C  Cabin altitude.  Cabin pressure in terms of equivalent altitude  above sea level.  Cage.  The black markings on the ball instrument indicating  its neutral position.  Calibrated.  The instrument indication compared with a  standard value to determine the accuracy of the instrument.  Calibrated orifice.  A hole of specific diameter used to delay  the pressure change in the case of a vertical speed indicator.  Calibrated airspeed.  The speed at which the aircraft  is moving through the air, found by correcting IAS for  instrument and position errors.  Camber.  The camber of an airfoil is the characteristic curve  of its upper and lower surfaces. The upper camber is more  pronounced, while the lower camber is comparatively flat.  This causes the velocity of the airflow immediately above the  wing to be much higher than that below the wing.  Canard.  A horizontal surface mounted ahead of the main  wing to provide longitudinal stability and control. It may  be a fixed, movable, or variable geometry surface, with or  without control surfaces.  Canard configuration.  A configuration in which the span  of the forward wings is substantially less than that of the  main wing.  Cantilever.  A wing designed to carry loads without external  struts.  CAS.  Calibrated airspeed.  CDI.  Course deviation indicator.  Ceiling.  The height above the earth’s surface of the lowest  layer of clouds, which is reported as broken or overcast, or  the vertical visibility into an obscuration.  Center of gravity (CG).  The point at which an airplane  would balance if it were possible to suspend it at that point.  It is the mass center of the airplane, or the theoretical point  at which the entire weight of the airplane is assumed to  be concentrated. It may be expressed in inches from the  reference datum, or in percentage of mean aerodynamic  chord (MAC). The location depends on the distribution of  weight in the airplane.  Circling approach.  A maneuver initiated by the pilot to  align the aircraft with a runway for landing when a straight- in landing from an instrument approach is not possible or is  not desirable.  Chord line.  An imaginary straight line drawn through an  airfoil from the leading edge to the trailing edge.  Checklist.  A tool that is used as a human factors aid in  aviation safety. It is a systematic and sequential list of all  operations that must be performed to properly accomplish  a task.  Chart Supplement U.S. (formerly Airport/Facility  Directory).  An FAA publication containing information on  all airports, communications, and NAVAIDs.  Changeover point (COP).  A point along the route or  airway segment between two adjacent navigation facilities  or waypoints where changeover in navigation guidance  should occur.  CG.  See center of gravity.  Centripetal force.  A center-seeking force directed inward  toward the center of rotation created by the horizontal  component of lift in turning flight.  Centrifugal force.  An outward force that opposes centripetal  force, resulting from the effect of inertia during a turn.  Centrifugal flow compressor.  An impeller-shaped device  that receives air at its center and slings the air outward at high  velocity into a diffuser for increased pressure. Also referred  to as a radial outflow compressor.  Center of pressure.  A point along the wing chord line where  lift is considered to be concentrated. For this reason, the center  of pressure is commonly referred to as the center of lift.  Center of gravity range.  The distance between the forward  and aft CG limits indicated on pertinent airplane specifications.  Center of gravity limits.  The specified forward and aft  points within which the CG must be located during flight.  These limits are indicated on pertinent airplane specifications.  G-6 