Aviation Maintenance Terms beginning with U

Underspeed condition

A speed condition in which the engine is turning at an RPM lower than that for which the propeller governor is set.

Unidirectional fibers

Fibers in a piece of composite material arranged so that they sustain loads in only one direction.

Updraft carburetor

A carburetor that mounts on the bottom of a reciprocating engine. Air entering the engine flows upward through the carburetor.

Upper-deck pressure

The absolute pressure of air at the inlet to the fuel metering system of a turbocharged engine. Upper-deck pressure is the same as the turbocharger discharge pressure.