U

UAM-

See URBAN AIR MOBILITY

UAP-

See UNIDENTIFIED ANOMALOUS PHENOMENA

UAS FACILITY MAP (UASFM)- Defined grid squares showing maximum altitudes around airports where the FAA may authorize part 107 sUAS operations without additional safety analysis. The maps should be consulted prior to conducting UAS operations (part 91, part 107 or section 44809) in controlled airspace. The UASFM will aid in determining if the airspace authorization or waivers are necessary. UASFM(s) are charted on the UAS Data Delivery System (UDDS) at the following website address:
https://faa.maps.arcgis.com/apps/webappviewer/index.html?id=9c2e4406710048e19806ebf6a06754ad.

UAS TEST SITE- Independently owned UAS test & research sites, recognized by the FAA.

UAS TRAFFIC MANAGEMENT (UTM)-The unmanned aircraft traffic management ecosystem that will allow multiple low altitude BVLOS operations and which is separate from, but complementary to, FAA's Air Traffic Control System.

UASFM-

See UAS FACILITY MAP

UHF-

See ULTRAHIGH FREQUENCY

ULTRAHIGH FREQUENCY (UHF)- 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.

ULTRALIGHT VEHICLE- A single-occupant aeronautical vehicle operated for sport or recreational purposes which does not require FAA registration, an airworthiness certificate, or pilot certification. Operation of an ultralight vehicle in certain airspace requires authorization from ATC.

Refer to 14 CFR part 103

UNABLE- Indicates inability to comply with a specific instruction, request, or clearance.

UNASSOCIATED- A radar target that does not display a data block with flight identification and altitude information.

See ASSOCIATED

UNCONTROLLED AIRSPACE- Airspace in which aircraft are not subject to controlled airspace (Class A, B, C, D, or E) separation criteria.

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 the time-based flow management (TBFM) 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 and publications.

See CHART SUPPLEMENT

📖Refer to AIM (opens in new tab) ↗

UNIDENTIFIED ANOMALOUS PHENOMENA (UAP)– For aviation reporting purposes, a UAP may be airborne objects or other detected/observed objects that are not immediately identifiable, such as balloons, aircraft, or natural known phenomena, that demonstrate behaviors that are not readily understood by sensors or observers. A UAP may consist of one or more unidentified anomalous objects and may persist over an extended period of time. The full definition of UAP may be found on the All‐Domain Anomaly Resolution Office (AARO) website at https://www.aaro.mil.

UNMANNED AIRCRAFT (UA)- A device used or intended to be used for flight that has no onboard pilot. This device can be any type of airplane, helicopter, airship, or powered-lift aircraft. Unmanned free balloons, moored balloons, tethered aircraft, gliders, and unmanned rockets are not considered to be a UA.

UNMANNED AIRCRAFT SYSTEM (UAS)- An unmanned aircraft and its associated elements related to safe operations, which may include control stations (ground, ship, or air based), control links, support equipment, payloads, flight termination systems, and launch/recovery equipment. It consists of three elements: unmanned aircraft, control station, and data link.

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

See 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.

UNSERVICEABLE (U/S)

See OUT OF SERVICE/UNSERVICEABLE

UPLINK– CPDLC message sent from ATC to the flight deck.

UPWIND LEG-

See TRAFFIC PATTERN

URBAN AIR MOBILITY (UAM)- A subset of Advanced Air Mobility (AAM), referring to an air transportation system utilizing highly automated aircraft to transport passengers or cargo in urban/suburban areas.

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.

USAFIB-

See ARMY AVIATION FLIGHT INFORMATION BULLETIN

UTM-

(See UAS TRAFFIC MANAGEMENT.)