Blade loading.  The load imposed on rotor blades, determined by dividing the total weight of the helicopter by the combined area of all the rotor blades. 

Blade root.  The part of the blade that attaches to the blade grip. 

Blade span.  The length of a blade from its tip to its root. 

Blade stall.  The condition of the rotor blade when it is operating at an angle of attack greater than the maximum angle of lift. 

Blade tip.  The furthermost part of the blade from the hub of the rotor. 

Blade track.  The relationship of the blade tips in the plane of rotation. Blades that are in track will move through the same plane of rotation. 

Blade tracking.  The mechanical procedure used to bring the blades of the rotor into a satisfactory relationship with each other under dynamic conditions so that all blades rotate on a common plane. 

Blade twist.  The variation in the angle of incidence of a blade between the root and the tip. 

Blowback.  The tendency of the rotor disk to tilt aft in transition to forward flight as a result of unequal airflow. 

Calibrated airspeed (CAS).  Indicated airspeed of an aircraft, corrected for installation and instrumentation errors. 

Center of gravity.  The theoretical point where the entire weight of the helicopter is considered to be concentrated. 

Center of pressure.  The point where the resultant of all the aerodynamic forces acting on an airfoil intersects the chord. 

Centrifugal force.  The apparent force that an object moving along a circular path exerts on the body constraining the object and that acts outwardly away from the center of rotation. 

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.  For semirigid rotors, a term used to describe the flapping or teetering axis of the rotor. 

Coaxial 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 to or farther from the axis of rotation. 

Cyclic feathering.  The mechanical change of the angle of incidence, or pitch, of individual rotor blades, independent 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 disk and, consequently, the direction and velocity of horizontal movement. 

Degraded Visual Environment (DVE). Any flight environment of reduced visibility in which situational awareness of the aircrew or control of the aircraft may be severely diminished, completely lost, or may not be maintained as comprehensively as they are during flight operations within clear or undiminished visibility. DVE conditions are further categorized into eleven different types: smoke, smog, clouds, rain, fog, snow, whiteout, night, flat light, sand, and brownout. 

