combustor efficiency A measure of the percentage of fuel burned completely or Btus of heat attained as opposed to the Btu potential of fuel introduced. Typical figures are in the 99% range.

coming-in speed The speed of a magneto that is just sufficient to produce the voltage required to fire all of the spark plugs consistently.

comma cloud A cloud mass shaped like a comma as seen in satellite imagery.

commercial fastener A fastener manufactured to published standards and stocked by manufacturers or distributors. The material, dimensions, and finish of commercial fasteners conform to the quality level generally recognized by manufacturers and users as commercial quality.

commercial maneuvers Consists of maximum performance takeoffs and landings, steep turns, chandelles, lazy eights, and eights-on-pylons

commercial operator A person who, for compensation or hire, engages in the carriage by aircraft in air commerce of persons or property, other than as an air carrier or foreign air carrier or under the authority of Part 375. Where it is doubtful that an operation is for compensation or hire , the test applied is whether the carriage by air is merely incidental to the person s other business or is, in itself, a major enterprise for profit.

commercial pilot An FAA pilot certificate that allows the pilot to operate an aircraft for hire.

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.

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 uncontrolled airport. The CTAF may be a UNICOM, MULTICOM, FSS, or tower frequency and it is identified in appropriate aeronautical publications.

communication process Consists of three basic elements: the source, the symbols used to communicate the message, and the receiver. In addition, feedback is essential for effective communication to take place.

communication skills The skills an instructor must develop to communicate effectively with students. The ability to communicate effectively as an instructor begins with an understanding of the communication process and is enhanced by experience and training.

communications In electronics, changing information (audible or digital) into a form that can be transmitted and then changed back into information at the receiver.

communications receiver A device that receives electronic data and converts it into information appropriate for use.

communications satellite A satellite placed in geo-stationary orbit used for the relay of communications transmissions from Earth.

community aerodrome radio station (CARS) An aerodrome radio that provides weather, field conditions, accepts flight plans and position reports.

commutator The copper bars on the end of a generator armature to which the rotating coils are attached. AC is generated in the armature and the brushes riding on the commutator act as a mechanical rectifier to convert it into DC.

compact disk (CD) A small plastic optical disk that contains recorded music or computer data. Also, a popular format for storing information digitally. The major advantage of a CD is its capability to store enormous amounts of information.

comparator A device for inspecting parts by comparing them with a greatly enlarged standard chart.

compartment A separate and enclosed space in an aircraft structure.

compass 1. A device for determining direction measured from magnetic north. 2. A drafting instrument used to create circles or arcs.

compass card In navigation, a card affixed to a magnet and allowed to rotate freely so as to show the direction of travel. Divided into degrees and cardinal compass headings.

compass compensation The procedure of adjusting the magnetic compass in an aircraft for deviation caused by magnetic forces within the aircraft.

compass correction card A card mounted near a compass and in full sight of the pilot that indicates the difference between the compass reading and the actual magnetic heading.

compass heading A compass reading that will make good the desired course. It is the desired course (true course) corrected for variation, deviation, and wind.

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 at distances of approximately 15 miles or as authorized in the approach procedure.

a. Outer Compass Locator (LOM) A compass locator installed at the site of the outer marker of an instrument landing system.

b. Middle Compass Locator (LMM) A compass locator installed at the site of the middle marker of an instrument landing system.

compass locator A low-frequency, non-directional beacon (NDB) co-located with the marker beacons on an ILS approach. Used to help establish the pilot s position on the localizer.

compass north The north to which a compass actually points. Its field is produced by the combination of the Earth s magnetic field and the local magnetic fields within the aircraft.

compass rose A circle marked out on a flat part of an airport away from magnetic interference. It is marked every thirty degrees of magnetic direction. The airplane is taxied onto this rose, and the magnetic compass is adjusted to agree with the heading of each of the marks.

compass saw A small, thin-bladed saw used to cut intricate designs into a material.

compass swinging The process of aligning the aircraft on a series of known magnetic headings and adjusting the compensating magnets to bring the compass heading as near the magnetic heading as possible.

compass turns Maintaining heading and making turns with reference to the magnetic compass only.

compensated cam The magneto cam used on high-performance radial engines. One lobe is provided for each cylinder, and the lobes are ground in such a way that the magneto points will open when the piston is a given linear distance from the top of the cylinder rather than a given angular distance. This compensates for the relationship of the master rod pistons and those connected to the crankshaft through the link rods.

compensated relief valve An oil pressure relief valve with a thermostatic valve that decreases the regulated oil pressure when the oil warms up. High pressure is allowed to force the cold oil through the engine, but the pressure is automatically decreased when the oil temperature increases.

compensating cam A cam used in conjunction with the collective pitch control to add the correct amount of engine power for the pitch of the rotor. Used on turbine powered helicopters.

compensating port A port inside a brake master cylinder that vents the wheel cylinder to the reservoir when the brake is not applied. It prevents fluid expansion from causing the brakes to drag when temperatures increase.

compensating winding A series winding in a high-output generator wound between the main pole and the interpoles to aid in brushless commutation and overcoming armature reaction.

compensation A defense mechanism that attempts to disguise a weak or undesirable quality by emphasizing a more positive one. Students may lower the scope of their goals to avoid possible failure in achieving goals that are more difficult.

compiler A special computer program that converts a high-level computer language used by a programmer into machine language that can be used by the computer.

complement of an angle The angle that, when added to the original angle, makes a 90 angle.

complex airplane An airplane that has a retractable landing gear, flaps, and either a controllable pitch propeller or a full authority digital engine control.

complex circuit A circuit consisting of a number of components, where some are arranged in series and others in parallel.

complex number The sum of a real number and an imaginary number.

compliance Being in accordance with a regulation or directive.

component Any one of several parts in a combination of parts that make up a unit or whole.

composite Two or more substances which are combined to produce material properties not present when either substance is used alone.

composite fan blades An advanced technology blade design not yet in current use. Its composition is an epoxy-resin material and graphite fiber. It is stronger than fiberglass and 20% to 30% lighter than metals of the same strength.

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.

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.

composite structure A structure made up of two or more substances that, when combined, produce a structure with properties not present when the individual substances are used alone.

composition resistor An electrical device made up of carbon and some insulator. The amount of resistance to current flow depends on the relative amounts of carbon and the insulator.

compound A new entity formed by a union of elements or parts. The constituents lose their original identity and assume the characteristics of the compound.

compound curve A metal surface curved in more than one plane.

compound lever A series of two or more levers connected to achieve a result. Usually used to multiply force.

compound-wound generator A generator with both a series and a shunt field.

comprehensiveness A characteristic of a measuring instrument when it is based on a liberal sampling of the knowledge or skill to be measured. It must be broad enough to ensure that conclusions are representative of the whole.

compressed air Air compressed until its pressure is above ambient.

compressibility The capability of a material to be compressed to a smaller volume. Gases are compressible; liquids are not.

compressibility burble A region of disturbed flow produced by a shock wave. The region is produced aft of the shock wave.

compressibility error An error introduced to the pitot system due to the compressibility of air. The air entering the pitot tube is compressed slightly as a result of impacting air that has stopped within the system. At altitudes below 10,000 feet and airspeeds below 200 knots the amount of error is negligible, but it becomes significant at higher altitudes and airspeeds.

compressible flow In aerodynamics, airflow that is inconsistent in the degree of compressibility, that is, it experiences a fractional volume change per unit of pressure change.

compression The resultant of two forces that act along the same line and also act toward each other.

compression failure The failure of a material due to compression. Usually causes material to buckle or bulge.

compression fastener A fastener with the primary function of resisting forces that tend to compress it.

compression ignition An ignition used in diesel engines. Rather than an electrical discharge causing ignition, the fuel ignites when compression causes the temperature of the fuel-air mixture to rise to the ignition point.

compression member or strut A heavy member, usually of tubular steel, that separates the spars in a Pratt truss wing and is used to carry only compression loads.

compression molding The creation of parts by compressing a material into a mold. This ensures the complete filling of all parts of the mold.

compression ratio 1. The ratio of the volume of an engine cylinder with the piston at the bottom center to the volume when the piston is at top center. 2. Sometimes used to refer to compressor pressure ratio; however, this is not entirely correct because compression ratio infers a ratio of volumes as in a piston engine.

compression rib A heavy-duty rib made with heavy cap strips and extra strength webs. A compression rib is designed to withstand compression loads between the wing spars.

compression rings In reciprocating engines, the top piston rings. Used to provide a seal for the gases in the cylinder and to transfer heat from the piston into the cylinder walls.

compression spring A spring used to withstand compression. The coils are loosely wound in order to leave room for compression.

compression stress Stress applied to a material by a squeezing force.

compression strut A brace that fits between two structural members. The members tend to move toward each other in compression. One example is the compression struts used between upper and lower spar sections in Pratt truss construction.

compression test A test used to determine the condition of the cylinders on a reciprocating engine. The test pressurizes the cylinder and then measures excessive loss of pressure, which indicates bad rings or bad exhaust or intake valves.

compressive load A load or a force that tends to compress or squeeze an object together.

compressive strength The ability of a body to resist a force that tends to shorten, compress, or squeeze it.

compressive stress The basic stress that tends to shorten an object by pressing its ends together.

compressor In gas turbine engines, an impeller or a multi-bladed rotor assembly. A component which is driven by a turbine rotor for the purpose of compressing incoming air.

compressor blade A rotating airfoil in a turbine engine. Compresses and accelerates the air before arrival at the combustion chamber.

compressor bleed air Air taken out of the compressor section of a turbine engine to prevent stall and to operate certain components.

compressor case The outer compressor housing, usually split front to rear or top to bottom. This case provides support for the stator vanes.

compressor discharge pressure (Pt4) A measurement taken at the compressor exit and sent to the fuel control unit for fuel scheduling purposes.

compressor disk The inner section of the compressor to which the blades are attached. A disk assembly is made up of one segment per stage and bolted together to form one large rotating piece.

compressor efficiency A measure of aerodynamic efficiency, one important factor of which is the ability to compress air to the maximum pressure ratio with the minimum temperature rise.

compressor front frame The compressor inlet case.

compressor hub The front and rear portion of the compressor to which the compressor shafts attach.

compressor pressure ratio The ratio of compressor discharge pressure to compressor inlet pressure.

compressor stage 1. Each section of a compressor in which the air pressure is progressively increased. A stage of compression consists of one row of blades and one row of stator vanes in an axial flow compressor. 2. A rotor blade set followed by a stator vane set. The rotating airfoils create air velocity, which then changes to pressure in the numerous diverging ducts formed by the stator vanes.

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.

compressor stall-margin curve A curve showing a relationship between the compression ratio and mass air flow that must be maintained for a particular engine. If either of the factors goes out of limits, a compressor stall results.

compressor surge 1. A severe compressor stall across the entire compressor that can result in severe damage if not quickly corrected. This condition occurs with a complete stoppage of airflow or a reversal of airflow. 2. An operating region of violent pulsating air flow usually outside of the operating limits of the engine flow control settings. A primary cause is compressor blade stall. Surge can result in flameout and, in severe cases, structural damage.

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 A device (usually electronic) that receives information, performs some sort of operation on the data, and then produces an output.

computer assisted instruction (CAI) Similar to computer-based training, except emphasizes the point

computer-based instruction (CBI) Synonymous with computer-based training. The use of the computer as a training device.

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.

concave surface An inwardly curved surface.

concentration cell corrosion A corrosion in which the electrode potential difference is caused by a difference in ion concentration of the electroyte instead of a difference in galvanic composition within the metal.

concentric Having a common center.

concentric circles Circles having the same center point.

concentric shafts Two shafts having a common axis, one inside the other.

concurrent lines Lines that pass through a common point.

condensation The process of changing state from a vapor into a liquid.

condensation level The height at which a rising parcel or layer of air would become saturated if lifted adiabatically.

condensation nuclei Small particles in the air on which water vapor condenses.

condensation trail (or contrail) A cloud-like streamer frequently observed to form behind aircraft flying in clear, cold, humid air.

condenser 1. Another name for capacitor. 2. The component in a vapor cycle air conditioning system where heat energy is given up to the air and the refrigerant vapor is changed into a liquid.

condition lever A turboprop cockpit lever. On some aircraft, it serves as prop control lever for flight (alpha range). On other engines, it serves only as a fuel shut-off lever.

conditional routes (CDR) (Europe) Category 1,2,3. Category 1: Permanently plannable CDR during designated times. Category 2: Plannable only during times designated in the Conditional Route Availability Message (CRAM) published at 1500Z for the 24 hour period starting at 0600Z the next day. Category 3: Not plannable. Useable only when directed by ATC.

conditionally unstable air Unsaturated air that will become unstable on the condition it becomes saturated.

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

conductance The ability of a substance to conduct electricity.

conduction The transfer of heat through a substance or from one substance in contact with another; transfer is always from warmer to colder temperature.

conductive coating A coating applied to the surface of a material in order to allow it conduct electricity or to make it able to conduct electricity more efficiently.

conductivity The characteristic of a material that makes it possible for it to transmit heat or electrical energy by conduction.

conductor A material whose outer ring electrons are loosely bonded. Therefore, a relatively low voltage will cause a flow of these electrons.

conduit A duct or tube enclosing electrical wires or cable.

cone A three-dimensional geometric surface formed by the rotation of a line around a fixed axis such that the line always passes through a fixed point on the axis (called the vertex) and always makes the same angle with the axis.

cone clutch A drive clutch consisting of nesting cones as the contact surface.

cone of confusion The cone shaped area above a VOR station in which there is no signal and the TO/FROM flag momentarily flickers to OFF.

cones The cells concentrated in the center of the retina which provide color vision and fine detail.

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 immediate attention/action.

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.

conformity Meeting all of the requirements of its original conditions as specified in the Type Certificate Data (TCD) Sheets and the manufacturer s specifications, or properly altered per Supplemental Type Certificates (STC).

conformity inspection An inspection of an aircraft or component to verify that all components installed on the aircraft are approved either in the original Type Certificate Data and manufacturer s specifications or as modified by Supplemental Type Certificates or Field Approvals (337 s).

confusion between the symbol and the symbolized object Results when a word is confused with what it is meant to represent. Words and symbols create confusion when they mean different things to different people.

congeal Changing from a fluid to a solid state, or from a free flowing liquid state to one that is less free flowing.

congealed oil Oil that has solidified because of cold or contaminants.

conical Cone-shaped.

conifer A softwood cone-bearing tree.

coning In rotorcraft, an upward sweep of rotor blades as a result of lift and centrifugal force.

coning angle The angle formed by the rotor blades and the axis of rotation of a helicopter rotor system. The magnitude of the angle is determined by the relationship between the centrifugal force and the lift produced by the blades.

connecting rod The component in an internal combustion engine that connects the piston to the crankshaft.

connector A device used to join two pieces of wire, tubing, or hose to a component.

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

console The pedestal or panel in an aircraft cockpit where the operating controls are located.

constant A value used in a mathematical computation that is the same every time. For instance, the relationship between the circumference of a circle and its diameter is a constant, 3.1416 (pi, П).

constant current charge A method of charging a battery in which the voltage is adjusted as the charge progresses in order to keep the current constant.

constant displacement pump A pump that displaces a constant amount of fluid each time it turns. The faster it turns, the greater the output.

constant pressure chart A weather chart that represents conditions on a constant pressure surface; may contain analyses of height, wind, temperature, humidity, and/or other elements.

constant pressure cycle The thermodynamic cycle of a gas turbine engine to produce thrust. This is a varying volume, constant pressure, cycle of events. A more recent term is continuous combustion cycle because of the four continuous and constant events, including the intake, compression, expansion (including power), and exhaust. Also referred to as the Brayton cycle.

constant section That part of an aircraft s fuselage having a uniform cross-sectional shape.

constant voltage charge A method of charging a battery in which the voltage across the battery remains constant. The current is high at the start of the charge but tapers off to a low value as the charge progresses.

constantan A copper-nickel alloy used as a negative lead in thermocouples used for measuring temperatures in reciprocating engines.

constant-force spring A spring that exerts a constant pressure regardless of how much the spring is compressed or extended.

constant-speed drive (CSD) A hydraulic transmission that can be controlled either electrically or mechanically. It is used for alternators and enables the alternator to produce the same frequency regardless of the engine s variation of speed from idle to maximum RPM.

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.

constant-voltage power supply A voltage supply that is regulated so that voltage remains constant through a range of loads.

constrained-gap igniter A turbine igniter plug that has the center electrode recessed in the insulator in order to cause the spark to arc well past the tip of the igniter. This allows it to operate at cooler temperatures than other igniter plugs.

constructivism Provides a unique way of thinking about how students learn. Constructivism is based upon the idea that learners construct knowledge through the process of discovery as they experience events and actively seek to understand their environment.

contact 1. Establish communication with (followed by the name of the facility and, if appropriate, the frequency to be used). 2. A flight condition wherein the pilot ascertains the attitude of his aircraft and navigates by visual reference to the surface.

contact approach An approach where an aircraft on an IFR flight plan, having an air traffic control authorization, operating clear of clouds with at least one mile flight visibility, and a reasonable expectation of continuing to the destination airport in those conditions, may deviate from the instrument approach procedure and proceed to the destination airport by visual reference to the surface. This approach will only be authorized when requested by the pilot and the reported ground visibility at the destination airport is at least one statute mile.

contact cement A syrupy adhesive that bonds on contact.

contact cooling The process by which heat is conducted away from the warmer air to the colder earth.

contactor A heavy-duty electrical switch. Used to connect high current loads to the power supply.

contaminant An impurity or foreign substance present in a material or environment that affects one or more properties of the material.

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 (Available Landing Distance) falls below the recommended minimum friction level and the average friction value in the adjacent 500-foot segments fails below the maintenance planning friction level.

contamination The entry of foreign materials into the fuel, oil, hydraulic, or other system.

conterminous U.S. The 48 adjoining States and the District of Columbia.

continental control area Obsolete term. Formerly a control area consisting of the airspace covering the continental United States above 14,500 feet, not including airspace below 1,500 feet AGL, and most prohibited and restricted areas.

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.

continuity The condition of being unbroken or uninterrupted.

continuity light A simple test device in which a light indicates continuity in an electrical circuit while an open circuit prevents the light from illuminating.

continuous airworthiness program 1. A maintenance program consisting of the inspection and maintenance necessary to maintain an aircraft or a fleet of aircraft in airworthy condition. Large or turbine powered aircraft typically go through a continuous airworthiness program. 2. A program of Federal Aviation Administration-approved inspection schedules that allows aircraft to be continually maintained in a condition of airworthiness without being taken out of service for long periods of time. Usually consists of a system of letter checks.

continuous casting A manufacturing method that injects a molten substance into a mold, but is then continuously pulled from the mold as it cools; similar to extrusion.

continuous curved-line graphs A graph utilizing a smooth and even line to convey data.

continuous filament An individual reinforcement that is flexible and indefinite in length. The fibers used to weave fabric are considered continuous filaments.

continuous gusset A brace used to strengthen corners in a structure. It runs the full width of the structure.

continuous ignition system A secondary, lower power, ignition system installed along with the main system. It is used to fire one igniter plug during takeoff, landing, and in bad weather, or for relight purposes in case of flameout.

continuous load In electrical equipment, a non-intermittent draw of electrical current. Many electrical devices have a continuous-duty rating that specifies the maximum continuous load the device can withstand.

continuous wave (cw) An RF carrier wave whose successive oscillations are identical in magnitude and frequency. Often used to indicate Morse code.

continuous-duty ignition system An ignition system used on turbine engines where an igniter plug continues firing even after the engine is operating. Used in situations where there is danger of flameout. One area of use would be in icing conditions where airflow to the turbine could be interrupted.

continuous-duty rating Many electrical devices are limited to operation only for a specified percentage of time without being turned off for cooling. A device that can run continuously will specify the amount of continuous load.

continuous-element-type detector A fire detection system consisting of a stainless steel tube containing a discrete element that has been processed to absorb gas in proportion to the operating temperature set point. When the temperature rises due to fire, overheating, etc., the gas is released from the element, causing a pressure increase in the tube. This mechanically actuates a diaphragm switch, activating the warning lights and an alarm bell.

continuous-flow oxygen system Any oxygen system that provides a continuous flow of oxygen at a rate constant for any given altitude.

continuous-loop fire detector system A fire detection system utilizing a continuous loop consisting of two conductors separated by a thermistor material. At normal temperatures, the thermistor is an insulator, but in the presence of a fire or overheat condition, the thermistor becomes conductive and signals the presence of a fire.

contour 1. The outline of a figure. 2. In meteorology, a line of equal height on a constant pressure chart; analogous to contours on a relief map.

contour map A map with lines of equal elevation drawn on it. Closely-spaced lines indicate steeper terrain.

contour template A tool used to measure or duplicate the contour of a surface.

contouring circuit An electronic circuit that adjusts output devices to match the following input stage. Often used to match amplifier characteristics to speakers.

contract To become reduced in size by squeezing or drawing together.

contrail Condensation trail. Cloud-like streamer that frequently forms behind an aircraft. There are two types of contrails. Aerodynamic contrails are caused by sudden lowering of pressure over wings and propellers. Exhaust contrails are caused by the hot, moist air from turbine engines mixing with the cold air at high altitudes.

contrarotating propellers Two propellers mounted on concentric shafts that turn in opposite directions. This type of rotation cancels the torque forces caused by the rotation of propellers.

control The act of regulating, directing, or coordinating any device or activity.

control and performance concept A method of teaching attitude instrument flying, which focuses on controlling attitude and power as necessary to produce the desired performance. This method divides the instruments into three categories: control, performance, and navigation. It is used predominantly with high-performance turbine aircraft.

control area A controlled airspace extending upwards from a specified limit above the Earth.

control cable Specially designed steel cable connected to linkages used in flight control systems and engine controls.

control circuit Any one of a variety of circuits designed to exercise control of an operating device, to perform counting, timing, switching, and other operations.

control column A vertical column in the cockpit on which a yoke is mounted. The ailerons are controlled by rotation of the yoke and the elevators are controlled by its fore-and-aft movement.

control grid The electrode in a vacuum tube to which the signal is applied.

control locking devices Devices used to secure control surfaces in their neutral positions when the aircraft is parked. Prevents damage from strong winds that could force the controls violently against the stops.

control rod A rigid, tubular rod used to actuate control surfaces. Also referred to as a push-pull rod or torque tube.

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.

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 narrow-band (digitized) mode, the control slash is converted to a target symbol.

control snubber A method of protecting control surfaces equipped with a hydraulic booster unit.

control stick A vertical stick in the cockpit of an airplane used to move the elevators by fore-and-aft movement or the ailerons by side-to-side movement.

control surface Any of the major flight controls such as the ailerons, elevator, and rudder.

control wheel The hand-operated wheel in the cockpit of an airplane used to actuate the elevators by in-and-out movement and the ailerons by rotation of the wheel. Also referred to as the yoke.

control zone Obsolete term. Formerly controlled airspace extending upward from the surface of the Earth to a specified upper limit.

control zone (ICAO) A controlled airspace extending upwards from the surface of the earth to a specified upper limit.

controllability A measure of the response of an aircraft relative to the pilot s flight control inputs.

controllable-pitch propeller A propeller with a pitch that can be changed in flight.

controlled airport An airport which has a control tower, sometimes called a tower airport.

coordinated universal time Greenwich Mean Time. Referred to as coordinated universal time because the time is the average of the times from a network of atomic clocks around the world. Abbreviated UTC. (Formerly abbreviated Z.)

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.

copal resins A natural resin that is used in some aircraft finishes.

copilot A pilot on a flight crew who assists in flying the aircraft, but who is not the pilot-in-command.

coping saw A small handsaw with a U-shaped frame and a thin blade. Used for making curved cuts.

copper A metallic element with a symbol of Cu and an atomic number of 29.

copper brazing A method of joining metals where molten copper is used to stick to and flow between two or more metallic objects. Differs from welding in that the object metals are not melted and fused together.

copper crush gasket A copper gasket with a fiber core that crushes when tightened between mating surfaces. Takes the shape of the mating surfaces for the purpose of creating a leakage-free seal.

copper steel When any minimum copper content is specified, the steel is classed as copper steel. The copper is added to enhance corrosion resistance of the steel.

copper-constantan thermocouple A low-temperature thermocouple that has a copper positive element and a constantan reference element.

copper-oxide rectifier A rectifier that utilizes a copper-oxide coating to restrict the flow of electrons to one direction and not the other. Such a device is used to convert alternating current to direct current.

copperweld An electrical conductor that uses a steel core for strength and copper coating for good conductance of electricity.

copter Slang expression for helicopter

cord body The diagonal layers of rubber-coated nylon cord fabric (running at right angles to one another), which provide the strength to a tire.

core In composites, the central member of a sandwich part (usually foam or honeycomb). Produces a lightweight, high strength component when laminated with face sheets.

core crush In composites, compression damage of the core.

core depression In composites, a gouge or indentation in the core material.

core engine The basic portion of a turbine engine consisting of the compressor that supplies air for combustion, the combustor section, and the turbine section.

corrosion inhibiting primer A primer formulated to stop, slow down, or prevent corrosion on the surface of the material to which the primer is applied..

corrosion inhibitor A substance added to a coating that slows down, stops, or prevents corrosion on the surface of the material to which the coating is applied.

corrosion prevention compound An oil that has special corrosion prevention properties that is added to a reciprocating engine to prevent corrosion while the engine is in storage.

corrosion resistant steel Stainless steel. A steel that has resistance to corrosion.

corrugated fastener A fastener made up of wrinkles or folds that is used to hold two pieces of wood together in a butt joint.

corrugated sheet metal Metal sheets that have been formed into wrinkles or folds in order to increase rigidity.

corrugation Parallel wrinkles or folds in a material that increase the material s rigidity.

cosecant In trigonometry, the ratio of the hypotenuse of a right triangle of which the angle is considered part and the leg opposite the angle.

cosine In trigonometry, the ratio between the leg adjacent to the angle when it is considered part of a right triangle and the hypotenuse.

cotter pin A metal fastener with a shank that splits into two halves. It is used to lock castellated nuts onto drilled bolts by passing the cotter pin through the hole and then spreading the ends of the cotter pin.

cotton braid A loosely woven fabric used to encase rubber hoses and shock cords to protect them from wear and ultraviolet radiation.

coulomb A measure of electrical charge. Equal to 6.28 X 1018 electrons. One ampere of electricity is equal to the flow of one coulomb per second.

counter bore A tool used to cut a counterbore. A counterbore is cut into the surface of a material at the top of a smaller hole to allow the head of the bolt or the nut to be recessed below the surface.

counterboring The act of cutting a counterbore into a material.

counterelectromotive force When alternating current is conducted through a winding, a small current is generated that is 180 out of phase with the primary current. This is a counterelectromotive force (CEMF).

counterrotating engine An engine designed to allow the crankshaft and other moving parts to rotate in the direction opposite the manner of a conventional engine. As a result, the propeller rotates in a counterclockwise fashion from the pilot s perspective.

countersink A cutting tool used to cut a recess into material so the rivet or screw head is flush with the surface of the material.

countersunk-head rivet A rivet designed with a cone shaped head that allows the rivet to fit flush with the skin of the material being riveted.

counterweight (control surface) A weight attached to a control surface in order to reduce the effort required to move the surface and to eliminate flutter in flight.

counterweight (crankshaft) A weight attached to the crankshaft of a reciprocating engine to balance the piston/ connecting rod/crankshaft assembly.

coupled approach A coupled approach is an instrument approach performed by the aircraft autopilot which is receiving position information and/or steering commands from onboard navigation equipment. In general, coupled nonprecision approaches must be discontinued and flown manually at altitudes lower than 50 feet below the minimum descent altitude, and coupled precision approaches must be flown manually below 50 feet AGL (See Autoland Approach). NOTE: Coupled and autoland approaches are flown in VFR and IFR. It is common for carriers to require their crews to fly coupled approaches and autoland approaches (if certified) when the weather conditions are less than approximately 4,000 RVR.

course 1. The intended direction of flight in the horizontal plane measured in degrees from north. 2. The ILS localizer signal pattern usually specified as front course or back course. 3. The intended track along a straight, curved, or segmented MLS path.

course deviation indicator (CDI) The instrument used for flying along a VOR-defined course. Also referred to as a left-right indicator.

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.

course reversal A method of reversing course, which is depicted on an instrument approach procedure. Some procedures do not provide for straight-in approaches unless the airplane is being radar vectored. In these situations, the pilot is required to complete a course reversal, generally within 10 nautical miles of the primary navaid or fix designated on the approach chart, to establish the aircraft inbound on the intermediate or final approach segments.

covalent bond A bond between two atoms that comes about when valence electrons are shared by atoms.

cowl flaps Movable doors on the air exit of an aircraft engine cowling. The cylinder head temperature can be controlled by varying the amount the flaps are opened.

cowl panels The detachable coverings that cover areas requiring regular access.

cowl support ring A large ring attached to a radial engine mount to provide firm support for cowl panels and also for attachment of cowl flaps.

cowling A removable cover or housing placed over or around an aircraft component or section, especially an engine.

cowling, NACA A cowling enclosing a radial air-cooled engine, consisting of a hood, O-ring, and a portion of the body behind the engine, so arranged that the cooling air smoothly enters the hood at the front and leaves through a smooth annular slot between the body and the rear of the hood; the whole forming a relatively low-drag body with a passage through a portion of it for the cooling air.

crab The procedure of altering the heading of an aircraft into the wind in order to maintain a desired course across the ground.

crack A partial separation of material usually caused by vibration, overloading, internal stresses, defective assemblies, fatigue, or too rapid changes in temperature.

crack arrester A hole drilled into a material in order to stop the spread of a crack. This hole, created by stop drilling, distributes stresses over a larger area and keeps the crack from continuing. Commonly used in both sheet metal and acrylic plastics.

cradle A support with pads used for cradling fuselage and wings during assembly, disassembly, or repairs.

crankcase The housing that serves as an engine s foundation and encloses the different mechanisms of the engine.

crankpin That part of a crankshaft to which the connecting rods attach.

crankshaft A shaft with a series of throws used for transforming the reciprocating motion of the pistons into rotary motion used to turn the propeller of an aircraft.

crankshaft runout A measurement of how much a crankshaft is bent. The crankshaft is rotated and the amount of out-of-round is measured using a dial indicator.

crankshaft throw The distance from the crankshaft centerline to the centerline of the rod journal. Crankshaft throw is equal to half the stroke.

crater A small pool of molten metal in the flame or arc during the process of welding.

craze To produce minute cracks on the surface of a material.

crazing Region of ultrafine cracks, which may extend in a network on or under the surface of a resin or plastic material.

creep A condition of permanent elongation in a material, often due to stretching and high heat.

creeper A platform with small wheels that allows a person to lie prone and work on the undersurface of a machine or vehicle being repaired.

crepe masking tape A paper tape with a crinkled surface and adhesive on one side. Used to shield a surface from paint spray.

Crescent wrench An adjustable open-end wrench manufactured by Crescent . Often used incorrectly to describe any adjustable wrench.

crest The surface of a thread that joins the flanks of the thread and is farthest from the cylinder or cone from which the thread projects.

crest clearance As in a thread assembly, the distance, measured perpendicular to the axis, between the crest of a thread and the root of its mating thread.

crew member A person assigned to perform duty in an aircraft during flight.

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.

crimping Forming a series of small bends into a piece of sheet metal in order to shorten its length. Also used to create a bend in angle stock by crimping the sock on one leg of the angle.

crimping tool Device used to create small bends in sheet metal for the purpose of shortening the sheet or bending angle stock.

crimp-on terminals A solderless terminal placed on the end of a wire and then squeezed around the wire to make a solid electrical connection.

crinkle finish A protective finish that dries to a wrinkled surface. Often used on surfaces that should not reflect light.

criteria Part of a performance-based objective. The standards against which the desired outcome is measured.

criterion reference testing (CRT) System of testing where students are graded against a measurable standard or criterion rather than against each other.

critical altitude The maximum altitude at which a turbocharged reciprocating engine can deliver its rated horsepower.

critical angle of attack The angle of attack at which maximum lift is generated. Above this angle of attack, an aircraft will stall. Also referred to as the stalling angle of attack.

critical compression ratio On a diesel engine, the lowest compression ratio that will still allow ignition of a particular fuel.

critical coupling In electricity, the relationship between primary and secondary windings of a transformer that provides maximum transfer of electrical energy.

critical engine The engine that would have the most adverse effect on controllability and climb performance if it were to fail. Multi-engine airplanes with propellers turning in the same direction are designed so the descending blade of one engine is further from the centerline of the aircraft than the descending blade of the engine mounted on the other side. This makes the failure of one engine more critical than the other because there is a greater yawing moment created by the engine that is producing thrust further from the aircraft centerline. To eliminate the critical engine, manufacturers use counter-rotating engines. In this case, the descending propeller blades of both engines are the same distance from the aircraft centerline, and neither engine would affect climb performance or controllability more than the other if it were to fail.

critical height Lowest height in relation to an aerodrome specified level below which an approach procedure cannot be continued in a safe manner solely by the aid of instruments.

critical Mach number That airspeed for a specific airframe where supersonic airflow is first encountered at any point on the aircraft.

critical part That part in an assembly that would cause total failure of the assembly.

critical pressure The highest compression of a fuel-air mixture in a reciprocating engine that allows normal ignition of the mixture without premature spontaneous detonation.

critical strain The strain at the yield point.

critical stress area The area of a structure that would first cause total failure of the structure when overstressed.

critical temperature The highest temperature of a fuel-air mixture in a reciprocating engine that allows normal ignition of the mixture without premature spontaneous detonation.

critique Informal appraisals of student performance, designed to quickly convey feedback. Use critiques to summarize and complete a lesson, as well as to prepare students for the next lesson.

crocus cloth A fabric embedded with abrasive compound, used to polish metal surfaces.

cross coat A technique used in painting where a second coat is sprayed on at a right angle to the first coat. This method is used to ensure full coverage of material.

cross country In soaring, any flight out of gliding range of the take-off airfield. Note that this is different than the definition in the FARs for meeting the experience requirements for pilot certificates and/or ratings.

cross feed An assembly of valves installed in a fuel system to allow any engine to receive fuel from any fuel tank, or to move fuel from one tank to another for fuel balance.

cross firing High voltage discharge from one ignition lead to another, causing a spark plug to fire at the incorrect time.

cross (fix) at (altitude) Used by ATC when a specific altitude restriction at a specified fix is required.

cross (fix) at or above (altitude) Used by ATC when an altitude restriction at a specified fix is required. It does not prohibit the aircraft from crossing the fix at a higher altitude than specified; however, the higher altitude may not be one that will violate a succeeding altitude restriction or altitude assignment.

cross (fix) at or below (altitude) Used by ATC when a maximum crossing altitude at a specific fix is required. It does not prohibit the aircraft from crossing the fix at a lower altitude; however, it must be at or above the minimum IFR altitude.

cross linking In composites, with thermosetting and certain thermoplastic polymers, the setting up of chemical links between the molecular chains.

cross member A structural member that joins two longerons or other lengthwise structural members. It carries loads other than the primary loads.

cross modulation The modulation of a desired signal by an unwanted signal resulting in two signals in the output.

cross section The representation on a drawing of a part s interior cut at right angles to the viewing axis.

cross sectional area The area of the plane section of an object cut at right angles to its length.

cross talk In electronics, where signals in one portion of the equipment bleed over to another section where the signal is not desired.

cross-bleed An assembly of valves installed in an air ducting system of a multi-engine turbine powered aircraft that allows bleed air from one engine to be used in starting another engine.

cross-brace wires Wires arranged in an X fashion across rectangular sections in order to stiffen the structures by triangulation.

cross-check A systematic way of observing instrument indications during attitude instrument flying. Also called scanning, it requires logical and systematic observation of the instrument panel. It saves time and reduces the workload of instrument flying because the pertinent instruments are observed as needed.

cross-country flying Flying from one airport to another over a distance that requires some sort of navigation.

crosscut saw A saw with closely spaced teeth used for cutting across the grain of wood.

crossed-control stall A demonstration stall that a flight instructor shows a student pilot. This type of stall can occur during a skidding turn, and is most likely to occur when a pilot tries to compensate for overshooting a runway during a turn from base to final while on landing approach.

cross-hatching A series of parallel lines on a mechanical drawing. Denotes a section of the drawing has been removed. The style of the lines indicates the type of material depicted in the drawing

crossover A condition that exists in a helicopter rotor system in which the climbing and diving blades cross.

crossover tube A small tube connecting multiple burner cans together for the purpose of flame propagation during starting.

cross-ply laminate In composites, a laminate with plies usually oriented at 0 and 90 only.

cross-sectional view A view in a mechanical drawing that depicts the shape of a cross-sectional area of the object at an indicated point.

crosswind Wind that is blowing across the flight or taxi path of the aircraft. When used in conjunction with traffic patterns, the term is short for crosswind leg.

crosswind component Component of the wind (in knots) perpendicular to flight or taxi path of aircraft.

crosswind landing A landing where the wind is blowing from other than parallel to the runway. Landings with small crosswind angles or velocities are of little consequence and are not usually considered to be crosswind landings.

crosswind landing gear Landing gear on an aircraft that is specially adapted to landing in a crosswind. They are spring loaded on pivots to allow the gear to align with the runway when the aircraft is landed in a crab.

crowfoot wrench An open or box-end wrench with a short extension and a square drive to be driven with a ratchet and an extension bar. A crowfoot wrench allows a fastener in a recess to be driven when a normal ratchet or wrench would not work.

crucible steel Steel made from heating iron and steel in a crucible until impurities have been boiled off. Alloying elements are then added and the resulting high-grade steel is cast into ingots.

crude petroleum Unrefined petroleum, in a raw or natural condition, before being refined for use.

cruise 1. A moderate speed of travel at optimum speed for sustained flight. 2. 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 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 FARs 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 nor does it imply that ATC is exercising control over aircraft in Class G airspace; however, it provides a means for the aircraft to proceed to destination airport, descend and land in accordance with applicable FARs governing VFR flight operations. Also, this provides search and rescue protection until such time as the IFR flight plan is closed.

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.

cruise control Engine operation procedures that allow the best efficiency for power and fuel consumption during cruising.

cruise power Sixty percent to 70 percent of maximum continuous power; used for fuel economy and engine life during cruising.

cruise propellers A fixed-pitch propeller that provides the aircraft with the best performance during cruise flight.

cruising altitude An altitude or flight level maintained during enroute level flight. This is a constant altitude and should not be confused with a cruise clearance.

cruising level See cruising altitude.

crush gasket A gasket usually formed of a sandwich of copper with an asbestos core. When the gasket is crushed between mating surfaces, it conforms to the surfaces and creates a leak-proof seal.

cryogenic liquid A gas that has been cooled to a temperature low enough for it to be liquefied. Liquid oxygen and liquid nitrogen are commonly found cryogenic liquids.

crystal 1. A thin piece of piezoelectric material having a specific resonant frequency used to control the frequency of an oscillator. 2. A small piece of galena or lead sulfide that allows electron flow in only one direction.

crystal diode An electronic component that passes electrons in one direction, but not the other. A crystal diode is constructed from a germanium or silicon crystal.

crystal earphones Earphones that reproduce sound by use of piezoelectric crystals. Audio-frequency alternating voltage is applied to the crystal and the crystal vibrates in accord with the frequency of the voltage. The crystal is attached to a sound diaphragm that causes the pressure of the air to change in phase with the voltage. These changes in air pressure are perceived by the ear as sound.

crystal filter A crystal filter vibrates at a certain frequency. This absorbs vibrations at that frequency, but passes frequencies above and below the frequency of the crystal.

crystal lattice The basic pattern in which atoms are arranged, repeated throughout the solid.

crystal microphone A microphone making use of the piezoelectric properties of a crystal, acted on by the pressure of sound waves.

crystal oscillator An electronic device that produces an alternating current. A crystal oscillator produces a frequency determined by a crystal.

crystal transducer An electronic device that converts vibrations into electronic signals. A crystal transducer uses a piezoelectric crystal that converts vibrations to a minute alternating current.

crystal-controlled oscillator See crystal oscillator.

crystalline Arranged in a definite pattern, with the atoms or molecules tending to be developed in precisely oriented plane surfaces.

C-stage In composites, the final stage in the curing of the mixed thermoset resin system. It cannot be softened by heat and is insoluble at this stage.

cube A three dimensional geometric figure consisting of six congruent square sides.

cube root In mathematics, the cube root is the number that, when multiplied by itself twice, is the given number. Example: The cube root of 27 is 3 (3 X 3 X 3).

cumuliform A term descriptive of all convective clouds exhibiting vertical development in contrast to the horizontally extended stratiform types.

cumulonimbus (Cb) 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. Also referred to as thunderclouds.

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

cumulus (Cu) A principle cloud type having a flat base and sharp rounded tops and sides. Clouds develop vertically and tops often resemble a cauliflower.

cumulus stage The initial stage of a thunderstorm. The cloud grows from cumulus to towering cumulus and usually lasts 10 or 15 minutes.

Cuno filter The proprietary name of a fluid filter made up of a stack of discs separated by scraper blades. Contaminants collect on the edge of the discs and are periodically scraped out and collected in the bottom of the filter case.

cup washer A cup-shaped, spring steel washer. When compressed, the spring action prevents the nut on a bolt from loosening.

cure time The time required for a resin to complete its solidification.

curing agent A catalytic or reactive agent that causes polymerization when added to resin. Also referred to as a hardener.

current The flow of electricity. Technically, it is electrons that flow, but more commonly, this is called current-flow. Current-flow is measured in amperes.

current amplifier An electronic device whose output current is greater than its input current.

current density The amount of electrical current per cross-sectional area of a conductor. Expressed in amperes per square inch.

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

current limiter A device that limits the generator output to a level within that rated by the generator manufacturer.

current plan The ATC clearance the aircraft has received and is expected to fly.

current regulator An electronic device in a circuit that maintains a constant current .

current switch A switch used to activate a separate circuit in response to a specified current. When the AC current being monitored reaches or exceeds the switch setting, the switch will conduct to activate another AC or DC control circuit connected to that switch.

current transformer An electronic device used to indicate the amount of current in an alternating current transmission line. The primary winding is connected in series with the line current and the secondary winding is connected to an indicator that reads out in volts, which are proportionate to the amperage in the primary.

current-fed antenna A half-wave antenna fed in its center.

current-limiting resistor A resistor placed in an electronic circuit to limit the amount of amperage flowing in the circuit.

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.

curvature The shape of a surface that has a smooth, bending surface.

curvic coupling A circular set of gear-like teeth on each of two mating flanges that provide a positive engagement when meshed together and bolted. Used to attach together turbine wheels, compressor disks, etc.

cusp The indentation on each side at the floor level when a fuselage shape has a figure eight shape. The cusp design is used to avoid unneeded width in this area.

cut off To sever an object or to stop a flow.

cut thread A thread produced by removing material from the surface with a form cutting tool.

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

cutaway drawing A mechanical drawing with a portion of the outside not drawn in order to show what the inside of the object looks like.

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

cutout switch An electrical switch that interrupts the power to a motor or actuator when the limit of its desired travel is reached.

cuts out The intermittent operation of a magneto or ignition system.

cutting edge The edge of a tool or device used to remove material when some type of force is applied.

cutting fluid A fluid, often consisting of oil and water that is flowed over the cutting surface of a cutting tool. Its purpose is to cool the surfaces, lubricate the cutting device, flush chips away, and inhibit corrosion.

cutting plane A line on an aircraft drawing that indicates the surface of an auxiliary view.

cutting speed The speed at which a cutting tool moves across or through a material. The speed must be set according to the material being cut and the cutting tool type in order to reduce wear and optimize the speed of the cutting procedure.

cutting torch A torch used to cut metals. It consists of pre-heating jets to heat the work to near melting and a cutting jet to burn through the metal.

CVFP (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.

cyaniding A hardening metal where the heated metal is introduced to a cyanide bath. The metal absorbs nitrogen and carbon from the cyanide and creates a hardened surface.

cyanoacrylate A single-component, polyester-type resin that hardens by exposure to ambient moisture and surface alkalinity.

cybernetics The comparative study of the interaction of biological, mechanical, and electrical systems.

cycle A period of time during which a sequence of recurring events is completed. In aviation, a cycle can be one takeoff and one landing, one extension and retraction of the flaps, one retraction and extension of the landing gear, etc.

cycle A complete series of events or operations that recur regularly. The series ends at the same condition as it started so that the next series of events can immediately take place.

cycles per second A measure of how often something is repeated or oscillates (cycles) per second. One cycle per second is called one hertz (Hz).

cyclic feathering In rotorcraft, 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 in the cockpit of a helicopter with which the pilot can change the pitch of the rotor blades at a specific point in their rotation. The resulting change imparts lateral, forward, or backward movement to the helicopter.

cycling The operation of a unit such as the landing gear retraction system through its full range of operation.

cycling switch A switch that opens and closes the circuit, permitting a unit to cycle on and off.

cyclogenesis Any development or strengthening of cyclonic circulation in the atmosphere.

cyclone In meteorology, the closed circulation around a low pressure area. The flow is counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. Large tropical cyclones are referred to as typhoons or hurricanes.

cyclonic flow In the Northern Hemisphere the counterclockwise flow of air around an area of low pressure and a clockwise flow in the Southern Hemisphere.

cyclostrophic wind A wind in a circular path, in which Coriolis acceleration is negligible as compared to centrifugal forces and pressure gradient acceleration.

cylinder 1. A geometric shape having ends of a circular form and parallel sides. 2. That component of a reciprocating engine in which the fuel is burned and in which the piston moves up and down.

cylinder barrel That portion of the cylinder or a reciprocating engine in which the piston moves up and down.

cylinder bore The diameter of the cylinder barrel.

cylinder fins Metal fins on a cylinder that increase the area of metal exposed to air. Allows the heat to radiate out into the air for cooling.

cylinder flange The base of a cylinder that incorporates a machined mounting flange by which the cylinder assembly is attached to the crankcase.

cylinder head The closed end of the combustion chamber of a reciprocating engine.

cylinder head temperature The temperature of the cast-aluminum head of an air-cooled reciprocating aircraft engine cylinder.

cylinder honing A machining process that trues the inside surface of a cylinder. The process also prepares the inner surface of a reciprocating engine cylinder to receive proper lubrication.

cylinder pads The machined surfaces on the crankcase of an aircraft engine on which the cylinders are mounted.

cylinder skirt That portion of a reciprocating engine s cylinder that extends below the mounting flange.

cylinder taper Many reciprocating engine cylinders are tapered so that the top portion of the cylinder (nearest the combustion chamber) is slightly smaller than the opposite end. This allows for increased expansion due to higher temperatures and increased mass at the combustion end of the cylinder. Also referred to as a choke-bore cylinder.