Glossary of Aircraft-Related Terms

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aerodyne
A heavier-than-air craft, deriving its lift from motion.

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. (See 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 aeroplane, 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. (See also aeroplane)

airship
A lighter-than-air craft that can be steered and propelled through the air. (See 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.

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.

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 subsidary 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).

chord
The dimension of a wing parallel to the direction of motion.(Compare with span and thickness.)

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.

dry lease
A lease in which just the aircraft is provided with no maintenance guarantees.

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.

elevators
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.

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.

glider
An unpowered fixed-wing heavier-than-air craft. (See also sailplane)

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.

Instrument flight rules (IFR)
A regulatory term describing a flight which may be conducted in conditions where the pilot cannot see outside the aircraft (e.g. in cloud and fog) and must fly only by his instruments. Compare to Visual flight rules.

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 on water.

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).

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 aircrafts 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).

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.

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.

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.

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.

wing
A lifting surface of an airplane/aeroplane or sailplane.

yaw
Rotation in a horizontal plane about the normally vertical axis - turning to left or right.

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