Tap. Instrument used to cut threads on the inside of a hole.

Tare weight. The weight of any chocks or devices used to hold an aircraft on scales when it is weighed. The tare weight must be subtracted from the scale reading to get the net weight of the aircraft.

Tempering. Process that reduces the brittleness imparted by hardening and produces definite physical properties within the steel. Tempering always follows, never precedes, the hardening operation.

Thermal expansion. The increase in size of a material as temperature increases.

Tolerance. The sum of the plus and minus allowance figures.

Torque. The tendency of a force to cause or change rotational motion of a body.

Transformer. A device that changes electrical energy of a given voltage into electrical energy at a different voltage level. It consists of two coils that are not electrically connected, but arranged so that the magnetic field surrounding one coil cuts through the other coil.

Transistor. A three-terminal device primarily used to amplify signals and control current within a circuit.

Trapezoid. A four-sided figure with one pair of parallel sides.

True power. The power dissipated in the resistance of a circuit, or the power actually used in the circuit.

Triangle. A three-sided figure in which the sum of the three angles equal 180°.

Trigonometry. The study of the relationships between the angles and sides of a triangle.

Type Certificate Data Sheet (TCDS). The FAA issues a type certificate when a new aircraft, engine, propeller, etc., is found to meet safety standards set forth by the FAA. The TCDS lists the specifications, conditions and limitations under which airworthiness requirements were met for the specified product, such as engine make and model, fuel type, engine limits, airspeed limits, maximum weight, minimum crew, etc.

Ultrasonic inspection. Uses high frequency sound energy to conduct examinations and make measurements. Ultrasonic inspection can be used for flaw detection/evaluation, dimensional measurements, and material characterization.

Useful load. Fuel, any other fluids that are not part of empty weight, passengers, baggage, pilot, copilot, and crewmembers. It is determined by subtracting the empty weight from the maximum allowable gross weight.

Vapor pressure. The portion of atmospheric pressure that is exerted by the moisture in the air (expressed in tenths of an inch of mercury).

Volt. The basic unit of electrical potential or electromotive force. A potential of one volt appears across a resistance of one ohm when a current of one ampere flows through that resistance.

Voltmeter. A current-measuring instrument, designed to indicate voltage by measuring the current flow through a resistance of known value.