thrust bearing. A form of bearing used in a mechanism to absorb rotating loads parallel to the axis of the shaft on which the bearing is mounted. Aircraft engines have thrust bearings to transmit thrust loads from the propeller into the crankcase.
thruster (space vehicle component). A small rocket engine whose thrust is used to change the attitude of a space vehicle.
thrust horsepower (reciprocating or turboprop engine). The actual amount of horsepower an engine-propeller combination transforms into thrust.
thrust horsepower (turbojet or turbofan engine). The horsepower equivalent of the thrust produced by a turbojet or turbofan engine.
Since power requires movement, thrust horsepower must take into consideration the speed of the aircraft in which the engine is mounted.
Thrust horsepower may be found by multiplying the net thrust, measured in pounds, by the speed of the aircraft measured in miles per hour or feet per second. This value is then divided by a constant.
thrust line (airplane reference line). An imaginary line, parallel to the propeller shaft of an engine installed in an airplane.
thrust loading. The gross weight of an aircraft, in pounds, divided by the thrust, in pounds, produced by the engines.
thrust loads (bearing loads). Axial loads in a bearing installed in an aircraft engine. These loads are caused by the thrust produced by the engine.
thrust reverser (gas turbine engine component). A device in the tail pipe of a gas turbine engine installed in an airplane that deflects some of the exhaust gases forward to produce a rearward thrust. This reverse thrust slows the aircraft and decreases its landing roll.
thulium. A bright, silvery, rare-earth chemical element. Thulium’s symbol is Tm, its atomic number is 69, and its atomic weight is 168.934. Thulium is used as a source of X-rays.
thumbscrew. A type of machine screw with a flat head in line with the length of the screw. A thumbscrew can be turned by hand by gripping the flat head between the thumb and first finger. Thumbscrews are used to lock one part to another when the parts must be locked and released without the use of tools.
thunder (meteorology). The loud rumbling sound caused by lightning. When lightning (a large spark) jumps from one cloud to another or from a cloud to ground, a great amount of heat is produced. This heat causes the air to expand violently, and this expansion causes shock waves that travel outward at the speed of sound. These shock waves cause the noise we know as thunder.
thundercloud (meteorology). The commonly used name for a cumulonimbus cloud. Violent up and down air currents inside the cloud produce static electricity that discharges in the form of lightning. Lightning causes the thunder heard inside thunderclouds.
thunderstorm (meteorology). A local storm invariably produced by a cumulonimbus cloud and always accompanied by lightning and thunder.
thyratron (electronic component). A hot-cathode, gas-filled electron tube in which one or more control electrodes start a flow of electrons between the cathode and anode. A pulse of high voltage on the control grid ionizes the gas inside the tube and allows electrons to flow.
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