Capillary tube.  A soft copper tube with a small inside  diameter. The capillary tube used with vapor-pressure  thermometer connects the temperature sensing bulb to the  Bourdon tube. The capillary tube is protected from physical  damage by enclosing it in a braided metal wire jacket. Center of lift.  The location of the chord line of an airfoil at  which all the lift forces produced by the airfoil are considered  to be concentrated. Center of pressure.  The point on the chord line of an airfoil  where all of the aerodynamic forces are considered to be  concentrated. Carbon monoxide detector.  A packet of chemical crystals  mounted in the aircraft cockpit or cabin where they are easily  visible. The crystals change their color from yellow to green  when they are exposed to carbon monoxide. Carbon-pile voltage regulator.  A type of voltage regulator  used with high-output DC generators. Field current is  controlled by varying the resistance of a stack of thin carbon  disks. This resistance is varied by controlling the amount the  stack is compressed by a spring whose force is opposed by  the pull of an electromagnet. The electromagnet’s strength  is proportional to the generator’s output voltage. Centering cam.  A cam in the nose-gear shock strut that  causes the piston to center when the strut fully extends.  When the aircraft takes off and the strut extends, the wheel is  straightened in its fore-and-aft position so it can be retracted  into the wheel well. Charging stand (air conditioning service equipment). A handy and compact arrangement of air conditioning  servicing equipment. A charging stand contains a vacuum  pump, a manifold gauge set, and a method of measuring and  dispensing the refrigerant. Carburizing flame.  An oxyacetylene flame produced by  an excess of acetylene. This flame is identified by a feather  around the inner cone. A carburizing flame is also called a  reducing flame. Carcass (tire component).  The layers of rubberized fabric  that make up the body of an aircraft tire. Chatter.  A type of rapid vibration of a hydraulic pump  caused by the pump taking in some air along with the  hydraulic fluid. Check (wood defect).  Longitudinal cracks that extend across  a log’s annual rings. Check valve.  A hydraulic or pneumatic system component  that allows full flow of fluid in one direction but blocks all  flow in the opposite direction. Case pressure.  A low pressure that is maintained inside  the case of a hydraulic pump. If a seal becomes damaged,  hydraulic fluid will be forced out of the pump rather than  allowing air to be drawn into the pump. Cathode-ray tube (CRT).  A display tube used for  oscilloscopes and computer video displays. An electron gun  emits a stream of electrons that is attracted to a positively  charged inner surface of the face of the tube. Acceleration and  focusing grids speed the movement of the electrons and shape  the beam into a pinpoint size. Electrostatic or electromagnetic  forces caused by deflection plates or coils move the beam  over the face of the tube. The inside surface of the face of  the tube is treated with a phosphor material that emits light  when the beam of electrons strikes it. Chemical oxygen candle system.  An oxygen system used  for emergency or backup use. Solid blocks of material that  release oxygen when they are burned are carried in special  fireproof fixtures. When oxygen is needed, the candles are  ignited with an integral igniter, and oxygen flows into the  tubing leading to the masks. Chevron seal.  A form of one-way seal used in some fluid- power actuators. A chevron seal is made of a resilient material  whose cross section is in the shape of the letter V. The pressure  being sealed must be applied to the open side of the V. Cavitation.  A condition that exist in a hydraulic pump when  there is not enough pressure in the reservoir to force fluid to  the inlet of the pump. The pump picks up air instead of fluid. Chromel.  An alloy of nickel and chromium used as the  positive element in a thermocouple for measuring exhaust  gas temperature. Circle.  A closed plane figure with every point an equal  distance from the center. A circle has the greatest area for  its circumference of any enclosed shape. CDI.  Course deviation indicator. CDU.  Control display unit. Center of gravity.  The location on an aircraft about which  the force of gravity is concentrated. G-7