o/r - on request.
o/t - other times.
OAT - outside air temperature. The temperature of the air
outside an aircraft measured by a probe with a cockpit gauge readout.
OAT affects the measurement of indicated airspeed and its value is
needed to calculate true airspeed. At high speeds kinetic heating
demands correction to the indicated OAT for true outside air
OATS - Oxford Air Training School, a large commercial pilot
training school at Oxford Airport, UK.
OBS - omni-eighth of the sky is covered.
obst - obstruction.
OCH - obstacle clearance height. The lowest height above the
elevation of the runway threshold or above aerodrome elevation used to
establish compliance with obstacle clearance criteria in an instrument
approach. Also OCA, obstacle clearance altitude, and OCL, obstacle
OCU - Operational Conversion Unit.
OEM - original equipment manufacturer.
okta - a measurement of cloud cover. One okta means one eighth
of the sky is covered.
Omega - high accuracy, very-low frequency (VLF) long range
navigation system of the hyperbolic type, covering the entire earth
down to the surface from eight ground based transmitters. Used
principally by airliners, military aircraft and intercontinental
OTU - Operational Training Unit.