CEP
(See CENTRAL EAST PACIFIC.)

CERAP
(See COMBINED CENTER-RAPCON.)

CERTIFICATED FLIGHT INSTRUCTOR (CFI)
A flight instructor authorized by the FAA to provide flight instruction in designated category of aircraft.

CERTIFIED FLIGHT INSTRUCTOR WITH A SPORT PILOT RATING (CFIS)
A flight instructor authorized by the FAA to provide flight instruction in designated category of aircraft for sport pilots only.

CERTIFIED TOWER RADAR DISPLAY (CTRD)
A FAA radar display certified for use in the NAS.

CFI
See Certified Flight Instructor.

CFIS
See Certified Flight Instructor with a Sport Pilot Rating.

CFR
(See CALL FOR RELEASE.)

CFR
See Code of Federal Regulations.

CG
See center of gravity.

CHAFF
Thin, narrow metallic reflectors of various lengths and frequency responses, used to reflect radar energy. These reflectors when dropped from aircraft and allowed to drift downward result in large targets on the radar display.

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.

CHARLES’ LAW
If the pressure of a gas is held constant and its absolute temperature is increased, the volume of the gas will also increase. This principle is particularly relevant in gas ballooning.

CHARTED VFR FLYWAYS
Charted VFR Flyways are flight paths recommended for use to bypass areas heavily traversed by large turbine-powered aircraft. Pilot compliance with recommended flyways and associated altitudes is strictly voluntary. VFR Flyway Planning charts are published on the back of existing VFR Terminal Area charts.

CHARTED VISUAL FLIGHT PROCEDURE APPROACH
An approach conducted while operating on an instrument flight rules (IFR) flight plan which authorizes the pilot of an aircraft to proceed visually and clear of clouds to the airport via visual landmarks and other information depicted on a charted visual flight procedure. This approach must be authorized and under the control of the appropriate air traffic control facility. Weather minimums required are depicted on the chart.

CHARTS
(See AERONAUTICAL CHART.)

CHASE
An aircraft flown in proximity to another aircraft normally to observe its performance during training or testing.

CHASE AIRCRAFT
(See CHASE.)

CHECK RIDE
A practical test administered by an FAA examiner or designated examiner for the purpose of issuing an FAA certificate or rating.

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.

CHINE
The longitudinal seam joining the sides to the bottom of thefloat. The chines serve a structural purpose, transmitting loads from the bottoms to the sides of the floats.They also serve a hydrodynamic purpose, guiding water away from the float, reducing spray, and contributng to hydrodynamic lift.

CHINOOK
See Foehn.

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.

CHOP
A roughened condition of the sea surface caused by local winds. It is characterized by its irregularity, short distance between crests, and whitecaps.

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

CHORD LINE
An imaginary straight line drawn through an airfoil from the leading edge to the trailing edge.

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

CIRCLE TO RUNWAY (RUNWAY NUMBER)
Used by ATC to inform the pilot that he/she must circle to land because the runway in use is other than the runway aligned with the instrument approach procedure. When the direction of the circling maneuver in relation to the airport/runway is required, the controller will state the direction (eight cardinal compass points) and specify a left or right downwind or base leg as appropriate; e.g., “Cleared VOR Runway Three Six Approach circle to Runway Two Two,” or “Circle northwest of the airport for a right downwind to Runway Two Two.” (See CIRCLE-TO-LAND MANEUVER.) (See LANDING MINIMUMS.) (Refer to AIM.)

CIRCLE-TO-LAND MANEUVER
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. At tower controlled airports, this maneuver is made only after ATC authorization has been obtained and the pilot has established required visual reference to the airport. (See CIRCLE TO RUNWAY.) (See LANDING MINIMUMS.) (Refer to AIM.)

CIRCLING APPROACH
(See CIRCLE-TO-LAND MANEUVER.)

CIRCLING MANEUVER
(See CIRCLE-TO-LAND MANEUVER.)

CIRCLING MINIMA
(See LANDING MINIMUMS.)

CIRCUIT BREAKER
A circuit-protecting device that opens the circuit in case of excess current flow. A circuit breaker differs from a fuse in that it can be reset without having to be replaced.

CL
See coefficient of lift.

CLASS
According to Title 14 of the Code of Federal Regulations: (1) As used with respect to the certification, ratings, privileges, and limitations of airmen, means a classification of aircraft within a category having similar operating characteristics. Examples include: single-engine; multiengine; land; water; gyroplane; helicopter; airship; and free balloon; and (2) As used with respect to the certification of aircraft, means a broad grouping of aircraft having similar characteristics of propulsion, flight or landing. Examples include: airplane, rotorcraft, glider, balloon, landplane, and seaplane.” (14 CFR part 1)

CLASS A
Generally, that airspace from 18,000 feet MSL up to and including FL 600, including the airspace overlying the waters within 12 nautical miles of the coast of the 48 contiguous States and Alaska. Unless otherwise authorized, all persons must operate their aircraft under

CLASS A AIRSPACE
Airspace from 18,000 feet MSL up to and including FL 600, including the airspace overlying the waters within 12 NM of the coast of the 48 contiguous states and Alaska; and designated international airspace beyond12 NM of the coast of the 48 contiguous states and Alaska within areas of domestic radio navigational signal or ATC radar coverage, and within which domestic procedures are applied.

CLASS B AIRSPACE
Airspace from the surface to 10,000 feet MSL surrounding the nation’s busiest airports in terms of IFR operations or passenger numbers. The configuration of each Class B airspace is individually tailored and consists of a surface area and two or more layers, and is designed to contain all published instrument procedures once an aircraft enters the airspace. For all aircraft, an ATC clearance is required to operate in the area, and aircraft so cleared receive separation services within the airspace.

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 feetabove 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
Generally, that 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. Arrival extensions for instrument approach procedures may be Class D or Class E airspace. Unless otherwise authorized, each person must establish two-way radio communications with the ATC facility providing air traffic services prior to entering the airspace and thereafter maintain those communications while in the airspace. No separation services are provided to VFR aircraft. 5.

CLASS E
Generally, if the airspace is not Class A, Class B, Class C, or Class D, and it is controlled airspace, it is Class E airspace. Class E airspace extends upward from either the surface or a designated altitude to the overlying or adjacent controlled airspace. When designated as a surface area, the airspace will be configured to contain all instrument procedures. Also in this class are Federal airways, airspace beginning at either 700 or 1,200 feet AGL used to transition to/from the terminal or en route environment, en route domestic, and offshore airspace areas designated below 18,000 feet MSL. Unless designated at a lower altitude, Class E airspace begins at 14,500 MSL over the United States, including that airspace overlying the waters within 12 nautical miles of the coast of the 48 contiguous States and Alaska, up to, but not including 18,000 feet MSL, and the airspace above

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.

CLEAN CONFIGURATION
A configuration in which all flight control surfaces have been placed to create minimum drag. In most aircraft this means flaps and gear retracted.

CLEAR AIR TURBULENCE
Turbulence not associated with any visible moisture.

CLEAR AIR TURBULENCE (CAT)
Turbulence encountered in air where no clouds are present. This term is commonly applied to high-level turbulence associated with wind shear. CAT is often encountered in the vicinity of the jet stream. (See WIND SHEAR.) (See JET STREAM.)

CLEAR ICE
A glossy, clear, or translucent ice formed by the relatively slow freezing or large supercooled water droplets.

CLEAR OF THE RUNWAY
Taxiing aircraft, which is approaching a runway, is clear of the runway when all parts of the aircraft are held short of the applicable runway holding position marking. A pilot or controller may consider an aircraft, which is exiting or crossing a runway, to be clear of the runway when all parts of the aircraft are beyond the runway edge and there are no restrictions to its continued movement beyond the applicable runway holding position marking. Pilots and controllers shall exercise good judgment to ensure that adequate separation exists between all aircraft on runways and taxiways at airports with inadequate runway edge lines or holding position markings.

CLEARANCE
ATC permission for an aircraft to proceed under specified traffic conditions within controlled airspace, for the purpose of providing separation between known aircraft.

CLEARANCE DELIVERY
Control tower position responsible for transmitting departure clearances to IFR flights.

CLEARANCE LIMIT
The fix, point, or location to which an aircraft is cleared when issued an air traffic clearance. (See ICAO term CLEARANCE LIMIT.)


CLEARANCE LIMIT [ICAO]
The point to which an aircraft is granted an air traffic control clearance.

CLEARANCE ON REQUEST
An IFR clearance not yet received after filing a flight plan.

CLEARANCE VOID IF NOT OFF BY (TIME)
Used by ATC to advise an aircraft that the departure clearance is automatically canceled if takeoff is not made prior to a specified time. The pilot must obtain a new clearance or cancel his/her IFR flight plan if not off by the specified time. (See ICAO term CLEARANCE VOID TIME.)

CLEARANCE VOID TIME
Used by ATC, the time at which the departure clearance is automatically canceled if takeoff has not been made. The pilot must obtain a new clearance or cancel the IFR flight plan if not off by the specified time.

CLEARANCE VOID TIME [ICAO]
A time specified by an air traffic control unit at which a clearance ceases to be valid unless the aircraft concerned has already taken action to comply therewith.

CLEARED APPROACH
ATC authorization for an aircraft to execute any standard or special instrument approach procedure for that airport. Normally, an aircraft will be cleared for a specific instrument approach procedure. (See CLEARED (Type of) APPROACH.) (See INSTRUMENT APPROACH PROCEDURE.) (Refer to 14 CFR Part 91.) (Refer to AIM.) CLEARED (Type of)

CLEARED AS FILED
Means the aircraft is cleared to proceed in accordance with the route of flight filed in the flight plan. This clearance does not include the altitude, DP, or DP Transition. (See REQUEST FULL ROUTE CLEARANCE.) (Refer to AIM.)

CLEARED FOR TAKEOFF
ATC authorization for an aircraft to depart. It is predicated on known traffic and known physical airport conditions.

CLEARED FOR THE OPTION
ATC authorization for an aircraft to make a touch-and-go, low approach, missed approach, stop and go, or full stop landing at the discretion of the pilot. It is normally used in training so that an instructor can evaluate a student’s performance under changing situations. (See OPTION APPROACH.) (Refer to AIM.)

CLEARED THROUGH
ATC authorization for an aircraft to make intermediate stops at specified airports without refiling a flight plan while en route to the clearance limit.

CLEARED TO LAND
ATC authorization for an aircraft to land. It is predicated on known traffic and known physical airport conditions.

CLEARWAY
An area beyond the takeoff runway under the control of airport authorities within which terrain or fixed obstacles may not extend above specified limits. These areas may be required for certain turbine-powered operations and the size and upward slope of the clearway will differ depending on when the aircraft was certificated. (Refer to 14 CFR Part 1.)

CLIMB TO VFR
ATC authorization for an aircraft to climb to VFR conditions within Class B, C, D, and E surface areas when the only weather limitation is restricted visibility. The aircraft must remain clear of clouds while climbing to VFR. (See SPECIAL VFR CONDITIONS.) (Refer to AIM.)

CLIMBOUT
That portion of flight operation between takeoff and the initial cruising altitude.

CLOSE PARALLEL RUNWAYS
Two parallel runways whose extended centerlines are separated by less than 4,300 feet and at least 3000 feet (750 feet for SOIA operations) that are authorized to conduct simultaneous independent approach operations. PRM and simultaneous close parallel appear in approach title. Dual communications, special pilot training, an Attention All Users Page (AAUP), NTZ monitoring by displays that have aural and visual alerting algorithms are required. A high update rate surveillance sensor is required for certain runway or approach course spacing.

CLOSED RUNWAY
A runway that is unusable for aircraft operations. Only the airport management/ military operations office can close a runway.

CLOSED TRAFFIC
Successive operations involving takeoffs and landings or low approaches where the aircraft does not exit the traffic pattern.

CLOUD
A cloud is a visible accumulation of minute water droplets and/or ice particles in the atmosphere above the Earth’s surface. Cloud differs from ground fog, fog, or ice fog only in that the latter are, by definition, in contact with the Earth’s surface.

CLOUD STREETS
Parallel rows of cumulus clouds. Each row can be as short as 10 miles or as long as a 100 miles or more.

CLT
(See CALCULATED LANDING TIME.)

CLUTTER
In radar operations, clutter refers to the reception and visual display of radar returns caused by precipitation, chaff, terrain, numerous aircraft targets, or other phenomena. Such returns may limit or preclude ATC from providing services based on radar. (See CHAFF.) (See GROUND CLUTTER.) (See PRECIPITATION.) (See TARGET.) (See ICAO term RADAR CLUTTER.)

CMNPS
(See CANADIAN MINIMUM NAVIGATION PERFORMANCE SPECIFICATION AIRSPACE.)

COASTAL FIX
A navigation aid or intersection where an aircraft transitions between the domestic route structure and the oceanic route structure.

COATING
A thin synthetic added to the surface of balloon fabric to lessen porosity and ultraviolet-light damage.

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.

CODE OF FEDERAL REGULATIONS (CFR)
Regulations issued by the U.S. Federal Government as published in the Federal Register.

CODES
The number assigned to a particular multiple pulse reply signal transmitted by a transponder. (See DISCRETE CODE.)

COEFFICIENT OF LIFT (CL)
The ratio between lift pressure and dynamic pressure.

COGNITIVE DOMAIN
A grouping of levels of learning associated with mental activity. In order of increasing complexity, the domains are knowledge, comprehension, application, analysis, synthesis, and evaluation.

COLD FRONT
The boundary between two air masses where cold air is replacing warm air.

COLD INFLATION
Forcing cold air into the envelope, giving it some shape to allow heating with the heater.

COLD SOAKED
Condition of a self-launch or sustainer engine making it difficult or impossible to start in flight due to long time exposure to cold temperatures. Usually occurs after along soaring flight at altitudes with cold temperatures (e.g.,a wave flight).

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.

COMBINATION SKI
A type of aircraft ski that can be used on snow or ice, but that also allows the use of the ski plane’s wheels for landing on runways.

COMBINED CENTER-RAPCON
An air traffic facility which combines the functions of an ARTCC and a radar approach control facility. (See AIR ROUTE TRAFFIC CONTROL CENTER.) (See RADAR APPROACH CONTROL FACILITY.)

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.

COMMERCIAL PILOT
A person who, for compensation or hire, is certificated to fly an aircraft carrying passengers or cargo.

COMMON POINT
A significant point over which two or more aircraft will report passing or have reported passing before proceeding on the same or diverging tracks. To establish/maintain longitudinal separation, a controller may determine a common point not originally in the aircraft’s flight plan and then clear the aircraft to fly over the point. (See SIGNIFICANT POINT.)

COMMON PORTION
(See COMMON ROUTE.)

COMMON ROUTE
That segment of a North American Route between the inland navigation facility and the coastal fix.

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, FSS, or tower frequency and is identified in appropriate aeronautical publications. (Refer to AC 90-42, Traffic Advisory Practices at Airports Without Operating Control Towers.)

COMPASS COURSE
A true course corrected for variation and deviation errors.

COMPASS LOCATOR
A low power, low or medium frequency (L/MF) radio beacon installed at the site of the outer or middle marker of an instrument landing system (ILS). It can be used for navigation.

COMPASS ROSE
A circle, graduated in degrees, printed on some charts or marked on the ground at an airport. It is used as a reference to either true or magnetic direction.

COMPLEX AIRCRAFT
An aircraft with retractable landing gear, flaps, and a controllable pitch propeller.

COMPLY WITH RESTRICTIONS
An ATC instruction that requires an aircraft being vectored back onto an arrival or departure procedure to comply with all altitude and/or speed restrictions depicted on the procedure. This term may be used in lieu of repeating each remaining restriction that appears on the procedure.

COMPOSITE FLIGHT PLAN
A flight plan which specifies VFR operation for one portion of flight and IFR for another portion. It is used primarily in military operations. (Refer to AIM.)

COMPOSITE ROUTE SYSTEM
An organized oceanic route structure, incorporating reduced lateral spacing between routes, in which composite separation is authorized.

COMPOSITE SEPARATION
A method of separating aircraft in a composite route system where, by management of route and altitude assignments, a combination of half the lateral minimum specified for the area concerned and half the vertical minimum is applied.

COMPREHENSIVENESS
The degree to which a test measures the overall objective.

COMPRESSOR PRESSURE RATIO
The ratio of compressor discharge pressure to compressor inlet pressure.

COMPRESSOR STALL
In gas turbine engines, a condition in an axial-flow compressor in which one or more stages of rotor blades fail to pass air smoothly to the succeeding stages. A stall condition is caused by a pressure ratio that is incompatible with the engine rpm. Compressor stall will be indicated by a rise in exhaust temperature or rpm fluctuation, and if allowed to continue, may result in flameout and physical damage to the engine.

COMPULSORY REPORTING POINTS
Reporting points which must be reported to ATC. They are designated on aeronautical charts by solid triangles or filed in a flight plan as fixes selected to define direct routes. These points are geographical locations which are defined by navigation aids/fixes. Pilots should discontinue position reporting over compulsory reporting points when informed by ATC that their aircraft is in “radar contact.”

COMPUTER NAVIGATION FIX
A point used to define a navigation track for an airborne computer system such as GPS or FMS.

COMPUTER-ASSISTED INSTRUCTION
Instruction in which the instructor is responsible for the class and uses the computer to assist in the instruction.

COMPUTER-BASED TRAINING (CBT)
The use of the computer as a training device. CBT is sometimes called computer-based instruction (CBI); the terms and acronyms are synonymous and may be used interchangeably.

CONCENTRIC RINGS
Dashed-line circles depicted in the plan view of IAP charts, outside of the reference circle, that show en route and feeder facilities.

CONDENSATION
A change of state of water from a gas (water vapor) to a liquid.

CONDENSATION NUCLEI
Small particles of solid matter in the air on which water vapor condenses.

CONDITION
The second part of a performance-based objective which describes the framework under which the skill or behavior will be demonstrated.

CONDITIONALLY UNSTABLE
The state of a column of air when its temperature lapse rate is less than the dry adiabatic lapse rate but greater than the moist adiabatic lapse rate. When an air parcel is displaced vertically, it will be stable if unsaturated and unstable if saturated.

CONE OF CONFUSION
A cone-shaped volume of airspace directly above a VOR station where no signal is received, causing the CDI to fluctuate.

CONFIDENCE MANEUVER
A confidence maneuver consists of one or more turns, a climb or descent, or other maneuver to determine if the pilot in command (PIC) is able to receive and comply with ATC instructions.

CONFIGURATION
This is a general term, which normally refers to the position of the landing gear and flaps.

CONFLICT ALERT
A function of certain air traffic control automated systems designed to alert radar controllers to existing or pending situations between tracked targets (known IFR or VFR aircraft) that require his/her immediate attention/action. (See MODE C INTRUDER ALERT.)

CONFLICT RESOLUTION
The resolution of potential conflictions between aircraft that are radar identified and in communication with ATC by ensuring that radar targets do not touch. Pertinent traffic advisories shall be issued when this procedure is applied. Note: This procedure shall not be provided utilizing mosaic radar systems.

CONFORMANCE
The condition established when an aircraft’s actual position is within the conformance region constructed around that aircraft at its position, according to the trajectory associated with the aircraft’s Current Plan.

CONFORMANCE REGION
A volume, bounded laterally, vertically, and longitudinally, within which an aircraft must be at a given time in order to be in conformance with the Current Plan Trajectory for that aircraft. At a given time, the conformance region is determined by the simultaneous application of the lateral, vertical, and longitudinal conformance bounds for the aircraft at the position defined by time and aircraft’s trajectory.

CONING
See blade coning.

CONSOLAN
A low frequency, long-distance NAVAID used principally for transoceanic navigations.

CONSTANT-SPEED PROPELLER
A controllable-pitch propeller whose pitch is automatically varied in flight by a governor to maintain a constant rpm in spite of varying air loads.

CONTACT
a. Establish communication with (followed by the name of the facility and, if appropriate, the frequency to be used). b. A flight condition wherein the pilot ascertains the attitude of his/her aircraft and navigates by visual reference to the surface. (See CONTACT APPROACH.) (See RADAR CONTACT.)

CONTACT APPROACH
An approach wherein an aircraft on an IFR flight plan, having an air traffic control authorization, operating clear of clouds.

CONTAMINATED RUNWAY
A runway is considered contaminated whenever standing water, ice, snow, slush, frost in any form, heavy rubber, or other substances are present. A runway is contaminated with respect to rubber deposits or other friction-degrading substances when the average friction value for any 500-foot segment of the runway within the ALD fails below the recommended minimum friction level and the average friction value in the adjacent 500-foot segments falls below the maintenance planning friction level.

CONTERMINOUS US
The 48 adjoining States and the District of Columbia.

CONTINENTAL UNITED STATES
The 49 States located on the continent of North America and the District of Columbia.

CONTINUE
When used as a control instruction should be followed by another word or words clarifying what is expected of the pilot. Example: “continue taxi,” “continue descent,” “continue inbound,” etc.

CONTINUOUS FLOW OXYGEN SYSTEM
System that supplies a constant supply of pure oxygen to a rebreather bag that dilutes the pure oxygen with exhaled gases and thus supplies a healthy mix of oxygen and ambient air to the mask. Primarily used in passenger cabins of commercial airliners.

CONTROL AND PERFORMANCE
A method of attitude instrument flying in which one instrument is used for making attitude changes, and the other instruments are used to monitor the progress of the change.

CONTROL AREA [ICAO]
A controlled airspace extending upwards from a specified limit above the earth.

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 DISPLAY UNIT
A display interfaced with the master computer, providing the pilot with a single control point for all navigations systems, thereby reducing the number of required flight deck panels.

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 SECTOR
An airspace area of defined horizontal and vertical dimensions for which a controller or group of controllers has air traffic control responsibility, normally within an air route traffic control center or an approach control facility. Sectors are established based on predominant traffic flows, altitude strata, and controller workload. Pilot-communications during operations within a sector are normally maintained on discrete frequencies assigned to the sector. (See DISCRETE FREQUENCY.)

CONTROL SLASH
A radar beacon slash representing the actual position of the associated aircraft. Normally, the control slash is the one closest to the interrogating radar beacon site. When ARTCC radar is operating in narrowband (digitized) mode, the control slash is converted to a target symbol.

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.

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. a. Controlled airspace is a generic term that covers Class A, Class B, Class C, Class D, and Class E airspace. b. Controlled airspace is also that airspace within which all aircraft operators are subject to certain pilot qualifications, operating rules, and equipment requirements in 14 CFR Part 91 (for specific operating requirements, please refer to 14 CFR Part 91). For IFR operations in any class of controlled airspace, a pilot must file an IFR flight plan and receive an appropriate ATC clearance. Each Class B, Class C, and Class D airspace area designated for an airport contains at least one primary airport around which the airspace is designated (for specific designations and descriptions of the airspace classes, please refer to 14 CFR Part 71).

CONTROLLED AIRSPACE [ICAO]
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 which covers ATS airspace Classes A, B, C, D, and E.

CONTROLLED FIRING AREA
Airspace wherein activities are conducted under conditions so controlled as to eliminate hazards to nonparticipating aircraft and to ensure the safety of persons and property on the ground.

CONTROLLED TIME OF ARRIVAL
Arrival time assigned during a Traffic Management Program. This time may be modified due to adjustments or user options.

CONTROLLER
(See AIR TRAFFIC CONTROL SPECIALIST.)

CONTROLLER [ICAO]
A person authorized to provide air traffic control services.

CONTROLLER PILOT DATA LINK COMMUNICATIONS (CPDLC)
A two-way digital communications system that conveys textual air traffic control messages between controllers and pilots using ground or satellite-based radio relay stations.

CONVECTION
Generally, the transfer of heat energy in a fluid. As applied to weather, the type of heat transfer occurring in the atmosphere when the ground is heated by the sun.

CONVECTIVE CONDENSATION LEVEL (CCL)
The level at which cumulus forms from surface-based convection. Under this level, the air is dry adiabatic and the mixing ratio is constant.

CONVECTIVE SIGMET
A weather advisory concerning convective weather significant to the safety of all aircraft. Convective SIGMETs are issued for tornadoes, lines of thunderstorms, embedded thunderstorms of any intensity level, areas of thunderstorms greater than or equal to VIP level 4 with an area coverage of 4/10 (40%) or more, and hail 3/4 inch or greater. (See AIRMET.) (See AWW.) (See CWA.) (See SIGMET.) (Refer to AIM.)

CONVECTIVE SIGNIFICANT METEOROLOGICAL INFORMATION
(See CONVECTIVE SIGMET.)

CONVECTIVE WEATHER
Unstable, rising air found in cumuliform clouds.

CONVENTIONAL LANDING GEAR
Landing gear employing a third rear-mounted wheel. These airplanes are also sometimes referred to as tail wheel airplanes.

CONVENTIONAL TAIL
A glider design with the horizontal stabilizer mounted at the bottom of the vertical stabilizer.

CONVERGENCE
A net increase in the mass of air over a specified area due to horizontal wind speed and/or direction changes. When convergence occurs in lower levels, it is usually associated with upward air motions.

CONVERGENCE ZONE
An area of convergence, sometimes several miles wide, at other times very narrow. These zones often provide organized lift for many miles (e.g., a sea-breeze front).

COOLING VENT
A vent, in the side or top of the balloon envelope, which opens to release hot air, and that closes after the release of air automatically.
COOPERATIVE OR GROUP LEARNING
An instructional strategy which organizes students into small groups so that they can work together to maximize their own and each other’s learning.

COORDINATED FLIGHT
Flight with a minimum disturbance of the forces maintaining equilibrium, established via effective control use.

COORDINATED TURN
Turn made by an aircraft where the horizontal component of lift is equal to the centrifugal force of the turn.

COORDINATES
The intersection of lines of reference, usually expressed in degrees/minutes/ seconds of latitude and longitude, used to determine position or location.
COORDINATION FIX
The fix in relation to which facilities will handoff, transfer control of an aircraft, or coordinate flight progress data. For terminal facilities, it may also serve as a clearance for arriving aircraft.

COP
See changeover point.

COPTER
(See HELICOPTER.)

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.

CORIOLIS ILLUSION
The illusion of rotation or movement in an entirely different axis, caused by an abrupt head movement, while in a prolonged constant-rate turn that has ceased to stimulate the brain’s motion sensing system.

CORRECTION
An error has been made in the transmission and the correct version follows.

CORRELATION
A basic level of learning where the student can associate what has been learned, understood, and applied with previous or subsequent learning.

COUPLED AILERONS AND RUDDER
Rudder and ailerons are connected with interconnected springs in order to counteract adverse yaw. Can be overridden if it becomes necessary to slip the aircraft.

COUPLED APPROACH
An instrument approach performed by the aircraft autopilot, and/or visually depicted on the flight director, which is receiving position information and/or steering commands from onboard navigational equipment. In general, coupled non-precision approaches must be flown manually (autopilot disengaged) at altitudes lower than 50 feet AGL below the minimum descent altitude, and coupled precision approaches must be flown manually (autopilot disengaged) below 50 feet AGL unless authorized to conduct auto land operations. Coupled instrument approaches are commonly flown to the allowable IFR weather minima established by the operator or PIC, or flown VFR for training and safety.

COURSE
a. The intended direction of flight in the horizontal plane measured in degrees from north. b. The ILS localizer signal pattern usually specified as the front course or the back course. c. The intended track along a straight, curved, or segmented MLS path. (See BEARING.) (See INSTRUMENT LANDING SYSTEM.) (See MICROWAVE LANDING SYSTEM.) (See RADIAL.)

COURSE OF TRAINING
A complete series of studies leading to attainment of a specific goal, such as a certificate of completion, graduation, or an academic degree.

COWL FLAPS
Shutter-like devices arranged around certain air-cooled engine cowlings, which may be opened or closed to regulate the flow of air around the engine.

CPDLC
(See CONTROLLER PILOT DATA LINK COMMUNICATIONS.)

CPL [ICAO]
(See ICAO term CURRENT FLIGHT PLAN.)

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.

CREST
The top of a wave.

CREW CHIEF
A crew member who is assigned the responsibility of organizing and directing other crewmembers.

CREW RESOURCE MANAGEMENT (CRM)
The application of team management concepts in the flight deck environment. It was initially known as cockpit resource management, but as CRM programs evolved to include cabin crews, maintenance personnel and others, the phrase “crew resource management” has been adopted. This includes single pilots, as in most general aviation aircraft. Pilots of small aircraft, as well as crews of larger aircraft, must make effective use of all available resources; human resources, hardware, and information. A current definition includes all groups routinely working with the cockpit crew who are involved in decisions required to operate a flight safely. These groups include, but are not limited to: pilots, dispatchers, cabin crewmembers, maintenance personnel, and air traffic controllers. CRM is one way of addressing the challenge of optimizing the human/machine interface and accompanying interpersonal activities.

CREWMEMBER
A person assigned to perform duty in an aircraft during flight time.

CRITERIA
The third part of a performance-based objective, descriptions of standards that will be used to measure the accomplishment of the objective.

CRITERION-REFERENCED TESTING
System of testing where students are graded against a carefully written, measurable standard or criterion rather than against each other.

CRITICAL ALTITUDE
The maximum altitude under standard atmospheric conditions at which a turbocharged engine can produce its rated horsepower.

CRITICAL ANGLE OF ATTACK
The angle of attack at which a wing stalls regardless of airspeed, flight attitude, or weight.

CRITICAL AREAS
Areas where disturbances to the ILS localizer and glide slope courses may occur when surface vehicles or aircraft operate near the localizer or glide slope antennas.

CRITICAL ENGINE
The engine which, upon failure, would most adversely affect the performance or handling qualities of an aircraft. CROSS (FIX)

CRM
See crew resource management.

CROSSBAR
The structural component of the WSC wing that holds the leading edges in place.

CROSS-CHECK
The first fundamental skill of instrument flight, also known as “scan,” the continuous and logical observation of instruments for attitude and performance information.

CROSS-COUNTRY
In soaring, any flight out of gliding range of the takeoff airfield. Note that this is different from the definitions in the 14 CFR for meeting the experience requirements for various pilot certificates and/or ratings.

CROSSWIND
Wind blowing across rather than parallel to the direction of flight. In a traffic pattern, the crosswind leg is a flight path at right angles to the landing runway off its upwind end.

CROSSWIND COMPONENT
The wind component measured in knots at 90 degrees to the longitudinal axis of the runway.

CROSSWIND CORRECTION
Correction applied in order to maintain a straight ground track during flight when a crosswind is present.

CROSSWIND LANDING
Landing made with a wind that is blowing across rather than parallel to the landing direction.

CROSSWIND LEG
A flight path at right angles to the landing runway off its upwind end.


CROSSWIND TAKEOFFS
Takeoffs made during crosswind conditions.

CROWN LINE
A line attached to the top of most balloons to assist in the inflation and deflation of the envelope. Sometimes referred to as apex line or top handling line.

CRUISE
Used in an ATC clearance to authorize a pilot to conduct flight at any altitude from the minimum IFR altitude up to and including the altitude specified in the clearance. The pilot may level off at any intermediate altitude within this block of airspace. Climb/descent within the block is to be made at the discretion of the pilot. However, once the pilot starts descent and verbally reports leaving an altitude in the block, he/she may not return to that altitude without additional ATC clearance. Further, it is approval for the pilot to proceed to and make an approach at destination airport and can be used in conjunction with: a. An airport clearance limit at locations with a standard/special instrument approach procedure. The CFRs require that if an instrument letdown to an airport is necessary, the pilot shall make the letdown in accordance with a standard/special instrument approach procedure for that airport, or b. An airport clearance limit at locations that are within/below/outside controlled airspace and without a standard/special instrument approach procedure. Such a clearance is NOT AUTHORIZATION for the pilot to descend under IFR conditions below the applicable minimum IFR altitude.

CRUISE CLEARANCE
An ATC clearance issued to allow a pilot to conduct flight at any altitude from the minimum IFR altitude up to and including the altitude specified in the clearance. Also authorizes a pilot to proceed to and make an approach at the destination airport.

CRUISE CLIMB
A climb technique employed by aircraft, usually at a constant power setting, resulting in an increase of altitude as the aircraft weight decreases.

CRUISING ALTITUDE
An altitude or flight level maintained during en route level flight. This is a constant altitude and should not be confused with a cruise clearance. (See ALTITUDE.) (See ICAO term CRUISING LEVEL.)

CRUISING LEVEL
(See CRUISING ALTITUDE.)

CRUISING LEVEL [ICAO]
A level maintained during a significant portion of a flight.

CT MESSAGE
An EDCT time generated by the ATCSCC to regulate traffic at arrival airports. Normally, a CT message is automatically transferred from the traffic management system computer to the NAS en route computer and appears as an EDCT. In the event of a communication failure between the traffic management system computer and the NAS, the CT message can be manually entered by the TMC at the en route facility.

CTA
(See CONTROLLED TIME OF ARRIVAL.) (See ICAO term CONTROL AREA.)

CTAF
See Common Traffic Advisory Frequency.

CTAS
(See CENTER TRACON AUTOMATION SYSTEM.)

CTRD
(See CERTIFIED TOWER RADAR DISPLAY.)

CUMULONIMBUS (CB)
Also called thunderclouds, these are deep convective clouds with a cirrus anvil and may contain any of the characteristics of a thunderstorm: thunder, lightning, heavy rain, hail, strong winds, turbulence, and even tornadoes.

CUMULUS CONGESTUS
A cumulus cloud of significant vertical extent and usually displaying sharp edges. In warm climates, these sometimes produce precipitation. Also called towering cumulus, these clouds indicate that thunderstorm activity may soon occur.

CURRENCY
Common usage for recent flight experience. In order to carry passengers, a pilot must have performed three takeoffs and three landings within the preceding 90 days. In order to carry passengers at night, a pilot must have performed three takeoffs and three landings to a full stop at night (the period beginning 1 hour after sunset and ending 1 hour before sunrise).

CURRENT
The horizontal movement of a body of water.

CURRENT FLIGHT PLAN [ICAO]
The flight plan, including changes, if any, brought about by subsequent clearances.

CURRENT INDUCTION
An electrical current being induced into, or generated in, any conductor that is crossed by lines of flux from any magnet.

CURRENT PLAN
The ATC clearance the aircraft has received and is expected to fly.

CURRICULUM
A set of courses in an area of specialization offered by an educational institution. A curriculum for a pilot school usually includes courses for the various pilot certificates and ratings.

CUT-AWAY
Model of an object that is built in sections so it can be taken apart to reveal the inner structure.

CVFP APPROACH
(See CHARTED VISUAL FLIGHT PROCEDURE APPROACH.)

CWA
(See CENTER WEATHER ADVISORY and WEATHER ADVISORY.)

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.