Chapter 4 the Airfield

Chapter 4 The airfield

Outline• The components of an

airport• The airfield• Runways• Taxiways markings/lightings• Other airfield

markings/airfield areas/ airfield lighting/airfield signage

• Air Traffic Control towers• Wind indicators• Security infrastructure on

airfields

• Navigational aids (NAVAIDS) located on airfields

• Non-directional radio beacons (NDB)

• Very-high-frequency omni-directional range radio beacons (VOR

• Instrument Landing System (ILS)

• Microwave Landing System (MLS)

• GPS Local Area Augmentation System (LAAS)

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The components of an airport (1)

The components of an airport are typically placed into two categories:

The airside – consisted of airfield and airspaceThe airfield component includes all facilities located on the

physical property of the airport to facilitate aircraft operations, such as Runways, taxiways, aircraft parking areas (aprons), navigational aids, lighting systems, signage and markings. The air rescue and fire fighting (ARFF) facilities, snow plowing, aircraft de-icing and fuel facilities are located near the airfield.

The airspace – surrounding an airport, of the ground, where aircraft maneuver, after takeoff, before landing or pass through on the way to another airport Pg.100

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The landside – consisted of terminal and ground access.

The airport terminal – component is designate to facilitate the movement of passengers and luggage from landside to aircraft on the airside.

The airport’s ground access component accommodates the movement of ground-based vehicles to and from the surrounding city area, as well between the various buildings found on the airport property (premises) pg.100

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Runways - The single most important facility on the airfield. Regulations on the management and planning of runway systems are most comprehensive and strict in airport management.

Utility runways are designed to handle operations of propeller-driven aircraft weighing 12,500 pounds or less.

Runway orientationWhen the Wright brothers made their first flight at Kitty Hawk in 1903, there were no runaways to facilitate the flight. However, certain conditions existed during the flight that led directly to the orientation of today’s runways.

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Runway Orientation (continued)

Runways are defined by their orientation to magnetic north divided by 10. E.g.;

A runways oriented to the east, i.e., 90 degrees from magnetic north is identified as runway 9. A northerly oriented runway is identified as runway 36. The construction of this runway would take into consideration the direction of headwind. If a runway is used in a easterly and westerly direction (i.e., 270 degrees from magnetic north) would be identified as runway 9 - 27. Pg.103

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Runway Orientation (continued)

However, certain conditions existed during the flight that led directly to the orientation of today’s runways. The appropriate direction to take off an aircraft was against the wind (headwind). So same wind direction, if to land an aircraft. Thus, the runways that are oriented into the prevailing winds is known as the primary runways.Some airports are facilitated with crosswind runways and

parallel primary runways Pg.103

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Runway Pavements

The first paved runway was constructed in 1928 at Ford Terminal in Dearborn, Michigan. Before that it was a grass field.

Runways pavements may be constructed of flexible (asphalt) or rigid (concrete) materials. The thickness of pavements may range from 6 inches for light aircraft to over 3 feet for large commercial aircraft.

The life of asphalt runways may last between 15 years and 20 years pg.105/6

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Runway markings

Three (3) types of marking for runways:

1. Visual

2. Non-precision instrument

3. Precision instrument – such as Instrument Landing System (ILS) or precision approach radar (PAR) that provide both horizontal vertical guidance to the runway. All runway markings are painted in white.Pg.106

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Runway threshold markings

These markings help identify the beginning of the runway that is available for landing. In some instances, the landing threshold may be relocated or displaced due to construction, maintenance, or other activities being carried out. Pg.107

Relocated threshold is marked by a runway threshold bar measuring 10-foot-wide white-painted stripe that extends across the width of the runway. The distance between the beginning of the runway pavement and the relocated threshold is marked by yellow-painted chevrons, which indicates that the pavement is unusable for landing, takeoff or taxing of aircraft. Pg.108

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A Displaced threshold

Displaced of the runway threshold reduces the length of runway available for landing.

A 10-foot-wide white threshold bar is located across the width of runway at the displaced threshold. White arrows are located along the centre line in the area between the beginning of the runway and displaced threshold. White arrow heads are located across the with of the runway prior to the threshold bar. pg. 108

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No of Runway Threshold Stripes

Runway Width, ft (m)

60 (18)

75 (23)

100 (30)

150 (45)

200 (60)

Number of Stripes

4

6

8

12

16Pg. 109

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Runway aiming points

Runway aiming points serve as visual for a landing aircraft. These two rectangular markings consist of broad white stripe located on each side of the runway centerline and approximately 1,000 feet (300 m) from the landing threshold, i.e.; the beginning of the runaway allowable for landing.

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RUNWAY MARKINGS

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Runway touchdown zone markings

The Runway touchdown zone markings identify the touchdown zone for landing operations. There are coded to provide distance information in 500-foot (150 m) increments for a distance of 2,500 feet from the threshold. These markings consists of groups of one, two and three rectangular bars, symmetrically arranged in pairs about the runway centerline. For runways having touchdown zone markings at both ends, those pairs of marking that extend within 900 feet (270 m) of the midpoint between the thresholds are eliminated.

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Runway side stripes

Runway side stripes delineate the edges of the runway. They provide a visual contrast between the runway and abutting terrain or shoulder. Side stripes consist of continuous white stripes located on each side of the runway.

Runway shoulder stripes are painted in yellow marked at a 45-degree angle to the direction of the runway, upward in the direction of operation, from the threshold to the midpoint of the run way.

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Runway lighting

Runway lighting is extremely important for night time aircraft operations or in poor visibility weather conditions. There are three categories of runway lighting systems:

1. Approach lighting system.2. Visual glide slope indicators, runway end

identifiers, runway edge light systems.3. In-runway lighting systems. Pg.110

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Airport Lighting

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Lighting Continued…

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Lighting Continued…

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A runway’s imaginary surfaces

Aircraft landing to or taking off from a runway need an area free of obstructions to safely operate. The FAA’s FAR Part 77 – Objects Affecting Navigable Airspace defines a series of imaginary surfaces that define the maximum allowable height of any structure that may be placed in the vicinity of an active runway. Pg.120

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Taxiways (1)

The major function of taxiways is to provide access for aircraft to travel to and from the runways to other areas of the airport in an expeditious manner. Taxiways are identified as parallel taxiways, entrance taxiways, bypass taxiways, or exit taxiways.

Parallel taxiways are typically identified by alphabetical designators. E.g.; a taxiway on the north side of an airfield might be designate taxiway N, whereas on the south side, will be S.

A series of entrance, exit and bypass taxiways associated with parallel taxiway north may be numbered consecutively in series as N1, N2, N3 and so on. Pg.122

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Taxiways (2)

Taxiways are planned with the following principles in mind:1. Aircrafts that have just landed should not interfere with

aircraft taxiing to take off.2. Taxi routes should provide the shortest distance between

aircraft parking areas and runways.3. At busy airports, taxiways are normally located at various

points along runways so that landing aircraft can leave the runways as quickly as possible.

4. A taxiway designed to permit higher turnoff speeds reduces the time a landing aircraft is on the runway. Such taxiways are called high-speed exit taxiways and are to typically aligned at a 30 to 45 degree angle connecting the runway with the parallel taxiway.

5. When possible, taxiways are planned so as not to cross an active runway Pg.123

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Surface Movement Guidance Control

System (SMGCS)At some busy airports that have complex taxiway systems and are prone to low visibility conditions, airport management may implement a Surface Movement Guidance Control System (SMGCS). As part of this plan, points along taxiway routed may be marked with geographic position markings. These markings are used to identify the location of taxiing aircraft during low-visibility operations. Pg. 124

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Navigational aids (NAVAIDS) located on airfields

Various types of navigational aids (NAVAIDS) are in use to aid aircraft both to fly between locations and to approach an airport for landing, particularly in poor weather conditions. Often these aids are located on airport airfields.

Non-directional radio beacons (NDB) is the oldest of the radio signal-based Navigational Aids used on Airfields. NDB emit low or medium-frequency radio signals whereby the pilot of an aircraft properly equipped with an automatic direction finder (ADF) can determine bearing and “home” in on the station. It is normally mounted on a 35-foot-high pole. pg.138

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Very-high-frequency omni-directional range radio beacons (VOR)

The VOR is the most common ground-based electronic navigational aid found in the USA and the world over. The VOR transmit a set of very-high-frequency navigational signals, which, when identified by navigation instruments in aircraft determine the location of the VOR from the aircraft with respect to magnetic north. It has a typical operational service volume of 25 nautical miles in radius from the airport. It should located at least 500 feet from the centerline of any runway.

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Instrument Landing System (ILS)

The most common navigational aid used by aircraft for both lateral and vertical guidance on approach to runways is the Instrument Landing System (ILS). ILS is designed to provide an approach path for exact alignment and descent of an aircraft on approach to a runway. It is considered a precision approach system, and is associated with precision approach markings on its associated runway. It was introduced in the US in 1941. Pg.139

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Instrument Landing System (ILS) (continued)

The ILS provides guidance by radio beams that define a straight-line path to the runway at a fixed slope of approximately 3 degrees, beginning 5 to 7 miles from the runway threshold. All aircraft approaching the airport under ILS guidance must follow this in single line.

The ILS ground equipment consists two highly directional transmitting systems and, along the approach, up to three marker beacons. The directional transmitters are know as the localizer and glide slope. Pg.139

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The localizer transmitter operates on of the 40 ILS channels within the frequency range of 108.10 to 111.95 MHz.

The glide slope transmitter transmits UHF frequencies on of the 40 ILS channels within the frequency range 329.15 to 335.00 MHz radiating in the direction of the approach. In addition to the localizer and glide slope, the ILS is equipped with marker beacons to assist the pilots in identifying their location on approach, known as the Outer marker, Middle marker and advanced (i.e.; Cat II or Cat III) ILS system, the Inner marker, respectively.

The ILS may also be accompanied by runway visual range(RVR) Pg.139

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The outer marker is located from 5 to 7 miles from end of the runway threshold. A vertically emitted radio signal activates rapidly flashing blue light on the aircraft marker beacon receiver when the aircraft passes overhead. Two Morse code dashes per second alert the pilot to the aircraft position on approach.The middle marker indicates a position approximately 3,500 feet from the runway threshold or at altitude of 200 feet above the landing area.The inner marker identifies the location on the approach may be less than 200 feet for the pilot to land or overshoot. The Morse code dot emits a high tone signals. Pg. 141

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ILS Ceiling and Visibility Minima

ILS Category

I

II

III a. (auto land)

III b. (auto rollout)

III c. (auto taxi)

Cloud Ceiling

200 feet

100 feet

0 - 100 feet

0 – 50 feet

0 feet

Visibility

1,800 – 2,400 feet

1,200 feet

700 feet

150 feet

0 feet

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Microwave Landing System (MLS)

Another precision approach navigational aid found at airport is the MLS which was developed in the early 1970 and at the time was slated to replace the ILS. In 1995, these plans were discontinued by FAA.

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GPS Local Area Augmentation System (LAAS)

Since mid 1990s, FAA has embarked on several programs to take advantage of the existing Global Positioning System (GPS) to provide satellite-based navigational aids with sufficient accuracy and information to allow precision approached to runways.

To improve the accuracy of the GPS system for approaches, system equipment enhancement infrastructure, know as the Local Area Augmentation System (LAAS) is being implemented on airport airfields. Pg. 143

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GPS Local Area Augmentation System (LAAS) - continued

LAAS infrastructure includes a ground facility (LGF), called pseudolites, are located precisely surveyed ground location on the airfield, to ensure accurate and consistent data transfer between the LAAS, GPS satellites, and aircraft.

LAAS is designed to allow precision approach capabilities to ILS CAT II and III standards. Different from ILS system which provide navigation aid to only one runway per installation, one LAAS system can provide service for multiple runways as long as the runway approaches are within the LAAS operation range. It is intended to improve the safety and efficiency of the airport. Pg. 143

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Air traffic control and surveillance facilities located on the airfield

At many airports, especially, the busy and high level of operational activity, air traffic control and surveillance procedures are located on the airfield to control and facilitate the safe and efficient movement of aircraft to, from, and around the airport’s airfield.Air traffic control towers (ATCT) – perhaps the most prominent air traffic facility located on an airfield. From control towers, air traffic control personnel control flight operations within the airport’s designated airspace; within a 5-mile radius of the airport, from the ground to 2,500 feet above the ground level (AGL) and the operation of aircraft and vehicles on the airfield’s movement area. Pg. 144

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Airport surveillance radar (ASR)

ASRs are radar facilities located on the airport airfield used to control air traffic. ASR antennas scan through 360 degrees to present an air traffic controller with the location of all aircraft within 60 nautical miles of the airport.

The location of an ASR antenna should be close to the ATCT control room as practical. Typical distances between the ASR antenna and ATCT range between 12,000 and 20,000 feet. Antenna should be located at least 1,500 feet from any building or object that might cause signal reflections and at least one-half mile from other electronic equipment. ASR antennas are typically elevated from 25 to 85 feet above the ground so as to maintain proper line-of-site clearance. Pg 145

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Airport Surface Detection Equipment (ASDE)

Surveillance and control of aircraft movement on the airport surface is normally accomplished largely by visual means, during period of low visibility caused by rain, fog and night, the surface movement of aircraft and service vehicles are drastically reduced.

To improve the safety and efficiency during the low visibility situation, controllers will use two radar-based systems, especially, at busier airports. These systems are called airport surface detection equipment (ASDE-3) and Airport Movement Area Safety Systems (AMASS). Pg. 145

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Weather reporting facilities located on airfields (1)

Many airports are equipped with automated weather reporting facilities to provide pilots with up-to-date meteorological information including cloud height, visibility, wind speed and direction, temperature, dew point temperature, and precipitation information. The most common systems are:

1) Automated Weather Observing System (AWOS)

2) Automated Surface Observing System (ASOS)

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Wind indicators

The simplest system located on airfields that report meteorological conditions are wind indicators. Three most common wind indicators include wind socks, wind tees, and tetrahedrons. These systems provide vital information at airports where no other sources of

weather information are provided so that pilots may appropriately determine the appropriate runway to use for take-off and landing. Pg. 146/8

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A wind sock is a hollow flag-like object the depicts approximate wind direction and speed. As air flows into the wind sock, it becomes oriented so that it is pointing away from the source of the wind, i.e., in the downwind direction. The stronger the wind, the straighter the extension of the wind sock.

A wind tee is similar to that of a typical weather vane. The wind tee points into the direction of the source of the wind. The wind tee does not provide any information regarding the speed of the wind.

A tetrahedron is a landing indicator typically located near a wind direction indicator. Tetrahedron may swing around with the small end point into the wind, or it may be manually positioned to depict recommended landing direction pg. 147

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Security infrastructure on airfields

Airport facilities require protection from acts of vandalism, theft, and potential terrorist attach. To provide a measure of protection, unauthorized persons must be precluded from having access to all airfield facilities.

To safeguard the airfield facilities, perimeter fencing around the airfield is strong recommended. In addition, security procedures should be forthwith established, such as issuing identification cards and number combination to open electronically secured access points

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Concluding remarks(the airfield)

The facilities that are located on an airport’s airfield comprise a wide variety of technologies that together accommodate the operation of aircraft between the airport and the local airspace. Proper planning and management of the airfield and associated facilities are necessary component of successful airport operation

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Chapter 4 the Airfield

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