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Aeronautical Information Manual (AIM), page 618

Pilot/Controller Glossary 5/26/16


area navigation reference capabilities that are not
subject to slant range errors.

ALPHANUMERIC DISPLAY- Letters and numer-

als used to show identification, altitude, beacon code,
and other information concerning a target on a radar
display.
(See AUTOMATED RADAR TERMINAL
SYSTEMS.)

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

12/10/15

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- 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.)


PCG A-10

Page 618 of the Aeronautical Information Manual (AIM.pdf)
AIM: Official Guide to Basic Flight Information and ATC Procedures

Index   617 -- Page 618 -- 619