Above Ground Level (AGL): Altitude expressed as feet above the ground or terrain. It is usually set to indicate the airport fi
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 A
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, m
Adcock Range: National low-frequency radio navigation system (c.1930-c.1950) replaced by an omnirange (VOR) system
Adiabatic Lapse Rate: The rate at which ascending air cools and descending air warms, given that no heat is added or taken
Adjustable Stabilizer: a kind of horizontal stabilizer that can be adjusted in flight to trim the airplane, thereby allowin
Adverse Yaw: Yaw generated when the ailerons are used. The lifting wing generates more drag, causing an airplane
Aileron: The movable areas of a wingform that control or affect the roll of an aircraft by working opposite o
Air Defense Identification Zone (ADIZ): The area of airspace over land or water, extending upward from the surface, within which the ready i
Air Route Traffic Control Center (ARTCC): A facility established to provide air traffic control service to aircraft operating on IFR flight pl
Air Speed Indicator: An instrument or device that measures the air speed of an aircraft through an air mass, but not its
Air Taxi: An aircraft operator who conducts operations for hire or compensation in accordance with FAR Part 13
Air Traffic Control (ATC): A service operated by the appropriate authority to promote the safe, orderly, and expeditious flow o
Airfoil: The shape of any flying surface, but principally a wing, as seen in side-view ('cross-section'). Its
Airframe: the structure of an aircraft without the powerplant. It is generally considered to consist of five p
Airport Traffic Control Tower (ATCT): A terminal facility that uses air/ground communications, visual signaling, and other devices to prov
Airspeed Indicator: An instrument or device that measures the airspeed of an aircraft through an air mass but not its gr
Alclad: Trademark name of Alcoa for high-strength sheet aluminum clad with a layer (approximately 5.5% thick
Alphabet (Phonetic): Devised for reasons of clarity in aviation voice radio, this is the current NATO version in global u
Altimeter: An adjustable aneroid-barometric cockpit instrument used to measure an aircraft's altitude.
Altimeter Setting: A reference setting on the altimeter so that the instrument indicates an accurate altitude.
Amphibian: A SEAPLANE or FLOATPLANE with retractable wheels for use on land, as well. The latter spelling was u
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 DIHE
Apron: The hard-surfaced or paved area around a hangar.
Arm: In aircraft weight and balance, as well as load distribution, it is the distance from the CENTER OF
Artificial Horizon: A vacuum-powered panel instrument that displays pitch and roll movements about the lateral and longi
Aspect Ratio: The ratio of the span to the chord of an airfoil—a high-aspect ratio wing has wide span and narrow
Auto-Rotation: Automatic rotation of rotary blades from a helicopter in an unpowered glide or the forward movement
Autogyro: An aircraft, often wingless, with unpowered rotary airfoil blades that auto-rotate and serve as wing
Automatic Terminal Information Service (ATIS): Continuous broadcast of recorded non-control information in selected terminal areas, to improve cont
Axial: Motion along a real or imaginary straight line on which an object supposedly or actually rotates.
Back Pressure: The pressure caused by a reciprocating engine’s exhaust system that opposes the burned gases disch
Balanced Control Surface: A movable control surface, as an aileron or rudder, having an added physical extension or weights fo
Balloon: lighter-than-air non-steerable aircraft that is not engine driven. Its rising capability comes from
Bay: Any specific compartment in the body of the aircraft. It may also refer to a portion of a truss, or
Bench Check: a functional check performed on a part that has been removed from an aircraft to determine its condi
Bernoulli Effect: Since the pressure of a fluid is proportional to its velocity, airflow over the upper surface of an
Biplane: An airplane having two wings, one placed above the other.
Blade Angle: The angle between the plane of propeller rotation and the face of the
Bleed Air: Hot air at high pressure, usually from the bypass section of a gas turbine engine, for de-icing, hea
Boundary Layer: the layer of air immediately adjacent to the surface of an airfoil. Its flow, rather than being lami
Boundary-Layer Control: The design or control of slotted or perforated wings with suction methods to reduce undesirable aero
Bumped Cowling: An engine FAIRING, generally circular, with welts or compound shapes in its surface to accommodate c
Cabane Strut: Wing strut attached to the fuselage.
Calibrated Airspeed (CAS): The indicated airspeed of an aircraft, corrected for position and instrument error. CAS is equal to
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
Carburetor: consists of a main air passage through which the engine draws its supply of air, a mechanism to cont
Cat: Clear-Air Turbulence.
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
Center: An Air Route Traffic Control Center (ARTCC).
Center Of Gravity (Cg): The longitudinal and lateral point in an aircraft where it is stable: the static balance point.
Certificated Airport: An airport operating under FAR Part 139. The FAA issues airport operating certificates to all airpor
Chord: The measurable distance between the leading and trailing edges of a wingform.
Class A Airspace: Airspace between 18,000 and 60,000 feet MSL (Mean Seal Level) over the contiguous United States. IFR
Class B Airspace: Airspace area around the busiest U.S. hub airports (i.e. Chicago O’Hare), typically to a radius of
Class C Airspace: Airspace area around busy U.S. airports (other than Class B). Radio contact with approach control is
Class D Airspace: Airspace around an airport with an operating control tower: typically to a radius of 5 miles and fro
Class E Airspace: General controlled airspace comprising control areas, transition areas, Victor airways, the Continen
Class G Airspace: Uncontrolled airspace, generally the airspace from the surface up to 700 feet or 1,200 feet AGL in m
Coaming: A padded, protective rim around an open cockpit.
Coastal Air Defense Identification Zone: An ADIZ over the coastal waters of the United States.
Collective Pitch: A cockpit control that changes the PITCH of a helicopter's rotor blades: used in climbing or descend
Collector Ring: A circular duct on a radial engine into which exhaust gases from its cylinders are safely discharged
Common Traffic Advisory Frequency (CTAF): A communications radio frequency designed for the purpose of carrying out airport advisory practices
Commuter: An air carrier operator operating under 14 CFR 135 that carries passengers on at least five round tr
Compass Course: A bearing as indicated by the horizontal angle between the compass needle and the centerline of the
Compass North: The North point at which a liquid compass needle points, rather than Geographical, or True, North. C
Constant-Speed Propeller: A hydraulically-controlled propeller that governs an engine at its optimum speed by the blade pitch
Contact Flight: Navigation in which altitude and flight path can be maintained by visual reference to the ground and
Contour Flight: Contact Flight in and around mountainous areas following visual reference to the terrain's countours
Contrail: Trailing streak of condensed water vapor created in the air by heat from an aircraft engine at high
Controlled Airspace: A generic term including all airspace classes in which ATC services are available. VFR aircraft may
Controlled Airspace Class A: (formerly PCA - Positive Control Area) generally, that airspace from 18,000' mean sea level (MSL) up
Controlled Airspace Class B: (formerly TCA - Terminal Control Area) Generally, that airspace from the surface to 10,000' MSL surr
Controlled Airspace Class C: (formerly ARSA - Airport Radar Service Area) Generally, that airspace from the surface to 4,000' MSL
Controlled Airspace Class D: (formerly ATA - Airport Traffic Area and CZ - Control Zone) Generally, that airspace from the surfac
Controlled Airspace Class E: (formerly General Controlled Airspace) Generally, if the airspace is not Class A, B, C, or D, and is
Conventional Gear: Having two main landing wheels at the front and a tail wheel at the rear (as opposed to a “tricycl
Coriolis Force: The force that is produced when a particle moves a long a path in a plane while the plane itself is
Cowl: A circular, removable FAIRING around an aircraft engine (generally radial) for the purposes of strea
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
Data Plate: a permanent identification plate affixed to an aircraft, engine, or component.
Dead Reckoning: In pioneer flight before radio, beacons, and accurate maps, flying distances much by instinct and gu
Deadstick: Descending flight with engine and propeller stopped.
Decalage: The difference in angular settings [Angles of Attack] of the wings of a biplane or multiplane.
Decision Height: With respect to the operation of aircraft, the height at which point a decision must be made during
Delta-Wing: A triangularly-shaped aircraft wing having a low aspect ratio, a sharply-tapered leading edge, a str
Departure Stall: A stall in the takeoff configuration with power.
Detonation: The almost instantaneous release of heat energy from fuel in an engine caused by the fuel-air mixtur
Deviation (Magnetic): The error of a Magnetic Compass due to inherent magnetic influences in the structure and equipment o
Dial Indicator: A precision linear measuring instrument whose indication is much amplified and is read on a circular
Differential Pressure: A difference between two pressures. The measurement of airspeed is an example of the use of a differ
Dihedral: The acute angle, usually upward, between the wing of an airplane and a horizontal cross-section line
Dimpling: a process that is used to indent the hole into which a flush rivet is to be installed.
Directional Gyro: A panel instrument providing a gyroscopic reading of an aircraft's compass heading.
Dirigible: A lighter-than-air craft capable of being propelled and steered for controlled flight. Latin: dirigo
Distance Measuring Equipment (DME): A radio navigation device that determines an aircraft's distance from a given ground station, as wel
Distant Early Warning Identification Zone (DEWIZ): An ADIZ over the coastal waters of the State of Alaska. ADIZ locations and operating and flight plan
Domestic Air Defense Identification Zone: An ADIZ within the United States along an international boundary of the United States.
Dope: Preservative and pigmented coloring for fabric aircraft covering and paints, generally nitrate lacqu
Dorsal Fin: A lateral fin/rudder extension on the top of a fuselage. Opposite of VENTRAL FIN.
Downwash: The air deflected perpendicular to the direction of movement of an airfoil.
Drag: The resisting force exerted on an aircraft in its line of flight opposite in direction to its motion
Drag Wire: A wire designed to resist DRAG forces, usually running from a forward inboard point to an outboard a
Drift: The angle between the heading of an aircraft and its Track [flight path] over the ground as affected
Dry Weight: The weight of an engine exclusive of any fuel, oil, and coolant.
Dural: Originally a tradename for a wrought aluminum-copper alloy created by Bausch Machine Tool Co, now fa
Dzus Fastener: ('Zoose') Very singular to aircraft, a patented slotted screw that binds to a wire for fast release
Earth-Inductor Compass: One whose indications depend on the current generated in a coil revolving in the earth's magnetic fi
Effective Pitch: The actual distance a propeller moves through the air in one revolution. It is the difference betwee
Elephant Ear: (1) An air intake characterized by twin inlets, one on each side of the fuselage. (2) A type of bala
Elevator: The movable part of a horizontal airfoil which controls the pitch of an aircraft, the fixed part bei
Elevator: A horizontal, movable control surface on the tail of an airplane that changes its pitch and therefor
Elevon: A hinged device on the rear portion of an aircraft wing combining the functions of an elevator and a
Empennage: An aircraft's tail group, includes rudder and fin, and stabilizer and elevator. Old French: empenner
Empty Weight: the weight of the structure of an aircraft, its powerplant, and all of the fixed equipment.
En Route Air Traffic Control Services: Air traffic control services provided aircraft on IFR flight plans, generally by centers, when these
Fairing: An added streamlining structure or auxiliary member, most often of light metal, whose only purpose i
Far Part 61: The section or part of the Federal Aviation Regulations (FARs) covering pilot certification and stan
Far Part 91: The section or part of the Federal Aviation Regulations (FARs) covering the flight rules and regulat
Feathering: In the event of engine failure, the process of adjusting a controllable-pitch propeller to a pitch p
Ferry Flight: A flight for the purpose of (1) returning an aircraft to base: (2) delivering an aircraft from one l
Fin: The fixed part of a vertical airfoil that controls the yaw of an aircraft: the movable part being th
Firewall: A fire-resistant bulkhead that isolates the engine from other parts of an airplane's structure.
Fishtailing: A rudder-controlled side-to-side [yawing] motion to reduce air speed, generally prior to landing.
Five-By-Five (5x5): In radio jargon, affirms that a radioed transmission was received as clear and loud. Rated one to fi
Fixed Base Operator (FBO): An airport-based business that parks, services, fuels, and may repair aircraft: often rents aircraft
Flap: A movable, usually hinged AIRFOIL set in the trailing edge of an aircraft wing, designed to increase
Flaperon: A control surface combining the functions of a FLAP and an AILERON.
Flare: A simple maneuver performed moments before landing in which the nose of an aircraft is pitched up to
Flight Envelope: An aircraft’s performance limits, specifically the curves of speed plotted against other variables
Flight Level (FL): A level of constant atmospheric pressure related to a reference datum of 29.92 inches of mercury. Ea
Flight Plan: Specified information relating to the intended flight of an aircraft, filed orally or in writing wit
Flight Service Station (FSS): Air traffic facilities which provide pilot briefing, enroute communications and VFR search and rescu
Floatplane: A water-based aircraft with one or more mounted pontoons, as differentiated from a hulled SEAPLANE [
Flying Wires: Interplane bracing wires that help support wingloads when the plane is in flight. Direction of trave
Fowler Flap: Trademark name of a split-flap attached to a wing's trailing edge with a system of tracks and roller
Frise Aileron: A type of aileron that has a beveled leading edge projecting beyond its inset hinges. When lowered,
Fuel Pressure Gage: a gage that indicates the pressure at which fuel is delivered to the carburetor.
Fuselage: An aircraft's main body structure housing the flight crew, passengers, and cargo and to which the wi
Gap: The distance between two adjacent wings of a biplane or multiplane.
Gear Indicators: a device in the cockpit of an airplane with a retractable landing gear to inform the pilot of the co
General Aviation: The 92 percent of U.S. aircraft and more than 65 percent of U.S. flight hours flown by other than ma
Geographic North: The northern axis around which the Earth revolves: aka 'Map North' and TRUE NORTH. Also see MAGNETIC
Glass Cockpit: Said of an aircraft's control cabin which has all-electronic, digital and computer-based, instrument
Glide Slope: (1) The angle between horizontal and the glide path of an aircraft. (2) A tightly-focused radio beam
Glider: An unpowered aircraft capable of maintaining altitude only briefly after release from tow, then glid
Green Light: Approval for landing. A carryover expression from days when aircraft for the most part had no radios
Gross Weight: The total weight of an aircraft when fully loaded, sometimes referred to as takeoff weight. The airc
Ground Control: Tower control, by radioed instructions from air traffic control, of aircraft ground movements at an
Ground Effect: Increased lift generated by the interaction between a lift system and the ground when an aircraft is
Ground Speed: The actual speed that an aircraft travels over the ground (its “shadow speed”): it combines the
Gull-Wing: Descriptive of wing in frontal view bent as the wing of a seagull: a distinctive shallow, inverted '
Gyroplane: A rotorcraft whose rotors are not engine-driven, except for initial starting, but are made to rotate
Hangar: An enclosed structure for housing aircraft. Originated with lake-based floating homes of the origina
Hard Landing: An improper landing of an aircraft that has transmitted undue stresses into the structure.
Head Wind: A wind that is blowing in the opposite direction the aircraft is flying, thereby impeding its forwar
Heat Load: the amount of heat that the air conditioner is required to remove from an airplane cabin in order to
Helicopter: A wingless aircraft acquiring its lift from revolving blades driven by an engine about a near-vertic
High Blower: A blower-type supercharger set at high rpm.
High-Speed Stall: Any stall made to occur at more than 1g, such as pulling out of a dive or while turning.
High-Wing Airplane: a monoplane with the single supporting surface mounted on top of the fuselage.
Horsepower: The motive energy required to raise 550# one foot in one second, friction disregarded.
Hypersonic: Speed of flight at or greater than Mach 5.0, exceeding SUPERSONIC.
Hypoxia: Deprivation of oxygen, aka 'altitude sickness,' which can adversely affect human judgment and moveme
Indicated Airspeed (IAS): A direct instrument reading obtained from an air speed indicator uncorrected for altitude, temperatu
Inertia Force: A force due to inertia, or the resistance to acceleration or deceleration.
Inspection Authorization: An authorization issued by the FAA to experienced A&P technicians meeting certain requirements. This
Instrument: a device to show visually or aurally the attitude, altitude, or operation of an aircraft or aircraft
Instrument Flight Rules (IFR): Governing flight under instrument meteorological conditions.
Instrument Landing System (ILS): A radar-based system allowing ILS-equipped aircraft to find a runway and land when clouds may be as
Instrument Meteorological Conditions (IMC): Meteorological conditions expressed in terms of visibility, distance from clouds, and ceiling less t
Interphone System: A communication system normally carried out between in-flight crewmembers using microphones and earp
Iron Compass: Railroad tracks, favored by pilots of yore as a dependable aid to surface navigation before radio.
Jet A: A kerosene-type turbine engine fuel similar to the military JP-5. It has very low vapor pressure and
Jet Propulsion: that form of propulsion produced when a relatively small mass of air is given a large amount of acce
Joystick: A single floor- or roof-mounted control stick—sideways movement produces ROLL, and forward/backwar
Jumbo Jets: the name given to wide-bodied airplanes such as the Boeing 747, 757, McDonald Douglas DC-10, Lockhee
Knock: A loud banging noise made inside a reciprocating engine cylinder during the compression stroke. The
Knot: (Nautical mile per hour) The most common measure of aircraft speed. 100 knots is equal to 115 miles
Kreuger Flap: A type of leading edge wing flap hinged at the bottom side of the airfoil. When it is actuated, the
Laminar-Flow Airfoil: A low-drag airfoil designed to maintain laminar (smooth, continuous) flow over a high percentage of
Landing Flaps: a secondary control surface built into the wing by which the overall wing area, or lift-drag ratio,
Landing Gear: The wheels, floats, skis, and all of the attachments that support the airplane when it is resting on
Landing Roll: the distance an aircraft travels on the ground after touchdown to the point it can be stopped or exi
Landing Wires: Interplane bracing wires that help support wingloads when the plane is on the ground. Direction of t
Leading Edge Flap: a portion of the leading edge of an airplane wing which folds downward to increase the camber of the
Lift: The force exerted on the top of a moving airfoil as a low-pressure area [vacuum] that causes a wingf
Lift Wires: Interplane bracing wires that help support wingloads when the plane is in flight. Direction of trave
Lift-Drag Ratio: The lift coefficient of a wing divided by the drag coefficient, as the primary measure of the effici
Light Sport Aircraft: Special FAA certification class (LSA) for an aircraft other than a helicopter or powered-lift—sing
Lighter-Than-Air Craft (LTAC): Generally referring to powered blimps and dirigibles, but often also includes free balloons.
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
Lofting: Design or fabrication of a complex aircraft component, as with sheet metal, using actual-size patter
Longeron: A principal longitudinal member of a fuselage's framing, usually continuous across a number of suppo
Longeron: the main longitudinal strength-carrying member of an aircraft fuselage or engine nacelle.
Loop Antenna: A circular radio antenna, either in the open or in a streamlined, teardrop housing, remotely turned
Loran: Long Range Navigation system, which utilizes timing differences between multiple low-frequency trans
Lunkenheimer Valve: A manual fuel drain placed handily along a fuel line for checking avgas, such as for water or sedime
Mach (M): A number representing the ratio of the speed of an object to the speed of sound in the surrounding a
Magnetic Compass: The most common liquid-type compass, capable of calibration to compensate for magnetic influences wi
Magnetic Course: COMPASS COURSE ± deviation.
Magnetic North: The magnetic North pole, located near 71° North latitude and 96° West longitude, that attracts a m
Magneto (MAG): An accessory that produces and distributes a high-voltage electric current for ignition of a fuel ch
Magnus Effect: The effect on a spinning cylinder or sphere moving through a fluid, in which force acts perpendicula
Maintenance Manual: A manual produced by the manufacturer of an aircraft, aircraft engine, or component that details the
Major Overhaul: the complete disassembly, cleaning, inspection, repair, and reassembly of an aircraft, engine, or ot
Maximum Takeoff Weight: The maximum weight of any aircraft on takeoff without exceeding its load factor. (MTOW)
Mean Sea Level (MSL): The average height of the surface of the sea for all stages of tide: used as a reference for elevati
Metar: Acronym in FAA pilot briefings and weather reports simply means an 'aviation routine weather report,
Monocoque: Type of fuselage design with little or no internal bracing other than bulkheads, where the outer ski
N-Numbers: Federal government aircraft registration numbers. U.S. registered aircraft numbers begin with “N�
Nacelle: A streamlined enclosure or housing to protect something such as the crew, engine, or landing gear. F
National Airspace System (NAS): The common network of US airspace: air navigation facilities, equipment and services, airports or la
Nautical Mile: The most common distance measurement in aviation. A nautical mile is equivalent to 1.15 statute (sta
Navigation Lights: lights on the aircraft consisting of a red light on the left wing, a green light on the right wing,
Non-Directional Beacon (NDB): An LF, MF, or UHF radio beacon transmitting non-directional signals whereby the pilot of an aircraft
Nontowered Airport: An airport without a control tower - the majority of America’s 13,000 airports. Only 680 airports
Octane Rating: The rating system of aviation gasoline with regard to its antidetonating qualities. Fuel with an oct
On The Beam: A leftover phrase from ADCOCK Radio Range days still means the same thing today—'You are headed in
Overhang: the distance from the outer strut attachment to the tip of the wing.
Overload: to apply a load in excess of that for which a device or structure is designed.
Overshoot: To land beyond a runwway or planned spot. Opposite of UNDERSHOOT.
Overspeed Condition: A condition of the propeller operating system in which the propeller is operating above the RPM for
Pancake Landing: an aircraft landing procedure in which the aircraft is on an even plane with the runway. As the airc
Pants: A popular word for streamlined, non-load bearing fairings to cover landing wheels. Also sometimes ca
Pattern: The path of aircraft traffic around an airfield, at an established height and direction. At tower-co
Payload: Anything that an aircraft carries beyond what is required for its operation during flight, theoretic
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. Compa
Pitot Tube: More accurately but less popularly used, Pitot-Static Tube, a small tube most often mounted on the o
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.
Precision Approach Radar (PAR): A ground-radar-based instrument approach providing both horizontal and vertical guidance
Prohibited Area: Airspace designated under FAR Part 73 within which no person may operate an aircraft without the per
Pusher: A propeller mounted in back of its engine, pushing an aircraft through the air, as opposed to a TRAC
Quadraplane: An aircraft having four or more wingforms.
Radar Approach Control Facility (RAPCON): A terminal ATC facility that uses radar and non-radar capabilities to provide approach control servi
Radial Engine: A reciprocating aircraft engine in which all of the cylinders are arranged radially, or spoke-like,
Ramjet: An aerodynamic duct in which fuel is burned to produce a high-velocity propulsive jet. It needs to b
Ramp: the apron or paved surface around a hangar used for parking aircraft.
Resistance: Symbol: R. The opposition to the flow of electrons offered by a device or material. Opposition by re
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
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
Rotorcraft: A heavier-than-air aircraft that depends principally for its support in flight on the lift generated
Rudder: The movable vertical control surface used to rotate the airplane about its vertical axis. The pilot
Sailplane: An unpowered, soaring aircraft capable of maintaining level flight for long periods of time after re
Scramjet: Acronym for supersonic combustion ramjet, in which combustion occurs at supersonic air velocities th
Scud: A low, foglike cloud layer.
Seaplane: A water-based aircraft with a boat-hull fuselage, often amphibious.The term is also used generically
Secondary Stall: Any stall resulting from pulling back too soon and too hard while recovering from any other stall. U
See-And-Avoid: The FAA requirement that all pilots are ultimately responsible for separation from other aircraft wh
Service Ceiling: The height above sea level at which an aircraft with normal rated load is unable to climb faster tha
Sesqui-Wing: A lesser-span additional wingform, generally placed below the main planes of an aircraft, generally
Shoulder-Wing: A mid-wing monoplane with its wing mounted directly to the top of the fuselage without use of CABANE
Sideslip: A movement of an aircraft in which a relative flow of air moves along the lateral axis, resulting in
Sinking Speed: The speed at which an aircraft loses altitude, especially in a glide in still air under given condit
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 lif
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 an
Slotted Flap: A flap that, when depressed, exposes a SLOT and increases airflow between itself and the rear edge o
SMOH: Since Major Overhaul, an acronym seen in reference to the operating hours, or time remaining, on an
Solo: After typically 12-20 hours of initial flight training, qualified student pilots are permitted to un
Special Use Airspace (SUA): Airspace of defined dimensions identified by an area on the surface of the earth wherein activities
Split Flap: A FLAP built into the underside of a wing, as opposed to a Full Flap wherein a whole portion of the
Spoiler: A long, movable, narrow plate along the upper surface of an airplane wing used to reduce lift and in
Sponson: A short, winglike protuberance on each side of a seaplane fuselage to increase lateral stability.
Sport Pilot: Special FAA certification enabling 'budget' pilotry: see LIGHT SPORT AIRCRAFT and LSA feature.
Squawk: A four-digit number dialed into his transponder by a pilot to identify his aircraft to air traffic c
Stabilator: A movable horizontal tail that combines the actions of a stabilizer and elevator, increasing longitu
Stagger: The relative longitudinal position of the wings on a biplane. Positive Stagger is when the upper win
Stall: (1) Sudden loss of lift when the angle of attack increases to a point where the flow of air breaks a
Standard Air (Standard Atmosphere): An arbitrary atmosphere established for calibration of aircraft instruments. Standard Air Density is
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
Student Pilot: A pilot who is training for a sport pilot or private pilot certificate, either before or after the f
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 ofte
Swing-Wing: A wing whose horizontal angle to the fuselage centerline can be adjusted in flight to vary aircraft
Tachometer: an instrument that measures the rotating speed of an engine in revolutions per minute (RPM) or in pe
Tarmac: (1) A bituminous material used in paving: a trade name for Tar MacAdam. (2) An airport surface paved
Taxi: To move an airplane on the ground under its own power.
Terminal Radar Service Area (Trsa): Airspace surrounding designated airports wherein ATC provides radar vectoring, sequencing, and separ
Tetrahedron: Ground-based, free-rotating, triangular-shaped wind direction indicator, generally placed near a run
Thrust: The driving force of a propeller in the line of its shaft or the forward force produced in reaction
Torque: A twisting, gyroscopic force acting in opposition to an axis of rotation, such as with a turning pro
Touch-And-Go: Landing practice wherein an aircraft does not make a full stop after a landing, but proceeds immedia
Tractor: A propeller mounted in front of its engine, pulling an aircraft through the air, as opposed to a PUS
Trailing Edge: The rearmost edge of an AIRFOIL.
Transponder: An airborne transmitter that responds to ground-based interrogation signals to provide air traffic c
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
True Air Speed (TAS): Because an air speed indicator indicates true air speed only under standard sea-level conditions, tr
True North: The northern direction of the axis of the Earth: aka 'Map North.' GEOGRAPHIC NORTH, as opposed to MA
Turbojet: An aircraft having a jet engine in which the energy of the jet operates a turbine that in turn opera
Turboprop: An aircraft having a jet engine in which the energy of the jet operates a turbine that drives the pr
Turn and Bank Indicator: Primary air-driven gyro instrument, a combined turn indicator and lateral inclinometer to show force
Twilight Zone: Long before Rod Serling's tv series was this consumer-lever definition for a glitch in the ADCOCK RA
Ultralight: An aeronautical vehicle, operated for sport or recreational purposes, that does not require FAA regi
Uncontrolled Airspace: Class G Airspace: airspace not designated as Class A, B, C, D or E.
Uncontrolled Spin: A spin in an airplane in which the controls are of little or no use in effecting a recovery.
Undercarriage: The landing gear of a land-based aircraft, including struts, frames, and wheels. A very British word
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-towe
Upwash: The slight, upward flow of air just prior to its reaching the leading edge of a rapidly moving airfo
Upwind Turn: Long a point of contest among pilots, there is in reality no such thing as far as the airplane is co
Useful Load: The weight of crew, passengers, fuel, baggage, and ballast, generally excluding emergency or portabl
Useful Load: Weight of the occupants, baggage, usable fuel, and drainable oil. The difference between maximum and
Variometer: A panel instrument, often as simple as a tiny ball in a vertical tube, indicating subtle PITCH movem
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 creat
Vertical Speed Indicator: A panel instrument that gauges rate of climb or descent in feet-per-minute (fpm). Also Rate Of Climb
VFR On Top: Flight in which a cloud ceiling exists but modified VISUAL FLIGHT RULES are in effect if the aircraf
VHF OmniRange (VOR): A ground-based navigation aid transmitting very high-frequency (VHF) navigation signals 360° in azi
Visual Flight Rules (VFR): A defined set of FAA regulations and “rules of the road” covering operation of aircraft primaril
Visual Meteorological Conditions (VMC): Meteorological conditions expressed in terms of visibility, distance from clouds, and ceiling equal
Vortac: VOR + TACAN (Tactical Air Navigation): combined radio navigation aids.
Wash-In: A method of increasing lift by increasing (Wash-In) or decreasing (Wash-Out) the ANGLE OF INCIDENCE
Wing Loading: The maximum take-off gross weight of an aircraft divided by its wing area.
Winglet: A small, stabilizing, rudderlike addition to the tips of a wing to control or employ air movement.
Yaw: Of the three axes in flight, this specifies the side-to-side movement of an aircraft on its vertical
Yoke: The control wheel of an aircraft, akin to a automobile steering wheel.