Coverite surface thermometer. The registered trade name for a small surface-type bimetallic thermometer used to calibrate the temperature of an iron used to heat-shrink polyester fabrics.
cowl flaps (reciprocating engine cooling system component). Movable flaps located at the exit of the cowling that houses an air-cooled aircraft engine.
Opening or closing the cowl flaps controls the amount of air flowing through the cowling, and this in turn controls the amount of heat removed from the engine cylinders.
cowling (aircraft component). The removable cover which encloses an aircraft engine.
CPU (central processing unit). The portion of a computer that contains the main storage, the arithmetic-logic-unit, or ALU, and special register groups.
The CPU performs arithmetic and logic functions, controls the processing of instructions, and furnishes timing signals for other computer functions.
crab (aircraft flight condition). Aircraft flight in which the nose of the aircraft is pointed into the wind, while the flight path over the ground is partially across the wind. An airplane is crabbed into the wind to keep it from drifting off the runway when making an approach for a cross-wind landing.
crack (material defect). A partial separation in a piece of material caused by vibration, overloading, or internal stresses.
crack arrester (aircraft structure). A small hole drilled in the end of a crack to prevent the crack continuing. Drilling this hole is called stop-drilling the crack.
A crack in a piece of metal will continue to grow as long as the stresses concentrated at the end of the crack are greater than the tensile strength of the metal. A hole drilled at the end of a crack spreads these stresses out over the entire circumference of the hole, rather than allowing them to concentrate at the extremely small area of the end of the crack.
cracked gasoline. A hydrocarbon fuel (gasoline) manufactured by heating crude petroleum products under pressure, usually in the presence of a catalyst. The heavier hydrocarbons in the crude oil are broken down by the cracking process into products that are distilled into gasoline.
cradle (maintenance fixture). A supporting fixture used to hold an aircraft structure while it is being repaired or stored. The cradle is padded so it will not damage the lightweight aircraft structure placed in it.
crankcase (reciprocating engine component). The housing which encloses the crankshaft, camshaft, and many of the accessory drive gears of a reciprocating engine. The cylinders mount on the crankcase, and the engine is attached to the airframe by the crankcase.
crankpin (reciprocating engine crankshaft component). The portion of a crankshaft to which the connecting rod is attached. The force produced by the expanding gases pushing on the piston is applied to the crankpin by the connecting rod. The crankpin travels in a circular path and causes the crankshaft to rotate.