Combustor (combustion chamber).  The section of a gas  turbine engine in which fuel is injected. This fuel mixes with  air from the compressor and burns. The intense heat from the  combustion expands the air flowing through the combustor  and directs it our through the turbine. Combustors are also  called burners. Circular magnetism.  A method of magnetizing a part for  magnetic particle inspection. Current is passed through the  part, and the lines of magnetic flux surround it. Circular  magnetism makes it possible to detect faults that extend  lengthwise through the part. Circumferential coil spring (garter spring).  A coil spring  formed into a ring. This type of spring is used to hold segmented  ring-type carbon seals tightly against a rotating shaft. Commutator.  A mechanical rectifier mounted on the  armature shaft of a DC generator or motor. It consists of a  cylindrical arrangement of insulated copper bars connected  to the armature coils. Carbon brushes ride on the copper bars  to carry current into or out of the commutator, providing a  unidirectional current from a generator or a reversal of current  in the motor coils.  Claret red.  A dark purplish pink to a dark gray purplish  red color. Class A fire.  A fire with solid combustible materials such  as wood, paper, and cloth as its fuel. Class B fire.  A fire that has combustible liquids as its fuel. Class C fire.  A fire which involves energized electrical  equipment. Class D fire.  A fire in which a metal such as magnesium  burns. Compensating winding.  A series winding in a compound- wound DC generator. The compensating windings are  embedded in the faces of the field poles and their varying  magnetic field works with the fields from the interpoles to  effectively cancel the field distortion caused by armature  current. Composite propeller blade.  A propeller blade made from  several materials such as metal, graphite, glass or aramid  fibers, and foam. Closed-loop control.  A type of control in which part of  the output is fed back to the input. This allows the input to  continually compare the command signals with the output  to determine the extent to which the commands have been  complied with. Compression ratio (reciprocating engine).  The ratio of  the volume of a cylinder of a reciprocating engine with the  piston at the bottom of its stroke engine to the volume of the  cylinder with the piston at the top of its stroke. Coke.  The solid carbon residue left when all volatile parts  of a mineral oil have been evaporated by heat. Compression ratio (turbine engine).  The ratio of the  pressure of the air at the discharge of a turbine engine  compressor to the pressure of the air at its inlet. Cold-cranking simulation.  A method used for specifying  the characteristics of a lubricating oil at low temperature. Oils  rated by this test have the letter W (standing for Winter) in  their designation. For example, SAE 15W50.  Compressor (air conditioning system component).  The component in a vapor-cycle cooling system in which  the low-pressure refrigerant vapors, after they leave the  evaporator, are compressed to increase both their temperature  and pressure before they pass into the condenser. Some  compressors are driven by electric motors, others by  hydraulic motors and, in the case of most light airplanes, are  belt driven from the engine. Cold section.  The portion of a gas turbine engine ahead of  the combustion section. The cold section includes the inlet,  compressor, and diffuser. Cold-tank lubrication system.  A turbine engine lubricating  system in which the oil cooler is in the scavenge subsystem. Collector ring.  A ring made of thin corrosion-resistant steel  tubing that encircles a radial engine and collects exhaust  gases from each cylinder. The ring ends with a connection  to the exhaust tail pipe. Compressor bleed air.  Air that is tapped off from a turbine  engine compressor. Compressor bleed air is used for anti- icing the inlet ducts and for cooling the turbine inlet guide  vanes and first stage turbine blades. Bleed air is also used for  certain airframe functions. See customer bleed air. G-7