tyre pressure /ta.. pre../ noun
the air pressure in a tyre . maximum allowable tyre pressure

U

UAR abbreviation upper air route UAS abbreviation upper air space UHF abbreviation ultra high frequency UIR abbreviation upper air region UK abbreviation United Kingdom ultimate /'Alt.m.t/ adjective final,
from which no further advance can be made 0 To determine the ultimate load which a structure must be capable of withstanding, a multiplier, called the ultimate factor of safety is used. 0 The ultimate responsibility for safety rests with the crew.
ultra-/Altr./ prefix beyond ultra high frequency /，Altr. ha. 'fri:kw.nsi/, ultra high frequency band /，Altr. ha. 'fri:kw.nsi ，b.nd /
noun a radio frequency range between 300 MHz and 3000 MHz. Abbreviation
UHF ultralight /'Altr.la.t/ noun a small single-seat or two-seat aircraft con-structed of light materials and powered by a small motor, flown mainly for rec-reation
ultrasonic /，Altr.'s.n.k / adjective
referring to frequencies in the range of 20,000 Hz which cannot be heard by the human ear
ultrasonic inspection
/，Altr.s.n.k .n'spek.(.)n/ a non-destructive inspection of materials using extremely high frequency vibra-tions. Also called ultrasonic detection ultraviolet /，Altr.'va..l.t / adjective
referring to or occurring in the invisible part of the light spectrum beyond violet. Abbreviation UV口 ultraviolet radia-tion the invisible part of the light spec-trum beyond violet

unaccompanied /，An.'kAmp.nid /
adjective口 unaccompanied baggage
baggage that travels on a different flight from the passenger who owns it.中

accompanied uncontrolled airspace
/，Ank.ntr.υld 'e.spe.s / noun airspace in which air traffic control does not pro-vide a service and in which an ATC clearance is not required to fly 0 While first learning to handle an aircraft, stu-dent pilots fly in uncontrolled airspace.
(NOTE: Pilots must still follow certain rules when flying through uncontrolled airspace.)
uncoordinated flight noun flight, especially during turns, in which the horizontal and vertical forces acting on the aircraft are out of balance. This can result in the aircraft going into a slip or a skid.
undercarriage /'And.k.r.d3/ noun
the landing gear of aircraft 0 To reduce the effect of drag by fixed under-carriages a retractable type of under-carriage was introduced. (NOTE: The undercarriage is often called the land-ing gear or simply gear.)
COMMENT: The main landing gear are nearest the aircraft’s centre of gravity. Main landing gear are designed to withstand a greater landing shock than the nose wheel or tail wheel and consequently should make contact with the surface first when landing.

undercarriage assembly
/，And.k.r.d3 .'sembli / noun wheels, struts and linkages which make up the complete unit