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Pilot/Controller Glossary

3/29/18

PCG A−10

ALTERNATE AERODROME [ICAO]− An aero-

drome to which an aircraft may proceed when it

becomes either impossible or inadvisable to proceed

to or to land at the aerodrome of intended landing.

Note: The aerodrome from which a flight departs

may also be an en-route or a destination alternate

aerodrome for the flight.

ALTERNATE AIRPORT− An airport at which an

aircraft may land if a landing at the intended airport

becomes inadvisable.

(See ICAO term ALTERNATE AERODROME.)

ALTIMETER SETTING− 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− 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− Altitude expressed in feet

measured from mean sea level.

b. AGL Altitude− Altitude expressed in feet

measured above ground level.

c. Indicated Altitude− 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]− The vertical distance of a level,

a point or an object considered as a point, measured

from mean sea level (MSL).

ALTITUDE READOUT− 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)− 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.

(See AIR TRAFFIC CONTROL SYSTEM

COMMAND CENTER.)

ALTITUDE RESTRICTION− An altitude or alti-

tudes, 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−

Adherence to previously imposed altitude restric-

tions is no longer required during a climb or descent.

ALTRV−

(See ALTITUDE RESERVATION.)

AMVER−

(See AUTOMATED MUTUAL-ASSISTANCE

VESSEL RESCUE SYSTEM.)

APB−

(See AUTOMATED PROBLEM DETECTION

BOUNDARY.)

APD−

(See AUTOMATED PROBLEM DETECTION.)

APDIA−

(See AUTOMATED PROBLEM DETECTION

INHIBITED AREA.)

APPROACH CLEARANCE− Authorization by

ATC for a pilot to conduct an instrument approach.

The type of instrument approach for which a

clearance and other pertinent information is provided

in the approach clearance when required.

(See CLEARED APPROACH.)
(See INSTRUMENT APPROACH

PROCEDURE.)

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

APPROACH CONTROL FACILITY− A terminal

ATC facility that provides approach control service in

a terminal area.

(See APPROACH CONTROL SERVICE.)
(See RADAR APPROACH CONTROL

FACILITY.)

APPROACH CONTROL SERVICE− Air traffic

control service provided by an approach control

facility for arriving and departing VFR/IFR aircraft

and, on occasion, en route aircraft. At some airports