Appendix:Glossary of aviation, aerospace, and aeronautics Articles on aviation - General
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Appendix:Glossary of aviation, aerospace, and aeronautics

By Wikipedia,
the free encyclopedia,,_aerospace,_and_aeronautical_terms

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 w:List of aircraft manufacturers and w:List of aircraft.

Table of Contents: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z


Term Definition
aerodyne A heavier-than-air craft, deriving its lift from motion.
aeronaut Pilot or crew of lighter-than-gas craft.
aeroplane A power driven heavier than air aircraft 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 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. The ailerons are on the outside of the wings and operate oppositely (If one goes up, the other goes down).
aircraft A vehicle that can travel through the air.
airplane A powered aircraft that derives its lift from the movement of air over fixed lifting surfaces. (Also aeroplane)
airship A lighter-than-air craft that can be steered and propelled through the air. (Also dirigible)
attitude The orientation of an aircraft with respect to the horizon.
autogyro A rotor-craft with unpowered blades - it requires a separate engine to provide forward motion before lift is developed.
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 (Obsolete, potentially offensive in modern use.)
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.


Term Definition
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.
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.


Term Definition
camber The curved upper surface of the wing.
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). Another combined controls is the ruddalator (combined elevator and rudder as on the "V" tailed Beech Model 35). Other subsidiary controls are pitch, roll, and rudder trim tabs and the stabalator (the whole horizontal stabilizer moves to trim the pitch axis).
center of gravity (CG) The point at which the mass of the aircraft is balanced. This changes depending on the loading of the aircraft: fuel, passengers, luggage, etc. Different aircraft have CG limits specified by their manufacturer. If the CG of the aircraft in its current configuration is outside of the specified limits, the aircraft may be unsafe to fly. For example, if the CG is behind the aft (rear) CG limit, the aircraft will tend to stall.
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).
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).
crab A crab is a maneuver used to eliminate the drift of an aircraft caused by wind. 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.
chord The dimension of a wing parallel to the direction of motion.(Compare with span and thickness.)


Term Definition
dihedral angle The angle that an aeroplane's wings make with a horizontal plane. 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.
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.


Term Definition
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.


Term Definition
feather To rotate the pitch of the propeller blades until they are oriented directily 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.


Term Definition
glider An unpowered fixed-wing heavier-than-air craft. (Also sailplane)
glideslope An instrument on the ground to allow an instrumental landing.


Term Definition
heading The direction in which an aircraft is pointing measure 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.


Term Definition
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.




Term Definition
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.


Term Definition
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).





Term Definition
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.
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).



Term Definition
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.


Term Definition
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.
SPS Standard Positioning Services.


Term Definition
tailplane Usually synonymous with Stabilator (q.v.).
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
triplane An aeroplane with three similar-sized wings (or pairs of wings), exactly or approximately in vertical alignment.


Term Definition
ultralight A small, powered aircraft which is extremely light and seats only one or two occupants. Ultralights are popular among hobbyists for being cost-effective and having lenient regulation.


Term Definition
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 decent.


Term Definition
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.



Term Definition
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


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Published in July 2009.

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