Aeronautical Terms beginning with U
User-defined Waypoint
User-defined waypoints typically are created by pilots for use in their own random RNAV direct navigation. They are newly established, unpublished airspace fixes that are designated geographic locations/positions that help provide positive course guidance for navigation and a means of checking progress on a flight. They may or may not be actually plotted by the pilot on enroute charts, but would normally be communicated to ATC in terms of bearing and distance or latitude/longitude. An example of user defined waypoints typically includes those derived from database-driven area navigation (RNAV) systems whereby latitude/longitude coordinate-based waypoints are generated by various means including keyboard input, and even electronic map mode functions used to establish waypoints with a cursor on the display. Another example is an offset phantom waypoint, which is a point in space formed by a bearing and distance from NAVAIDs such as VORs, VORTACs, and TACANs, using a variety of navigation systems.
User Request Evaluation Tool (URET)
The URET helps provide enhanced, automated flight data management. URET is an automated tool provided at each radar position in selected en route facilities. It uses flight and radar data to determine present and future trajectories for all active and proposed aircraft flights. A graphic plan display depicts aircraft, traffic, and notification of predicted conflicts. Graphic routes for current plans and trial plans are displayed upon controller request. URET can generate a predicted conflict of two aircraft, or between aircraft and airspace.
Ultimate Load Factor
In stress analysis, the load that causes physical breakdown in an aircraft or aircraft component during a strength test, or the load that according to computations, should cause such a breakdown.
Unfeathering Accumulator
Tanks that hold oil under pressure which can be used to unfeather a propeller.
UNICOM
A non-government air/ground radio communication station which may provide airport information at public use airports where there is no tower or FSS.
Unusable Fuel
Fuel that cannot be consumed by the engine. This fuel is considered part of the empty weight of the aircraft.
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.
Utility Category
An airplane that has a seating configuration, excluding pilot seats, of nine or less, a maximum certificated takeoff weight of 12,500 pounds or less, and intended for limited acrobatic operation.
Ultra-high frequency (UHF)
The range of electromagnetic frequencies between 962 MHz and 1213 MHz.
Uncaging
Unlocking the gimbals of a gyroscopic instrument, making it susceptible to damage by abrupt flight maneuvers or rough handling.
Underpower
Using less power than required for the purpose of achieving a faster rate of airspeed change.
United States Terminal Procedures Publication (TPP).
Booklets published in regional format by the NACO that include DPs, STARs, IAPs, and other information pertinent to IFR flight.
Unusual attitude
An unintentional, unanticipated, or extreme aircraft attitude.
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.
Understanding
A basic level of learning at which a student comprehends or grasps the nature or meaning of something.
Usability
The functionality of tests.
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.
United States air carrier
A citizen of the United States who undertakes directly by lease, or other arrangement, to engage in air transportation.
Undrainable Oil
Oil that does not drain from an engine lubricating system when the aircraft is in the normal ground attitude and the drain valve is left open. The weight of the undrainable oil is part of the empty weight of the aircraft.
Unusable Fuel
(GAMA) Fuel remaining after a runout test has been completed in accordance with governmental regulations.
Usable Fuel
(GAMA) Fuel available for flight planning.
Useful Load
(GAMA) Difference between takeoff weight, or ramp weight if applicable, and basic empty weight.
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.
Undercast
A cloud layer of ten-tenths (1.0) coverage (to the nearest tenth) as viewed from an observation point above the layer.
Unlimited ceiling
A clear sky or a sky cover that does not meet the criteria for a ceiling.
Unstable
Instability. A general term to indicate various states of the atmosphere in which spontaneous convection will occur when prescribed criteria are met; indicative of turbulence.
Updraft
A localized upward current of air.
Upper front
A front aloft not extending to the earth’s surface.
Upslope fog
Fog formed when air flows upward over rising terrain and is, consequently, adiabatically cooled to or below its initial dew point.
Ultra-high frequency (UHF)
The range of electromagnetic frequencies between 962 MHz and 1213 MHz.
Ultimate load factor
In stress analysis, the load that causes physical breakdown in an aircraft or aircraft component during a strength test, or the load that according to computations, should cause such a breakdown.
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.
Underpower
Using less power than required for the purpose of achieving a faster rate of airspeed change.
United States Terminal Procedures Publication (TPP)
Booklets published in regional format by the NACO that include DPs, STARs, IAPs, and other information pertinent to IFR flight.
Unusual attitude
An unintentional, unanticipated, or extreme aircraft attitude.
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.
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