Aeronautical Terms beginning with U
Ultralight Vehicle
An aeronautical vehicle operated for sport or recreational purposes which does not require FAA registration, an airworthiness certificate, nor pilot certification. They are primarily single occupant vehicles, although some two-place vehicles are authorized for training purposes. Operation of an ultralight vehicle in certain airspace requires authorization from ATC.
Unable
Indicates inability to comply with a specific instruction, request, or clearance.
Uncaging
Unlocking the gimbals of a gyroscopic instrument, making it susceptible to damage by abrupt flight maneuvers or rough handling.
Uncontrolled airspace
Class G airspace that has not been designated as Class A, B, C, D, or E. It is airspace in which air traffic control has no authority or responsibility to control air traffic; however, pilots should remember there are VFR minimums which apply to this airspace.
Under The Hood
Indicates that the pilot is using a hood to restrict visibility outside the cockpit while simulating instrument flight. An appropriately rated pilot is required in the other control seat while this operation is being conducted.
Underpower
Using less power than required for the purpose of achieving a faster rate of airspeed change.
Unicom
A nongovernment communication facility which may provide airport information at certain airports. Locations and frequencies of UNICOMs are shown on aeronautical charts and publications.
United States
In a geographical sense means (1) the States, the District of Columbia, Puerto Rico, and the possessions, including the territorial waters, and (2) the airspace of those areas.
Unreliable (GPS/WAAS)
An advisory to pilots indicating the expected level of service of the GPS and/or WAAS may not be available. Pilots must then determine the adequacy of the signal for desired use.
Unusual attitude
An unintentional, unanticipated, or extreme aircraft attitude.
Upwind Leg
A flight path parallel to the landing runway in the direction of landing.
Urgency
A condition of being concerned about safety and of requiring timely but not immediate assistance; a potential distress condition.
Useful load
The weight of the pilot, copilot, passengers, baggage, usable fuel, and drainable oil. It is the basic empty weight subtracted from the maximum allowable gross weight. This term applies to general aviation aircraft only.
User-defined waypoints
Waypoint location and other data which may be input by the user, this is the only GPS database information that may be altered (edited) by the user.
Utility Category
A category of aircraft certificated under 14 CFR part 23 and CAR part 3 that permits limited acrobatic maneuvers but restricts the weight and the CG range.
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