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OATA
2 Operational acceptance test.
3 Operational air traffic (ie military).
4 Oxide aligned transistor.
5 Operational, or optional, auxiliary terminal (Acars).
6 Operational airfield test set.
7 Orbit and attitude tracking; S adds system.
8 One at a time [experiments].
OATA Overall ATM/CNS target architecture
(Eurocae, Eurocontrol).
OAV Organic air vehicle.
OAVUK Society for aviation and gliding of Ukraine
and Crimea.
OB 1 Outbound.
2 Balloon club (Austria).
3 Off-boresight.
4 Operations base (USA).
5 Operational Bulletin.
O/B 1 Outbound.
2 Outboard.
OBA Outbound boom avoidance (SST).
OBAP 1 Organization of Black Airline Pilots (US).
2 Off-boresight angle.
OBC 1 Optical barrel, or BAR, camera.
2 On-board computer.
OBCO(S) On-board cargo operations (system).
Ob.dL Oberkommando der Luftwaffe (G).
OBDMS On-board data-monitoring systems.
OBE 1 Off-board expendables.
2 Overtaken by events.
OBEWS 1 On-board electronic warfare simulation.
2 On-board EW system(s).
OBFM Offensive basic flight manoeuvres.
OBI Omni-bearing indicator.
Obiggs On-board inert gas generating system.
OBIS On-board information system.
objective 1 Normally, in optical, EO or IR system, first
lens or lens group to receive incoming radiation.
2 Military target for capture or other action by surface
forces; not used for target for aerial attack.
oblique Oblique photograph.
oblique camera One mounted in aircraft with axis
between vertical and horizontal.
oblique flying wing Aeroplane [airplane] designed to fly
with wing set diagonally, one side swept forward, the
other back.
oblique photograph One taken by oblique camera; subdivided
into high * in which apparent horizon appears and
low * in which it does not.
oblique projection Map projection with axis inclined at
oblique angle (say, 20° to 60°) to plane of Equator.
oblique-shock inlet Inlet designed for use in supersonic
vehicle and provided with centrebody, wedge or other
projecting portion intended to focus oblique shockwave
on opposite lip.
oblique shockwave Inclined shock formed whenever
supersonic flow has to turn through finite angle in
compressive direction.
oblique wing 1 Wing arranged to pivot at mid-point as
single unit so that, as one half is swept back, other half is
swept forwards. Also called slew wing.
2 See oblique flying wing.
OBLMS On-board life-monitoring system.
OBMS On-board medical site.
Oboe WW2 precision navaid of SSR type with Cat
obstruction angle
station near Dover and Mouse station in Norfolk sending
synchronized pulses which formed continuous note along
correct flightpath over distant target; Mouse operators
also sent signals to tell aircrew when to release bombs or
TIs.
Obogs On-board oxygen generation, or generating,
system.
OBP 1 On-board processor, or processing [satcom].
2 Omnidirectional ball panel.
3 Operational build plan.
OBPR Office of Biological and Physical Research
(NASA).
OBR Optical beam rider, or riding.
OBRC Operating budget review committee.
OBRM On-board replacement module.
OBS 1 Omni-bearing selector.
2 Observe/observed/observing (ICAO).
3 On-board simulation.
4 Organizational breakdown structure.
5 Optical bypass switch.
6 Observation-balloon system (tethered near major
highway).
obs 1 Obstruction lights.
2 Observe[d], observation.
3 Obstacle.
Obsc, OBSC Obscure/obscured/obscuring (ICAO).
obscuration methods Instrument techniques for
measuring visible smoke (eg from jet engine) such as HSU
and PSU where cutoff of calibrated light beam is
measured over known distance.
observation 1 Many military definitions, most agreeing
that * platform is for gathering all possible tactical information
about an enemy. Increasingly [1942–, and
especially in Korea and SE Asia] US * aircraft guided
tactical aircraft to point targets.
2 Complete set of meteorological readings at one place
and time.
observation balloon In bygone wars, tethered balloon
carrying human who reported on fall of shot and on
enemy activity.
observation balloon system In US, usually tethered at
airfield to monitor potentially conflicting road traffic, eg
at runway crossing.
observation mirror A horizontal mirror with superimposed
graticule used in the same way as a camera obscura.
observed value Measured, not calculated.
observer Common title for second crew member in twoseat
military (especially combat) aircraft whose functions
may include navigation, systems management, electronic
warfare, command guidance of weapons and other tasks;
title is traditional and may bear no relation to actual
duties.
OBSS Orbiter boom sensor system.
OBST, obst Obstruction, obstacle.
obstacle clearance height Lowest height above runway
threshold or aerodrome elevation used to establish
compliance with obstacle clearance criteria in instrument
approach.
obstn Obstruction (FAA).
obstruction Also called obstacle, a real or notional solid
body forming hazard to aircraft on or near runway or
flight path. For certification purposes has height of 10.7
mm (35 ft) or 15 m (50 ft).
obstruction angle Angle between horizontal and line
459