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airspeed indicator, ASI
connected to airspeed indicator (ASI) to give airspeed
indicator reading (ASIR). When corrected for instrument
error (IE), result is indicated airspeed (IAS). When
corrected for position error (PE), result is rectified
airspeed (RAS). Most ASIs calibrated acccording to ideal
incompressible flow (½ρV 2 ), so from RAS subtract
compressibility correction to give equivalent airspeed
(EAS). Finally density correction, proportional to difference
between ambient air density and calibration density
(1,225 gm –3 ), applied to give true airspeed (TAS). This
sequence ignores errors, usually transient, due to major
changes in angle of attack (eg, in manoeuvres). Some ASIs
calibrated to allow for compressibility according to ISA
SL, indicating calibrated airspeed (CAS). Confusion
caused by fact most authorities now use ‘calibrated
airspeed’ to mean ASIR corrected for IE and PE; CAS
thus defined would have to be corrected for density and
compressibility. Thus since 1980 CAS must be regarded as
ASIR + IE + PE; if allowing for compressibility then at
ISA/SL CAS = TAS.
airspeed indicator, ASI Instrument giving continuous
indication of airspeed.
airspeed transducer In flight testing, or performance
measurement of unmanned vehicle in atmosphere,
transducer giving electrical signal proportional to
airspeed. In simple systems signal is d.c. voltage.
airsplint Lightweight splint, inflated for rigidity.
air spotting Correcting adjustment of friendly surface
bombardment based on air observation.
airspray nozzle Fuel burner in gas-turbine engine which
itself mixes fuel spray with primary air, avoiding smoke
from fuel-rich combustion and incidentally reducing
required fuel feed pressure.
AIRSS 1 Advanced IR suppressor, or suppression,
system.
2 Alternative IR satallite system (USAF).
air staging Gas-turbine combustion chamber having
variable geometry to redistribute air under different
engine operating conditions.
air staging unit Military unit stationed at airfield to
handle all assigned air traffic calling at that airfield.
airstairs Passenger and/or crew stairway forming integral
part of aircraft and, after use, folded or hinged up
and stowed on board.
Airstar Airborne surveillance and target-acquisition
radar.
airstart, air start Action of starting or re-starting
aircraft main propulsion or lift engines in flight.
air-starter unit Apron vehicle or trailer providing air at
2.8–3.5 bar.
airstream, air stream 1 Moving air mass, esp. that
penetrates and divides more stationary mass.
2 Loosely, any localised airflow.
airstrip Prepared operating platform for aeroplanes,
usually from STOL to CTOL, distinguished from airfield
by either: hasty construction under battlefield conditions;
lack of permanent paved surfaces; lack of permanent
accommodation for personnel or hardware; or lack of
facilities, other than temporary fuel supply or ATC.
air superiority Degree of airspace dominance sufficient
to prevent prohibitive enemy interference with one’s own
operations.
air-superiority fighter Combat aircraft designed specif.
to clear airspace of hostile aircraft.
air-transportable units
air supremacy Degree of air superiority sufficient to
prevent effective enemy interference with one’s own
operations.
air surface zone Restricted area established to protect
friendly surface vessels and aircraft and permit ASW
operations unhindered by presence of friendly
submarines.
air surveillance Systematic observation of airspace by
visual electronic or other means to plot and identify all
traffic.
air survey See aerial survey.
AIRT Air-intercept radar training.
air taxi Aircraft below 12,500 lb TOGW, licensed to ply
for hire for casual passenger traffic.
air taxiing Positioning helicopter or other VTOL or
STOVL aircraft by short translational flight at very low
altitude. Standardised ** manoeuvres form part of VTOL
flying insruction.
air terminal Facility in city centre at which passengers
can check in for flights and board coach to airport.
air time Elapsed time from start of takeoff run to end of
landing run.
Airto Association of Independent Research &
Technology Organisations (UK).
air-to-air From one aerial position to another, esp.
between one airborne aircraft and another.
air-to-ground Between aerial position, esp. airborne
aircraft, and land surface.
air-to-surface Between aerial position, esp. airborne
aircraft, and any part of Earth’s surface or target thereon.
air-to-underwater Between aerial position, esp. airborne
aircraft, and location below water surface, esp. flight
profile of ASW weapons and operating regime of ASW
detection systems.
AIRTP Air Troop.
Air Track Landing Early form of ILS developed by NBS
and Washington Institute of Technology.
air traffic Aircraft operating in air or on airport surface,
exclusive of loading ramps and parking areas (FAA);
aircraft in operation anywhere in airspace and on
manoeuvring area of aerodrome (BSI). To air carriers
‘traffic’ has entirely different meaning, but this is never
qualified by ‘air’.
air traffic clearance See clearance (1).
air traffic control radar beacon system Beacons along
airways which trigger responses from airborne transponders
providing identity, location and [usually] FL of
equipped traffic. See secondary radar.
air traffic control centre Unit combining functions of
area control centre and flight information centre.
air traffic control service Service provided for promoting
safe, orderly and expeditious flow of air traffic, including
airport, approach and en route ATC service.
air traffic engineer Maintains navaids and airport
communications systems.
air traffic service assistant Provides admin. & support,
such as flight-plan acceptance and preflight briefing for
pilots.
air train Aerial tug towing two or more gliders in lineahead.
air-transportable hangar Modular lightweight hangar
erected over temporary site, such as crashed repairable
aircraft.
air-transportable units Military units, other than
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