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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.
Monoplane An aircraft that possesses one main supporting aerodynamic surface (wing).
Oleo-Pneumatic Strut A type of hydro-pneumatic (oil-air) shock absorber used on aircraft landing gear.
Otto Cycle The fundamental four-stroke cycle of the internal combustion engine.
Pressurisation An aircraft system by which the pressure of air within the cabin is increased to permit occupants a normal atmospheric environment whilst an aircraft is at high altitude.
Propeller A rotating aerofoil driven by an aircraft engine to produce thrust to pull, or push, the aircraft through the air.
Q-Feel A system of control force feedback to the pilot that provides additional resistance to control movement directly proportional to dynamic pressure.
Radial Engine A piston engine in which the cylinders are arranged centrally, in a radial pattern, about the crankshaft.
Radome A nose cone which is transparent to radar transmissions.
Relative Airflow RAF Is the relative direction and speed of the air before it is influenced by the presence of the aircraft.
The RAF is always equal and opposite to the flight path of the aircraft.
Retreating Blade The rotor blade that is moving with the ongoing airstream caused by forward flight of the aircraft. For most gyroplanes, the retreating blade is on the left side of the aircraft. The retreating blade has less relative airspeed than the advancing blade. At higher airspeeds and low Rotor RPM, the retreating blade can possibly stall and Flap.
Ribs A structural component within the wing, perpendicular to the spar, designed to provide the aerofoil shape and stiffen the skin.
Rotary Engine A piston engine in which the cylinders are arranged centrally in a radial pattern about a central cam. The crankcase, cylinders and propeller rotate around the cam.
Rudder A primary control surface located on the trailing edge of the vertical fin used to control the aircraft in the yawing plane.
Runaway Trim Uncommanded and/or uncontrolled movement of the trimming system.
Semi-Monocoque An aircraft structure that bears the majority of stresses in its outside skin, but gains shape, strength and increased rigidity from a substructure of formers and stringers.
Shimmy Abnormal vibration of the nosewheel.
Slat A leading-edge, lift-augmentation device that delays the separation of the airflow at high angles of attack.
Slotted Flap A type of trailing edge flap that forms a space between its leading edge and the flap well, or its preceding flap.
Solid State An electronic component that controls the flow of electrons without the use of any heated filaments, vacuum spaces or moving parts.
Solidity Ratio The ratio of the total actual area of all rotor blades in a rotor system to the total rotor area; expressed in percent (%)
Spar The main structural component of a wing extending from the fuselage to the wingtip.
Spoiler An aircraft control that consists of panels that can be raised into the airflow to destroy part of the lift and increase drag.
Squat Switch A switch located on the aircraft's main landing gear whose actuation depends upon the compression of the landing gear leg.
Stabilator A combined horizontal stabiliser and elevator in which the whole assembly may be moved.
Stability The tendency of an aircraft to return to its original condition after being disturbed.
Standpipe A pipe sticking up in a tank, or reservoir, that allows part of the tank to be used as a reserve, or standby, source of fluid.
Stick-Shaker A tactile alert system generated through the control column to warn the pilot of an approaching stall.
Stringers A structural component within the wing, running parallel to the spar, designed to assist the ribs in providing an aerofoil shape and stiffening the skin.
Swept Wing A wing which is angled backwards.
Tailerons These surfaces on the F-111C are called tailerons. See Elevons.
Tailwheel Undercarriage A landing gear configuration where the main wheels are located ahead of the tail wheel.
Thrust The equal and opposite reaction to the aerodynamic force produced by the propeller or jet engine, which accelerates a mass of air rearwards.
Tip Speed The speed of the tip of the rotor blades, usually expressed in ft/sec
Tricycle Undercarriage A landing gear configuration where the nose wheel is located ahead of the main wheels.
Trim Tab A small control tab mounted on a primary flight control to relieve static control force.
Turbocharger An exhaust gas-driven air compressor, used to increase the power of a reciprocating engine.
Turbofan A gas turbine engine that produces thrust by the acceleration of air through and around the engine (bypass). A high-bypass ratio indicates that the majority of airflow is directed around the engine.
Turboprop A gas turbine engine configuration which drives a propeller.
Un-Commanded A control input that is not commanded by the pilot. Usually refers to a cyclic input from motions of the airframe that cause the rotor Spindle to change
Variable sweep A wing whose sweep can be adjusted in flight.
Viscosity The resistance of a fluid to flow.
Vortex A whirling motion in a fluid and the form of air spilling over the wingtips of an aircraft.
Wash-Out A wing which is twisted so that its angle of incidence is less at the tip than the root.
Weight A measure of the force of gravity acting upon a body.