(See DIRECTION FINDER.)
(See ULTRAHIGH FREQUENCY.)
ULTRAHIGH FREQUENCY- The
frequency band between 300 and 3,000 MHz. The bank of radio frequencies used for
military air/ground voice communications. In some instances this may go as low
as 225 MHz and still be referred to as UHF.
aeronautical vehicle operated for sport or recreational purposes which does not
require FAA registration, an airworthiness certificate, nor pilot certification.
Operation of an ultralight vehicle in certain airspace requires authorization
Indicates inability to comply with a specific instruction, request, or
UNASSOCIATED- A radar
target that does not display a data block with flight identification and
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.
(Refer to 14 CFR Part 91.)
UNFROZEN- The Scheduled
Time of Arrival (STA) tags, which are still being rescheduled by traffic
management advisor (TMA) calculations. The aircraft will remain unfrozen until
the time the corresponding estimated time of arrival (ETA) tag passes the preset
freeze horizon for that aircraft's stream class. At this point the automatic
rescheduling will stop, and the STA becomes "frozen."
UNICOM- A nongovernment
communication facility which may provide airport information at certain
airports. Locations and frequencies of UNICOMs are shown on aeronautical charts
(Refer to AIM.)
UNPUBLISHED ROUTE- A route
for which no minimum altitude is published or charted for pilot use. It may
include a direct route between NAVAIDs, a radial, a radar vector, or a final
approach course beyond the segments of an instrument approach procedure.
(See PUBLISHED ROUTE.)
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.
(See TRAFFIC PATTERN.)
(See USER REQUEST EVALUATION
URGENCY- A condition of
being concerned about safety and of requiring timely but not immediate
assistance; a potential distress condition.
(See ICAO term URGENCY.)
URGENCY [ICAO]- A
condition concerning the safety of an aircraft or other vehicle, or of person on
board or in sight, but which does not require immediate assistance.
(See ARMY AVIATION FLIGHT
USER REQUEST EVALUATION
TOOL (URET)- User Request Evaluation Tool is an automated tool provided at each
Radar Associate position in selected En Route facilities. This tool utilizes
flight and radar data to determine present and future trajectories for all
active and proposal aircraft and provides enhanced, automated flight data
(See DIRECTION FINDER.)