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O 1 Opposed configuration (US piston engine designation).
2 Operating cost over given period.
3 Ground speed ‘on’ (onwards from critical point).
4 Observation aircraft category (US services from
1922).
5 Aircraft category: hang gliders and paragliders
(FAA).
6 Instantaneous e.m.f., unit volt.
7 Origin of axes or graphical plot.
8 Omni-directional.
9 Other meanings include odd, over, oxygen and
optional.
o Lateral acceleration.
O 2 Oxygen.
O 3 Ozone.
O-ring Flexible fluid-sealing ring having O-section in
free state.
OA 1 Output axis.
2 Operational analysis.
3 Observation amphibian (USAAC, USAAF,
1925–47).
O/A On or about.
OAA 1 Orient Airlines Association.
2 Open Aviation Area.
OAAN Organismo Autónomo Aeropuertos Nacionales
(Spain).
OAB Outer air battle.
OAC 1 Operations Advisory Committee (UK CAA).
2 Oceanic Area Control [C adds Centre].
3 Oesterreichischer aero club [office, Vienna] (Austria).
OACE Open-architecture computing environment.
OACI ICAO (F).
OACS Optically active coding system.
OAD Office of Aviation Development [CAA, 1949 on].
OADF Overseas Aircraft Delivery Flight (RAF).
OADS Omnidirectonal air-data system (helicopter).
OAE Optimized after erosion (helicopter blade profile).
OAF Optical-alignment facility.
OAFS Open apron, free-standing (ie, no air-bridge).
OAFU Observers advanced flying unit.
OAG 1 Operational Advisory Group (BATA, USN).
2 Official Airline Guide.
OAI Office of Accident Investigation (FAA).
OAIRMS Open-architecture integrated radio management
system.
OALC Ogden Air Logistics Center (Hill AFB, Utah).
OALT Operationally acceptable level of traffic.
OAM 1 Office of Aviation Medicine (FAA).
2 Oil/air mist.
OAMCM Organic airborne mine countermeasures.
OAMO Office of Air and Marine Operations (ICE8).
OAMP Optical airborne measurement platform.
OAMS Orbital attitude and manoeuvre system.
O&C Operations and checkout.
O&D Origin and destination.
O&I Operations and integration.
O&M Operations & maintenance [CM adds configuration
management].
O&O Organizational and operational (RPV).
O&S 1 Operational, or operating, and support (costs).
2 Operations & Sustainment, of hardware in service
(USAF).
OANS Observers air navigation school.
OAO 1 Orbiting astronomical observatory.
2 Out-of-area operations.
OAOI On-and-off instruments.
OAP 1 Organizzazione dell’Aviazione Privata e
d’Affari (I).
2 Offset aiming point.
3 On-board attitude processor.
OAPD Online airline product database (IATA).
OAPEC Organization of Arab Petroleum Exporting
Countries.
OAPP Office of Aviation Policy and Plans (FAA 1).
OAPS Oblique air photograph strip.
OAR Office of Aerospace Research (USAF and
FAA/DoT).
OARB Orient airlines research bureau.
OARF Outdoor Aerodynamic Research Facility
(NASA, Ames).
OARN Off-airways R-nav.
OART Office of Advanced Research & Technology
(NASA; now AST).
OAS 1 Offensive avionics system.
2 Offensive air support (air support directly linked to
land operations, US).
3 Omnidirectional airspeed system (helo).
4 Open-access service.
5 Optimal aircraft scheduling.
6 Obstacle assessment surface.
7 Office of Aviation Safety (CAA).
8 On active service.
9 Oceanic Automation System (FAA/USN).
OASC Officer and Aircrew Selection Centre, [Biggin
Hill, now Cranwell] (RAF).
OASD Office of the Assistant SecDef (US).
OASF Orbiting astronomical support facility.
Oasis 1 Oceanic and atmospheric scientific information
system (NOAA).
2 Operational application of special intelligence system
(AAFCE).
3 Omnidirectional approach-slope indicator system.
4 Operational and supportability implementation
system (USAF/FAA).
5 Organic airborne and surface-influence sweep [sea
mines] (USN).
6 Oceanic Area system improvement study.
7 On-board aircraft server and information system.
8 Opto-electronic application-specific integrated
subsystem.
9 Trade name (du Pont) for sandwich for aerospace
wiring, red/white fluoropolymers on polyamide core.
OASPL Overall sound pressure level.
OAST Office of Aeronautics and Space Technology
(NASA), more usually AST.
Oasys Obstacle-avoidance, or awareness, system.
OAT 1 Outside air temperature.
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