Lake in the Sky Air Show Saturday, June 28, 2008 at the Lake Tahoe Airport - TVL
Aviation Glossary
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A Glossary of Aviation Terms and Abbreviations

Aviation related terms and definitions used in association with civil flight obtained from the Code of Federal Regulations, Federal Aviation Regulations, and many other sources.

ABSOLUTE ALTITUDE - The measureable height of an aircraft above the actual terrain.

ABSOLUTE CEILING - The maximum altitude above sea level at which an aircraft can maintain level flight under Standard Air conditions.

ACCELERATED STALL - Any stall made to occur at other than 1g.

ACCESSORY GROUP - Mechanical and electrical units mounted on an engine necessary for its operation, such as starter, magnetos, fuel pumps, etc.

ADCOCK RANGE - National radio navigation system replaced after World War 2 by the omnirange system. It consisted of segmented quadrants broacasting Morse Code "A" (dot-dash) and "N" (dash-dot) signals in opposing quadrants so that pilots could orient their position relative to a "beam" broadcasting a steady tone, and a Morse Code station identifier. Using a "build-and-fade" technique, a pilot could (ideally) pinpoint his location by the strength or weakness of a signal.

ADF - Automatic Direction Finding via automated radio.

ADIABATIC LAPSE RATE - The rate at which ascending air cools and descending air warms, given no heat is added or taken away. The rate for dry air is based on 5.4° F per 1000' altitude (1° per 100 meters); saturated rates vary with barometric pressures and temperatures, and must be adjusted for accuracy.

ADVERSE YAW - Yaw generated when the ailerons are used. The lifting wing generates more drag, causing an airplane to yaw toward it.

AGL - Above Ground Level, as a measurement of altitude above a specific land mass, and differentiated from MSL.

AILERON - The movable areas of a wingform that control or affect the roll of an aircraft by working opposite one another—up-aileron on the right wing and down-aileron on the left wing. French: aileron small wing, diminutive of aile, from Latin: ala, wing. The word "aisle" also derives from the same root. (Above pic proves that birds invented ailerons long before man did.)

AIR DEFENSE IDENTIFICATION ZONE (ADIZ) - The area of airspace over land or water, extending upward from the surface, within which the ready identification, the location, and the control of aircraft are required in the interest of national security.

Domestic Air Defense Identification Zone - An ADIZ within the United States along an international boundary of the United States.

Coastal Air Defense Identification Zone - An ADIZ over the coastal waters of the United States.

Distant Early Warning Identification Zone (DEWIZ) - An ADIZ over the coastal waters of the State of Alaska. ADIZ locations and operating and flight plan requirements for civil aircraft operations are specified in FAR Part 99.

AIRFOIL - The shape of any flying surface, but principally a wing, as seen in side-view ("cross-section"). Its characteristics are Center of Pressure (CP), DRAG (CD), LIFT (CL), Lift-Drag Ratio (L/D), and Moment (CM).

AIR ROUTE TRAFFIC CONTROL CENTER (ARTCC) or "CENTER" - A facility established to provide air traffic control service to aircraft operating on IFR flight plans within controlled airspace and principally during the en route phase of flight. When equipment capabilities and controller workload permit, certain advisory/assistance services may be provided to VFR aircraft.

AIR SPEED INDICATOR - An instrument or device that measures the air speed of an aircraft through an air mass, but not its ground speed.

AIR TAXI - An aircraft operator who conducts operations for hire or compensation in accordance with FAR Part 135 in an aircraft with 30 or fewer passenger seats and a payload capacity of 7,500# or less. An air taxi operates on an on demand basis and does not meet the "flight scheduled" qualifications of a commuter.

AIR TRAFFIC CONTROL (ATC) - A service operated by the appropriate authority to promote the safe, orderly, and expeditious flow of air traffic.

AIRPORT TRAFFIC CONTROL TOWER (ATCT) - 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 flight plan or weather conditions (IFR or VFR). A tower may also provide approach control services (radar or non-radar).

ALCLAD - Trademark name of Alcoa for high-strength sheet aluminum clad with a layer (approximately 5.5% thickness per side) of high-purity aluminum, popularly used in airplane manufacture.

ALPHABET (PHONETIC) - Devised for reasons of clarity in aviation voice radio, this is the current NATO version in global use:

HOTEL    INDIA    JULIET    KILO    LIMA    MIKE    NOVEMBER

OSCAR    PAPA    QUEBEC    ROMEO    SIERRA    TANGO

UNIFORM    VICTOR    WHISKY    X-RAY    YANKEE    ZULU

The original, from early in World War 2, was:

ABLE    BAKER    CHARLEY    DOG    EASY    FOX    GEORGE

HOW    ITEM    JIG    KING    LOVE    MIKE    NAN    OBOE

PETER    QUEEN    ROGER    SUGAR    TARE    UNCLE    VICTOR

WILLIAM    X-RAY    YOKE    ZEBRA

ALFA    BRAVO    CHARLEY    DELTA    ECHO    FOXTROT    GOLF

ALTIMETER - An adjustable aneroid-barometic cockpit instrument used to measure an aircraft's altitude.

AMPHIBIAN, AMPHIBION - A SEAPLANE or FLOATPLANE with retractable wheels for use on land, as well. The latter spelling was used in the '20s and '30s but has since fallen out of favor.

ANGLE OF ATTACK - The acute angle at which a moving airfoil meets the airstream.

ANGLE OF INCIDENCE - The angle at which an airfoil is normally fixed in relation to the longitudinal axis of an aircraft.

ANHEDRAL - The downward angle of a wing in relation to a horizontal cross-section line; aka CATHEDRAL. SEE DIHEDRAL.

APPROACH CONTROL  SEE  RADIO NAVIGATION

APRON - The hard-surfaced or paved area around a hangar.

ARSA  SEE  CONTROLLED AIRSPACE

ARTIFICIAL HORIZON - A vacuum-powered panel instrument that displays pitch and roll movements about the lateral and longitudinal axes; aka Attitude Indicator.

ASPECT RATIO - The ratio of the span to the chord of an airfoil—a high-aspect ratio wing has wide span and narrow chord, and vice-versa.

ATA  SEE  CONTROLLED AIRSPACE

ATC - (1) Aircraft license as Approved Type Certificate; (2) AIR TRAFFIC CONTROL.

ATIS  SEE  AUTOMATIC TERMINAL INFORMATION SERVICE

AUTOGYRO, AUTOGIRO - An aircraft, often wingless, with unpowered rotary airfoil blades that auto-rotate and serve as wings as it moves through the air when driven by an engine. The latter spelling is a trademark of the Autogiro Corporation.

AUTO-ROTATION - Automatic rotation of rotary blades from a helicopter in an unpowered glide or the forward movement of an autogyro.

AUTOMATIC TERMINAL INFORMATION SERVICE (ATIS) - Continuous broadcast of recorded noncontrol information in selected terminal areas, to improve controller effectiveness and to relieve frequency congestion by automating repetitive transmissions of essential but routine information.

BALANCED CONTROL SURFACE - A movable control surface, as an aileron or rudder, having an added physical extension or weights forward of the hinge-point to reduce forces on a joystick or yoke. See ELEPHANT EARS (2).

BERNOULLI EFFECT (or LAW or THEOREM) - Since the pressure of a fluid is proportional to its velocity, airflow over the upper surface of an airfoil causes suction [lift] because the airstream has been speeded up in relation to positive pressure of the airflow on the lower surface.

BLEED AIR - Hot air at high pressure, usually from the bypass section of a gas turbine engine, for de-icing, heating, and other uses.

BOUNDARY-LAYER CONTROL - The design or control of slotted or perforated wings with suction methods to reduce undesirable aerodynamic effects caused by the boundary layer, that region adjacent to the boundary where shear stresses dominate in the airflow over a wingform.

BUMPED COWLING - An engine fairing, generally circular, with welts or compound shapes in its surface to accommodate cylinder heads.

CABANE STRUT - Wing strut attached to the fuselage.

CALIBRATED AIRSPEED (CAS) - The indicated air speed of an aircraft, corrected for position and instrument error. CAS is equal to true air speed in standard atmosphere at sea level. Compare INDICATED AIRSPEED and TRUE AIRSPEED.

CAMBER - The convex or concave curvature of an airfoil.

CANARD - An arrangement in which the horizontal stabilizer and elevators of an aircraft are mounted in front of the main wing(s).

CAT - Clear-Air Turbulence.

CATHEDRAL  SEE  ANHEDRAL

CAVU - Ceiling and Visibility Unlimited; ideal flying weather.

CEILING - (1) The heights above the earth's surface of the lowest layer of clouds or obscuring phenomena that is reported as "broken," "overcast," or "obscuration," and not classified as "thin" or "partial". (2) The maximum height above sea level in Standard Air attainable by an aircraft under given conditions—SEE ABSOLUTE CEILING, SERVICE CEILING.

CENTER - An Air Route Traffic Control Center (ARTCC).

CENTER OF GRAVITY (c/g) - The longitudinal and lateral point in an aircraft where it is stable; the static balance point.

CERTIFICATED AIRPORTAn airport operating under FAR Part 139. The FAA issues airport operating certificates to all airports serving scheduled or unscheduled air carrier aircraft designed for more than 30 passenger seats. Certificated airports must meet minimum safety standards in accordance with FAR Part 139.

CHORD - The measurable distance between the leading and trailing edges of a wingform.

CLASS G AIRSPACE (Uncontrolled Airspace) - Airspace not designated as Class A, B, C, D or E Controlled Airspace.

COAMING - A padded, protective rim around an open cockpit.

COLLECTIVE PITCH - A cockpit control that changes the pitch of a helicopter's rotor blades; used in climbing or descending.

COLLECTOR RING - A circular duct on a radial engine into which exhaust gases from its cylinders are discharged.

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.

COMMUTER - An air carrier operator operating under 14 CFR 135 that carries passengers on at least five round trips per week on at least one route between two or more points according to its published flight schedules that specify the times, day of the week, and places between which these flights are performed. The aircraft that a commuter operates has 30 or fewer passenger seats and a payload capability of 7,500# or less.

COMPASS COURSE - A bearing as indicated by the horizontal angle between the compass needle and the centerline of the aircraft. A Compass Course is equal to a True Course ± variation and deviation; also equal to a Magnetic Course ± deviation.

COMPASS NORTH - The North point at which a liquid compass needle points, rather than Geographical, or True, North. Compare MAGNETIC NORTH.

CONE OF SILENCE  SEE  RADIO NAVIGATION

CONSTANT-SPEED PROPELLER - A hydraulically-controlled propeller that governs an engine at its optimum speed by the blade pitch being increased or decreased automatically.

CONTACT FLIGHT - Navigation in which altitude and flight path can be maintained by visual reference to the ground and its landmarks. Similar to VFR.

CONTOUR FLIGHT - Contact Flight in and around mountainous areas following visual reference to the terrain's countours.

CONTRAILS - Streaks of condensed water vapor created in the air by aircraft flying at high altitudes; aka Vapor Trails.

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. Controlled airspace is a generic term that covers Class A, B, C, D, and E airspace. Controlled airspace is also that airspace within which all aircraft operators are subject to certain pilot qualifications, operating rules, and equipment requirements in FAR 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 B, C, and 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, refer to FAR Part 71.

  • Class A (formerly PCA - Positive Control Area) generally, that airspace from 18,000' mean sea level (MSL) up to and including flight level (FL) 600 (60,000' pressure altitude), 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 IFR.
  • Class B (formerly TCA - Terminal Control Area) Generally, that airspace from the surface to 10,000' MSL surrounding the nation's busiest airports in terms of airport operations or passenger enplanements. The configuration of each Class B airspace area is individually tailored and consists of a surface area and two or more layers (some Class B airspace areas resemble upside-down wedding cakes), and is designed to contain all published instrument procedures once an aircraft enters the airspace. An ATC clearance is required for all aircraft to operate in the area, and all aircraft that are so cleared receive separation services within the airspace. The cloud clearance requirement for VFR operations is "clear of clouds."
  • Class C (formerly ARSA - Airport Radar Service Area) Generally, that airspace from the surface to 4,000' MSL above the airport elevation surrounding those airports that have an operational control tower, are serviced by a radar approach control, and that have a certain number of IFR operations or passenger enplanements. Although the configuration of each Class C area is individually tailored, the airspace usually consists of a surface area with a 5 nautical mile (nm) radius, an outer circle with a 10 nm radius that extends from 1,200' to 4,000' above the airport elevation and an outer area. 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 within the airspace. VFR aircraft are only separated from IFR aircraft within the airspace.
  • Class D (formerly ATA - Airport Traffic Area and CZ - Control Zone) Generally, that airspace from the surface to 2,500' MSL above the airport elevation 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 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.
  • Class E (formerly General Controlled Airspace) Generally, if the airspace is not Class A, B, C, or D, and 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' AGL used to transition to/from the terminal or enroute environment, enroute domestic, and offshore airspace areas designated below 18,000' MSL. Unless designated at a lower altitude, Class E airspace begins at 14,500' MSL over the USA, 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' MSL, and the airspace above Flight Level 600.

CONVENTIONAL GEAR - Having two main landing wheels at the front and a tailwheel or tailskid at the rear as opposed to having a tricycle gear with three main wheels. Such an aircraft is popularly called a TAILDRAGGER.

COWL, COWLING - A circular, removable fairing around an aircraft engine (generally radial) for the purposes of streamling or cooling; aka RING COWLING.

COWL FLAP - A controllable louvre to regulating airflow through an engine's cowling.

CRAB - A rudder-controlled yawing motion to compensate for a crosswind in maintaining a desired flight path, as in a landing approach.

CTAF  SEE  COMMON TRAFFIC ADVISORY FREQUENCY

DEADSTICK - Descending flight with engine and propeller stopped.

DECALAGE - The difference in angular settings [Angles of Attack] of the wings of a biplane or multiplan