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Glossary - Aircraft Technical

Advancing Blade The rotor blade that is moving into the oncoming airstream caused by forward flight of the aircraft. For most gyroplanes, the advancing blade is on the right side of the aircraft. The advancing blade has a higher relative airspeed than the retreating blade.
Adverse Aileron Yaw A condition of flight in which the nose of an aircraft yaws in the opposite direction to the direction of roll when the ailerons are deflected.
Aerodynamics The study of the interaction between air and a solid body passing through it.
Aerofoil A surface designed to generate lift.
Aileron A primary control surface, usually located at the outer rear edge of the wing used to control the aircraft in the rolling plane.
Airframe The aircraft's primary structure.
Airspeed The rate at which an aircraft moves through the air.
All-Flying Tail An tailplane where the variable incidence function is used as the primary pitch control and trim.
Alpha Angle of attack.
Ammeter A cockpit instrument used to indicate electrical current.
Angle of Attack The angle formed between the chord line of an aerofoil and the relative airflow.
Angle of Incidence The angle formed between the chord line of the wing root and the longitudinal axis of the aircraft.
Anhedral The negative angle formed between the lateral axis of the aircraft and the main spar.
Anti-Icing Prevention of ice forming.
Anti-Skid A system of control for aircraft brakes that releases the hydraulic pressure to the brake in the event the wheel begins to lock up or skid.
Aquaplaning A condition when fluids on the surface of a runway are of sufficient quantity to lift the tyre clear of the surface. Aquaplaning can result in loss of braking and steering.
Artificial Feel A system of force feedback provided for the pilot in automatic or powered flight control systems.
Aspect Ratio The ratio of span squared divided by wing area.
Auxiliary Power Unit A self contained motor-generator carried in an aircraft primarily as a ground supply for air conditioning, electrical services and engine starting.
Backlash In flight controls, the freeplay about neutral, before the control movement takes effect.
Baffles A baffle changes the course of airflow or re-directs it. Any device that directs airflow to another location to keep heated parts cooler can be considered a baffle.
Biplane An aircraft that possesses two main supporting aerodynamic surfaces (wings).
Blade Angle The angle formed between the face of a propeller blade and the plane of rotation.
Bleed Air Compressed air taken from one or more stages of the compressor of a gas turbine. Bleed air is used for anti-icing, de-icing, cabin pressurisation and environmental control.
Bogie The landing gear of an aircraft using tandem sets of wheels on each undercarriage leg. There may be two or more wheels per bogie.
Boundary Layer The layer of air adjacent to surface.
Bus Bar A component used to distribute power in an aircraft electrical system.
Cabin Altitude The equivalent altitude at which the cabin pressure of a pressurised aircraft is maintained.
Cabin Differential The difference between atmospheric pressure and the cabin pressure within a pressurised aircraft. Described in psi.
Camber The degree of curvature of the line of mean camber.
Canard An aircraft configuration where fixed or controllable aerodynamic surfaces are placed ahead of the mainplane.
Chord The straight line distance from the leading edge to the trailing edge of an airfoil
Chord Line An imaginary line drawn through an aerofoil from its leading edge to the trailing edge.
Constant Speed Propeller A type of propeller whose pitch is controlled by a governor to keep the rpm constant.
Creep The tendency for a tyre to slip or move around the rim of the wheel.
De-Icing The removal of ice from a surface.
De-Icing Boot A rubberised panel on the leading edge that is pulsated pneumatically to physically break any accumulation of ice.
Dihedral The positive angle formed between the lateral axis of the aircraft and the main spar of the wing.
Drag The resistance to motion when a body is moved through the air.
Drop Tank An externally mounted, jettisonable fuel tank.
Efflux The mass of air expelled from the hot exhaust of a gas turbine engine.
Elevator A primary control surface located on the trailing edge of the horizontal stabiliser.
Elevons Control surfaces which operate symmetrically for pitch and differentially for roll.
Empennage The tail assembly.
Fairing A part of a structure whose primary purpose is to produce a smooth junction.
Feathering Propeller A propeller where the blades can be rotated edgeon to the airflow.
Feedback The control forces that the pilot feels through the control linkage and the aircraft's response.
Firewall A steel sheet barrier on which the engine is mounted. On single engine aircraft this separates the engine from the cockpit.
Fixed Pitch Propeller A type of propeller where the blade angle is set.
Flapping Movement of a rotor blade in the vertical sense relative to the plane of rotation.
Flutter A flight condition of rapid and uncontrolled oscillation of a flight control surface.
Fly-by-Light A flight control system which utilises signalling via optical fibre cables to the flight control actuators.
Fly-by-Wire A flight control system where inputs from the pilot's controls are converted to digital signals that are interpreted and applied by digital flight control computers which electrically signal the hydraulic actuators.
Fowler Flap A flap that extends rearwards, increasing the camber and total area of the wing.
Fretting surface to surface type of wear
Gear An alternative, colloquial term for the undercarriage.
Generator A generic term for a device that generates electricity and can either be an AC (Alternating Current) or DC (Direct Current) device.
Ground Power Unit A piece of ground support equipment that includes a motor-generator and air compressor.
Gyroscope A rapidly spinning rotor with two useful qualities – rigidity and precession.
Jettison To release something from an aircraft in flight.
Kruger Flap A hinged leading edge flap which increases the radius of the leading edge.
Lift The component of the total reaction perpendicular to the relative airflow.
Lift Dump The intentional destruction of aerodynamic lift on touch down achieved by spoiler deployment.
Load Factor The ratio of the acceleration imposed on an aircraft to the weight of the structure itself in level flight.
Mach Number A speed measurement based on the ratio of the true airspeed to the local speed of sound.
Manual Reversion The manual reversionary mode of a powered fight control system.
Mass Balancing A device involving the use of weights to counter control surface flutter.
Master Switch The primary switch used to control an aircraft's electrical system.
Monocoque An aircraft structure that bears the stresses in its outside skin.