approach climb and had to be prompted by the test director. The pilot was flying with the Default NAV page while entering the K8127-K8128 leg. Halfway through the leg, the test director allowed use of the moving map. With the addition of the moving map, the pilot became oriented, recognized the excessive deviation, then corrected right to re-establish on course. He commented “It’s a lot better with a map…can see a big difference in the approach”.

Figure 73. Pilot 001 FTE Exceedance, K8127-K8128

Flight 645, N4878S, Pilot 008

This flight was Pilot 008’s first flight in the Cherokee and first flight of the project. The pilot exceeded 0.5 nm FTE toward the end of the K8104-K8105 leg while on the outside of the leg centerline. The exceedance carried through to the inside of the K8105-K8106 leg very briefly before the pilot executed more aggressive maneuvering to re-establish course.

Figure 74. Pilot 008 FTE Exceedance, K8104-K8105-K8106


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At the beginning of the RWY 3 approach, the pilot chose to fly the approach with the GNS 430W configured to display the Default NAV page. The pilot noted he typically does not use the Default NAV page but he wanted to use it on his first RF leg approach, believing future approaches with the map would only be easier. Setting up for the approach, the pilot slowed the aircraft on the K8102-K8103 RF leg. About mid-way through the approach, the pilot began actively managing the “Set course” messaging on the GNS 430W. The pilot managed the aircraft well and demonstrated effective situational awareness by verbally calling out the approach altitudes and included the approach chart within his scan. Without the moving map, no wind vector was available to the pilot, and the approach workload did not permit the pilot to mentally compute wind correction using available numeric data. The relatively benign nature of the previously flown K8102-K8103 RF leg did not cue the pilot in to the maneuvering required to maintain FTE on the tighter radius legs ahead. Compounding the matter were 30-38 knot winds as indicated by wind vectors on Figure 74. As the pilot made the right turn on K8104-K8105, what was a ~30 knot tailwind became a strong right crosswind; consequently, the initial bank angle was not sufficient to maintain course. As the pilot was managing the descent on the leg and the “Set course” messages, FTE began to increase. By reviewing the ground track plot, it is apparent the pilot began to correct momentarily, but FTE then begins to increase again, leading to the first 0.5 nm FTE exceedance toward the end of the leg. At this time, the pilot was verbally calling out the next waypoint and altitude criteria, with his attention momentarily set on the approach chart, possibly explaining why after making an initial correction the aircraft began to deviate again. Once the excessive course deviation was recognized, the pilot began using the TKE field for course corrections, which he noted was at the very far extent of his field of vision (on the far right edge of the GNS 430W display). Without the map, the pilot had difficulty visualizing the aircraft position relative to the RF leg reversal immediately ahead, although he was fully aware of the “S” turn due to his chart scan. As shown in Figure 74, the pilot continued making course corrections to the right after the K8105-K8106 leg became active. This caused the aircraft to fly through the centerline and to the outside of the K8105-K8106 leg. At this point, the radio chatter between the safety pilot and ATC increased significantly. Once the pilot recognized the left turn was active, he executed a more aggressive left turn, keeping the aircraft from exceeding ~0.25 nm FTE. The pilot mentioned “these are busy little guys!” referring to the “Set course” messages. As the CDI scaling narrowed, the aircraft again approached full scale deflection. The pilot recognized this condition, making one further significant left correction to establish inbound on course. The pilot then executed a stabilized approach.


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The pilot started the missed approach prior to reaching the missed approach waypoint. Consequently, the GNS 430W had not yet suspended sequencing. The pilot vocalized the missed approach procedure by saying “ok, the missed approach goes, initially, to K8109”, misinterpreting the direction of the K8107-K8108 leg while reading the paper chart. Additionally, since the pilot was task saturated with maintaining the climb and reading the chart, the pilot failed to note when the GNS 430W entered SUSP mode. The blue ‘X’ in Figure 75 shows the point at which the pilot finally pressed the SUSP key after being prompted by the safety pilot, beginning sequencing for the K8107-K8108 leg. However the pilot pressed the SUSP key twice, causing the GNS 430W to enter OBS mode, which required further prompting by the safety pilot. The safety pilot also clarified the missed approach turn direction was to the left. The pilot continued to fly the leg, still without the moving map or wind vector. Given the high crosswinds, the pilot’s bank angle was insufficient to stay on course and the aircraft drifted outside of 0.5 nm. The pilot overcorrected to the left, flying across the course centerline to the inside of the leg. After flying the remainder of the missed approach RF leg, the pilot was questioned on workload. Noting the abnormal scan, pilot ranked workload as being High. He mentioned his prior training and tendency to fly to a constant heading was creating mental difficulties while flying RF legs.

Flight 647, N4878S, Pilot 009 This flight was Pilot 009’s first flight in the Cherokee and his first RF leg approach. The pilot exceeded 0.5 nm FTE toward the end of the K8105-K8106 leg, flying outside of the leg to the final approach course. A strong right crosswind was present and the pilot was flying with the moving map for this approach. Prior to the K8104-K8105-K8106 “S” turn, the safety pilot held the subject pilot high at 5500 ft due to visibility concerns as there were scattered cloud tops at 4000 ft. After passing K8104, the safety pilot cleared the pilot down to 3800 ft from 5500 ft, at best rate of descent, after observing a break in cloud


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cover. The pilot initiated the steep descent and began making the K8104-K8105 leg simultaneously, nearly reaching the airspeed indicator’s yellow arc. The safety pilot cleared the pilot to fly “altitudes as published”; the pilot went wings level, looked down, and reviewed the chart. At this point, the pilot momentarily lost situational awareness after passing K8105 not recognizing that the K8105-K8106 leg was active. After being reminded that K8105 had already been passed, the pilot initiated the left turn but did not turn aggressively enough to fly the leg profile on course. The aircraft overshot to the outside of the leg and remained outside with full scale CDI deflection well past the K8106 FAF.


The significant weather deviation and associated steep descent is believed to have saturated the pilot’s mental capacity on the K8104-K8105 leg. The pilot was focused on flying the aircraft and making the descent as requested. Once leveled off, he returned to his normal scan but was not able to quickly determine where he was at and required safety pilot coaching. The pilot later commented that he simply “got behind the approach” further remarking that “it’s a chore”. Workload was rated High by the pilot.

Flight 649, N4878S, Pilot 010 This flight was FAA Pilot 010’s first and only flight in the Cherokee. The pilot exceeded 0.5 nm FTE toward the end of the K8105-K8106 leg, flying outside of the leg to the final approach course. The approach was flown with the Default NAV page, as the pilot expressed a preference to have more numeric data fields. Moderate turbulence was observed on the approach, and the test director noted the pilot began showing signs of fatigue on the approach due to the summer heat. The K8104-K8105 leg was executed with acceptable FTE with the pilot commenting that he was “slightly outside of the turn”. However, once the K8105-K8106 leg became active, the pilot attempted to allow the course to “come back” and was briefly distracted by having to turn on the fuel pump then cross checking his altitude with the chart. At this point, the aircraft drifted through the leg centerline. The exceedance occurred as the CDI scaling began to narrow and resulted in full scale deflection just prior to the K8106 FAF. At this point, the pilot recognized the excessive deviation and made the comment “busted!” He then executed a steeper left turn and began correcting back onto the final approach course.


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Flight 652, N4878S, Pilot 011 This flight was FAA Pilot 011’s first and only flight in the Cherokee. The pilot initially exceeded 0.5 nm FTE on the very first RF leg given as a familiarization maneuver for the aircraft. As can be seen from Figure 78, the pilot initially misjudged the amount of bank angle required to make the turn and ended up cutting inside the leg. Upon realizing this, the pilot leveled off to intercept instead of correcting to the left, very nearly resulting in 0.5 nm FTE at one point. Due to the steep intercept angle, the pilot overshot to the outside of the leg and then banked steeply back to the right to correct. Here again the level of aggressiveness in overcorrecting caused the 0.5 nm FTE exceedance to the inside of the leg. As this leg was very early in the flight, fatigue was not a factor. Workload was low as the leg was made in level flight. The pilot was clearly relaxed, simply trying to learn the RF leg flying technique. After passing K8135, a 360° turn was executed by the safety pilot to set up for the first RWY 21 approach.


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After flying the RWY 21 approach once, the pilot flew the K8129-K8132 305 degree arc on the missed segment (the second RWY 21 approach was skipped due to time constraints). The pilot switched to the Default NAV page, and by his choice continued to use this page for the RWY 3 approach. The pilot flew the RWY 3 approach, with acceptable FTE until reaching the K8104-K8105-K8106 series of legs. Choosing to continue flying without the moving map, the pilot banked right tightly and cut to the inside of the K8104-K8105 leg. When crossing course to the outside of the leg, the pilot recognized the condition and leveled off. As the aircraft crossed the course centerline, the GNS 430W sequenced to the K8105-K8106 leg. The pilot began banking right to re-intercept course and overcompensated, flying across the course centerline at a high angle of intercept (40°). At this point the pilot stated that he “could see the value of the map”. The left turn correction was too little and the aircraft exceeded 0.5 nm FTE on the outside of the K8105-K8106 leg. The pilot recognized this and corrected left again saying “I’m going to go right over to the final approach course”. At this point the pilot noticed the advisory glidepath was alive, and yet, due to workload and concern for the off-course condition, flew through the glidepath. The pilot was not able to bring the aircraft back to course center, resulting in full scale deflection at the FAF.


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After flying the final approach segment, the pilot executed the missed approach. He re-sequenced the GNS 430W by pressing SUSP and configured the aircraft for climb. While configuring the aircraft for climb, the pilot vocalized: “It’s gonna be a right leg, going to 3700 ft’. After several moments the pilot recognized the “backwards” course deviation data and stated aloud “I’m a little confused on how we got right of course”. The safety pilot then asked the pilot for clarification of turn direction, whereupon the pilot immediately recognized the error and began correcting left. However, 0.5 nm FTE was momentarily exceeded before the pilot brought the aircraft back on course.



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Appendix C – Data Post-Processing A script searches the post-processed data points to locate RF legs and straight legs and generates separate files for each leg. To detect the beginning of an RF leg:

• The GPS position must be within the RF leg’s “sweep” • The GPS position must be within 1 nm of the desired RF leg path • The GPS track angle must be within 30 degrees of a tangent to the RF leg arc at the “Start

Waypoint” Once the start of an RF leg has been found, the script checks each subsequent data point to determine if it is a continuation of the current RF leg using the following criteria:

• The GPS position must be within the RF leg’s “sweep” • The GPS position must be within 1 nm of the desired RF leg path • The GPS track angle must be within 65 degrees of a tangent to the arc at the data point

Figure 81 depicts the process of detecting an RF leg for the purpose of calculating FTE.

Figure 81. Detecting an RF Leg for Calculating FTE

Straight legs are detected by placing a gate at the start waypoint, and then placing a gate every tenth of a nautical mile until the end waypoint. A gate is comprised of two points, one 2 nm to the left and one 2 nm to the right of the desired path, and an imaginary line between the two points. The script uses the flight data to determine which data point is closest to being on the imaginary line for each gate. The data points that are found to be in a gate are marked with the gate number in the files. This method of determining aircraft position provides a known number of evenly distributed data points. The straight leg data points are used for plots and FTE calculations while the RF leg data points are used for vertical profile plots to provide an evenly scaled along-track distance which the method depicted in Figure 81 does not provide. Figure 82 shows gates on part of RWY 3 approach.


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Figure 82. Detecting a Straight Leg and RF Leg Vertical Profile


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Appendix D – Abbreviations 14 CFR Title 14 of the Code of Federal Regulations AC Advisory Circular ACO Aircraft Certification Office ADI Attitude Direction Indicator AEG Aircraft Evaluation Group AFM Aircraft Flight Manual AFS FAA Flight Standards AMEL Airplane Multi Engine Land AML Approved Model List AP Autopilot APS Aircraft Preparation Sheet ARINC Aeronautical Radio, Inc. ARP Airport Reference Point ASCII American Standard Code for Information Interchange ASEL Airplane Single Engine Land ATP Airline Transport Pilot BRG Bearing to waypoint CDI Course Deviation Indicator CFI Certificated Flight Instructor CFII Certificated Flight Instructor – Instrument Rating CFR Code of Federal Regulations CI Confidence Interval CSTA Chief Scientific and Technical Advisor DIS Distance to waypoint DME Distance Measuring Equipment DTK Desired Track EFIS Electronic Flight Information System ETE Estimated Time En route FAA Federal Aviation Administration FAF Final Approach Fix FD Flight Director FGS Flight Guidance System ft Feet FMS Flight Management System FTE Flight Technical Error GA General Aviation GNSS Global Navigation Satellite System GPS Global Positioning System GS Ground Speed GSL Geometric Altitude Relative to Mean Sea Level GST Garmin System Test HF Human Factors HFOM Horizontal Figure of Merit HSI Horizontal Situation Indicator Hz Hertz (cycles per second) ICAO International Civil Aviation Organization IFPP Instrument Flight Procedure Panel IFR Instrument Flight Rules kt Knots (nautical miles/hour) KTAS Knots True Airspeed LNAV Lateral Navigation LNAV/VNAV Lateral Navigation/Vertical Navigation LOC Localizer


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LPV Localizer Performance with Vertical guidance MAP Missed Approach Point MDA Minimum Descent Altitude MEI Multi-Engine Instructor MFD Multi-Function Display MFW Multi-Function Window MLS Microwave Landing System MSL Mean Sea Level m Meters NASA National Aeronautics and Space Administration ND Navigation Display NLR Nationaal Lucht- En Ruimtevaartlaboratorium (National Aerospace Laboratory),

the Netherlands nm Nautical Miles n/a Not Applicable OBS Omni-Bearing Selector OEA Obstacle Evaluation Area OTA Other Transaction Authority PAR Precision Approach Radar PFD Primary Flight Display PIC Pilot In Command PTS Airman Practical Test Standards Radar Radio Detection and Ranging RF Radius-to-Fix RNAV Area Navigation RNP Required Navigation Performance RTCA RTCA, Inc., formerly Radio Technical Commission for Aeronautics SAD Small Aircraft Directorate SBAS Satellite Based Augmentation System SEP Single Engine Piston STC Supplemental Type Certificate TAA Technically Advanced Aircraft TAS True Airspeed TC Type Certificate TKE Track angle Error TP Technical Paper / Technical Publication TRK Ground Track TSO Technical Standard Order US United States VDI Vertical Deviation Indicator VFOM Vertical Figure of Merit VHF Very High Frequency VMC Visual Meteorological Conditions VOR VHF Omni-directional Range WAAS Wide Area Augmentation System WGWHL Working Group of the Whole XTK Cross(X)-Track Error


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Appendix E – Referenced Documents 1) FAA, AC 20-138C, Airworthiness Approval of Positioning and Navigation Systems, May 8, 2012 2) FAA, AC 20-163, Displaying Geometric Altitude Relative to Mean Sea Level, July 9, 2009 3) FAA, AC 90-105, Approval Guidance for RNP Operations and Barometric Vertical Navigation in

the U.S. National Airspace System, January 23, 2009 4) FAA, AIM, Aeronautical Information Manual, February 9, 2012 5) FAA, FAA-H-8083-15A, Instrument Flying Handbook, 2008 6) FAA, FAA-H-8261-1A, Instrument Procedures Handbook, 2007 7) FAA, FAA-S-8081-4E, Instrument Rating Practical Test Standards for Airplane, Helicopter, and

Powered Lift, w/changes 1, 2, & 3, January 2010 8) FAA, NextGen Implementation Plan, March 2012 9) FAA, Order 8260.52, United States Standard for Required Navigation Performance (RNP)

Approach Procedures with Special Aircraft and Aircrew Authorization Required (SAAAR), June 3, 2005

10) FAA, Order 8260.54A, The United States Standard for Area Navigation (RNAV), December 7, 2007

11) FAA, Order 8260.58, United States Standard for Performance Based Navigation (PBN) Instrument Procedure Design, September 21, 2012

12) FAA, TSO-C129a, Airborne Supplemental Navigation Equipment Using the Global Positioning System (GPS), February 20, 1996

13) FAA, TSO-C146c, Stand-Alone Airborne Navigation Equipment Using the Global Positioning System Augmented by the Satellite Based Augmentation System, May 9, 2008

14) FAA/Garmin, DTFAWA-11-A-80009 Mod 2, Memorandum of Agreement DTFAWA-11-A-80009 Between Federal Aviation Administration (FAA) and Garmin International, Inc., Effective May 2, 2012, Signed August 6, 2012

15) ICAO, IFPP/10 WGWHL Working Paper (WP) 28 rev. 12, RF Design Criteria, March 28, 2012 16) The MITRE Corporation, F083-L08-047-001, Analysis of Advanced Flight Management Systems

(FMSs), Flight Management Computer (FMC) Field Observations Trials, Radius-to-Fix Path Terminators, July 31, 2008

17) The MITRE Corporation, F03L-L12-013, Analysis of Advanced Flight Management Systems (FMSs), Flight Management Computer (FMC) Field Observations Trials: Standard Instrument Departure with Radius-to-Fix (RF) Path Terminators, July, 2012

18) The MITRE Corporation, Document No. MP120612, “FOR TEST ONLY” Instrument Procedures for Avionics Hardware and Software Development and Testing, October 2012

19) NASA, Technical Paper (TP) 3255, Manual Flying of Curved Precision Approaches to Landing with Electromechanical Instrumentation: A Piloted Simulation Study, February 1993

20) NLR, Technical Publication (TP) 91446 L, Flight Simulator Evaluation of Advanced MLS Procedures, November 29, 1991

21) RTCA, DO-208, Minimum Operational Performance Standards for Airborne Supplemental Navigation Equipment Using Global Positioning System (GPS), July 12, 1991

22) RTCA, DO-229D, Minimum Operational Performance Standards for Global Positioning System/Wide Area Augmentation System Airborne Equipment, December 13, 2006

23) RTCA, DO-283A, Minimum Operational Performance Standards for Required Navigation Performance for Area Navigation, October 28, 2003

Garmin Radius to Fix Leg Project Report -...

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