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UMV
UMV Unmanned vehicle, from 2004 standard term in
US military.
UN United Nations, many suffixes.
UNA Unable.
unaccelerated flight Flight without imposed acceleration,
but there are several conflicting definitions and term
needs redefining to avoid ambiguity; (1) flight along
straight-line trajectory at constant V, thus no imposed
acceleration; (2) rectilinear flight (eg straight and level)
with no imposed acceleration normal to flightpath other
than Earth gravity; (3) weightless flight with not even
gravitational acceleration, thus curvilinear around Earth.
Definition (2) allows acceleration along line of flight, thus
speed can vary.
unaccompanied baggage Not carried on same aircraft
with pax or crew to which it belongs; DoD definition adds
‘not carried free on ticket used for personal travel’.
unanimity rule Basic IATA principle that fare from A to
B is same as from B to A and same for all carriers offering
identical service; can be relaxed.
UNAP Unable to approve.
unapproved Not tested to established requirements, thus
flown on special dispensation, eg VW engines with single
ignition.
unapproved part Can physically be installed but does not
fulfil requirements. See counterfeit.
unaugmented In case of turbojet or turbofan, not
equipped with afterburner, or not using afterburner.
unavbl Unavailable.
Unavia Italian national organization for study and
development of aircraft technology.
unbalanced cell Cell of Ni/Cd battery which has
discharged more than others; first step to thermal
runaway.
unbalanced field Any takeoff in which accelerate/stop
distance is not the same as for normal takeoff to 35 ft.
unbalanced turn One with slip or skid.
unblown 1 STOL aircraft with USB, IBF, EBF or other
powered blowing system in flight mode with blowing
inoperative.
2 Of piston engine, not equipped with supercharger.
unburnt hydrocarbons Essentially unburnt fuel, contaminant
emitted by engines and subject to emissions
legislation.
UNC United Nations command; followed by various
force initials.
uncertain Category of aircraft whose safety is not
known, normally applied when 30 minutes have elapsed
since arrival message or ETA and not answering radio
call; hence uncertainty phase.
Uncertificated Aircraft category; airworthiness not
established.
UNCL 1 Unified numerical-control language.
2 Unclassified.
Unclassified 1 Security category for official matter
which requires no safeguards but may be controlled for
other reasons.
2 Performance category for aircraft, usually civil
transports, in service prior to 1951 and thus not built to
CAR.4(b), BCARs or SR.422A/B.
uncontrolled airspace Airspace where no ATC service is
provided.
uncontrolled mosaic Made up of uncorrected images
matched from print to print without ground control or
unduplicated
other orientation, giving mosaic on which distances and
bearings cannot be accurately measured.
uncooled Descriptive of turbine blade devoid of internal
or transpiration cooling.
uncooperative Generalized adjective for vehicle of essentially
passive nature, devoid of helpful emissions and not
responding when electronically challenged; applied to
aircraft, usually means not equipped with transponder.
uncoupled Vibration mode wholly independent of others
at same time.
Unctad UN Conference on Trade and Development.
unctld Uncontrolled airspace (FAA).
undamped Vibration of free nature dependent only on
internal mass and elastic and inertia forces.
UNDB U.h.f. non-directional beacon.
underbreathing See hypoventilation.
undercarriage Landing gear (UK usage; original BSI
definition included main wheels, skids or floats and
support and explicitly excluded tail wheel or skid). Hence
* door, indicator, same as landing gear door, indicator.
Note: floats are usually called alighting gear.
undercast Solid cloud cover seen from above.
underdeck spray Pad deluge directed up at underside of
launch pad (in some cases deliberately including underside
of base of launched vehicle).
undergraduate Aircrew (esp. pilot) pupil who has not yet
qualified, ie won his/her wings.
underlay Lowest stratum of layered defence.
undershoot 1 Faulty approach by aerodyne, usually
fixed wing, which if continued to ground results in landing
short of desired area, eg before threshold; normally
corrected by go-around (overshoot).
2 To fail to capture desired flight condition, eg altitude,
IAS, by falling short when approaching value from
below, normally through small lack of aircraft energy.
under the hood Instrument flight training in which pupil
is prevented from seeing outside aircraft, originally by
unfolding opaque hood, later by two-stage amber or other
method.
under the radar Flight levels as close as possible (see lo)
to ground in attempt to thwart hostile attempts to obtain
positive track by defensive radars; becoming pious hope.
underwater missile Launched below water surface.
under way Marine aircraft, moving on water [some
authorities: under weigh, from weighing the anchor].
underwedge bleed Secondary airflow extracted from
location on underside of variable wedge above supersonic
airbreathing inlet, usually from point of maximum wedge
depth at throat.
under wing In service [engine possibly hung on rear fuselage],
thus 30,000 h * = total time.
undevelopable 3-D curvature, which cannot be drawn
accurately on flat sheet and can be made only by some
type of sheet forming.
undk Undock(ing).
undock 1 To separate two vehicles in space previously
joined and with intercommunication but not necessarily
sharing common atmosphere.
2 To remove airship from hangar.
unducted fan Engine in which gas-turbine core drives fan
blades external to cowled engine. Blades can be mounted
on ring of turbine blades in gas flow, or driven via gearbox
(tractor or pusher) from separate turbine.
unduplicated Generalized term meaning that in
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