Aviation Terms Glossary
Aileron
A hinged flight control surface on the trailing edge of each wing used to control the aircraft in roll.
Air Brake
A type of flight control surface used on an aircraft to increase drag and reduce airspeed during flight.
Air Traffic Control (ATC)
A ground-based service responsible for separating aircraft operating in controlled airspace and on airports.
Airfoil
The shape of a wing or blade of a propeller, helicopter rotor, or turbine, the cross-sectional shape of which is designed to produce lift when air flows over it.
Altitude
The height of an object or point in relation to sea level or ground level.
Approach
The final phase in landing an aircraft, when the aircraft is aligned with the runway and is descending.
Apron
A paved area on an airport, distinct from the runway and taxiway, used for parking aircraft, loading and unloading passengers and cargo, refueling, etc.
Aspect Ratio
The ratio of the span of an aircraft's wing to its mean chord.
ATC Clearance
An authorization by air traffic control for an aircraft to proceed under specified traffic conditions within controlled airspace.
Autopilot
A system used to control the flight of an aircraft without constant manual control by a pilot.
Avionics
The electronic systems used on aircraft, including communications, navigation, flight control, and display systems.
Bearing
The horizontal direction of one point relative to another, usually expressed in degrees.
Boundary Layer
The thin layer of air in the immediate vicinity of a moving surface where the effects of viscosity are significant.
Buffet
A vibration or shaking of an aircraft in flight, caused by separated airflow or turbulence.
Cabin Altitude
The simulated altitude inside the pressurized cabin of an aircraft during flight.
Canard
An aircraft configuration in which a small forewing or horizontal stabilizer is located ahead of the main wing.
Ceiling
The maximum altitude an aircraft can reach under specific conditions.
Center of Gravity (CG)
The theoretical point where the entire weight of the aircraft is considered to be concentrated.
Chord
The straight line joining the leading edge and trailing edge of an airfoil.
Cockpit
The compartment where the pilot(s) sit and control the aircraft.
Compass Rose
A circle showing the principal directions printed on a chart or marked on the ground.
Control Surface
Movable aerodynamic surfaces used to control an aircraft's attitude and direction of flight (e.g., ailerons, elevators, rudder, flaps, slats).
Course
The intended horizontal direction of travel of an aircraft.
Crosswind
A wind blowing across the direction of an aircraft's motion or the runway.
Density Altitude
The altitude relative to standard atmospheric conditions at which the air density would be equal to the indicated air density at the place of observation.
Departure
The act of an aircraft leaving the ground; takeoff.
Drag
The aerodynamic force that opposes an aircraft's motion through the air; air resistance.
Elevator
A hinged flight control surface on the tailplane of a fixed-wing aircraft, used to control the aircraft's pitch.
Empennage
The tail assembly of an aircraft, including the tailplane and fin.
Engine Failure
A loss of power from one or more of an aircraft's engines.
Fairing
A structure whose primary function is to produce a smooth outline and reduce drag.
Final Approach
The last segment of an instrument approach procedure in which alignment is made for landing and descent is continued until the landing.
Flaps
Hinged flight control surfaces on the trailing edge of the wing that can be extended to increase lift and drag, especially during takeoff and landing.
Flight Level (FL)
An altitude expressed in hundreds of feet above a standard pressure datum of 29.92 inches of mercury.
Flight Plan
Specified information relating to the intended flight of an aircraft that is filed orally or in writing with air traffic control.
Force Majeure
Unforeseeable circumstances that prevent someone from fulfilling a contract (e.g., natural disasters, wars).
Fuel Flow
The rate at which fuel is consumed by an engine, usually measured in gallons or kilograms per hour.
Fuselage
The main body of an aircraft, to which the wings and tailplane are attached, and which usually contains the cockpit and cabin.
Glide Slope
A radio beam projected upward from the approach end of a runway that provides vertical guidance to aircraft during an ILS approach.
GPS (Global Positioning System)
A satellite-based radionavigation system that allows users to determine their exact location anywhere on Earth.
Ground Speed
The speed of an aircraft relative to the surface of the Earth.
Heading
The direction in which the nose of an aircraft is pointing, usually expressed in degrees relative to north.
Holding Pattern
A predefined maneuver that keeps an aircraft within a specified airspace while awaiting further clearance from air traffic control.
Hypoxia
A deficiency in the amount of oxygen reaching the tissues.
Icing
The formation of ice on aircraft surfaces, which can adversely affect aerodynamic performance and control.
IFR (Instrument Flight Rules)
Regulations and procedures for flying aircraft by reference to instruments in the flight deck, and navigation by electronic signals.
ILS (Instrument Landing System)
A precision runway approach aid based on two radio beams which together provide pilots with both horizontal and vertical guidance during the approach to land.
Inertial Navigation System (INS)
A navigation device that uses motion sensors (accelerometers) and rotation sensors (gyroscopes) to continuously calculate by dead reckoning the position, orientation, and velocity (direction and speed of motion) of a moving object without the need for external references.
Jet Stream
A narrow, variable band of very strong, predominantly westerly air currents encircling the globe several miles above the earth.
Knot
A unit of speed equal to one nautical mile per hour, used especially by ships and aircraft.
Leading Edge
The foremost edge of an airfoil or wing.
Lift
The aerodynamic force that opposes the weight of an aircraft and holds it in the air, generated by the flow of air over the wings.
Load Factor (G-force)
The ratio of the total aerodynamic force acting on the aircraft to its gross weight.
Localizer
The component of an ILS that provides lateral guidance to an aircraft approaching a runway.
Mach Number
The ratio of the speed of an object to the speed of sound in the surrounding medium.
Maneuvering Speed (Va)
The maximum airspeed at which full deflection of the aircraft's flight control surfaces can be made without risking structural damage.
Mayday
The international radio distress signal used by ships and aircraft.
METAR (Meteorological Aerodrome Report)
A routine weather report issued at regular intervals for an airport.
Minimum Safe Altitude (MSA)
The lowest altitude that provides at least 1,000 feet of clearance above all obstacles within a specified radius of a navigational aid.
Nautical Mile
A unit of distance equal to approximately 1.15 statute miles (1.852 kilometers), used in navigation.
Navigation
The process of accurately ascertaining one's position and planning and following a route.
NOTAM (Notice to Airmen)
A notice containing information essential to personnel concerned with flight operations but not known far enough in advance to be publicized by other means.
Obstacle Clearance Altitude (OCA) / Obstacle Clearance Height (OCH)
The lowest altitude or the lowest height above the elevation of the relevant runway threshold or the aerodrome elevation as applicable, used in establishing compliance with appropriate obstacle clearance criteria in non-precision instrument approach procedures or in missed approach procedures.
Payload
The revenue-producing cargo carried by an aircraft, including passengers, freight, and mail.
Pilot in Command (PIC)
The pilot responsible for the safe and orderly conduct of a flight.
Pitch
The rotation of an aircraft around its lateral axis (nose up or down).
Pitot Tube
A pressure-sensitive instrument used to measure airspeed.
Pre-flight Check
A routine check performed by the pilot before each flight to ensure the aircraft is safe for flight.
Pressure Altitude
The altitude indicated when the altimeter setting is adjusted to the standard sea-level pressure of 29.92 inches of mercury.
Propeller
An airfoil-shaped blade which, when rotated, produces thrust.
Radar
A system for detecting the presence, direction, speed, and altitude of aircraft, ships, etc., by emitting pulses of radio waves that are reflected off the object.
Radio Altimeter
An aircraft instrument that indicates the height above the terrain directly beneath the aircraft by measuring the time taken for a radio signal to travel to the ground and return.
Rudder
A movable control surface on the tail of an aircraft that controls yaw (movement around the vertical axis).
Runway
A strip of pavement or prepared area on an airfield used by aircraft for takeoff and landing.
Squawk Code
A four-digit transponder code assigned by air traffic control to identify an aircraft on radar.
Stall
A condition in aerodynamics and aviation where the angle of attack of the airfoil increases beyond a critical point such that lift begins to decrease.
Standard Atmosphere
A model of the Earth's atmosphere defined by the International Civil Aviation Organization (ICAO). It is used as a common reference for temperature and pressure at different altitudes.
Static Port
An opening on the exterior of an aircraft that is used to measure the ambient atmospheric pressure.
Strobe Lights
High-intensity flashing lights on an aircraft, used for collision avoidance.
Taxi
The movement of an aircraft on the ground, under its own power, in contrast to towing or pushing.
TAF (Terminal Aerodrome Forecast)
A concise statement of the expected meteorological conditions at an airport during a specified period.
Tailwind
A wind blowing in the same direction as the aircraft's motion.
Takeoff
The phase of flight in which an aircraft leaves the ground and becomes airborne.
TAS (True Airspeed)
The speed of an aircraft relative to the air mass through which it is flying.
Thrust
The force produced by an aircraft engine that propels the aircraft forward.
Transponder
A radio receiver-transmitter that transmits a coded signal when it receives a radio-frequency interrogation.
Turbulence
Irregular motion of the air resulting in gusts and eddies.
VOR (VHF Omnidirectional Range)
A type of short-range radio navigation system for aircraft, enabling aircraft with a receiving unit to determine their position and stay on course by receiving radio signals transmitted by a network of fixed ground radio beacons.
VFR (Visual Flight Rules)
Regulations that govern the procedures for conducting flight under visual meteorological conditions (VMC).
Wake Turbulence
Turbulence created by the passage of an aircraft through the air, especially in the vicinity of the wingtips.
Wind Shear
A sudden change in wind speed or direction over a short distance in the atmosphere.
Winglet
A small, usually vertical extension at the tip of an aircraft wing, designed to improve aerodynamic efficiency.
Yaw
The rotation of an aircraft around its vertical axis (nose left or right).