Pilot/Controller Glossary 

5/19/22 

AUTOMATIC ALTITUDE REPORTING

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 That 

function of a transponder which responds to Mode C 
interrogations by transmitting the aircraft’s altitude 
in 100-foot increments. 

AUTOMATIC CARRIER LANDING SYSTEM

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U.S. Navy final approach equipment consisting of 
precision tracking radar coupled to a computer data 
link to provide continuous information to the aircraft, 
monitoring capability to the pilot, and a backup 
approach system. 

AUTOMATIC DEPENDENT SURVEILLANCE 
(ADS) [ICAO]

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 A surveillance technique in which 

aircraft automatically provide, via a data link, data 
derived from on

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board navigation and position 

fixing systems, including aircraft identification, four 
dimensional position and additional data as 
appropriate. 

AUTOMATIC  DEPENDENT SURVEILLANCE

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BROADCAST (ADS-B)

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 A surveillance system in 

which an aircraft or vehicle to be detected is fitted 
with cooperative equipment in the form of a data link 
transmitter. The aircraft or vehicle periodically 
broadcasts its GNSS

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derived position and other 

required information such as identity and velocity, 
which is then received by a ground

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based or 

space

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based receiver for processing and display at an 

air traffic control facility, as well as by suitably 
equipped aircraft. 

(See AUTOMATIC DEPENDENT 

SURVEILLANCE

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BROADCAST IN.) 

(See AUTOMATIC DEPENDENT 

SURVEILLANCE

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BROADCAST OUT.) 

(See COOPERATIVE SURVEILLANCE.) 
(See GLOBAL POSITIONING SYSTEM.) 
(See SPACE

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BASED ADS

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B.) 

AUTOMATIC  DEPENDENT SURVEILLANCE

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BROADCAST IN (ADS

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B In)

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 Aircraft avionics 

capable of receiving ADS

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B Out transmissions 

directly from other aircraft, as well as traffic or 
weather information transmitted from ground 
stations. 

(See AUTOMATIC DEPENDENT 

SURVEILLANCE

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BROADCAST OUT.) 

(See AUTOMATIC DEPENDENT 

SURVEILLANCE

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REBROADCAST.) 

(See FLIGHT INFORMATION 

SERVICE

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BROADCAST.) 

(See TRAFFIC INFORMATION 

SERVICE

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BROADCAST.) 

AUTOMATIC  DEPENDENT SURVEILLANCE

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BROADCAST OUT (ADS

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B Out)

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 The transmitter 

onboard an aircraft or ground vehicle that 
periodically broadcasts its GNSS

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derived position 

along with other required information, such as 
identity, altitude, and velocity. 

(See AUTOMATIC DEPENDENT 

SURVEILLANCE

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BROADCAST.) 

(See AUTOMATIC DEPENDENT 

SURVEILLANCE

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BROADCAST IN.) 

AUTOMATIC  DEPENDENT SURVEILLANCE

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CONTRACT (ADS

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C)

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 A data link position 

reporting system, controlled by a ground station, that 
establishes contracts with an aircraft’s avionics that 
occur automatically whenever specific events occur, 
or specific time intervals are reached. 

AUTOMATIC DEPENDENT SURVEILLANCE-
REBROADCAST (ADS-R)

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 A datalink translation 

function of the ADS

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B ground system required to 

accommodate the two separate operating frequencies 
(978 MHz and 1090 MHz). The ADS

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B system 

receives the ADS

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B messages transmitted on one 

frequency and ADS

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R translates and reformats the 

information for rebroadcast and use on the other 
frequency. This allows ADS

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B In equipped aircraft 

to see nearby ADS

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B Out traffic regardless of the 

operating link of the other aircraft. Aircraft operating 
on the same ADS

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B frequency exchange information 

directly and do not require the ADS

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R translation 

function. 

AUTOMATIC DIRECTION FINDER

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 An aircraft 

radio navigation system which senses and indicates 
the direction to a L/MF nondirectional radio beacon 
(NDB) ground transmitter. Direction is indicated to 
the pilot as a magnetic bearing or as a relative bearing 
to the longitudinal axis of the aircraft depending on 
the type of indicator installed in the aircraft. In certain 
applications, such as military, ADF operations may 
be based on airborne and ground transmitters in the 
VHF/UHF frequency spectrum. 

(See BEARING.) 
(See NONDIRECTIONAL BEACON.) 

AUTOMATIC FLIGHT INFORMATION SER-
VICE (AFIS) 

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 ALASKA FSSs ONLY

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 The 

continuous broadcast of recorded non

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control 

information at airports in Alaska where a FSS 
provides local airport advisory service. The AFIS 
broadcast automates the repetitive transmission of 
essential but routine information such as weather, 
wind, altimeter, favored runway, braking action, 

PCG A

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