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AOTD
AOTD Active optical target detector.
AO2 Automated observation from unattended ASOS.
AO2A AO-augmented, from an attended ASOS.
AOU Area of uncertainty.
A ov Area of overlap [twin-rotor helicopter].
AOW All-operators wire [AOT is preferred].
AOY Angle of yaw.
AP 1 Armour-piercing [–DS adds discarding sabot, –E
explosive, –F finned, –I incendiary, –T tracer; there are
other suffixes).
2 Ammonium perchlorate (solid rocket fuel).
3 Air Publication (UK).
4 Airport (ICAO, Acars).
5 Autopilot.
6 Aviation regiment (USSR).
7 Allied publication (NATO).
8 Advance[d] procurement.
9 Airframe parachute [S adds system].
10 Action Panel [materials R&D].
11 Array processor.
12 Anti-personnel.
13 Anomalous propagation.
14 Approach [apch preferred].
15 Assessment Phase (UK).
16 Automotive [i.e., automatic] picture [transmission].
17 Aeroklub-Polski [Warsaw PL-00-071] (Poland).
18 Aluminised phosphor.
Ap Approach light[s].
A/P 1 Autopilot.
2 Airplane(s).
3 Airport.
4 Aim point.
APA 1 Airline Passengers Association (US).
2 Airport (or airfield) pressure altitude.
3 Allied Pilots’ Association [Fort Worth, TX76155-
2512] (US).
4 Army Parachute Association (UK).
5 Autopilot amplifier.
6 Automatic plotting aid.
7 Aerobatic practice area.
8 Accidents to private aviation [now Saga].
9 Altitude preselect/alert[er].
10 Aviation Policy Area.
11 Aerodromes Protection Agency, found necessary to
fight closures (UK).
12 Airline performance analyses.
13 Associazione Pionieri dell’ Aeronautica [previously
ANPA, pilots with brevet before 2 Aug. 14; I-00192
Rome] (Italy).
14 Airline Professionals Association [pilot union] (US).
APAC Association of Professional Aviation
Consultants (UK).
APACCS Aerial-port command and control systems
(USAF).
Apacs Atlas prompting and checking system.
APADS Advanced precision air-delivery system.
APAG Allied Policy Advisory Group (NATO).
Apals Autonomous precision-approach and landing
system.
AP/AM Anti-personnel/anti-material (last word often
spelt materiel).
APAMA Asia/Pacific Aviation Media Association.
APAP Approach-path alignment panels.
Apapi Abbreviated Papi.
aperture
APAR Active phased-array radar (Canada, G, Neth.).
APATC Allied publication air traffic control.
Apatsi Airport/air-traffic system interface.
APAW Air-portable avionic workshop (RAF).
APB 1 Auxiliary power-breaker.
2 Aviation Policy Board (US Congress 1947–48).
3 Automated passenger bridge.
APC 1 Association of Parascendng Clubs.
2 Approach power control (or compensator).
3 Armament practice camp (RAF).
4 Avionics planning conference.
5 Aviation Press Club (Belg.).
6 Area positive control.
7 Aeronautical passenger communications.
8 Aeronautical public correspondence [public telephone].
9 Autopilot computer [also A/PC].
10 Adaptive packet compression.
APCA Association Professionnelle de la Circulation
Aérienne (F).
APCB Advanced plenum-chamber burning.
APCC Air Pollution Control Center (EPA, US).
apch, apchg Approach, approaching (FAA).
APCI The Aviation Postcard Club International [Old
Coulsdon, CR5 1QB, UK] (Int.).
APCO Air Pollution Control Office (EPA, US).
APCR Armour-piercing, composite rigid.
APCS 1 Air Photo and Charting Service (USAF,
Orlando AFB).
2 Approach-power compensation system.
APCTA Associacão Portuguesa dos Controladores de
Tráfego Aéreo [office, Lisbon P-1800] (Portugal).
APD 1 JETDS code: piloted aircraft, radar, DF/
reconnaissance/surveillance (usually SLAR).
2 Aerial position, digital (usually 4,096 pulses per 360°).
3 Avalanche photo-diode.
4 Amplifyng photo-diode.
5 Airports Policy Divisions [1 to 3] (DETR UK).
6 Air Procurement District.
7 Air Passenger Duty (UK).
APDMC, A/PDMC Aircraft and products, or aircraftpropulsion,
data-management computer.
APDS Air-picture display system; multi-radar C 2 .
APDZ Active parachute drop zone.
APE 1 Airline pallet extender.
2 Airborne polar experiment, study of ozone depletion
(R).
APEC Asia-Pacific Economic Co-operation.
APEP Armour-piercing, enhanced penetration.
aperiodic Of any dynamic and potentially oscillatory
system, so heavily damped as to have no period; unable to
accomplish one cycle of oscillation; thus * magnetic
compass, * electric circuit.
aperture 1 Diameter of objective of optical instrument,
either direct length or function of it; also angular *, minor
angle subtended at principal focus by extremes of objective
diameter; numerical *, n sin u, where n is refractive
index between lens and object and u is objective angular
radius (half angular aperture); and relative * (f-number)
relating focal length to objective diameter.
2 In radio or radar aerial, either greatest dimension; or,
with undirectional aerial, greatest length across plane
perpendicular to direction of maximum radiation, close to
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