Pilot's Handbook of Aeronautical Knowledge

Chapter 14: Airport Operations

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An airport is an area of land or water used or intended for landing or takeoff of aircraft. They can serve various types of aircraft, including fixed-wing, rotary wing, seaplane/floatplane, and tilt rotor. An airport comprises not only the takeoff/landing surfaces, but also movement areas, ramps, rights of way, buildings, facilities, and land associated with the airport.

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Categories of Airports

Commercial Service Airports are publicly owned, receive scheduled passenger service, and have at least 2,500 annual passenger boardings (also called "Enplanements").

Cargo Service Airports are served by aircraft providing air transportation of only cargo with a total annual landed weight of more than 100 million pounds. An airport may be both a Commercial Service and a Cargo Service Airport.

Reliever Airports are designated by the FAA to relieve congestion at Commercial Service Airports and to provide improved general aviation access to the overall community.

General Aviation Airports are the most common airports, can be publicly or privately owned, and do not fall within the above three definitions.

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Types of Airports

A towered airport has an operating control tower. Air traffic control (ATC) manages the flow of air traffic, and pilots are required to maintain two-way radio communication, as well as to acknowledge and comply with ATC instructions.

A non-towered airport does not have an operating control tower. Pilots transmit intentions on a Common Traffic Advisory Frequency (CTAF), although it is not required. Pilots also use specified procedures to enter traffic patterns.

At a non-towered airport, the CTAF can be a Universal Integrated Community (UNICOM), MULTICOM, Flight Service Station (FSS), or tower frequency (if the tower is not in operation). A UNICOM is a nongovernment air/ground radio communication station that may provide airport information at public use airports.

A Local Airport Advisory (LAA) service is available only in Alaska. The service is operated within 10 statute miles of an airport where a control tower is not operating but where a FSS is located on the airport. At such locations, the FSS provides a complete local airport advisory service to arriving and departing aircraft. (AIM 3-5-1)

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Sources for Airport Data

Sources for airport data include aeronautical charts, the Chart Supplement U.S. (formerly Airport/Facility Directory), Notices to Airmen (NOTAMs), and the Automated Terminal Information Service (ATIS), if available.

Aeronautical Charts include a legend that can be consulted to decipher airport information. Pilots also can consult the FAA's Chart User's Handbook, which includes more comprehensive information.

The Chart Supplement U.S. (formerly Airport/Facility Directory) provides comprehensive airport information. It is published for seven geographic regions and updated every eight weeks (56 days). A "Legend Sample" can be found at the front of each Chart Supplement. These publications also include an array of supplemental information for pilots, including telephone numbers, VFR waypoints, IFR routing, VOR receiver checkpoints, chart bulletins, full-page airport diagrams for large airports, and more.

Notices to Airmen (NOTAMs) transmit time-critical aeronautical information that is temporary in nature, or that is not sufficiently known in advance to permit print publication. This includes taxiway and runway closures, construction, communications, changes in status of navigational aids, and other essential information. NOTAMs should be consulted before every flight.

The Automated Terminal Information Service (ATIS) is a recording of the local weather conditions and other pertinent information broadcast in a looped format. It is updated once per hour or when changing local conditions warrant. Information includes weather observations, runways in use, specific ATC procedures, and any airport construction activity.

Each ATIS recording is appended with a code from the phonetic alphabet (e.g., "Delta"), with each subsequent recording updated with the next letter in the alphabet (e.g., "Echo", thence "Foxtrot"). Pilots are expected to listen to the ATIS prior to contacting the control tower, and upon initial contact advising the tower that they have the current ATIS — e.g. "Aurora Tower, Cessna 172SP is five the south, 2,000 feet, landing, with information Delta."

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Notices to Air Missions (NOTAMs)

(This content is found in Chapter 1 of the Pilot's Handbook of Aeronautical Knowledge, "Introduction to Flying." Also refer to the Aeronautical Information Manual 5-1-3.)

Notices to Airmen, or NOTAMs (and formerly "Notices to Airmen"), are time-critical aeronautical information either temporary in nature or not sufficiently known in advance to permit publication on aeronautical charts or in other operational publications. NOTAMs are eligible to be disseminated up to seven days before the start of the activity. Prior to departure, pilots must become familiar with all available information concerning that flight, including NOTAMs.

NOTAMs are issued for several reasons, including:

• Hazards, such as air shows, parachute jumps, kite flying, and rocket launches
• Closed runways
• Inoperable radio navigational aids
• Inoperable lights on obstructions
• Temporary obstacles near airfields
• Military exercises
• Passage of flocks of birds through airspace (a BIRDTAM)
• Notifications of runway/taxiway/apron status with respect to snow, ice, and standing water (a SNOWTAM)
• Notification of an operationally significant change in volcanic ash or other dust contamination (an ASHTAM)

There are several categories of NOTAMs.

Domestic NOTAMs, referred to as D NOTAMs or NOTAM (D), receive distant dissemination (and thus sometimes are referred to as "distant" NOTAMs). Information is disseminated for all navigational facilities that are part of the NAS, and for all facilities listed in the Chart Supplement. Examples include such data as taxiway closures, personnel and equipment near or crossing runways, and airport lighting aids that do not affect instrument approach criteria. All D NOTAMs are required to have one of the following keywords as the first part of the text: RWY, TWY, RAMP, APRON, AD, OBST, NAV, COM, SVC, AIRSPACE, (U), or (O).

Flight Data Center NOTAMs, referred to as FDC NOTAMs, are issued by the National Flight Data Center and contain information that is regulatory in nature. This includes changes to charts, procedures, and airspace usage. It also includes Temporary Flight Restrictions (TFRs).

Pointer NOTAMs are considered a type of NOTAM (D). They are issued to point to additional aeronautical information. Pointer NOTAMs should be issued for, but are not limited to, TFRs, Airshows, Temporary Special Use Airspace (SUA), and major NAS system interruptions. When pointing to another NOTAM, the keyword in the pointer NOTAM must match the keyword in the original NOTAM.

International NOTAMs are distributed to more than one country. They are published in ICAO format.

Military NOTAMs pertain to military airports or NAVAIDs that are part of the NAS. They should be reviewed by users of a military or joint-use facility. This is also referred to as a NOTAM (L), a type of NOTAM that was distributed to civil aviation at one time. However, all types of notices previously distributed as L NOTAMs to civil aviation are now classified as D NOTAMs

To view current NOTAMS, go to https://notams.aim.faa.gov/notamSearch.

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Airport Signs

There are six types of signs that may be found at airports:

• Mandatory instruction signs: Red background with white inscription. These signs denote an entrance to a runway, critical area, or prohibited area.
• Location signs: Black with yellow inscription and a yellow border, no arrows. They are used to identify a taxiway or runway location, to identify the boundary of the runway, or identify an instrument landing system (ILS) critical area.
• Direction signs: Yellow background with black inscription. The inscription identifies the designation of the intersecting taxiway(s) leading out of an intersection.
• Destination signs: Yellow background with black inscription and arrows. These signs provide information on locating areas, such as runways, terminals, cargo areas, and civil aviation areas.
• Information signs: Yellow background with black inscription. These signs are used to provide the pilot with information on areas that cannot be seen from the control tower, applicable radio frequencies, and noise abatement procedures. The airport operator determines the need, size, and location of these signs.
• Runway distance remaining signs: Black background with white numbers. The numbers indicate the distance of the remaining runway in thousands of feet.

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Runway Markings and Signs

Markings and signs at airports provide directions and assist pilots in airport operations. Chapter 2 of the Aeronautical Information Manual (AIM), "Aeronautical Lighting and Other Airport Visual Aids," includes comprehensive information.

Runways are laid out according to the local prevailing winds. Runway numbers are in reference to magnetic north. If two or more runways are laid out in the same direction, they are parallel runways and have a letter added to the runway number — e.g., runway 36L (left), 36C (center), and 36R (right).

When a portion of a runway is closed, the runway threshold is relocated as necessary. This is known as a relocated threshold. This is commonly marked with a ten foot wide white bar across the width of the runway, with yellow arrowheads across the width of the runway just prior to the threshold bar.

The closed portion of the runway is not available for use by aircraft for takeoff or landing, but it is available for taxi. This also shortens the length of the opposite direction runway.

A displaced threshold is a threshold located at a point on the runway other than the designated beginning of the runway. This reduces the length of runway available for landings. A displaced threshold is not as restrictive as a relocated threshold.

In addition to being available for taxi, the portion of runway behind a displaced threshold is available for takeoffs in either direction, and for landings from the opposite direction.

Along with a ten foot wide bar across the width of the runway, white arrowheads are placed along the centerline behind the displaced threshold and across the width of the threshold bar.

The Runway Safety Area (RSA) is a defined surface surrounding the runway prepared, or suitable, for reducing the risk of damage to airplanes in the event of an undershoot, overshoot, or excursion from the runway. It typically is graded or mowed. Dimensions vary. The lateral boundaries are usually identified by the presence of the runway holding position signs and markings on the adjoining taxiway stubs.

A runway safety area boundary sign is often found at runway exits to assist pilots in identifying when they have cleared the RSA.

A runway holding position sign designates the entrance to a runway. It displays one or more runway numbers, with white characters outlined in black on a red background. Pilots should never allow any part of the aircraft to cross the runway holding position sign without a clearance from ATC. When the tower is closed, at a non-towered airport, pilots may taxi past a runway holding position sign only when the runway is clear of aircraft and there are no aircraft on final approach.

If positioned at the takeoff end of the runway, one runway number is displayed. If positioned at a taxiway/runway intersection other than the takeoff end, two runway numbers will be presented, indicating the left/right direction of each runway threshold. Arrows also may be included to indicate turns required to reach a specific runway. Runway holding position signs may also be painted on the surface.

Where confusion during taxi is possible, due to a complex intersection of taxiway(s) and runway(s), an airport hot spot may be designated on the airport diagram. Extreme vigilance should be exercised when traversing a designated hot spot.

A runway holding position marking consists of four yellow lines (two solid and two dashed) painted on the surface of the taxiway. These markings indicate where the aircraft should stop when approaching a runway. They are collocated with runway holding position signs. Pilots are not permitted to cross the double-solid lines until a runway clearance from ATC has been received. A clearance is not needed to exit the runway and cross the double-dashed lines. Runway exits always should be expedited — hence the phrase "Dash through the dash."

Runway distance remaining signs indicates the distance of landing runway remaining, always in thousands of feet. They have a black background with a white number and may be installed along one or both sides of the runway. The last sign, which has the numeral "1," is located at least 950 feet from the runway end.

Runway designation markings, commonly called "runway numbers", are prominent markings at the threshold of each runway. The runway number is the whole number nearest one-tenth the magnetic azimuth of the centerline of the runway, measured clockwise from the magnetic north. In the case where there are parallel runways, the letters differentiate between left (L), right (R), or center (C).

Land and Hold Short Operations (LAHSO) permit simultaneous takeoffs and landings ("operations") on intersecting runways. Pilots may accept or decline any LAHSO clearance, and pilots should be aware if their aircraft can comply with the reduced runway distance before accepting an LAHSO clearance. Runway holding position signs and markings are installed on runways used for LAHSO, and pilots must stop short of the intersecting runway prior to the LAHSO signs and markings.

LAHSO are not authorized for student pilots who are performing a solo flight. Generally, LAHSO are not authorized at night, and they are not authorized on wet runways.

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Taxiway Markings and Signs

Taxiway direction signs identify the designation of a taxiway or intersecting taxiways. They have a yellow background and black characters. Arrows indicate the direction of turn that would place the aircraft on a designated taxiway, leading off a runway, or out of an intersection. Taxiway direction signs can also be displayed as surface painted markings.

An enhanced taxiway centerline marking is used to warn of an upcoming runway. It consists of yellow dashed lines on either side of the normal solid taxiway centerline. The dashes extend up to 150 feet prior to a runway holding position marking.

Destination signs indicating a destination at the airport. They have black characters on a yellow background, with an arrow showing the direction of the taxi route to that destination. Common destinations include runways, aprons, terminals, military areas, civil aviation areas, cargo areas, international areas, and fixed-base operators.

ATC may keep ILS critical areas clear of all obstacles in order to ensure quality of the Instrument Landing System (ILS) broadcast signal. This is uncommon when weather conditions are good and aircraft are not using the ILS for final approach. An ILS critical area hold sign and position markings may be found on a taxiway as it approaches a runway. Pilots are required to hold short of the ILS critical area when instructed by ATC. The marking appears as a horizontal yellow ladder extending across the width of the taxiway.

Holding position markings for taxiway/taxiway intersections consist of a single dashed yellow line extending across the width of the taxiway. They are painted on taxiways where ATC normally holds aircraft short of a taxiway intersection.

For runways and taxiways that are permanently closed, the lighting circuits are disconnected, all runway markings are obliterated, and yellow "X"s are placed at each end of the runway and at 1,000-foot intervals. For temporarily closed runways and taxiways, a visual indication is often provided with yellow "X"s or raised lighted yellow "X"s placed at each end of the runway.

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Airport Lighting

Airport Beacons

The airport beacon is normally operated from dusk until dawn. It helps pilots locate airports at night. They also may be turned on during daylight hours when weather is below VFR minimums (but this is not required). The combination of light colors from an airport beacon indicates the type of airport, for example:

• Civilian land airports: Flashing white and green.
• Water airports: Flashing white and yellow.
• Heliports: Flashing white, yellow, and green.
• Military airports: Two quick white flashes alternating with a green flash.

Visual Glideslope Indicators

Approach light systems are primarily intended to provide a means to transition from instrument flight to visual flight for landing. The system configuration depends on whether the runway is a precision or nonprecision instrument runway.

Visual glideslope indicators provide the pilot with glidepath information that can be used for day or night approaches. Visual Approach Slope Indicator (VASI) installations are the most common visual glidepath systems in use, providing obstruction clearance within 10° of the extended runway centerline and up to four nautical miles (NM) from the runway threshold.

VASI lights are arranged so the pilot sees a combination of lights to indicate below (red/red), on (red/white), or above (white/white) the glidepath. Two-bar VASI installations provide one visual glidepath that is normally set at 3°. The three-bar system provides two glidepaths — the lower glidepath normally set at 3 degrees, and the upper glidepath 0.25° above the lower glidepath.

A Precision Approach Path Indicator (PAPI) uses lights similar to the VASI system, except that four lights are installed in a single row, presenting all white when above the glideslope to all red when below the glideslope. Two white and two red PAPI lights indicates the aircraft is on the glideslope, while "slightly above glidepath" (three white) and "slightly below glidepath" (three red) can be seen as well.

A tri-color system consists of a single-light unit projecting a three-color visual approach path. Below the glidepath is indicated by red, on the glidepath is indicated by green, and above the glidepath is indicated by amber. When descending below the glidepath, there is a small area of dark amber that appears before the VASI transmits a red light.

A Pulsating VASI is a single-light unit projecting a two-color visual approach path into the final approach area of the runway. The "on glidepath" indication is a steady white light. The "slightly below glidepath" indication is a steady red light. If the aircraft descends further below the glidepath, the red light starts to pulsate.

Runway Lighting

Runway End Identifier Lights (REIL) mark the approach end of the runway with a pair of synchronized flashing lights located laterally on each side of the runway threshold. REILs may be either omnidirectional or unidirectional facing the approach area..

Runway edge lights outline the edges of runways at night or during low visibility conditions. They are white and classified by intensity: High Intensity Runway Lights (HIRL), Medium Intensity Runway Lights (MIRL), and Low Intensity Runway Lights (LIRL). On instrument runways, runway edge lights are amber on the last 2,000 feet or half the length of the runway, whichever is less. The lights marking the end of the runway are red.

A Runway Centerline Lighting System (RCLS) may be installed on some precision approach runways to facilitate landing under adverse visibility conditions. They are located along the runway centerline and are spaced at 50-foot intervals. Centerline lights are white, until the last 3,000 feet of the runway, where they alternate white/red for 2,000 feet. They are red for the final 1,000 feet.

Touchdown zone lights (TDZL) are installed on some precision approach runways to indicate the touchdown zone when landing under adverse visibility conditions. .

Taxiway centerline lead-off lights and lead-on lights provide visual guidance to persons exiting and entering the runway.

Land and hold short lights are used to indicate the hold-short point on certain runways which are approved for LAHSO. They are a row of pulsing white lights installed across the runway at the hold-short point. If installed, the lights are on anytime LAHSO is in effect.

Airport lighting is controlled by ATC at towered airports. At non-towered airports, the lights may be on a timer. The pilot may control the lighting by using the radio. This is done by selecting a specified frequency and clicking the radio microphone. The Chart Supplement includes information on pilot-controlled lighting.

Taxiway Lighting

Omnidirectional taxiway lights outline the edges of the taxiway and are blue in color. Some airports also have taxiway centerline lights that are green in color.

Clearance bar lights are installed at holding positions on taxiways in order to increase the conspicuity of the holding position in low visibility conditions. They are three in-pavement, steady-burning yellow lights.

Runway guard lights are installed at taxiway/runway intersections. They are either a pair of elevated flashing yellow lights installed on either side of the taxiway, or a row of in-pavement yellow lights installed across the entire taxiway, at the runway holding position marking.

Stop bar lights, when installed, are used to confirm the ATC clearance to enter or cross the active runway in low visibility conditions. They are a row of red, unidirectional, steady- burning in-pavement lights installed across the entire taxiway at the runway holding position, and elevated steady-burning on each side.

Obstruction Lights warn pilots of obstructions during daytime and nighttime conditions. They can be red, white, or a combination of both, and they may be flashing or be steady lights. No person may, from sunset to sunrise, park or move an aircraft in, or in dangerous proximity to, a night flight operations area of an airport unless the aircraft is clearly illuminated, has lighted position lights, or is in an area that is marked by obstruction lights.

The Runway Status Lights (RWSL) system indicate if it is unsafe to enter a runway, cross a runway, or takeoff from or land on a runway. They are red and indicate runway status only, not an ATC clearance. Runway Entrance Lights (REL) and Takeoff Hold Lights (THL) are the two subtypes of Runway Status Lights. These are only in use at large commercial terminals.

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Wind Direction Indicators

The wind direction indicator can be a wind cone, wind sock, tetrahedron, or wind tee. They may be placed in the center of a segmented circle, typically midfield. Wind tees and tetrahedrons can swing freely and align themselves with the wind direction, but they also can be manually set to align with the runway in use.

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Traffic Patterns

The segmented circle visual indicator system is designed to provide traffic pattern information. It includes wind direction indicators, landing direction indicators, landing strip indicators, and traffic pattern indicators. The small end of the tetrahedron points in the direction of landing, or into the wind if not manually set. Landing strip indicators are installed in pairs and are used to show the alignment of landing strips. Traffic pattern indicators show the direction of turns.

Information on airport traffic pattern operations can be found in Chapter 4, "Air Traffic Control," of the Aeronautical Information Manual (AIM). The recommended pattern altitude is 1,000 feet AGL, unless otherwise established. Pilots should:

• Enter the traffic pattern in level flight, abeam the midpoint of the runway.
• Fly at pattern altitude on the on downwind leg until abeam approach end of the landing runway.
• Complete the turn to final at least one-quarter mile from the runway.
• From the departure leg (after takeoff or go-around), turn to the crosswind leg within 300 feet of pattern altitude.
• If departing the traffic pattern, continue straight out on the departure leg; or exit with a 45° turn from the downwind leg, away from the airport.

Traffic Pattern Entries

The preferred method for entering the traffic pattern from the downwind side of the pattern is to approach the pattern on a pattern entry leg, which is a 45° track to the downwind leg, at traffic pattern altitude, joining the pattern at midfield (commonly called "the forty-five").

From the upwind side of the pattern, the pilot may enter the pattern with a mid-field crossing and teardrop entry, crossing 500 feet above the highest pattern altitude, clearing the pattern by two miles, and then making a descending right turn to pattern altitude, and then approaching on the pattern entry leg.

If the pattern is not busy, pilots can fly a midfield crosswind at pattern altitude and then turn to join the downwind leg.

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Radio Communications

There are no radio license requirements for pilots operating in the United States. Pilots operating internationally must hold a restricted radiotelephone permit, issued by the Federal Communications Commission (FCC). They may also need to hold a station license, under certain conditions.

VHF radios operate on frequencies between 118.0 and 136.975 MHz. VHF radios are limited to line-of-sight transmissions. Aircraft at higher altitudes are able to transmit and receive at greater distances.

The phonetic alphabet should be used in radio communications. The AIM includes a pilot/controller glossary, as well as examples of standard phraseology.

If a receiver becomes inoperative and a pilot needs to land at a towered airport, the direction and flow of traffic should be determined. The pilot should then enter the pattern watch for light signals from the tower. If the transmitter may still be operative, it is advised to state position reports and intentions on the tower frequency ("in the blind").

If a flight must be undertaken without a functional radio, tower may be contacted by telephone for a "no radio" (NORDO) procedure, after which the pilot should watch for light signals. This procedure is not accepted at busy airports.

When operating at a non-towered airport, no radio communication is necessary. However, pilots should be extra vigilant when not using the radio.

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Air Traffic Control (ATC) Services

Primary Radar provides information on range, azimuth, and/or elevation of objects in the path of the transmitted pulses. Radar signals degrade over distance, cannot penetrate through solid objects such as mountains, updates no faster than every 4.7 seconds.

The ATC Radar Beacon System (ATCRBS, or "secondary surveillance radar") consists of an interrogator, transponder, and radarscope, and has advantages over primary radar.

A transponder transmits a four-digit code, utilizing numbers from 0 to 7. When a controller requests a code or function on the transponder, the word "squawk" may be used. The AIM includes additional information concerning transponder operation.

The Automatic Dependent Surveillance–Broadcast (ADS–B) system enables the expansion of air traffic control (ATC) surveillance services into areas where none existed previously. Using GPS, onboard avionics transmit the aircraft's position (along with additional information) to ATC and nearby ADS-B equipped aircraft.

Radar-equipped ATC facilities provide radar assistance to aircraft on instrument flight plans, as well as to VFR aircraft ("flight following"), provided the aircraft can communicate with the facility and are within radar coverage.

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Wake Turbulence

Wingtip vortices from larger aircraft pose problems to encountering aircraft, including rolling moments and damage to components and equipment. Vortex circulation is outward, upward, and around the wingtips when viewed from either ahead or behind the aircraft.

En route wake turbulence events from large aircraft have been observed in excess of 30NM and 2,000 feet lower than the wake-generating aircraft.

When the vortices of larger aircraft sink close to the ground (within 100 to 200 feet), they tend to move laterally over the ground at a speed of 2-3 knots. Crosswinds and tailwinds can contribute to a ground vortex's impact on other aircraft.

To avoid wake vortices:

• When landing behind a larger aircraft on the same runway, stay at or above the larger aircraft's approach flight path and land beyond its touchdown point.
• When landing behind a larger aircraft on a parallel runway closer than 2,500 feet, consider the possibility of drift and stay at or above the larger aircraft's final approach flight path and note its touchdown point.
• When landing behind a departing aircraft on the same runway, land prior to the departing aircraft's rotating point.
• When departing behind a large aircraft, rotate prior to the large aircraft's rotation point and climb above its climb path until turning clear of the wake.
• En route, it is advisable to avoid a path below and behind a large aircraft.

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Collision Avoidance

Pilots can contribute to collision avoidance by being alert and scanning for other aircraft, which is accomplished with a series of short, regularly spaced eye movements that bring successive areas of the sky into the central visual field. Increments of scan should be no more than 10° and persist for at least one second.

Clearing Procedures

• Before takeoff pilots should scan the approach area for possible landing traffic.
• During climbs and descents, pilots should execute gentle banks left and right for visual scanning.
• Entries into traffic patterns while descending should be avoided.
• Vigilance should be maintained in the vicinity of VORs and intersections.
• Clearing turns should be made prior to a practice maneuver.
• Pilots should momentarily raise (high-wing) or lower (low-wing) the wing in the direction of a turn and look for traffic prior to commencing the turn.

Pilot Deviations (PDs)

A Pilot Deviation (PD) is an action of a pilot that violates any Federal Aviation Regulation. Examples include when a pilot strays from an assigned heading, altitude, or instrument procedure, or if the pilot penetrates controlled/restricted airspace without prior clearance. Regulations permit deviations from a clearance to avoid a collision.

Pilots should plan each flight, checking for Temporary Flight Restrictions along the route of flight. They should participate in Flight Following when available. And pilots should use GPS to avoid controlled/restricted airspace if they do not have a clearance.

Ground Deviations (also called surface deviations) include taxiing, taking off, or landing without clearance, deviating from an assigned taxi route, or failing to hold short of an assigned clearance limit.

A Vehicle or Pedestrian Deviation includes pedestrians, vehicles or other objects interfering with aircraft operations by entering or moving on the runway movement area without authorization from air traffic control.

Runway Incursion Avoidance

A runway incursion is "any occurrence in the airport runway environment involving an aircraft, vehicle, person, or object on the ground that creates a collision hazard or results in a loss of required separation with an aircraft taking off, intending to take off, landing, or intending to land."

The most common causes of runway incursions are failure to comply with ATC instructions, lack of airport familiarity, and pilots not following standard operating procedures.

It is mandatory to read back all runway "hold short" instructions verbatim.

At unfamiliar airports, a request may be made for progressive taxi instructions, which include step-by-step taxi routing instructions provided by ATC. Pilots operating with a progressive taxi should have a current airport diagram.

To avoid runway incursions, pilots should:

• Review airport layouts and NOTAMs as part of preflight planning.
• Use proper phraseology.
• Write down taxi instructions, especially at unfamiliar airports.
• Read back all runway crossing and/or hold instructions.
• Request progressive taxi instructions from A TC when unsure of the taxi route.
• Turn on aircraft lights and the rotating beacon while taxing.
• After landing, clear the active runway and obtain taxi instructions before further movement.

If you are operating from an airport with runway thresholds in close proximity to one another, exercise extreme caution when taxiing onto the runway. Runway Confusion can be caused by airport complexity, close proximity of runway thresholds, and joint use of a runway as a taxiway.

ATC Instructions

Pilots are required by regulation to follow all ATC clearances and instructions. If a pilot cannot safely comply with any of ATC's instructions, s/he is to inform ATC immediately by using the word "Unable." The final decision to act on ATC's instruction rests with the pilot. If there is uncertainty about any ATC instructions or clearances, the pilot should state "Say again" or request progressive taxi instructions.

The most important sign and marking on the airport is the hold sign and hold marking, which are located on a stub taxiway leading directly to a runway. When ATC issues a "hold short" clearance to a pilot, s/he should taxi up to — but not cross — any part of the runway holding marking. ATC is required to obtain a read-back from the pilot of all runway "hold short" instructions. The pilot's readback should include the runway identifier and aircraft call sign.

ATC is required to issue explicit instructions to "cross" or "hold short" of each runway, which is known as an Explicit Runway Crossing. Extra caution should be used when directed by ATC to taxi onto or across a runway.

ATC may issue a "Line Up and Wait" (LUAW) instruction when a takeoff clearance cannot be issued immediately due to traffic or other reasons. This is a clearance to enter the runway and hold in position for takeoff. The aircraft will then be referred to as "traffic holding in position" until a takeoff clearance is issued.

If a takeoff clearance is not received within 90 seconds after receiving a "line up and wait" instruction, contact ATC immediately.

When the available runway length has been temporarily or permanently shortened due to construction, the ATIS includes the words "warning" and "shortened" in the text of the message, and ATC will include the word "shortened" in their clearance instructions.

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Engineered Materials Arresting Systems (EMAS)

An overrun occurs when an aircraft passes beyond the end of a runway during an aborted takeoff or on landing rollout. At most commercial airports, the Runway Safety Area (RSA) is 500 feet wide and extends 1,000 feet beyond each end of the runway. This area is meant to minimize the hazards of overruns.

Many older airports cannot achieve the full standard RSA, due to obstacles, populated areas, or terrain. In these cases, Engineered Materials Arresting System (EMAS) may be installed as an alternative to a RSA beyond the runway end.

An EMAS uses materials — typically, lightweight and crushable concrete — at the end of a runway to stop or greatly slow an aircraft that overruns the runway. When an aircraft rolls into an EMAS arrestor bed, the tires of the aircraft sink into the material and the aircraft is decelerated. As of 2016, EMAS had been installed at 63 runway ends at 42 airports in the United States.

EMAS may not stop lightweight general aviation aircraft that are not heavy enough to sink into the arresting material. If approaching an arrestor bed, pilots should maintain deceleration efforts. Once stopped, pilots should not attempt to taxi.

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