Design of a System for Aircraft Fuselage Inspection...Widespread Fatigue Damage Design of a System...

Faculty Advisor Dr. Lance Sherry

Sponsor Integrity Applications Incorporated

Design of a System for Aircraft Fuselage Inspection Rui Filipe Fernandes Kevin Keller Jeffrey Robbins

Reduce Inspection Time Improve Crack Detection

Reduce Maintenance Cost

jchadwickco.com

Before

Crack

gasolinealleyantiques.com

aerospacetestinginternational.com

After

Computer Aided Detection

Manual Inspection Automated Inspection

Fatigue Damage

mechanicsupport.blogspot.com

Design of a System for Aircraft Fuselage Inspection 2

Agenda

Context • Aging Aircraft & Maintenance • Current Fuselage Inspection Process • Stakeholder Analysis • Problem and Need

Concept Of Operations Method of Analysis

Project Plan

3

Context: Aging Aircraft & Maintenance Aircraft Age Statistics

Min: 5.1 years Mean: 10.6 years Max: 24.9 years airsafe.com

Design of a System for Aircraft Fuselage Inspection

Average Aircraft Age Continues to Increase

4

iata.org

Context: Aging Aircraft & Maintenance Increasing Average Age


Rank Carrier Average Age

4 US Airways 14.7

5 Southwest 14.6

6 United 13.7

International Air Transport Association Bloomberg

Domestic Carriers among the oldest fleets

bloomberg.com

5

iata.org travelpulse.com

Widespread fatigue damage (WFD) is age-related structural fatigue cracking

Context: Aging Aircraft & Maintenance Widespread Fatigue Damage


WFD Leading to Aircraft Retirement


Southwest Airlines flight accidents: • Flight 812

• Fuselage skin approximately 60” x 8” had fractured above the left wing causing rapid depressurization

• Flight 2294 • Fuselage skin had fatigue cracking and

fracture of 18” x 12” flap causing rapid depressurization

http://www.ntsb.gov/investigations/AccidentReports/Pages/AAB1302.aspx

http://www.ntsb.gov/_layouts/ntsb.aviation/brief.aspx?ev_id=20090714X83900&key=1

lessonslearned.faa.gov

April 28, 1988, Boeing 737-200 Missing fuselage section caused by failure of lap joint at stringer S-10L

Context: Aging Aircraft & Maintenance Aloha Airlines Flight 243

Improved Maintenance Required

lessonslearned.faa.gov


Southwest Airlines flight accidents: • Flight 812

• Fuselage skin approximately 60” x 8” had fractured above the left wing causing rapid depressurization

• Flight 2294 • Fuselage skin had fatigue cracking and

fracture of 18” x 12” flap causing rapid depressurization

http://www.ntsb.gov/investigations/AccidentReports/Pages/AAB1302.aspx

http://www.ntsb.gov/_layouts/ntsb.aviation/brief.aspx?ev_id=20090714X83900&key=1

ntsb.gov

April 1, 2011, Boeing 737-300

Emergency Airworthiness Directive AD 2011-08-51

136 Aircraft Inspected:

4 Found With Cracks Around 1 Rivet 1 Found With Cracks Around 2 Rivets

40,000 – 45,000 Total Cycles

Context: Aging Aircraft & Maintenance Southwest Airlines Flight 812

Preventative Maintenance Failed to Detect Indicators of Fatigue

Factors that contribute to aircraft deterioration include: • Inflight vibrations • Number of takeoffs and landings • Fuselage pressurization cycles

30,000 ft. (4.38 psi)

8

newsweek.com

Context: Aging Aircraft & Maintenance Deterioration


Fatigue Caused by Repeated Pressurization Cycles

9

Context: Aging Aircraft & Maintenance Fuselage Pressurization Cycles


Stress From Change in Pressure Leads to Structural Fatigue

engineeringtoolbox.com

A 125 flight hours

or 200–300 cycles 20–50 man-hours Overnight

B Approximately every 6 months 120–150 man-hours 1-3 Days

C Approximately every

20–24 months Up to 6,000 man-hours 1–2 weeks

D Approximately every 6 years Up to 50,000 man-hours 2 Months

faa.gov

10

Time to Complete Inspection Type Time Between Inspections Number of Man Hours Required

Context: Aging Aircraft & Preventative Maintenance Scheduled Aircraft Maintenance Programs


Maintenance Intervals, A Delicate Balance of Risk and Cost

Context: Aging Aircraft & Maintenance Median Crack Growth Curve

11 Design of a System for Aircraft Fuselage Inspection

Minimize Number of Cracks Occurring Before Inspection

Earliest Expected Cracking

Latest Expected Cracking

Time of Inspection

Critical Crack Length

Cra

ck L

engt

h

Time

Median crack growth curve

Yang JN, Manning SD (1990) Stochastic Crack Growth Analysis Methodologies For Metallic Structures

Context: Aging Aircraft & Maintenance Distribution of Time to Critical Crack Length


Time of Inspection


Probability of cracks occurring BEFORE scheduled Maintenance

Minimize Probability of Cracks Occurring Before Inspection

Cra

ck L

engt

h

Time

Distribution of Time to Critical Crack Length


Context: Aging Aircraft & Maintenance Distribution of the Crack Length


Probability of crack growth beyond critical length


Time of Inspection

Minimize Crack Growth Beyond Critical Length

Distribution of the crack length

Cra

ck L

engt

h

Time


Context: Aging Aircraft & Maintenance Stochastic Crack Growth Model


Probability of crack growth beyond critical length


Time of Inspection

Probability of cracks occurring BEFORE scheduled Maintenance

Earliest Expected Cracking

Latest Expected Cracking

Early Crack Detection Can Minimize Corrective Maintenance

Distribution of Time to Critical Crack Length

Distribution of the crack length

Median crack growth curve

Cra

ck L

engt

h

Time


Context: Aging Aircraft & Maintenance Stochastic Crack Growth Model


The inspection schedule is chosen such that the probability of crack to grow beyond the critical crack size is less than 1 in 10,000,000

Taghipour, S., Banjevic, D., Jardine, A. K. S., “Periodic inspection optimization model for a complex repairable system”, Reliability Engineering and System Safety, Vol 95, 2010, Pg 944-952


16

When it finds an unsafe condition exists in the product and the condition is likely

to exist or develop in other products of the same type design

When Does FAA Issue Airworthiness Directives?

Context: Aging Aircraft & Corrective Maintenance Airworthiness Directive (AD)

Airworthiness Directives are legally enforceable regulations issued by the Federal Aviation Administration (FAA) in accordance with 14 CFR part 39 to correct an unsafe condition in a product

faa.gov


Corrective Maintenance is Disruptive to Airlines and Results in Unplanned Revenue Loss

Context: Aging Aircraft & Maintenance Title 14 of the Code of Federal Regulations (CFR)

17

faa.gov


Inspection Process Governed by Title 14 (CFR)

Changes in maintenance procedure is regulated by the FAA

18

Context: Current Fuselage Inspection Process Visual Inspection Process

• Job Cards Used For Every Component

• Many Human Factors/Prone to Errors

• 41.8% detected • 14.1% type 1 error (Misdiagnosed) • 43.7% type 2 error (Missed Detection)

• Non-Destructive Inspection (NDI)

methods used to assess marked regions


Inspection Process Begins with Visual Inspection

VISUAL INSPECTION RESEARCH PROJECT REPORT ON BENCHMARK INSPECTIONS FAA Aging Aircraft NDI Validation Center

19

Context: Current Fuselage Inspection Process Representative Regions of Aircraft

FAA Aging Aircraft NDI Validation Center Report

JC 501 Midsection Floor

JC 502 Main Landing Gear Support

JC 503 Midsection Crown (Internal)

JC 504 Galley Doors (Internal)

JC 505 Rear Bilge (External)

JC 506 Left Forward Upper Lobe

JC 507 Left Forward Cargo Compartment

JC 508/509 Upper and Lower Rear Bulkhead Y-Ring

JC 510 Nose Wheel Well Forward Bulkhead

JC 511 Lap-Splice Panels


ntl.bts.gov

Representative Regions Require Different Inspection Techniques

20

Context: Current Fuselage Inspection Process Current Visual Inspection Process


Inspection Process Modeled In Simulation

95704520

6

5

4

3

2

1

0

Shape 5.008

Scale 9.652

N 12

Inspection Time (Minutes)

Fre

qu

en

cy

Gamma

Inspection Time of Lap-Splice Panels (Minutes)


21

Context: Stakeholder Analysis Interactions, Tensions and Gap


Context: Problem and Need


Issues Consequences

Heavy D Check Inspection Process Requires up to 2 months to Complete

Aircraft maintenance/repair 12-15% of total airline annual expenditures

In 2013, 3.5 million flight cycles logged over 2,660 aircraft

Average $2,652 per flight cycle Amounts to $9.4 billion total

43.7% Type 2 Error (Missed Detection) 11 Airworthiness Directives Issued to Address Fuselage Cracking

Solutions Benefits

Reduce Time Required for Inspections Decreased Inspection Costs

Early Detection of Structural Fatigue Improved Scheduling of Preventive Maintenance / Minimize Corrective Maintenance Required

Reduce Human Error Improved Crack Detection Capabilities

Problem

Need

Current Inspection Process

Improved Inspection Process

Time

Cost

Quality

Win-Win: New Technology Introduced to Inspection Process

23

Agenda

Context Concept of Operations

• Operational Scenario • Design Alternatives • System and Design Requirements • Automated Inspection System IDEF.0

Method of Analysis Project Plan


24

Concept of Operations: Operational Scenario Levels of Human Involvement


Inspection Method

ConOps Introduces New Technology to Inspection Process

1 – Manual 2 - Enhanced

ntl.bts.gov aviationpros.com aviationpros.com

3 - Autonomous

25

Concept of Operations: Operational Scenario Non-Contact Delivery Method


Potential Implementation of Synthetic Aperture Imaging Technology

Track

Synthetic Aperture Imaging Device

26

Concept of Operations: Design Alternatives Exterior vs. Interior Surfaces

Exterior Surfaces Interior surfaces

Human Visual Human Visual

Human Remote Visual

Human Enhanced Visual Human Enhanced Visual

Robotic Crawler*

Non-Contact Automated Scan*

* Utilizes Image Processing Software


Limitations of Delivery Method Based on Region of Aircraft

27

Inspection Method

Time Cost Quality

Visual Visual Inspection time Documentation time

Hourly wage of inspectors Training Cost Cost of Human Errors

Limited by human eyesight Prone to human error Human decision making only

Enhanced Visual

Increased Inspection Time Imaging Time Evaluation Time Documentation Time

Hourly wage of inspectors Training/certification Maintenance Cost Cost of Human Errors

Improved by computer

aided decision making Interpretation/ Evaluation of data prone to human errors

Automated Faster Inspection Time

Imaging Time

Software Processing

Time

Acquisition/Development Cost Installation Cost Training Cost Maintenance Cost

Software for image

processing reduces

errors and eliminates

dependence on human

decision making

PRO CON

Concept of Operations: Design Alternatives Benefits by Category


28

Context: System Requirements Mission & Functional Requirements

Mission and Functional Requirements

M.1 The system shall reduce the airframe maintenance cost per flight hour of an aircraft by 5%

F.1. The system shall cost no more than $X to operate annually

F.2. The system shall accrue no more than $X in Type 1 errors annually

F.3. The system shall require an initial investment of no more than $X

F.4. The system shall process captured images at a rate of X m2 per Y seconds

M.2 The system shall detect cracks in the airframe of aircraft both visible, and not visible, by a human

inspector

F.1. The system shall detect cracks with a volume exceeding X mm3

F.2. The system shall have a Type 2 error rate of no more than X%

F.3. The system shall distinguish between cracks and pre-built parts of the aircraft

F.4. The system shall capture an image of the airframe of the aircraft of dimensions X meters by Y meters

without repositioning

M.3 The system shall reduce the variance of the airframe inspection process by X labor-hours

F.1. The system shall maintain the upper bound of a complete visual inspection at no more than X labor-

hours

F.2. The system shall reduce the variance of the visual inspection process by X labor-hours

M.4 The system shall allow aircraft to meet Federal Aviation Administration airworthiness standards

Context: System Requirements


29

Non-Functional Requirements

Maintainability

1. The system shall produce traceable error codes upon malfunction.

2. The system shall allow the replacement of individual parts.

Reliability

1. The system shall experience no more than X system failures per month.

2. The system shall require no more than X hours of preventative maintenance per month.

Usability

1. The system shall require no more than 40 hours of training for technician certification.

Context: Non-Functional Requirements


30

Concept of Operations: Design Requirements


Design Requirements

Enhanced Visual (Handheld)

D.1 The system shall weigh no more than X lbs.

D.2 The system shall accurately scan from a distance of up to X m.

Robotic Automated Inspection System

D.1 The system shall inspect at a rate of X cm3/s.

D.2 The system shall support autonomous function.

D.3 The system shall accept initial input from an operator.

D.4 The system shall utilize integrated software.

D.5 The system shall store the location of airframe problem areas.

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Concept of Operations: Automated Inspection System IDEF.0


32

Agenda

Context Operational Concept/Approach Method of Analysis

• Stochastic Simulation • Model Boundaries & Simulation Inputs/Outputs • Simulation Requirements • Simulation of Visual Inspection By Airframe Region • Case Study Variables & Assumptions • Validation

• Design of Experiments

Project Plan


33

Method of Analysis: Stochastic Simulation Model Boundaries and Simulation Inputs/Outputs


Inputs Outputs

• What design alternatives are utilized • Where design alternative are utilized

• Overall time for inspection • Time per section • Cracks detected per section • Type 1 errors per section • Type 2 errors per section

Aircraft Maintenance

Simulation

Uninspected aircraft

Inspected aircraft

• Time per inspection • Inspection & Section

• Cost per inspection • Labor hours • Implementing alt.

• Quality per inspection • Type 1 & 2 errors

Manual • Human • Handheld

Automated • Visual or thermal • Track or crawler

34

Method of Analysis: Stochastic Simulation Simulation Requirements

Simulation Requirements

The simulation shall break down the aircraft into ten sections, each having its own queue

The simulation shall support multiple inspectors processing multiple sections

The simulation shall assign a set number of cracks to each section of the aircraft

The simulation shall terminate upon the inspection of all ten sections of the aircraft

The simulation shall collect statistics on total time required for inspection

The simulation shall collect statistics on total time to complete each section

The simulation shall collect statistics on cracks detected per section

The simulation shall collect statistics on crack type one errors

Mark a crack where one would not register with an NDT

The simulation shall collect statistics on crack type two errors

Fail to mark a crack that exists


35

Method of Analysis: Stochastic Simulation Visual Inspection By Airframe Region


Initialization

Process

Statistics

36

Method of Analysis: Stochastic Simulation Initialization


Assignments

Manual / Automated (binary)

Process Restrictions (binary)

Process Distributions (minutes)

Crack Detection Rate (%)

Type 1 Error Rate (%)

Type 2 Error Rate (%)

37

Method of Analysis: Stochastic Simulation Process


38

Method of Analysis: Stochastic Simulation Statistics


39

Method of Analysis: Stochastic Simulation Distributions At a Glance



40

Method of Analysis Design of Experiments


Run Internal /

External

Technology Delivery Method

Type One Error Rate

Type Two Error Rate

Inspection Time

Cost of Inspection

1 Internal Human -- % % Hours Dollars

External Human --

2 Internal Human --

External Thermographic Crawler

3 Internal Synthetic Aperture Handheld

External Thermographic Crawler

…

Inputs Outputs

41

Simulation Preliminary Results Sample Output (Time per Process)

Section Minutes Half-Width


42

As-Is Simulation Preliminary Results Validation (Expected vs Simulation)

Section Actual (mins) Simulated (mins) Diff (mins) % err

1 122 116.47 -5.53 -4.53

2 28 27.83 -0.17 -0.61

3 75 75.38 0.38 0.51

4 68 67.71 -0.29 -0.43

5 37 36.1 -0.9 -2.43

6 104 105.64 1.64 1.58

7 95 100.23 5.23 5.51

8 35 34.68 -0.32 -0.91

9 16 15.2 -0.8 -5.00

10 48 49.56 1.56 3.25


Actual Total (mins) Sim Total (mins) Diff (mins) % err

628 628.81 0.81 <0.1%

Sim Half Width (mins)

6.18

43

Agenda

Context Operational Concept/Approach Method of Analysis

Project Plan

• WBS/Schedule • Critical Path/Project Risks • Budget/Performance


Project Plan: Work Breakdown Schedule

44

Aircraft Inspection

Project

1.1

Management

1.1.1 Timesheets

1.1.2 Acc.Summary

1.1.3

Email Communication

s

1.1.4

Sponsor Meetings

1.1.5 Meetings with

Professors

1.1.6 Individual Meetings

1.1.7

Team Meetings

1.1.8

WBS Upkeep

1.2 Research

1.2.1

Lead Initial Research

1.2.2 Kick-off

Presenation Research

1.2.3 Team Research

1.3

CONOPS

1.3.1 Context Analysis

1.3.2 Stakeholder

Analysis

1.3.3 Problem

Statement

1.3.4 Need Statement

1.3.5 Operational

Concept

1.3.6 System

Boundary

1.3.7 System

Objectives

1.3.8 Statement of

Work

1.3.9 Budget

1.3.10 Project Risks

1.4

Originating Requirements

1.4.1 Stakeholders Requirements

1.4.2 Performance Requirements

1.4.3 Application

Requirements

1.4.4 Analysis of

Requirements

1.4.5 Qualify the

qualification system

1.4.6 Obtain Approval

of Syst. Documentation

1.4.7 Functional

Requirements

1.4.8 Design

Requirements

1.5 Design

Alternatives

1.5.1 Develop Design

Alternatives

1.6 Analysis

1.6.1 Initial

Simulation Analysis

1.6.2 Sensitivity Analysis

1.7 Test

1.7.1 Verification and

Validation

1.8 Design

1.8.1 Initial Design of

Experiment

1.8.2 Refine DoE

1.9 Simulation

1.9.1 Simulation

Requirements

1.9.2 Simulation

Design

1.9.3 Simulation

Programming

1.10 Testing

Simulation De-bugging

1.11 Presentations

1.11.1 Brief 1

1.11.2 Brief 2

1.11.3 Brief 3

1.11.4 Brief 4

1.11.5 Faculty

Presentation

1.11.6 Final Fall

Presentation

1.12 Documentation

1.12.1 Preliminary Project Plan

1.12.2 Proposal

1.13 Competitions

1.13.1 Conference

Paper

1.13.2 Poster

1.13.3 UVA

1.13.4 West Point


1.1 Management 1.2 Research 1.3 CONOPS 1.4 Originating Requirements 1.5 Design Alternatives 1.6 Analysis 1.7 Test (V/V) 1.8 Design 1.9 Simulation 1.10 Testing (Simulation) 1.11 Competitions

45

Project Plan: Critical Path

Critical Path 1.4 Originating Requirements 1.5 Design Alternatives 1.6 Analysis 1.7 Test 1.8 Design 1.9 Simulation 1.10 Testing


46

Project Plan: Project Risks

Critical Tasks Foreseeable Risk Mitigation Routes

Acquire technology specifications

from Sponsor

Sponsor does not share information Alter design to trade off analysis of

crack inspection methods

Acquire data on inspection tasks Data is not available/accessible Use reasonable estimates based on

available data

Quantify requirements Data is not available/accessible Use reasonable estimates based on

available data

Sensitivity Analysis Data does not correspond to industry

practices

Ensure simulation is built correctly,

may need further development


47

Project Plan: Budget/Performance

31-Aug 7-Sep 14-Sep 21-Sep 28-Sep 5-Oct 12-Oct 19-Oct

1 2 3 4 5 6 7 8

1 Management $6,100.17 $913.40 $1,130.87 $1,652.81 $598.06 $543.69 $304.47 $521.94 $434.95

2 Research $3,958.05 $608.93 $565.44 $565.44 $521.94 $391.46 $478.45 $565.44 $260.97

3 CONOPS $1,652.81 $0.00 $0.00 $260.97 $391.46 $652.43 $173.98 $0.00 $173.98

4 Originating Requirements $391.46 $0.00 $0.00 $0.00 $0.00 $304.47 $0.00 $43.50 $43.50

5 Design Alternatives $217.48 $0.00 $0.00 $0.00 $0.00 $0.00 $130.49 $86.99 $0.00

6 Analysis $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00

7 Test $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00

8 Design $565.44 $0.00 $0.00 $0.00 $521.94 $0.00 $0.00 $0.00 $43.50

9 Simulation $1,261.36 $0.00 $0.00 $0.00 $217.48 $217.48 $347.96 $391.46 $86.99

10 Testing $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00

11 Presentations $3,349.12 $86.99 $86.99 $1,000.39 $391.46 $565.44 $521.94 $217.48 $478.45

12 Documantation $826.41 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 $826.41

13 Competitions $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00

Total Budgeted Hours 2,125 40 50 60 60 60 60 60 80

Total Budgeted Cost $92,426.88 $1,739.80 $2,174.75 $2,609.70 $2,609.70 $2,609.70 $2,609.70 $2,609.70 $3,479.60

Cumulative Planned Value (PV) $1,739.80 $3,914.55 $6,524.25 $9,133.95 $11,743.65 $14,353.35 $16,963.05 $20,442.65

Planned Value (PV) or Budgeted Cost of Work Scheduled (BCWS)

WBS Task Name TBC

-$518.68 -$1,075.78 -$463.95 $466.03 $1,672.74 $2,065.16 $1,808.75 $2,674.24

-649.16 -1597.72 -115.99 846.61 2118.56 1858.56 819.24 553.86

0.68 0.68 0.93 1.05 1.14 1.15 1.11 1.15

0.63 0.59 0.98 1.09 1.18 1.13 1.05 1.03

$136,382.63 $135,343.48 $99,118.41 $88,111.11 $81,273.83 $80,653.05 $83,025.53 $80,654.84

Project Performance Metrics

Cost Variance (CV = EV - AC)

Schedule Variance (SV = EV - PV)

Cost Performance Index (CPI = EV/AC)

Schedule Performance Index (SPI = EV/PV)

Estimated Cost at Completion (EAC)


Hourly Rate: $43.50/hr

48

Project Plan: Budget/Performance Earned Value Weeks 1-38


49

Project Plan: Budget/Performance Earned Value Weeks 1-11


50

Project Plan: Budget/Performance CPI/SPI Weeks 1-11


51

Future Work


• Determine attributes of design alternatives • Complete design of experiment • Sensitivity analysis • Quantify requirements • Utility - cost analysis • Conclusions

Now

February 2016

53

Utility Hierarchy


Utility

Time (-) Quality

Type 1 Error Rate (-)

Type 2 Error Rate (-)

(+) – Higher is better (-) – Lower is better

Non-Functional

Maintainability (+)

Reliability (+)

54

IDEF0 Analyze Data


Arena Total Time


55

56

Project Plan: Budget/Performance

Occupation 2012 Median Pay

Aerospace-Engineers $49.07/hr

Industrial-Engineers $37.92/hr

United States Department of Labor Bureau of Labor Statistics Occupational Outlook Handbook

Average: $43.50/hr

http://www.bls.gov/ooh/architecture-and-engineering/aerospace-engineers.htm http://www.bls.gov/ooh/architecture-and-engineering/industrial-engineers.htm


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Technology Description Contact Non-Contact

Thermographic Imaging

Heats area 1-2 degrees, algorithm determines if problematic

Contact

Synthetic Aperture Imaging

Captures 2-D images at different angles to create a 3-D image

Non-Contact

Concept of Operations: Design Alternatives Design Alternatives


Delivery Method

Description Level of Human Involvement

Applicable Technology

Robotic Crawler Travels along outside of aircraft, scans designated areas.

Autonomous Synthetic Aperture, Thermographic

Robotic Arm Utilizes track to move around.

Autonomous Synthetic Aperture

Handheld Scanner carried by inspector

Enhanced Synthetic Aperture

Design of a System for Aircraft Fuselage Inspection...Widespread Fatigue Damage Design of a System...

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