Class C Airspace.  Airspace from the surface to 4,000 feet  above the airport elevation (charted in MSL) surrounding  those airports having an operational control tower, serviced  by radar approach control, and having a certain number  of IFR operations or passenger numbers. Although the  configuration of each Class C airspace area is individually  tailored, the airspace usually consists of a 5 NM radius core  surface area that extends from the surface up to 4,000 feet  above the airport elevation, and a 10 NM radius shelf area  that extends from 1,200 feet to 4,000 feet above the airport  elevation. Class D Airspace.  Airspace from the surface to 2,500 feet  above the airport elevation (charted in MSL) surrounding  those airports that have an operational control tower. The  configuration of each Class D airspace area is individually  tailored, and when instrument procedures are published,  the airspace will normally be designed to contain the  procedures. Class E Airspace.  Airspace that is not Class A, Class B,  Class C, or Class D, and is controlled airspace. Class G Airspace.  Airspace that is uncontrolled, except  when associated with a temporary control tower, and has  not been designated as Class A, Class B, Class C, Class D,  or Class E airspace. Clear air turbulence.  Turbulence not associated with any  visible moisture. Clearance. ATC permission for an aircraft to proceed under  specified traffic conditions within controlled airspace, for the  purpose of providing separation between known aircraft. Code of Federal Regulations (CFR). Regulations issued  by the U.S. Federal Government as published in the Federal  Register. Coefficient of lift (C$_{L}$).  The ratio between lift pressure and  dynamic pressure.  Cold front.  The boundary between two air masses where  cold air is replacing warm air. Combustion.  Process of burning the fuel/air mixture in the  engine in a controlled and predictable manner. Combustion chamber.  The section of the engine into which  fuel is injected and burned. Common Traffic Advisory Frequency (CTAF).  A  frequency designed for the purpose of carrying out airport  advisory practices while operating to or from an airport  without an operating control tower. The CTAF may be a  UNICOM, Multicom, automated flight service station, or  tower frequency and is identified in appropriate aeronautical  publications. Controlled airspace.  An airspace of defined dimensions  within which air traffic control service is provided to IFR  flights and to VFR flights in accordance with the airspace  classification. Note: “controlled airspace” is a generic term  that encompasses Class A, Class B, Class C, Class D, and  Class E airspace. Control bar.  The structural part of the wing that connects  the flying wires the the wing and keel. This is also used for  the pilot to control the WSC pitch and roll in flight. Control frame.  The wing structural triangle which connects  the control bar to the wing keel and provides the structure  for the lower flying wire attachments. Control pressure.  The amount of physical exertion on the  control column necessary to achieve the desired attitude. Control tower.  A terminal facility that uses air/ground  communications, visual signaling, and other devices to  provide ATC services to aircraft operating in the vicinity of  an airport or on the movement area. Authorizes aircraft to  land or takeoff at the airport controlled by the tower or to  transit the Class D airspace area regardless of the flight plan  or weather conditions. May also provide approach control  services (radar or nonradar). Controllability.  A measure of the response of an aircraft  relative to the pilot’s flight control inputs. Course.  The intended direction of flight in the horizontal  plane measured in degrees from north. Coordinated turn.  Turn made by an aircraft where the  horizontal component of lift is equal to the centrifugal force  of the turn. Crab angle.  The angle formed between the direction an  aircraft is pointed and the direction it is tracking over the  ground, resulting from a crosswind component. Also called  the wind correction angle. Crewmember.  A person assigned to perform duty in an  aircraft during flight time. Crew resource management (CRM).  The application of  team management concepts in the flight deck environment,  including single pilots of general aviation aircraft. Pilots of  small aircraft, as well as crews of larger aircraft, must make  G-5