Five Mile Final | An Aviation Sandbox

Pilot's Handbook of Aeronautical Knowledge

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.

Categories of Airports

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 used specified procedures to enter traffic patterns.

At a non-towered airport, the CTAF frequency 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)

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."

Notices to Airmen (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, 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:

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 all facilites 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).

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.

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).

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

Airport Signs

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

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.

Relocated runway threshold.

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. In addition to 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.

Displaced runway threshold.

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.

Runway Safety Area.
Runway safety area boundary sign and marking.

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, to the left of the taxiway centerline.

Runway holding position sign at takeoff end of Runway 14 with collocated Taxiway Alpha location sign. Runway holding position sign at a location other than the takeoff end of Runway 18-36 with collocated Taxiway Alpha location sign.
Runway safety area boundary sign and marking. Runway holding position sign at a location other than the takeoff end of Runway 18-36 with collocated Taxiway Alpha location sign.

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 distance remaining sign indicating that there is 2,000 feet of runway remaining.
Runway holding position sign and marking for LAHSO.

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.

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.

Taxiway Bravo direction sign with a collocated Taxiway Delta location sign.
Surface painted taxiway direction signs.

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.

Runway destination sign.
Instrument landing system (ILS) holding position sign and marking.

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.

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:

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.

Precision approach path indicator.

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.

Tri-color visual approach slope indicator.

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. "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 nontowered 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. The 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.

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.

Wind direction indicators.

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:

Traffic pattern operations, single runway.

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 course 45° 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.

Preferred entry, crossing midfield.
Alternate midfield entry.

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 that 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.

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.

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:

Vortex behavior.

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

Pilot Deviations (PDs)

Confusing runway/runway intersection.

Confusing runway/runway intersection.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:

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

Holding position sign and marking.

Holding position sign and marking.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.

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.

Vortex behavior.

Control Tower Light-Gun Signals

Control towers communicate with aircraft that do not have a radio, as well as aircraft with radio failures, by use of light signals. This is done with a light-gun that a controller in the tower cabin will point directly at the aircraft.

There are three light-gun colors: red, green, and white. The lights can be steady, flashing, or alternating. Most of the signals have distinct meanings for aircraft in the air and aircraft on the ground.

There are a total of ten messages that are communicated with light-gun signals. As expected, red signals are "warning" or "stop" messages, while green signals are "proceed" messages. There is no steady white signal, since this would be difficult to differentiate with other airport lighting, and only one flashing-white signal, which is for ground operations.

Receiving ATC communications via light gun is exceedingly rare. The only reason these need to be memorized is because of knowledge test questions. Every retail kneeboard on the market has the signal codes etched on the face (along with a lot of other information), and various aviation organizations publish free kneeboard cards. However, because a wrong answer on a test can cost you a valuable point, there's no reason not to develop a memory system during test prep.

Steady Green:
   Air: Cleared to land
   Ground: Cleared for takeoff

The steady greens are easy, because they are just like traffic lights. They mean "proceed." However, these are runway traffic lights.

Flashing Green:
   Air: Return for landing
   Ground: Cleared for taxi

The flashing greens are a bit more ambiguous. They are "proceed," but on the ground it's for the movement area, not for entry into the RSA. In the air, it means fly a green dashed line in a circle (or otherwise) and come back.

Steady Red:
   Air: Give way to other aircraft
   Ground: Stop

Again, it's a traffic light. On the ground, stop. In the air, stopping is impossible, so it's "give way," just like the steady red wingtip light tells the aircraft to the left that it does not have the right-of-way.

Flashing Red:
   Air: Airport is unsafe; do not land.
   Ground: Vacate runway in use

Flashing red is an alert, not just a "stop." It means Don't use this runway. In the air it's "Go away, danger." On the ground, it's "Leave the RSA now, danger."

Flashing White:
   Air: unassigned
   Ground: Return to starting point

Aircraft in the sky aren't shown flashing white lights because there might be other flashing white lights in the vicinity. On the ground, it means "Return to your starting point." Think of it as you attempting to reach the runway and the tower is waving your white flag of surrender.

Alternating Red/Green:
   Air: Exercise extreme caution
   Ground: Exercise extreme caution

Alternating red/green is pretty confusing. Schizophrenic, even. Consider this a message from the tower on the current state of things, which might be disordered or worse. Watch out.

Steady White:
   Air: unassigned
   Ground: unassigned

Aircraft aren't shown steady white lights because there are an abundance of steady white lights everywhere.

Commercial Pilot & Flight Instructor Test Questions

Absence of the sky condition and visibility on an ATIS broadcast indicates that the ceiling is at least 5,000 feet and visibility is five miles or more.
— Absence of this information does not mean conditions are VFR, nor that they unlimited.

When are ATIS broadcasts updated? Upon receipt of any official weather, regardless of content change or reported values.

When an air traffic controller issues radar traffic information in relation to the 12-hour clock, the reference the controller uses is the aircraft's ground track.
— ATC cannot know any wind-correction angles applied by the pilot.

Which transponder code should the pilot of a civilian aircraft never use? 7777.
— 7777 is reserved for military interceptor operations.

The UNICOM frequency for airports with a control tower is 122.95.

As standard operating practice, all inbound traffic to an airport without a control tower should continuously monitor the appropriate facility from a distance of 10 miles.
— Monitoring is done via the Common Traffic Advisory Frequency (CTAF).

When landing at an airport that does not have a tower, FSS, or UNICOM, you should broadcast your intentions on 122.9.
— Use MULTICOM (122.9) for self-announce procedures.

If the aircraft's radio fails, what is the recommended procedure when landing at a controlled airport? Observe the traffic flow, enter the pattern, and look for a light signal from the tower.

A series of continuous red lights in the runway centerline indicates that 1,000 feet of runway remain.

A military airfield can be identified by a green and dual-peaked white rotating beacon.
— Look for two quick white flashes between the green flashes.

The visual glidepath of a 2-bar VASI provides safe obstruction clearance within plus or minus 10° of the extended runway centerline and to a distance of how many miles from the runway threshold? 4 NM.

Which indications would a pilot see while approaching to land on a runway served by a 2-bar VASI? If departing to the high side of the glidepath, the far bars will change from red to pink to white.

When on the upper glidepath of a 3-bar VASI, what would be the colors of the lights? The near and middle bars are white, and the upper bar is red.

An on-glidepath indication from a tri-color VASI is a green light signal.

An above-glidepath indication from a tri-color VASI is an amber light signal.

A slightly low indication on a PAPI glidepath is indicated by one white light and three red lights.

An airport has pilot-controlled lighting but runways without approach lights. How many times should you key your microphone to turn on the MIRL at medium intensity? Five (5) clicks.

The numbers 8 and 26 on the approach ends of the runways indicate that the runway is oriented approximately 080° and 260° magnetic.

What does a series of arrows painted on the approach end of the runway signify? That portion of the runway is not suitable for landing.

When approaching taxiway holding lines from the side with continuous lines, the pilot should not cross the lines without ATC clearance.

What is the purpose of the runway hold position sign? Denotes entrance to a runway from a taxiway.

What is the purpose for the runway hold position sign on the taxiway? Holds aircraft short of the runway.

What does a destination sign identify? Direction to takeoff runways.

What is the purpose of the taxiway ending marker sign? Indicates taxiway does not continue beyond intersection.

What is the purpose of No Entry sign? Identifies paved area where aircraft are prohibited from entering.

What is the purpose of the yellow demarcation bar marking? Delineates runway with a displaced threshold from a blast pad, stopway, or taxiway that precedes the runway.
— A tricky question, since the threshold is denoted with a thick white bar. See image 14-6. The demarcation bar is a line preceding the blast pad.

When turning on to a taxiway from another taxiway, what is the purpose of the taxiway direction sign? Indicates designation and direction of taxiway leading out of an intersection.

What purpose does the taxiway location sign serve? Identifies taxiway on which the aircraft is located.

When exiting the runway, what is the purpose of the runway exit sign? Indicates designation and direction of exit taxiway from a runway.

The recommended entry position to an airport traffic pattern is to enter 45° at the midpoint of the downwind leg at traffic pattern altitude.

Pilots are encouraged to turn on their landing lights when operating below 10,000 feet, day or night, and when operating within 10 miles of any airport.

How does the wake turbulence vortex circulate around each wingtip? Outward, upward, and around each tip.
— Wingtip spoilers limit the outward motion of vortices, preventing them from striking the top surface of the wing.

What effect would a crosswind of 5 knots or less have on the wingtip vortices generated by a large aircraft that had just taken off? The upwind vortex would tend to stay on the runway longr than the downwind vortex.

During takeoff made behind a departing large jet airplane, the pilot can minimize the hazard of wingtip vortices by being airborne prior to reaching the jet's flightpath until ale to turn clear of its wake.

When landing behind a large jet aircraft, at which point on the runway should you plan to land? Beyond the jet's touchdown point.

Which statement is true regarding wingtip vortices? Vortices generated by helicopters in forward flight are similar to those generated by fixed wing aircraft.

Due to the effects of wake turbulence, what minimum separation does ATC provide for small aircraft landing behind a heavy jet? Six (6) miles.

Information concerning parachute jumping sites may be found in the Chart Supplement.

When information is disseminated for a navigational facility, it will be located in NOTAM (D) information.
— FDC NOTAMs include changes to charts, procedures, and airspace usage. NOTAM (D) is distributed locally and advises the status of navigational facilities, including taxiways, airport beacons, and equipment.

When information is disseminated about a taxiway closure, it will be located in NOTAM (D) distribution.
— NOTAM (D) information includes taxiway closures, personnel and equipment crossing runways, beacons, and lighting aids not associated with instrument approach procedures.

Local Airport Advisory service is usually available at all airports where a Flight Service Station is located on the airport. (AIM 3-5-1)
— Per the AIM, this service is only available in Alaska.

A "stopway" can be defined as an area designated for use in decelerating the airplane during an aborted takeoff. (1.1)

When on the upper glidepath of a 3-bar VASI, what would be the colors of the lights? The near and middle bars are white and the upper bar is red.

Select the correct statement concerning Dallas Love Field. The runway gradient for Rwy 18 is less than .3 percent.
— Runway gradient is not specified in the Chart Supplement if it is less than .3%. "TCH" is a potential distractor. This is "Threshold Crossing Height," not the touchdown zone elevation (TDZE).

From sunset to sunrise, no person may park or move an aircraft in a night-flight operations area of an airport unless the aircraft is in an area marked by obstruction lights.
— Technically, this is permitted in a non-lighted area if the aircraft is clearly illuminated or has lighted position lights. However, this is a sample test question and the suggested correct answer.

Robert Wederquist   CP-ASEL - AGI - IGI
Commercial Pilot • Instrument Pilot
Advanced Ground Instructor • Instrument Ground Instructor

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