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A glossary of aviation terms and abbreviations, part 2...

JOYSTICK - A single floor- or roof-mounted control stick – sideways movement produces ROLL, and forward/backward movement produces PITCH (rudder pedals produce YAW).

KNOT - One nautical mile, about 1.15 statute miles (6,080'); eg: 125kts = 143.9mph.

LAMINAR-FLOW AIRFOIL - A low-drag airfoil designed to maintain laminar (smooth, continuous) flow over a high percentage of the CHORD about itself. Often relatively thin, especially along the leading edge, with most of its bulk near the center of the chord.

LANDING GEAR - Those components comprising the tires, wheels and related assembly upon which an aircraft lands, and which provides mobility for the aircraft while on the ground. Includes all supporting components, such as the tail wheel or tail skid. Retracted during flight.

LANDING WIRES - Interplane bracing wires that help support wingloads when the plane is on the ground. Direction of travel is downward and outward from the fuselage. Opposite of FLYING WIRES.

LARGE HELICOPTER - A helicopter with a certified gross weight over 12,500 pounds.

LIFT - The force exerted on the top of a moving airfoil as a low-pressure area [vacuum] that causes a wingform to rise. AIRFOILs do not "float" on air, as is often assumed – like a boat hull floats on water – but are "pulled up" [lifted] by low air pressures trying to equalize.

LIFT-DRAG RATIO - The lift coefficient of a wing divided by the drag coefficient, as the primary measure of the efficiency of an aircraft; aka L/D Ratio.

LIFT WIRES - Interplane bracing wires that help support wingloads when the plane is in flight. Direction of travel is upward from the bottom of the fuselage to the top of the interplane struts. Also known as FLYING WIRES, the opposite of LANDING WIRES.

LIGHT SPORT AIRCRAFT - Special FAA certification class (LSA) for an aircraft other than a helicopter or powered-lift—single-engine aircraft, airship, balloon, GLIDER, GYROCOPTER, ROTORCRAFT, weight-shift-control aircraft. While limiting the types of aircraft that could be flown by a Sport Pilot, it simplified requirements for a obtaining a pilot license and did not require a medical examination. See LSA feature.

LIQUID COMPASS - A non-electronic, calibratable compass floating in a liquid as a panel instrument; aka WET COMPASS.

LOAD FACTOR (g) - The proportion between lift and weight commonly seen as g (sometimes capitalized)—a unit of force equal to the force of gravity times one.

LOFTING - Design or fabrication of a complex aircraft component, as with sheet metal, using actual-size patterns or plans, generally laid out on a floor. The term was borrowed from boat builders.

LONGERON - A principal longitudinal member of a fuselage's framing, usually continuous across a number of supporting points.

LONGITUDE - Measurement east or west of the prime meridian in degrees, minutes and seconds.

LOOP ANTENNA - A circular radio antenna, either in the open or in a streamlined, teardrop housing, remotely turned 360° to fine-tune a station in league with other radio-directive devices. See also RADIO COMPASS, RADIO DIRECTION FINDER.

LORAN - Long Range Navigation system, which utilizes timing differences between multiple low-frequency transmissions to provide accurate latitude/longitude position information to within 50'. LORAN-C operates in the 100-110 kHz frequency band.

LTA - Lighter-than-air craft, generally referring to powered blimps and dirigibles, but often also includes free balloons.

LUNKENHEIMER VALVE - A manual fuel drain placed handily along a fuel line for checking avgas, such as for water or sediment contaminations.

Mach or m. - A number representing the ratio of the speed of an object to the speed of sound in the surrounding air or medium in which it is moving.

MAGNETIC COMPASS - The most common liquid-type compass, capable of calibration to compensate for magnetic influences within the aircraft.


MAGNETIC NORTH - The magnetic North pole, located near 71° North latitude and 96° West longitude, that attracts a magnetic compass which is not influenced by local magnetic attraction, as opposed to GEOGRAPHIC NORTH.

MAGNETO, MAG - An accessory that produces and distributes a high-voltage electric current for ignition of a fuel charge in an internal combustion engine.

MAGNUS EFFECT - The effect on a spinning cylinder or sphere moving through a fluid, in which force acts perpendicular to the direction of motion and to the direction of spin. This is used to advantage in baseball, in which the trajectory of a pitched ball is a distinct curve. Applied to aeronautics in experimental wingforms, the Magnus Theory states that if air is directed against a smooth, revolving cylinder, whose circumferential speed is greater than that of the air current, a force is directed against one side of the cylinder – air compressed on one side and vacuum formed on the other – creating lift. Named for physicist Heinrich Gustav Magnus (1802-70).

MAINTENANCE DEFICIENCY - An equipment defect or failure which affects or could affect the safety of operations, or that causes an interruption to the services being performed.



MEDIUM HELICOPTER - A helicopter with a certified gross weight between 6,000 and 12,500 pounds.

METAR - Acronym in FAA pilot briefings and weather reports simply means an "aviation routine weather report," but nobody seems certain about the original source. The format was introduced by the French on 1 Jan 1968, but was not adopted by USA and Canada until 1 July 1996, and is thought to be a contraction from MÉTéorologique ("Weather") Aviation Règuliére ("Routine"). FAA and NOAA specifically define METAR as "an approximate translation from the French."

MISHAP, AVIATION MISHAP - Includes aircraft accidents or incidents, incidents with potential, aviation hazards, and aircraft maintenance deficiencies.


MONOCOQUE - Type of fuselage design with little or no internal bracing other than bulkheads, where the outer skin bears the main stresses; usually round or oval in cross-section. Additional classifications are (1) Semi-Monocoque, where the skin is reinforced by longerons or bulkheads, but with no diagonal web members, and (2) Reinforced Shell, in which the skin is supported by a complete framework or structural members. French: monocoque, single shell.

MOUNTAIN FLYING (Airplanes) - Flight operations requiring special techniques such as takeoffs and landings at locations 5,000 feet above sea level or greater pressure altitudes, at temperature ranges above 75°F, and/or limited and unimproved airstrips.

MOUNTAIN FLYING (Helicopters) - Flight operations in mountainous terrain, including pinnacle landings and approaches at varying elevations and pressure altitudes of over 5,000 feet above sea level at temperature ranges above 75°F, and in areas of rugged peaks, deep canyons, cliffs, rock outcropping, steep slopes; including landing on mountain tops and confined areas surrounded by trees, brush, rocks, snow or ice.

MSL - Mean Sea Level. The average height of the surface of the sea for all stages of tide; used as a reference for elevations, and differentiated from AGL.

NACELLE - A streamlined enclosure or housing to protect something such as the crew, engine, or landing gear. French: nacelle, from Latin, navicella, little ship.

NATIONAL AIRSPACE SYSTEM (NAS) - The common network of US airspace; air navigation facilities, equipment and services, airports or landing areas; aeronautical charts, information and services; rules, regulations and procedures, technical information, and human resources and material. Included are system components shared jointly with the military.

NDB - Non-Directional Beacon. An LF, MF, or UHF radio beacon transmitting non-directional signals whereby the pilot of an aircraft equipped with direction finding equipment can determine his bearing to or from the radio beacon and "home" on or track to or from the station. When the radio beacon is installed in conjuncion with the Instrument Landing System (ILS) marker, it is normally called a Compass Locator.

OFFSHORE OPERATIONS - Operations beyond a point where navigation by visual reference to landmarks can be made.

ON THE BEAM - A leftover phrase from ADCOCK Radio Range days still means the same thing today—"You are headed in the right direction," as when you you hear a steady broadcast tone beamed from your target radio transmitter. Also as RIDING THE BEAM. Read about it here.

OVERSHOOT - To land beyond a runwway or planned spot. Opposite of UNDERSHOOT.

PANTS - A popular word for streamlined, non-load bearing fairings to cover landing wheels. Also sometimes called Spats or, when fully enclosing the wheel struts, Skirts.

PAR - Precision Approach Radar, a ground-radar-based instrument approach providing both horizontal and vertical guidance.

PASSENGER - Any person aboard an aircraft who does not perform the function of a flight crewmember or air crewmember.

PATTERN - The path of aircraft traffic around an airfield, at an established height and direction. At tower-controlled fields the pattern is supervised by radio (or, in non-radio or emergency conditions by red and green light signals) by air traffic controllers.

PAYLOAD - Anything that an aircraft carries beyond what is required for its operation during flight, theoretically that from which revenue is derived, such as cargo and passengers.



PILOT IN COMMAND (PiC) - The pilot responsible for the operation and safety of an aircraft during flight time.

PITCH - (1) Of the three axes in flight, this specifies the vertical action, the up-and-down movement. Compare ROLL and YAW. (2) The angle of a propeller or rotor blade in relation to its arc; also the distance advanced by a blade in one full rotation.

PITOT TUBE - More accurately but less popularly used, Pitot-Static Tube, a small tube most often mounted on the outward leading edge of an airplane wing (out of the propeller stream) that measures the impact pressure of the air it meets in flight, working in conjuction with a closed, perforated, coaxial tube that measures the static pressure. The difference in pressures is calibrated as air speed by a panel instrument. Named for French scientist Henri Pitot (1695-1771).

POSITIVE CONTROL - The separation of all air traffic within designated airspace by air traffic control.

POWER LOADING - The GROSS WEIGHT of an airplane divided by the rated horsepower, computed for Standard Air density.

PRECAUTIONARY LANDING - A landing necessitated by apparent impending failure of engines, systems, or components which makes continued flight unadvisable.

PRESSURIZED AIRCRAFT - An aircraft whose cabin is kept at a designated atmospheric pressure to enable passengers and crew to breathe normally.

PUSHER - A propeller mounted in back of its engine, pushing an aircraft through the air, as opposed to a TRACTOR configuration.

QUADRAPLANE, QUADRUPLANE - An aircraft having four or more wingforms.

RADAR - Term coined from the phrase "Radio Detecting and Ranging." It is based on the principle that ultra-high frequency radio waves travel at a precise speed and are reflected from objects they strike. It is used to determine an object's direction and distance.

RADAR APPROACH CONTROL FACILITY (RAPCON) - A terminal ATC facility that uses radar and non-radar capabilities to provide approach control services to aircraft arriving, departing, or transiting airspace controlled by the facility. This facility provides radar ATC services to aircraft operating in the vicinity of one or more civil/military airports in a terminal area. The facility may provide services of a ground-controlled approach (GCA). A radar approach control facility may be operated by FAA or a military service, or jointly. Specific facility nomenclatures are used for administrative purposes only and are related to the physical location of the facility and the operating service generally:

Army Radar Approach Control (ARAC) (Army)
Radar Air Traffic Control Facility (RATCF) (Navy/FAA)
Radar Approach Control (RAPCON) (Air Force/FAA)
Terminal Radar Approach Control (TRACON) (FAA)
Tower/Airport Traffic Control Tower (ATCT) (FAA-only towers delegated approach control authority)

RAMJET - An aerodynamic duct in which fuel is burned to produce a high-velocity propulsive jet. It needs to be accelerated to high speed before it can become operative.

RAMP - The aircraft parking area at an airport, usually adjacent to a terminal.

RATING - A statement that, as part of a certification, sets forth special conditions, privileges or limitations.


RING COWLING - A circular engine FAIRING.

ROGALLO WING - A flexible, delta-wing plan in which three rigid members are shaped in the form of an arrowhead and joined by a flexible fabric, which inflates upward under flight loads. Originally specific to paragliders, but now found on some powered aircraft.

ROLL - Of the three axes in flight, this specifies the action around a central point. Compare PITCH and YAW.

ROTARY ENGINE - A powerplant that rotates on a stationary propeller shaft. An American invention by Adams-Farwell Co (1896), it was first used for buses and trucks in the US (1903), then copied by French engineers for early aircraft engines (1914).

ROTORCRAFT - A heavier-than-air aircraft that depends principally for its support in flight on the lift generated by one or more rotors. Includes helicopters and gyroplanes.

RUDDER - The movable part of a vertical airfoil which controls the YAW of an aircraft; the fixed part being the FIN.

SAILPLANE - An unpowered, soaring aircraft capable of maintaining level flight for long periods of time after release from tow and of gaining altitude using wind currents, as opposed to a GLIDER.

SCRAMJET - Acronym for supersonic combustion ramjet, in which combustion occurs at supersonic air velocities through the engine.

SCUD - A low, foglike cloud layer.

SEAPLANE - A water-based aircraft with a boat-hull fuselage, often amphibious.The term is also used generically to define a similar Flying Boat and a pontoon FLOATPLANE.

SECONDARY STALL - Any stall resulting from pulling back too soon and too hard while recovering from any other stall. Usually a HIGH-SPEED or ACCELERATED STALL.

SERVICE CEILING - The height above sea level at which an aircraft with normal rated load is unable to climb faster than 100' per minute under Standard Air conditions.

SESQUI-WING - A lesser-span additional wingform, generally placed below the main planes of an aircraft, generally a biplane.

SHORE - That area of the land adjacent to the water which is above the high water mark and excludes land areas which are intermittently under water.

SHOULDER-WING - A mid-wing monoplane with its wing mounted directly to the top of the fuselage without use of CABANE STRUTs.

SIDESLIP - A movement of an aircraft in which a relative flow of air moves along the lateral axis, resulting in a sideways movement from a projected flight path, especially a downward slip toward the inside of a banked turn.

SINGLE-SKID LANDINGS - Landings that are used to drop off or pick up passengers or cargo while holding a helicopter with one full skid on the ground and the other suspended in the air. When in contact with the ground, the center of gravity can shift laterally. This type of landing is normally used in sloping terrain or when the helicopter cannot land and reduce the power to flat pitch.

SINK, SINKING SPEED - The speed at which an aircraft loses altitude, especially in a glide in still air under given conditions of equilibrium.

SKID - Too shallow a bank in a turn, causing an aircraft to slide outward from its ideal turning path.

SLATS - Movable vanes or auxiliary airfoils, usually set along the leading edge of a wing but able to be lifted away at certain angles of attack.

SLIP - Too steep a bank in a turn, causing an aircraft to slide inward from its ideal turning path.

SLIPSTREAM - The flow of air driven backward by a propeller or downward by a rotor. Compare DOWNWASH.

SLOT - A long, narrow, spanwise gap in a wing, usually near the leading edge, to improve airflow at high angles of attack for slower landing speeds.

SLOTTED FLAP - A flap that, when depressed, exposes a SLOT and increases airflow between itself and the rear edge of the wing.

SMALL HELICOPTER - Helicopter with a certified gross weight under 6,000 pounds.

SMOH - "Since Major Overhaul," an acronym seen in reference to the operating hours, or time remaining, on an engine.

SPECIAL USE AIRSPACE (SUA) - Airspace of defined dimensions identified by an area on the surface of the earth wherein activities must be confined because of their nature and/or wherein limitations may be imposed upon aircraft operations that are not a part of those activities:

Alert Area - Airspace which may contain a high volume of pilot training activities or an unusual type of aerial activity, neither of which is hazardous to aircraft. Alert Areas are depicted on aeronautical charts for the information of non-participating pilots. All activities within an Alert Area are conducted in accordance with Federal Aviation Regulations, and pilots of participating aircraft as well as pilots transiting the area are equally responsible for collision avoidance.
Military Operations Area (MOA) - Airspace established outside of Class A airspace area to separate or segregate certain non-hazardous military activities from IFR traffic and to identify for VFR traffic where these activities are conducted.
Prohibited Area - Airspace designated under part 73 within which no person may operate an aircraft without the permission of the using agency.
Restricted Area - Airspace designated under FAR Part 73, within which the flight of aircraft, while not wholly prohibited, is subject to restriction. Most restricted areas are designated joint use and IFR/VFR operations in the area may be authorized by the controlling ATC facility when it is not being utilized by the using agency. Restricted areas are depicted on enroute charts. Where joint use is authorized, the name of the ATC controlling facility is also shown.
Warning Area - A warning area is airspace of defined dimensions extending from 3 nautical miles outward from the coast of the USA, that contains activity that may be hazardous to non-participating aircraft. The purpose of such warning area is to warn non-participating pilots of the potential danger. A warning area may be located over domestic or international waters or both.

SPLIT FLAP - A FLAP built into the underside of a wing, as opposed to a Full Flap wherein a whole portion of the trailing edge is used.

SPOILER - A long, movable, narrow plate along the upper surface of an airplane wing used to reduce lift and increase drag by breaking or spoiling the smoothness of the airflow.

SPORT PILOT - Special FAA certification enabling "budget" pilotry; see LIGHT SPORT AIRCRAFT and LSA feature.

SPONSON - A short, winglike protuberance on each side of a seaplane fuselage to increase lateral stability.

SQUAWK - A four-digit number dialed into his transponder by a pilot to identify his aircraft to air traffic controllers

STABILATOR - A movable horizontal tail that combines the actions of a stabilizer and elevator, increasing longitudinal stability while creating a pitching moment.

STABILIZER - The fixed part of a horizontal airfoil that controls the pitch of an aircraft; the movable part being the ELEVATOR.

STAGGER - The relative longitudinal position of the wings on a biplane. Positive Stagger is when the upper wing's leading edge is in advance of that of the lower wing [eg: Waco YKS], and vice versa for Negative Stagger [eg: Beechcraft D17].

STALL - (1) Sudden loss of lift when the angle of attack increases to a point where the flow of air breaks away from a wing or airfoil, causing it to drop. (2) A maneuver initiated by the steep raising of an aircraft's nose, resulting in a loss of velocity and an abrupt drop.

STANDARD AIR (Standard Atmosphere) - An arbitrary atmosphere established for calibration of aircraft instruments. Standard Air Density is 29.92 inches of mercury and temperature of 59° F, equivalent to an atmospheric air pressure of 14.7# per square inch.

STANDARD RATE TURN - A turn in which the heading of an aircraft changes 3° per second, or 360° in two minutes.

STATIC WIRE - A clip-on wire used to ground an aircraft by drawing off static electricity, a potential fire hazard, during refueling.

STEP-OUT LANDINGS - Landings that are used to drop off or pick up passengers and cargo (other than rappel/short haul) while holding the helicopter in a hover. The helicopter is not in contact with the ground and the center of gravity can shift laterally and longitudinally. This type of landing is normally used in lieu of toe-in/single-skid landings in terrain where the helicopter cannot land and reduce power to flat pitch.


SUPERSONIC - Speed of flight at or greater than Mach 1.0; literally, faster than the speed of sound.

SWEEPBACK - A backward inclination of an airfoil from root to tip in a way that causes the leading edge and often the trailing edge to meet relative wind obliquely, as wingforms that are swept back.

SWING-WING - A wing whose horizontal angle to the fuselage centerline can be adjusted in flight to vary aircraft motion at differing speeds.


TARMAC - (1) A bituminous material used in paving; a trade name for Tar MacAdam. (2) An airport surface paved with this substance, especially a runway or an APRON at a hangar.

TAS - True Air Speed. Because an air speed indicator indicates true air speed only under standard sea-level conditions, true air speed is usually calculated by adjusting an Indicated Air speed according to temperature, density, and pressure. Compare CALIBRATED AIR SPEED and INDICATED AIR SPEED.


TERMINAL RADAR SERVICE AREA (TRSA) - Airspace surrounding designated airports wherein ATC provides radar vectoring, sequencing, and separation on a full-time basis for all IFR and participating VFR aircraft. Service provided at a TRSA is called Stage III Service. TRSAs are depicted on VFR aeronautical charts. Pilot participation is urged but is not mandatory.

TETRAHEDRON - Ground-based, free-rotating, triangular-shaped wind direction indicator, generally placed near a runway, often lighted at major airports.

THRUST - The driving force of a propeller in the line of its shaft or the forward force produced in reaction to the gases expelled rearward from a jet or rocket engine. Opposite of DRAG.

TOE IN LANDINGS - Landings that are used to drop off or pick up passengers or cargo by resting a helicopter on the toes of its skids. This requires holding a significant amount of hover power (within 15%) to keep the helicopter from falling backwards. When the helicopter is operated in this manner, there is the potential of significant lateral and longitudinal CG shift during loading/offloading operations. When the helicopter is balanced on the forward 1/3 or less of the skid tube, main rotor blade clearance is another significant concern (1/2 of flat surface/flat pitch blade clearance). These landings are normally used where landing areas are on slopes which exceed the capability of the helicopter. Identification criteria for toe-in landings are:

  1. Inability to reduce below hover power by 15%;
  2. Forward 1/3 or less of skid tube in contact with surface;
  3. 1/2 or less of flat pitch/flat surface blade clearance exists.

TORQUE - A twisting, gyroscopic force acting in opposition to an axis of rotation, such as with a turning propeller; aka Torsion.

TOUCH-AND-GO - Landing practice in which an aircraft does not make a full stop after a landing, but proceeds immediately to another take-off.

TRACTOR - A propeller mounted in front of its engine, pulling an aircraft through the air, as opposed to a PUSHER configuration.

TRAILING EDGE - The rearmost edge of an AIRFOIL.

TRANSPONDER - An airborne transmitter that responds to ground-based interrogation signals to provide air traffic controllers with more accurate and reliable position information than would be possible with "passive" radar; may also provide air traffic control with an aircraft's altitude.

TRIKE - Nickname for a weight-shift-control aircraft, such as a paraglider.

TRIM TAB - A small, auxiliary control surface in the trailing edge of a wingform, adjustable mechanically or by hand, to counteract ("trim") aerodynamic forces on the main control surfaces.

TRUE AIRSPEED - The speed of an aircraft along its flight path, in respect to the body of air (air mass) through which the aircraft is moving. Also see CALIBRATED AIRSPEED, GROUND SPEED, INDICATED AIRSPEED.

TRUE NORTH - The northern direction of the axis of the Earth; aka "Map North." GEOGRAPHIC NORTH, as opposed to MAGNETIC NORTH.

TURBOJET - An aircraft having a jet engine in which the energy of the jet operates a turbine that in turn operates the air compressor.

TURBOPROP - An aircraft having a jet engine in which the energy of the jet operates a turbine that drives the propeller.

TURN & BANK INDICATOR - Primary air-driven gyro instrument, a combined turn indicator and lateral inclinometer to show forces on an aircraft in banking turns. Also referred to as "needle & ball" indicator, the needle as the gyro's pointer and a ball encased in a liquid-filled, curved tube.

TWILIGHT ZONE - Long before Rod Serling's tv series was this consumer-lever definition for a glitch in the ADCOCK RANGE, officially called a Bi-Signal Zone. It was a portion of the overlapping area of a beam where the continuous monotone "on-course" signal became temporarily overlayed with the "A" or "N" code signals. Read more here.

ULTRALIGHT - An aeronautical vehicle, operated for sport or recreational purposes, that does not require FAA registration, an airworthiness certificate, or pilot certification. Primarily single-occupant vehicles, although some two-place vehicles are authorized for training purposes. Operation of an ultralight vehicle in certain airspaces requires authorization from ATC.

UNCONTROLLED AIRSPACE - Class G Airspace; airspace not designated as Class A, B, C, D or E.

UNDERCARRIAGE - The landing gear of a land-based aircraft, including struts, frames, and wheels. A very British word that has limited use in the USA.

UNDERSHOOT - To land short of a runwway or planned landing spot. Opposite is OVERSHOOT.

UNICOM - Universal Communication. A common radio frequency (usually 121.0 mHz) used at uncontrolled (non-tower) airports for local pilot communication.

UPWASH - The slight, upward flow of air just prior to its reaching the leading edge of a rapidly moving airfoil.

UPWIND TURN - Long a point of contest among pilots, there is in reality no such thing as far as the airplane is concerned. Proponents claim that airplanes lose air speed when turning upwind, while opponents (and the laws of physics) argue that an airplane, like a boat in a river whose speed is only relative to the water and not the shore, is unaffected within the movement of an air mass and that it loses only ground speed.

USEFUL LOAD - The weight of crew, passengers, fuel, baggage, and ballast, generally excluding emergency or portable equipment and ordnance.

V - Velocity, now used in defining air speeds:

VA = Maneuvering Speed (max structural speed for full control deflection)
VD = Max Dive Speed (for certification only)
VFE = Max Flaps Extended Speed
VLE = Max Landing Gear Extended Speed
VLO = Max Landing Gear Operation Speed
VNE = Never Exceed Speed
VNO = Max Structural Cruising Speed
VS0 = Stalling Speed Landing Configuration
VS1 = Stalling Speed in a specified Configuration
VX = Best Angle of Climb Speed
VXSE = Best Angle of Climb Speed, one engine out
VY = Best Rate of Climb Speed
VYSE = Best Rate of Climb Speed, one engine out


VARIOMETER - A panel instrument, often as simple as a tiny ball in a vertical tube, indicating subtle PITCH movements of an aircraft. Popular use in SAILPLANES.

VENTRAL FIN - A fin/rudder extension on the bottom of a fuselage. Opposite of DORSAL FIN.

VENTURI TUBE - A small, hourglass-shaped metal tube, usually set laterally on a fuselage in the slipstream to create suction for gyroscopic panel instruments. Now outdated by more sophisticated means.

VERTICAL STABILIZER - The large "tail" surface on the top rear of the fuselage used to increase stability. The rudder is attached to the trailing edge of the vertical stabilizer and controls the left or right movement of the airplane's nose. A trim system minimizes the force needed to hold the rudder in the proper position for various flight conditions.

VFR - Visual Flight Rules that govern the procedures for conducting flight under visual conditions. The term is also used in the US to indicate weather conditions that are equal to or greater than minimum VFR requirements. Also used by pilots and controllers to indicate a specific type of flight plan.

VFR ON TOP - Flight in which a cloud ceiling exists but modified VISUAL FLIGHT RULES are in effect if the aircraft travels above the cloud layer.

VISUAL METEOROLOGICAL CONDITIONS (VMC) - Meteorological conditions expressed in terms of visibility, distance from clouds, and ceiling equal to or better than specified minima.

VOR - VHF OmniRange. A ground-based navigation aid transmitting very high-frequency (VHF) navigation signals 360° in azimuth, on radials oriented from MAGNETIC NORTH. The VOR periodically identifies itself by Morse Code and may have an additional voice identification feature. Voice features can be used by ATC or FSS for transmitting information to pilots.

VORTAC - VOR + TACAN (Tactical Air Navigation); combined radio navigation aids.

VSI - Vertical Speed Indicator. A panel instrument that gauges rate of climb or descent in feet-per-minute (fpm). Also Rate Of Climb Indicator.

WASH-IN, WASH-OUT - A method of increasing lift by increasing (Wash-In) or decreasing (Wash-Out) the ANGLE OF INCIDENCE on the outer part of an airplane wing to counteract the effects of engine TORQUE.


WINDSHEAR - Weather phenomenon entailing a strong downdraft of air that can result in the loss of lift for an aircraft passing through it.

WINGLET - A small, stabilizing, rudderlike addition to the tips of a wing to control or employ air movement.

WING LOADING - The maximum take-off gross weight of an aircraft divided by its wing area.

YAW - Of the three axes in flight, this specifies the side-to-side movement of an aircraft on its vertical axis, as in skewing. Compare PITCH and ROLL.

YOKE - The control wheel of an aircraft, akin to an automobile steering wheel.

Editing by Ian C. Mills. © 1999-. All Rights Reserved.
Sources: Aerofiles, a site by the late K.O. Eckland. Interagency Aviation Training, sponsored by the U.S. government. PrivateFly, a site by Adam Twidell. Code of Federal Regulations, Federal Aviation Regulations.

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