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Terms & Definitions
 

 

Aerodynamics
The science of air in motion.
 
AGL
Above ground level – altitude.
 
Aileron
A control surface on the trailing edge of the wing which creates bank or helps reduce roll.
 
Air foil / Aerofoil
Any surface designed to react to the air through which it moves. Four basic typpes:
- Symetrical – curved on top and bottom
- Flat bottomed
- Under cambered – the bottom surface follows the camber of the upper surface; as in a flixible wing
- Reflexed – characterised by the turned up trailing edge
 
airfoil-types
 
Airframe
The main structure of an aircraft.
 
Airspeed
The speed of the aircraft through the air.
 
Angle of Attack
The angle of the wing in relation to the direction of the wind’s motion. The angle is created by the intersection of the line of the chord of the wing and wind flow.
 
AoA-diag
 
Anodising
An electrolytic process of corrosion protection for aluminium.
 
Apex
The point of an angle made by the two wing leading edges.
 
ASL
Above sea level – altitude 
 
Aspect ratio
Wingspan divided by average chord.
For Rogallo wing – square of the wingspan divided by wing area.

 

Autogiro
The autogiro has an engine-driven propeller like a fixed-wing aeroplane, and a rotor which is not engine-driven but is purely and simply a rotating wing. In flight the propeller drives the Autogiro forward, while the motion of the air now turns the rotor automatically (known as auto-rotation). As the rotor turns, air passes over its aerofoil shaped blades, developing lift in the same way as the wing of an aeroplane. As long as the Autogiro maintains a forward speed the rotor will develop sufficient lift to keep the machine airborne. If forward speed drops the rotor will still be turned, but lift will be reduced, and the Autogiro will glide to earth.
(In the direct take-off type of Autogiro, the rotor is geared to the engine temporarily prior to take-off, permitting a jump-start, without forward run.)
 
Autog-defn
 
 Axis
The line of any of the three planes (longitudinal, lateral, or vertical) that pass through an aircraft’s centre of gravity.
 
Axis-defn-01
 
Bank
The angle of lean to the side, or roll.
 
Battens
Strips of light wood or fibreglass inserted into pockets at the trailing edge of a wing to reduce flutter.

 

Billow
The upward curve of the flexibly lifting surface when filled with air. Billow substantially influences the handling on a hang glider.
 Billow
 
Biplane
The type of aircraft that has two wings, one above the other.
 
Cabane Strut
A wing strut which is attached to the fuselage.

 

Camber
The curvature revealed by a cross-section of a wing.
 Camber

 

Canard
An aircraft that flies tail first, with its main lift surface at the aft end of its structure.
 
Cannular
Type of combustion chamber for jet engines in which individual flame tubes are mounted inside an annular or circular chamber.
 
Cantilever
A fixed wing which has no external wires for bracing.
 
Centre of Gravity / C of G
The pivotal point within the aircraft mass around which all forces are balanced,
 
Centre of Pressure
The point of an airfoil where there is the most concentrated lift.
 
Chaff
Radar reflective and dispersing material released from an aircraft to confuse enemy radar equipment.
 
Chord
The width of the wing measured parallel to the centre line of the aircraft from the leading edge to trailing edge.

 

Convertiplane
The Convertiplane is an aircraft which takes off as a helicopter and "converts " into an Autogiro or fixed wing aeroplane for forward flight. Its rotor is engine-driven and it takes of like a normal helicopter. In the air, engine power is gradually transferred from the rotor to orthodox propellers. These propellers provide thrust (and counter torque), and the rotor is used solely to provide lift and control, as in an Autogiro.
Convertiplanes usually have small fixed wings as well as a rotor, and these provide most of the lift required in cruising flight, with the rotor in auto-rotation. Examples are the Farfadet, McDonnell XV-1, and Rotodyne.
Other types of convertiplane have rotors that tilt through 90 degrees to serve as propellers for cruising flight. Examples are the Bell XV-3 and Transcendental Model I-G.
 
Convert-defn
 
Co-Axial Propellers
Two propellers mounted one behind the other and driven independently in opposite directions.
 
Compressibility Drag
The increase of drag arising from the compression of air when flying at high speeds.
 
Constant Speed Propeller
One which governs an engine speed. The blade pitch being increased or decreased automatically to achieve this.
 
Cyclic Pitch Control
Means of changing the pitch of a helicopter rotor blades progressively, to provide a horizontal thrust component for flight in any horizontal direction.

 

Cylindrical wing
A helical twist of the leading edge of a Rogallo hang-glider produces a cylindrical sail.
 
Deflexers
Outrigger cables which counteract the tendency of the leading edge to bend while in flight.
 
Dihedral
The angle which the spanwise axis of an aerofoil makes the fuselage when the wing or tailplane tip is higher than its root attachment (positive dihedral).
 
Diurnal Winds
The daily wind pattern over a particular area.
 
Dive
A steep downward flight through the air.
 
Drag
The force of wind resistance which opposes the forward motion:
 
Drag chute
A heavy duty parachute attached to the aircraft structure to slow the aircraft on landing.
 
Drift
The crabbing motion – the angle between the actual forward motion and the direction the nose is pointed.
 
Delta
A triangular shape – generally of the wing.
 
Dihedral
The upward angle of the wings on the vertical plane for the purpose of greater stability.
 
 Dihedral

 

Duralumin
A wrought alloy of aluminium with small quantities of copper, magnesium and manganese added.
 
ECM
Electronic Counter Measures – Airborne equipment used to reduce the effectiveness of an enemy’s radar or other devices which generate electromagnetic radiation.
 
EFIS
Electronic Flight Information System
 
Elevator
Movable control surface on the trailing edge os an aircraft’s tailplane to control pitching movement.
 
Helicopter
The helicopter's rotor is turned continuously by the engine, and provides both lift and propulsion. It creates sufficient lift to keep the helicopter airborne without any forward speed. Thus the helicopter can take off and land vertically, and hover. Progress in any direction is achieved by tilting the whole rotor assembly, to provide thrust as well as lift: for example, by tilting it forward the helicopter is propelled forward. A helicopter can, therefore, fly forward, backward or sideways. Most single-rotor helicopters have a small tail rotor to counter torque of the main rotor, which would otherwise tend to rotate the whole fuselage in the opposite direction to the rotor.
 
Heli-defn
 
IATA
International Air Transport Association
 
ICAO
International Civil Air Organisation
 
IFF
Identification Friend or Foe – An electronic device to interrogate approaching aircraft.
 
IFR
Instrument Flight Rules – Flight by reference to on board instruments under conditions of poor visibility or darkness.
 
ILS
Instrument Landing System
 
Incidence angle
Angle between the chord of a wing and the horizontal centre line of the aircraft

 

Induced drag
Drag created by the generation of lift.
 
ISA
Agreed International Standard Atmosphere to permit accurate comparison of performance figures – 1013.2 millibars at 15 deg C.
 
JATO
Jet assisted takeoff – utilising solid or liquid fuel rockets to augment the takeoff power of an aircraft’s engines.
 
Kinetic heating
Heating of an aircraft’s structure as a result of air friction.
 
Kite
Usually a tethered heavier than air aircraft, sustained in the air by its aerofoil surfaces inclined to the wing to generate lift.
 
kN
Kilo-Newton – measurement of force. The force necessary to provide a mass of 1 kg with an acceleration of 1 m/sec.
 
Landing weight
The maximum weight at which an aircraft is permitted to land.
 
Landing wires
External bracing wires which support the wings when the aircraft is on the ground.
 
L/D
Lift / drag ratio
 
Leading edge
The front edge of an aerofoil which first meets the airstream in normal flight.
 
Lift
The force generated by an aerofoil section, acting at right angles to the airstream flowing past it .
 
Lomcevak
Translated from Czech – berserk-head-ache.
It begins as an outside climbing snap roll but becomes a tail-over-nose tumble of one-and-a-half rotations for a properly executed Lomcevak. Usual recovery is a vertical dive.
To enter a Lomcevak, from upside-down position apply hard down elevator and ailerons in the direction of the desired roll with hard full opposite rudder. Controls remain in this position throughout the entire manoeuvre, however engine power is reduced immediately following entry. Critical functions determining whether the inverted snap roll progresses into the end-over-end tumble are exact airspeed, angle of climb and the ‘G’ break on entry. These factors vary with different aircraft but are 130 mph, 45 degrees and 4 – 5 ‘G’ in a Great Lakes, slightly higher in the Pitts Special.

 

Longeron
A main structural load bearing fore and aft axis member within the fuselage.
 
LORAN
A long range radio based navigational aid
 
Mach
A means of recording speed as a ratio of the speed of sound in the same ambient conditions.
Named after the Austrian physicist Ernst Mach
 
MAD
Magnetic Anomaly Detector – carried by maritime reconnaissance aircraft to locate submarines beneath the surface.
 
Mayday
Distress call
 
Monocoque
A structure in which the outer skin carries the primary stresses and is free from internal bracing.
 
NACA
National Advisory Committee for Aeronautics (later NASA)
 
NASA
National Aeronautics and Space Administration
 
NATO
North Atlantic Treaty Organisation

 

N Number
The United States did not formally register aircraft until 1927. In January 1927 temporary numbers were issued to existing aircraft. Later in 1927 permanent registrations began to be issued (with NC26: 1 to 25 were reserved by the Dept of Commerce). The US used a NC / C / R / NR / NS / X / NX prefix depending upon the licence status.    

 

OCU
Operational Conversion Unit
 
Ornithopter
A flapping wing aircraft
 
OTU
Operational Training Unit
 
Pancaking
Landing an aircraft at an abnormally high rate of descent or low landing speed.
 
Pitch
The angle of incidence at which a propeller or rotor blade is set.
 
Pitching
The angular motion about the lateral axis.
 
Pitot tube
A small open ended tube for measuring airspeed and pressure.
 
Pressurisation
Artificially increased pressure in an aircraft to compensate for the reduced external pressure as the aircraft gains altitude.
 
Prototype
The first airworthy example of a new aircraft design or variant.

 

Parasitic Drag
Drag created by the aircraft structure.

 

Rigid Wing Hang Glider
Both leading edge and trailing edges are attached to and supported by the frame. Use various lateral controls, like tip rudders, spoilers or natural rudders to augment weight shift control. Sink rates vary from 180-250 fpm and the glide ratio is usually above 8-1.
 
Rogallo
Standard Rogallo – Hang gliders with the leading edge of usually between 15 and 20 feet long and the keel the same. The nose angle is between 80 and 90 degrees with a sail billow of 3 to 5 degrees. The trailing edge is unconnected to the frame. The glide ratio is in the range of 4-1 to 6-1.

 

VOR
VHF Omni-directional Receiver
 
VSTOL
Vertical / Short take-off and landing
 
VTOL
Vertical take-off and landing
 
Windsock
A conical streamer on an airfield to indicate wind direction and strength at ground level.
 
Window
A metallic material, in strip lengths that was dropped to confuse enemy radar.
 
Wing loading
The gross take-off weight of an aircraft divided by its wing area.
 
Wing warping
A method of lateral control used by early builders where the wing is flexible and is twisted or warped by the pilot to provide roll control.
 
Winglet
A small upright structure attached to the wing tip to reduce drag by reducing wing tip vortices.
 
W/no
Works number
 
Yaw
The movement of an aircraft about its vertical axis.
 
Zooming
Using kinetic energy of an aircraft’s motion to gain height.

 

 
 


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