CENTRIPETAL FORCE— The force that attracts a body toward its axis of rotation. It is opposite centrifugal force.

CHIP DETECTOR— A warning device that alerts you to any abnormal wear in a transmission or engine. It consists of a magnetic plug located within the transmission. The magnet attracts any metal particles that have come loose from the bearings or other transmission parts. Most chip detectors have warning lights located on the instrument panel that illuminate when metal particles are picked up.

CHORD— An imaginary straight line between the leading and trailing edges of an airfoil section.

CHORDWISE AXIS— A term used in reference to semirigid rotors describing the flapping or teetering axis of the rotor.

COAXIL ROTOR— A rotor system utilizing two rotors turning in opposite directions on the same centerline. This system is used to eliminated the need for a tail rotor.

COLLECTIVE PITCH CONTROL— The control for changing the pitch of all the rotor blades in the main rotor system equally and simultaneously and, consequently, the amount of lift or thrust being generated.

CONING— See blade coning.

CORIOLIS EFFECT— The tendency of a rotor blade to increase or decrease its velocity in its plane of rotation when the center of mass moves closer or further from the axis of rotation.

CYCLIC FEATHERING— The mechanical change of the angle of incidence, or pitch, of individual rotor blades independently of other blades in the system.

CYCLIC PITCH CONTROL— The control for changing the pitch of each rotor blade individually as it rotates through one cycle to govern the tilt of the rotor disc and, consequently, the direction and velocity of horizontal movement.

DELTA HINGE— A flapping hinge with a skewed axis so that the flapping motion introduces a component of feathering that would result in a restoring force in the flap-wise direction.

DENSITY ALTITUDE— Pressure altitude corrected for nonstandard temperature variations.

DEVIATION— A compass error caused by magnetic disturbances from the electrical and metal components in the aircraft. The correction for this error is displayed on a compass correction card place near the magnetic compass of the aircraft.

DIRECT CONTROL— The ability to maneuver a rotorcraft by tilting the rotor disc and changing the pitch of the rotor blades.

DIRECT SHAFT TURBINE— A shaft turbine engine in which the compressor and power section are mounted on a common driveshaft.

DISC AREA— The area swept by the blades of the rotor. It is a circle with its center at the hub and has a radius of one blade length.

DISC LOADING— The total helicopter weight divided by the rotor disc area.

DISSYMMETRY OF LIFT— The unequal lift across the rotor disc resulting from the difference in the velocity of air over the advancing blade half and retreating blade half of the rotor disc area.

DRAG— An aerodynamic force on a body acting parallel and opposite to relative wind.