Aviation Maintenance Terms beginning with U

Ultimate tensile strength

The tensile strength required to cause a material to break or to continue to deform under a decreasing load.

Ultraviolet-blocking dope

Dope that contains aluminum powder or some other pigment that blocks the passage of ultraviolet rays of the sun. The coat of dope protects the organic fabrics and clear dope from deterioration by these rays.

Undamped oscillation

Oscillation that continues with an unchanging amplitude once it has started.

Underslung rotor

A helicopter rotor whose center of gravity is below the point at which it is attached to the mast.

Unidirectional fabric

Fabric in which all the threads run in the same direction. These threads are often bound with a few fibers run at right angles, just enough to hold the yarns together and prevent their bunching.

Unloading valve

This is another name for system pressure regulator. See system pressure regulator.

Utility finish

The finish of an aircraft that gives the necessary tautness and fill to the fabric and the necessary protection to the metal, but does not have the glossy appearance of a show-type finish.