Appendix:Glossary of aviation, aerospace, and aeronautics

This is a glossary of terms used in relation to aviation, aircraft, aerospace, and aeronautics, in alphabetical order.

For specific makes and models of aircraft, see List of aircraft manufacturers and List of aircraft.

A

 * aerodrome: An airfield used for managed aircraft operation. In Britain, an alternative term for airport.
 * aerodyne: A heavier-than-air craft, deriving its lift from motion.
 * aeronaut: Pilot or crew of lighter-than-air craft.
 * aeroplane: A power-driven heavier-than-air craft that derives support in the atmosphere from the reactions of the air on its surfaces that remain fixed under given conditions of flight.(Also airplane)
 * aerostat: A lighter-than-air craft, such as a balloon or airship. Its lift is caused by buoyancy relative to the surrounding air.
 * ailerons: On an aircraft, the ailerons are a control surface usually on the trailing edge of the wings. The ailerons are used to control roll by generating asymmetric wing lift. The ailerons are on the outside of the wings and operate oppositely (If one goes up, the other goes down).
 * air base: A military airport.
 * aircraft: A vehicle that can travel through the air.
 * air force: Branch of a country's military devoted to air warfare.
 * airman: Pilot or crew member of an aircraft. The term is usually applied to the members of an air force.
 * airplane: A powered aircraft that derives its lift from the movement of air over fixed lifting surfaces. (Also aeroplane)
 * airport: An area designated for the takeoff and landing of aircraft.
 * airship: A lighter-than-air craft that can be steered and propelled through the air. (Also dirigible)
 * airstair: A set of steps used by passengers and crew to embark and disembark from a commercial aircraft.
 * apron: The paved area at an airport.
 * attitude: The orientation of an aircraft with respect to the horizon.
 * autogyro: A rotor-craft with unpowered blades that develop lift, and an engine-powered propeller to provide thrust.
 * aviator: Pilot or crew member of an aircraft.
 * available seat miles: Available seat miles (ASMs) is a measure of an airline flight's passenger carrying capacity. It is equal to the number of seats onboard an aircraft multiplied by the distance flown in miles.  For example, a 100-seat aircraft flying 100 miles would result in 10,000 ASMs.  Seats that are not available for sale to revenue-paying passengers (e.g., seats reserved for crew rest, etc.) are excluded from this calculation.  The amount of ASMs flown by an airline during a specified period equals the sum of ASMs flown on all flights during the period.
 * aviatrix: Female aviator (No longer commonly used, and may be offensive to some.)
 * available ton miles (ATMs): Tons multiplied by miles flown. It is an international measure of the capacity available for a carrier. It is also used to measure capacity available for freight carriers.

B

 * balloon: An unpowered lighter-than-air craft.
 * biplane: An aeroplane with two similar-sized wings (or pairs of wings), exactly or approximately in vertical alignment.
 * blimp: Non-rigid airship. Its shape is maintained by internal pressure.
 * bomber: Military aircraft designed to carry or drop bombs.
 * breakeven load factor: The load factor necessary for an airline to break even. It is a function of the percent of seats filled at a particular yield versus the airlines operating costs.

C

 * camber: The measure of asymmetry between the upper and lower surfaces of an aerofoil.
 * control surface: Any moveable surface on an aircraft which controls its motion about one of the three principal axes. ailerons, elevators, and the rudder are examples of control surfaces. In addition, other type of roll control surfaces are roll spoilers that dump lift on one wing or another (as opposed to ailerons), spoilerons (combined spoiler and aileron), and Flaperon (combined flap and aileron).  Other combined controls include the ruddervator (combined elevator and rudder as on the "V" tailed Beech Model 35), Elevons combining elevator and ailerons and Flailavators which control pitch & roll as well as flaps in wing trailing edge control surfaces.  Other subsidiary controls are pitch, roll, and rudder trim tabs and the adjustable pitch tailplane (the whole tailplane moves to trim the pitch axis).
 * center of gravity (CG): The point at which the mass of the aircraft would be balanced if it were placed on that single point. The point changes depending on the loading of the aircraft: fuel, passengers, luggage, etc. Each aircraft has CG limits specified by its manufacturer.  If the CG of the aircraft in its current configuration is outside of the specified limits, the aircraft may be unsafe to fly as the control surfaces will have insufficient authority to safely control the aircraft.  For example, if the CG is behind the aft (rear) CG limit, the aircraft will tend to stall.
 * chord: The dimension of a wing parallel to the direction of motion. (Compare with span and thickness.)
 * cockpit: The compartment of an aircraft where the pilot and crew are based and where the aircraft is controlled.
 * contrail: Artificial cloud produced by a moving aircraft in the air.
 * control tower: A building at an airport where the air traffic control monitors the movement of aircraft.
 * cost per available seat mile: (CASM) – The unit operating cost of a carrier, also known as unit cost. The cost, expressed in cents to operate each seat mile offered. Determined by dividing operating costs by ASM (available seat miles).
 * course: The direction in which the aircraft is moving, not to be confused with the heading which is the direction the aircraft is pointing. The course and heading will usually differ because of crosswinds (see crab). The course is also different from the track which is properly the path over the ground that the aircraft has already flown (although course and track are sometimes used synonymously).
 * crab: A maneuver used to counteract the drift of an aircraft caused by a crosswind. The pilot will offset the heading of the aircraft from the desired track by a calculated amount, and the aircraft's velocity combined with the wind through vector addition will give a net movement in the desired direction.

D

 * dihedral angle: The angle that an aeroplane's wings make relative to the lateral axis (horizontal plane, when on level ground). A larger dihedral angle gives greater roll(lateral) stability at the cost of efficiency. If the wings angle upwards, it is called the dihedral angle. Downward angled wings are said to have an anhedral angle (increasingly referred to as negative dihedral).
 * dirigible: A lighter-than-air craft that can be steered and propelled through the air. From the French word dirigeable meaning steerable. (This term is generally considered out-of-date.  The modern term is airship.)
 * dry lease: A lease in which just the aircraft is provided with no crew and maintenance guarantees


 * diverting: When an aircraft is unable to reach its original destination airport, and has to go somewhere else

E

 * elevons: On an aeroplane, elevons are a single control surface which combines the function of the elevators and ailerons in one. They are usually seen on delta-wing aircraft.
 * elevator: On an aeroplane, the elevators are a control surface usually on the trailing edge of the horizontal stabilizer. The elevators are used to control pitch.

F

 *  feather: To rotate the pitch of the propeller blades until they are oriented directly into the airflow, providing the least air resistance and no thrust. The propeller is usually feathered when an engine fails.
 * flight level: Flight level is the nominal altitude of an aircraft referenced to a standard pressure datum, as opposed to the real altitude above mean sea level.
 * flaps: Flaps (often confused with any of the other moveable surfaces) are used on wings to increase lift and/or increase drag as an aircraft flies progressively slower. Increased lift is usually achieved by increasing the wing area and the camber(shape) of the wing to a lesser extent. Increased drag will arise from increasing the area and camber but the greatest effect is achieved with large changes in camber.
 * fuselage: The main body of an aeroplane/airplane, to which the wings and fins are attached.

G

 * glider: An unpowered fixed-wing heavier-than-air craft. (Also sailplane)
 * glideslope: An instrument on the ground to allow an instrumental landing.
 * Gull Wing Flying Wing: A pure flying wing without a fuselage or vertical stabilizers. (Also "Gull Wing").

H

 * hangar: A large garage-like structure used for storage and repair of aircraft.
 * heading: The direction in which an aircraft is pointing, measured clockwise in degrees from North. Note that this is not necessarily the same as the aircraft's track because of wind.
 * helicopter: A rotor craft with one or more sets of powered blades.
 * HIGE: Hover In Ground Effect. Hovering within one rotor diameter of the ground in order where performance is increased by the interaction of the helicopters rotor downwash and the ground.
 * HOGE: Hover Out of Ground Effect. Hovering at greater than one rotor diameter from the ground where re is no interaction between rotor downwash and the ground.

I

 * instrument flight rules (IFR): A regulatory term describing a flight which may be conducted in atmospheric conditions where the pilot cannot fly the aircraft solely by reference to the natural horizon (e.g. in cloud and fog) and must fly only by reference to the aircraft instruments. Compare to visual flight rules.

J

 * jet bridge: An enclosed, movable connector linking a terminal with an aircraft, used by passengers and crew to embark and disembark from commercial aircraft.

L

 * landing gear: Structure that supports the aircraft's weight when it is not airborne, often including a shock absorbing mechanism. Wheels can be used for hard surfaces, skis or skids for ice or snow, and floats or pontoons if landing on the water.  Some aircraft like flying boats do not require landing gear, since their hull can support them
 * load factor (LF): The percentage of seats filled. Determined by dividing Revenue Passenger Miles by Available Seat Miles. Also a measure of the factor of loading on an aircraft, with comparison to gravity. Increases in steep turns and other abrupt manouvers. Given as a factor of gravity with 1g being the standardised acceleration at sea level on land.

M

 * mayday: International distress call, derived from the French "M'aidez" literal translation "help me".
 * metaplane: The configuration of the air vehicle that can be classified as an aerodyne but it uses static lift mostly to enhance stability.
 * moment: A measurement of weight at a specific distance (moment arm) from a reference point. This measurement is used to verify the aircraft is within the Center of Gravity (CG) limits. Reference points vary between aircraft.
 * monocoque: An object (as in a wing or fuselage) whose skin supports the load as opposed to an internal frame.
 * monoplane: An aeroplane with one wing (or pairs of wings).

P

 * panne: French for non critical breakdown, acronym PAN
 * paraglider: A paraglider is a gliding parakite or kite, a type of hang glider that uses one or more tethers to suspend payload.
 * pitch: A measure of the degree to which an aircraft's nose tilts up or down. Also a measure of the angle of attack of a propeller.
 * pitot tube: A Pitot tube is a measuring instrument used to measure fluid flow, and more specifically, used to determine airspeed on aircraft. The Pitot tube is named after its inventor, Henri Pitot, and was modified to its modern form by Henry Darcy.
 * port: The left-hand side of an aeroplane, when facing the front. An aeroplane's port wing has a red light on its underside.
 * powerplant: A powered aircraft's source of power, usually either a jet engine or a conventional engine and propeller.


 * pressure altitude: The indicated altitude when an altimeter is set to 1013 hPa (29.92 inHg US and Canada).

R

 * roll: Rotation about an axis aligned with the direction in which the aircraft is flying. This axis is also known as the longitudinal axis.
 * rotorcraft: An aircraft that derives its lift from rotating lifting surfaces (usually called blades)
 * rudder: On an aeroplane, the rudder is a control surface usually on the trailing edge of the vertical stabilizer or fin. The rudder is used to control yaw.
 * ruddervators: On an aeroplane, ruddervators are a single control surface which combine the function of the rudder and elevators in one. They are usually seen on V-tail aircraft.
 * runway: The part of an airport used for takeoff and landing of aircraft.

S

 * sailplane: An unpowered fixed-wing heavier-than-air craft. (Also glider)
 * sesquiplane: An aeroplane with two wings (or pairs of wings), where one (often the lower) is significantly smaller than the other in span and/or chord.
 * slip: A manoevre where an aeroplane pilot rolls the aircraft in one direction with the ailerons and yaws it in the opposite direction with the rudder. This results in the aircraft continuing to move forward but presenting a larger cross-section to the oncoming air - thereby creating drag and causing the aeroplane to lose altitude rapidly in a controlled manner.
 * span: The dimension of a wing perpendicular to the direction of motion. (Compare with chord and thickness.)
 * specific impulse: The specific impulse of a propulsion system is the impulse (change in momentum) per unit of propellant.
 * stabilator: On an aeroplane, a stabilator is a surface which combines the function of the horizontal stabilizer and elevators in one by allowing the entire horizontal stabilizer to move and control the pitch of the aircraft.
 * stall: a condition of an airplane or an airfoil in which lift decreases and drag increases due to the separation of airflow.
 * starboard: The right-hand side of an aeroplane, when facing the front. An aeroplane's starboard wing has a green light on its underside.
 * SPS: Standard Positioning Services.
 * synchropter: Any twin-rotor helicopter that uses intermeshing rotors for its flight capabilities.

T

 * tailplane: Usually synonymous with stabilator.
 * taxi: The movement of an aircraft on the ground under its own power.
 * taxiway: The part of an airport used for taxiing, which links the runways with the terminals and hangars.
 * terminal: A building at an airport where passengers transfer from ground transportation to the facilities that allow them to board aircraft; also, a building at an airport where freight is transferred from ground transportation to aircraft.
 * track: The path on the ground over which an aircraft has flown. Also used synonymously with course, the direction in which an aircraft is moving relative to the ground. Note that this is not necessarily the same as the aircraft's heading.
 * thickness: The vertical dimension of a wing. (Compare with span and chord.)
 * threshold: The beginning of the part of the runway usable for landing
 * thrust: Thrust is the force upon a system (such as a rocket or jet engine) generated when that system expels or accelerates mass. The resultant thrust force is equal to and in the opposite direction of the expelled mass.
 * touchdown zone (TDZ): The first 3000 feet of the runway or the first third of the runway, whichever is less, measured from the threshold.
 * transponder: A device on aircraft which uses radio frequencies to identify the aircraft on air traffic control radars
 * triplane: An aeroplane with three similar-sized wings (or pairs of wings), exactly or approximately in vertical alignment.
 * turbofan: A type of airbreathing jet engine that is widely used in aircraft propulsion.

U

 * ultralight: A small, powered aircraft which is extremely light(254 lbs or Less empty)and seats only one occupant. Ultralights are popular among hobbyists for being cost-effective and having lenient regulation. Ultralight type aircraft are generally heavier and can seat more than one occupant.

V

 * visual flight rules (VFR): A regulatory term describing flights that are conducted only in conditions where the pilot can see the ground, or in some instances is flying in the free space above a cloud. Compare to instrument flight rules.
 * V speeds: Speeds that define certain performance and limiting characteristics of an aircraft.
 * VSI: Vertical Speed Indicator, shows the rate of climb or descent.

W

 * wet lease: A wet lease is any leasing arrangement whereby a company agrees to provide an aircraft and at least one pilot to another company. It does not include a code sharing arrangement.
 * wind shear: a quick change in wind speed or direction.
 * wing: A lifting surface of an airplane/aeroplane or sailplane.

Y

 * yaw: Rotation in a horizontal plane about the normally vertical axis - turning to left or right. Generally the control surface to yaw is the rudder.

Z

 * zeppelin: A large rigid airship consisting of a long, cylindrical, covered framework containing compartments or cells filled with gas, and of various structures for holding the engines, passengers, etc.