Instrument Flight
Glossary
GLOSSARY
A
Airport Elevation/Field Elevation: The highest point of the usable runways measured in feet MSL.
Airport Surveillance Radar (ASR): Radar providing position of aircraft by azimuth and range data
without elevation data. Used for terminal approach and departure control. (See Surveillance Approach.)
Air Route Traffic Control Center (ARTCC): A facility established to provide traffic control service to IFR
flights operating within controlled airspace, principally during the enroute phase of flight.
Airway: Class E airspace or portion thereof established in the form of a corridor equipped with radio
navigational aids.
Alert Area: An airspace which may contain a high volume of pilot training activities or an unusual type of
aerial activity, neither of which is hazardous to aircraft.
Alternate Airfield: An airport specified in a flight plan to which a flight may proceed if the destination is
below minimums or safety considerations preclude a landing.
AOA: Angle of attack.
AOB: Angle of bank.
Approach Control: A term used to indicate an air traffic control unit providing approach control service,
without specifying the unit.
Approach Control Service: Service provided by a terminal area traffic control facility for arriving and/or
departing IFR flights and, on occasion, VFR flights.
ASR: See Airport Surveillance Radar.
Air Traffic Control (ATC): Any of the controlling agencies providing direction and traffic separation for
aircraft.
Automatic Terminal Information Service (ATIS): A continuous broadcast of recorded, non-control
information in selected high activity terminal areas. Its purpose is to improve controller effectiveness and
to relieve frequency congestion by automating the repetitive transmission of essential but routine
information.
B
BIT: Built-in test. Self-testing capabilities contained within an instrument or system.
C
Caution Area: An area within which military training activities, though not hazardous, are of interest to
nonparticipating pilots.
Ceiling: The height above the earth’s surface of the lowest layer of clouds or other obscuring
phenomena. This layer is described as “broken,” “overcast,” or “obscuration” and not classified as “thin”
or “partial.”
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