Centrifugal compressor.  A type of compressor that uses a  vaned plate like impeller. Air is taken into the center, or eye,  of the impeller and slung outward by centrifugal force into  a diffuser where its velocity is decreased and its pressure  increased. Capacitor.  An electrical component, formerly called a  condenser, that consists of two large-area conductors, called  plates, separated by an insulator. Electrons stored on one  of the plates produces an electrostatic pressure difference  between the plates. Capillary tube.  A glass or metal tube with a tiny inside  diameter. Capillary action causes the fluid to move within  the tube. Ceramic.  Any of several hard, brittle, heat-resistant,  noncorrosive materials made by shaping and then firing a  mineral, such as clay, at a high temperature. Channel-chromed cylinders.  Reciprocating engine  cylinders with hard chromium-plated walls. The surface of  this chrome plating forms a spider web of tiny stress cracks.  Deplating current enlarges the cracks and forms channels  that hold lubricating oil on the cylinder wall. Cheek (crankshaft).  The offset portion of a crankshaft that  connects the crankpin to the main bearing journals. Carbon pile voltage regulator.  A voltage regulator for a high  output DC generator that uses a stack of pure carbon disks for  the variable resistance element. A spring holds pressure on the  stack to reduce its resistance when the generator output voltage  is low. This allows maximum field current to flow. The field  from an electro-magnet, whose strength varies directly with  the generator voltage, opposes the spring to loosen the stack  and increase its resistance when the generator voltage needs  to be decreased. The increased resistance decreases the field  current and reduces the output voltage. Carbon track.  A trail of carbon deposited by an arc across a  high-voltage component such as a distributor block. Carbon  tracks have a relatively low resistance to the high voltage and  can cause misfiring and loss of engine power. Chip detector.  A component in a lubrication system that  attracts and holds ferrous metal chips circulating with the  engine oil. Some chip detectors are part of an electrical  circuit. When metal particles short across the two contacts  in the detector, the circuit is completed, and an annunciator  light is turned on to inform the flight crew that metal particles  are loose in the lubrication system. Choke of a cylinder.  The difference in the bore diameter of  a reciprocating engine cylinder in the area of the head and in  the center of the barrel. Cartridge starter.  A self-contained starter used on some  military aircraft. A cartridge similar in size to a shotgun  shell is ignited in the starter breech. The expanding gases  drive a piston attached to a helical spline that converts the  linear movement of the piston into rotary motion to rotate  the crankshaft. Choke-ground cylinder.  A cylinder of a reciprocating  engine that is ground so that its diameter at the top of the  barrel is slightly smaller than the diameter in the center of  the stroke. The large mass of metal in the cylinder head  absorbs enough heat to cause the top end of the barrel to  expand more than the rest of the barrel. At normal operating  temperature, the diameter of a choke-ground cylinder is  uniform throughout. Cascade effect.  The cumulative effect that occurs when the  output of one series of components serves as the input to  the next series. Catalyst.  A substance used to change the speed, or rate, of  a chemical action without being chemically changed itself. Cavitating.  The creation of low pressure in an oil pump  when the inlet system is not able to supply all of the oil  the pump requires. Prolonged cavitation can damage pump  components. Choke nozzle.  A nozzle in a gas turbine engine that limits  the speed of gases flowing through it. The gases accelerate  until they reach the speed of sound, and a normal shock wave  forms that prevents further acceleration. Chord line.  An imaginary line, passing through a propeller  blade, joining the leading and trailing edges. Cigarette.  A commonly used name for a spark plug terminal  connector used with a shielded spark plug. Center of pressure.  The point on the chord line of an airfoil  where all aerodynamic forces are concentrated. Center-line thrust airplane.  A twin-engine airplane with  both engines mounted in the fuselage. One is installed as a  tractor in the front of the cabin. The empennage is mounted  on booms.  G-6