Pilot/Controller Glossary

4/20/23

PCG A

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ALTERNATE AIRPORT

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 An airport at which an aircraft may land if a landing at the intended airport becomes

inadvisable.

(See ICAO term ALTERNATE AERODROME.)

ALTIMETER SETTING

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 The barometric pressure reading used to adjust a pressure altimeter for variations in

existing atmospheric pressure or to the standard altimeter setting (29.92).

(Refer to 14 CFR Part 91.)
(Refer to AIM.)

ALTITUDE

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 The height of a level, point, or object measured in feet Above Ground Level (AGL) or from Mean

Sea Level (MSL).

(See FLIGHT LEVEL.)

a.

MSL Altitude

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 Altitude expressed in feet measured from mean sea level.

b.

AGL Altitude

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 Altitude expressed in feet measured above ground level.

c.

Indicated Altitude

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 The altitude as shown by an altimeter. On a pressure or barometric altimeter it is altitude

as shown uncorrected for instrument error and uncompensated for variation from standard atmospheric
conditions.

(See ICAO term ALTITUDE.)

ALTITUDE [ICAO]

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 The vertical distance of a level, a point or an object considered as a point, measured from

mean sea level (MSL).

ALTITUDE READOUT

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An aircraft’s altitude, transmitted via the Mode C transponder feature, that is visually

displayed in 100-foot increments on a radar scope having readout capability.

(See ALPHANUMERIC DISPLAY.)
(See AUTOMATED RADAR TERMINAL SYSTEMS.)
(Refer to AIM.)

ALTITUDE RESERVATION (ALTRV)

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 Airspace utilization under prescribed conditions normally employed

for the mass movement of aircraft or other special user requirements which cannot otherwise be accomplished.
ALTRVs are approved by the appropriate FAA facility. ALTRVs must be classified as either “moving” or
“stationary.”

(See MOVING ALTITUDE RESERVATION.)
(See STATIONARY ALTITUDE RESERVATION.)
(See AIR TRAFFIC CONTROL SYSTEM COMMAND CENTER.)

ALTITUDE RESTRICTION

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 An altitude or altitudes, stated in the order flown, which are to be maintained until

reaching a specific point or time. Altitude restrictions may be issued by ATC due to traffic, terrain, or other
airspace considerations.

ALTITUDE RESTRICTIONS ARE CANCELED

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Adherence to previously imposed altitude restrictions is

no longer required during a climb or descent.

ALTRV

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(See ALTITUDE RESERVATION.)

AMVER

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(See AUTOMATED MUTUAL-ASSISTANCE VESSEL RESCUE SYSTEM.)

APB

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(See AUTOMATED PROBLEM DETECTION BOUNDARY.)

APD

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(See AUTOMATED PROBLEM DETECTION.)

APDIA

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(See AUTOMATED PROBLEM DETECTION INHIBITED AREA.)