Circuit breaker.  An electrical component that automatically  opens a circuit any time excessive current flows through it. A circuit breaker may be reset to restore the circuit after the  fault causing the excessive current has been corrected. Clad aluminum.  A sheet of aluminum alloy that has a  coating of pure aluminum rolled on one or both of its surfaces  for corrosion protection. Clamp-on ammeter.  An electrical instrument used to measure  current without opening the circuit through which it is flowing.  The jaws of the ammeter are opened, slipped over the current- carrying wire, and then clamped shut. Current flowing through  the wire produces a magnetic field which induces a voltage  in the ammeter that is proportional to the amount of current. Cleco fastener.  A patented spring-type fastener used to  hold metal sheets in position until they can be permanently  riveted together. Close-quarter iron.  A small hand-held iron with an  accurately calibrated thermostat. This iron is used for heat- shrinking polyester fabrics in areas that would be difficult  to work with a large iron. Closed angle.  An angle formed in sheet metal that has been  bent more than 90°. Closed assembly time.  The time elapsing between the  assembly of glued joints and the application of pressure. Closed-center hydraulic system.  A hydraulic system in  which the selector valves are installed in parallel with each  other. When no unit is actuated, fluid circulates from the  pump back to the reservoir without flowing through any of  the selector valves. Closed-center selector valve.  A type of flow-control valve  used to direct pressurized fluid into one side of an actuator,  and at the same time, direct the return fluid from the other  side of the actuator to the fluid reservoir. Closed-center  selector valves are connected in parallel between the pressure  manifold and the return manifold. Coaxial.  Rotating about the same axis. Coaxial rotors of a  helicopter are mounted on concentric shafts in such a way  that they turn in opposite directions to cancel torque. Coaxial cable.  A special type of electrical cable that consists  of a central conductor held rigidly in the center of a braided  outer conductor. Coaxial cable, commonly called coax, is used  for attaching radio receivers and transmitters to their antenna. Coefficient of drag.  A dimensionless number used in the  formula for determining induced drag as it relates to the  angle of attack. Coefficient of lift.  A dimensionless number relating to  the angle of attack used in the formula for determining  aerodynamic lift. Coin dimpling.  A process of preparing a hole in sheet metal  for flush riveting. A coining die is pressed into the rivet  hole to form a sharp-edged depression into which the rivet  head fits. Collective pitch control.  The helicopter control that changes  the pitch of all of the rotor blades at the same time. Movement  of the collective pitch control increases or decreases the lift  produced by the entire rotor disk. Collodion.  Cellulose nitrate used as a film base for certain  aircraft dopes. Combustion heater.  A type of cabin heater used in some  aircraft. Gasoline from the aircraft fuel tanks is burned in  the heater. Compass fluid.  A highly refined, water-clear petroleum  product similar to kerosene. Compass fluid is used to dampen  the oscillations of magnetic compasses. Compass rose.  A location on an airport where an aircraft can  be taken to have its compasses “swung.” Lines are painted on  the rose to mark the magnetic directions in 30° increments. Compass swinging.  A maintenance procedure that minimizes  deviation error in a magnetic compass. The aircraft is aligned on  a compass rose, and the compensating magnets in the compass  case are adjusted so the compass card indicates the direction  marked on the rose. After the deviation error is minimized on all  headings, a compass correction card is completed and mounted  on the instrument panel next to the compass. Compensated fuel pump.  A vane-type, engine-driven  fuel pump that has a diaphragm connected to the pressure  regulating valve. The chamber above the diaphragm is vented  to the carburetor upper deck where it senses the pressure  of the air as it enters the engine. The diaphragm allows the  fuel pump to compensate for altitude changes and keeps the  carburetor inlet fuel pressure a constant amount higher than  the carburetor inlet air pressure.  G-8