Pilots’ Glossary 1918

A Glossary of early aviation and flying terms circa 1918.
This glossary of terms is representative of the terminology which a suitably trained service of civilian pilot would be expected to be familiar with circa 1918. Many of the definitions are still valid today and help demonstrate the speed of development  of aviation and training methods given the relatively short period of time that powered controlled flight had been a reality.

Another legacy article from an earlier version of this website.

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Aerobatics – Aerial manoeuvre stunts.
Aeroplane – A heavier-than-air flying machine, supported by the action of air on fixed planes.
Ailerons – Hinged flaps let into the extremities of the main planes and operated by the control lever, to bank the machine and also to maintain its lateral level.
Ailerons Balanced – By connecting the ailerons of each wing, so that when one is pulled down and the other is pulled up the surfaces are made to balance.
Airbrake – A flap that can be let down so as to increase the resistance of the machine to the air.
Air Pocket – See ” Pocket.”
Air Speed – The speed of the machine through the air.
Air Speed Indicator – An instrument for registering the speed of the machine through the air.
Altimeter – An instrument for indicating the height of the machine from the ground where it started from.
Angle of Incidence – See “Incidence.”
Aspect Ratio – The proportion of span to chord of a plane.

Back – A change of wind in an anti-clockwise direction, i.e., from E. to N.
Backwash – The disturbed air in the wake of a machine in Right
Balloon – To The upward glide of a machine near the ground caused by the pilot descending too fast and pulling the control lever back too much or too quickly.
Bank – To To raise one wing for the purpose of turning.
Bay –  The space enclosed by two struts and their upper and lower adjoining surfaces.
Belt –  The safety strap which secures the pilot to his seat.
Bessoneau –  A tent for storing aeroplanes which can be erected and dismantled in a few days.
Biplane –  An aeroplane with two pairs of wings set one above the other.
Blimp –  Slang Term referring to small airships
Blip To –  To switch on and off rapidly.
Body –  That part of a machine which accommodates the engine, pilot, passenger and probably the petrol and oil tanks.
Boom –  See “Tail Boom”
Boss of a Propeller –  The centre portion by which it is attached to the engine.
Bounce –  The upward and forward movement of a machine which has struck the ground without flattening out sufficiently.
Brevet –  A certificate showing that a pilot has passed certain elementary flying tests and may be considered a qualified pilot.
Bumps –  Disturbances or roughness in the air due either to changes of temperature, clouds or wind.

Cabana –  The projecting arrangement of struts above the pilot’s head on a monoplane to which the anti-lift wires are attached.
Cabre –  Tail down.
Camber –  The maximum depth of curvature of the upper and lower surfaces of a wing.
Cartwheel –  particular type of aerial manouvre.
Cell –  The whole of the lower surface of a plane and the whole of the top surface of the plane above it, with the struts and wires holding them together.
Cellule –  The box-like rectangular compartments in a biplane formed by the upper and lower planes and the interplane struts.
Centre of Gravity –  Centre of weight
Centre of Pressure –  A line running from wing tip to wing tip, through which all the air forces on the wing may be said to act.
Centre Section –  The centre cellule of a biplane where this cellule is made detachable from the wings.
Chocks –  Wooden blocks placed in front of the wheels of a machine to prevent it moving when the engine is started.
Chord of a Wing –  The distance between the leading and trailing edge of a wing.
Cockpit –  The pilot’s seat.
Cold Feet –  A complaint, otherwise known as aerosthenia or nervousness of going into the air.
Combustion Chamber –  The space between the top of the piston and the cylinder where the explosion of the mixture takes place.
Compression – The upward stroke of the piston which compresses the mixture in the combustion chamber.
Conk –  The engine is said to “conk ” when it fails.
Contact –  Word used to denote that the switch is on.
Control Lever –  Generally known as the ” joy stick ” or stick. A vertical lever controlling the fore-and-aft and lateral movements of the machine.
Control Wires –  Wires connecting the rudder bar and control lever with their respective con-trolling surfaces.
Cowl –  A sheet-metal cover generally fitted over or round the engine.
Crash Helmet –  A specially-made flying helmet designed to save the pilot’s head in case of a crash.
Crash –  To To smash the machine.

Dihedral Angle –  A machine is said to possess a dihedral angle when the wings rise upward from the centre of the machine.
Dive –  To descend steeply.
Dope –  A preparation used to paint the wings in order to render them taut and weatherproof.
Dope –  Can A metal syringe containing petrol for priming the engine.
Drift –  The crabwise motion of a machine over the ground due to a side wind ; also used to denote head resistance.
Dual Control –  A system of levers and controls for the engine and machine, so that either the pilot or passenger can operate them.

Elevator –  A hinged controlling surface, or flap, operated by the fore-and-aft movement of the control lever. Always set parallel with the wings of the machine and generally behind them. Used to control the up-and-down motion of the machine and in steep banks to make the machine turn.
Empenage –  The tail unit of a machine, consisting of rudder, elevator and fixed tail plane.
Engine Bearer – The metal framework or tubing to which the engine is fixed.
Exhaust – The upward stroke of the piston which drives the burnt and exhaust gas out of the combustion chamber.
Explosion – The power stroke of the engine.
Extensions – Additional lifting surfaces added to the top planes.

Factor of Safety – Obtained by dividing the stress at which a body will collapse by the maximum stress it will be called upon to bear.
Fin – A fixed vertical plane generally fitted in front of the rudder to increase the stability of the machine.
Flares – Ground Waste soaked in petrol, or petrol in buckets, set on fire and used as a landing light for night flying.
Flares Parachute – Magnesium light electrically fired and attached to a parachute, which is re-leased near the ground to facilitate landing at night.
Flares Wing Tip – Magnesium lights electrically fired and used to facilitate landing at night.
Flattening Out – A phrase used to describe the gradual decreasing of the gliding angle of a machine until it merges into the horizontal a few inches off the ground.
Flight A – An organization consisting of a small group of machines.
Flying Speed – The speed of a machine through the air necessary to maintain its support.
Forced Landing – See “Landing.”
Formation Flying – The practice of a group of machines keeping station in the air.
Fuselage – The body of a tractor machine.

Gap – The distance between the upper and lcwer wings of a biplane.
Gas Bag – slang term for airships.
Glide – To descend with the engine cut off with the machine under control and at approximately the flying level speed.
Gliding Angle – The angle that the fore-and-aft line of the machine makes with the horizon in cider to make a correct gliding descent..
Ground Speed – The speed of the machine relative to the ground, which may be equal to, greater, or less than the air speed ; therefore, ground speed is equal to air speed + or – wind speed.

Hangar – An aeroplane shed.
Hate To Commit – To be extreme in doing a thing, i.e., excessive stunting near the ground.
Heavy Handed – Refers to a pilot who is clumsy with his controls and inclined to over-correct.
Height Indicator – See “Altimeter.”
Hoik To – To make the machine climb steeply and suddenly.
Horizon – The limit of ground in view.
Hun – Slang term for a person learning to fly.

Incidence Angle of – The angle that the chord’ of a wing makes with the direction of motion relative to the air. A particularly muddling term, as it is often measured as the distance in inches that the front spar is above the rear spar when the machine is in the flying-level position.
Inclinometer – An instrument for showing the angle of the machine relative to the ground.
Induction – The inlet stroke of the engine.

Joy Stick – See ” Control Lever.”

Kathedral – Angle A machine is said to possess a kathedral angle when the wings slope downwards. from the centre of the machine. (Anhedral?)
Keel Surface – The side surface of a machine as opposed to the head-on surface.
King Post – A bracing strut generally found on the top of controlling surfaces, such as rudder, ailerons and elevator, in which case it also acts as a lever.
Knock – A peculiar noise emanating from the engine and indicating some kind of mechanical trouble.
Knot – A nautical mile per hour, i.e., it is wrong to speak of knots per hour.

Landing – The action of a machine in coming to earth.
Landing Forced – The action of a machine in coming to earth other than at the will of the pilot, i e., in the case of the engine failing.
Leading Edge – The point or entering position of a wing.
Leeward – Away from the wind.
Leeway – Lateral drift to leeward.
Left and Right – Always refer to the left and right of the machine and engine as seen by the pilot sitting in his seat.
Lift – The force exerted by the air on a plane in a. direction perpendicular, or nearly so, to the motion.
Log Book – A book kept by pilots giving details of each flight.
Longerons – The longitudinal members of the fusel-age.
Loop – A manoeuvre in which the machine, after flying straight, does an upward and backward turn or circle, and then continues in the same direction as before.
Lubber Line – or Lubbers Point A mark on the body of a compass corresponding with the fore and aft line of the machine.

Machine – The aeroplane as apart from the engine.
Motor – An incorrect term for the power unit or engine.
M.P.H. – Miles per hour.

Nacelle – The body of a pusher machine.
Nose – The front part of a machine.
Nose Dive – A very steep descent with or without engine.
Nose Heavy – Backward pressure required on the control lever to make the machine fly level.
Nose Piece – The front central portion of a rotary engine.

Outrigger – The framework connecting an elevator placed in front of the machine with the main planes.

Pancake – To drop to earth from a height of a few feet owing to losing flying speed and flattening out too soon.
Pegging Down – Securing a machine by rope to pegs in the ground so as to prevent it capsizing in a wind.
Pilot – A person controlling an aeroplane in the air.
Pitch of a Propeller – The forward distance that the propeller would travel if it were allowed to cut its way, without slip, through some medium such as butter.
Pitot – Tube Consists of two tubes, one open to the air flow and the other protected. The other ends of the two tubes are connected to the air-speed indicator. One tube is called the pressure tube and the other the suction, or static, tube.
Plane – Term used to apply to the supporting surfaces of a flying machine. The planes may be cambered, as in the case of the wings, or flat, as in the case of the tail plane.
Plane Main – The wings of the machine.
Pocket Air – A disturbance in the air causing the machine to drop.
Propeller – The airscrew driven by the engine which forces the machine through the air, generally known as the “Prop.”
Protractor – An instrument for measuring angles.
Pusher – A machine in which the propeller is fitted behind the main planes.

Quirk – A person learning to fly ; slang term for pupil.

Race To – Refers to the practice of speeding up the revolutions of an engine to their maxi-mum.
Radial – Refers to a type of engine in which the cylinders are set radially round the crankshaft, and are stationary.
Radius of Action – The distance that a machine can fly from its starting point and return without replenishing the tanks. Greatly influenced by the wind factor.
Remou – A disturbance in the air.
Remorque – A motor trailer for carrying aeroplanes.
Revs – Short for revolution.
Revving – Short for revolving.
R.F. – Representative fraction. A term indicating the scale of a map.
Rib Compression – A rib designed to act as a strut between the front and rear spars of a wing.
Ribs – The members used in a wing to give, strength and shape in a fore and aft direction. Often called ” former ribs.”
Right and Left – Always refer to the right and left of the machine and engine as seen by the pilot sitting in his seat.
Right and Left of a Machine – Always refers to the machine as seen from the pilot’s seat.
Roll – A manoeuvre in which the machine does a sideways turn or circle, and then continues in the same direction as before.
Rotary – Refers to a type of engine in which the cylinders are set radially round the crankshaft and revolve.
R.P.M. – Revolutions per minute ; generally applied to the engine.
Rudder – A vertical controlling surface, or surfaces, set parallel with the fore and aft line of the machine, and used to control the direction of flight.
Rudder Balanced – A vertical controlling surface set parallel with the fore and aft line of the machine, but pivoted some way back from its leading edge.
Rudder Bar – A pivoted lever, foot-operated, control-ling the rudder.
Rudder Post – The upright member to which the rudder is hinged.

Scout – A small single-seater machine.
Sensitive – The reverse to soggy
Sideslip – A sideways movement of a machine through the air either outwards or in-wards.
Shock Absorbers – Devices for taking the shock of the machine in landing. Saaidow elastic, springs or oil are all used for this purpose.
Skid – An inclined portion of the undercarriage or attachment to the tail which helps to take the shock of landing and drags along the ground in doing so, thus slowing up the machine.
Slipstream of Propeller – The “wash ” set up in the wake of a revolving propeller.
Soggy – Slow on the control and heavy to handle.
Span – The measurement of a machine transversely from wing tip to wing tip.
Spar Main Front and Rear – The main members on which the wing is built. The front spar is generally considered the main spar, and some-times also forms the leading edge of the wing.
Spider – The front bearing supports and plate of a rotary engine.
Spin or Spinning Nose Dive – To go round and round in a small circle with the nose of the machine pointing directly downwards. A corkscrew descent.
Spiral – A steeply -banked, continuous-gliding turn (with engine off).
Splice – To unite the ends of two pieces’of wire, rope or wood. In splicing cable wire or rope the strands are interlaced.
Squadron – An organization consisting of several flights of machines.
Stability – The property of a machine whereby it tends to return to its normal flying position if left uncontrolled.
Stagger – The amount that the leading edge of one wing is set in advance or behind the leading edge of the other plane, measured with the machine in the flying-level position.
Stall – To lose flying speed.
Strainer – See ” Turnbuckle.” The word can also refer to gauge or chamois leather used to strain petrol through before refilling the tanks.
Streamline – A shape of a body that offers the least resistance to its path through the air.
Struts Vertical – members uniting spars in upper and lower planes.
Stunts – Unusual or exaggerated evolutions in the air.
” S ” Turns – A series of steeply-banked right and left-hand gliding turns (with engine off).
Switch – A device for allowing or interrupting the passage of electric current generally to the sparking plugs.

Tachometer – Engine revolution counter.
Tail – A group of planes set behind the main planes and consisting of both vertical and horizontal surfaces, used to control the balance of the machine.
Tail Boom – The long spar connecting the main plane with the tail on a pusher machine.
Tail Heavy – Forward pressure required on the control lever to make the machine fly level.
Tail Plane – A fixed plane fitted parallel with the main plane, to which the elevator is attached.
Tail Plane Lifting – A fixed plane fitted parallel witl} the main plane to which the elevator is attached. It also carries some of the weight of the machine.
Tail Skid – See ” Skid.”
Taxying – The progress of a machine on the ground with the engine running, though not fast enough to give flying speed.
Tee – A ground sign indicating the direction of the wind. Originally an arrow, but it was found to be an improvement to widen the tip of the arrow until it be-came a T. The wind blows from the cross piece down the body of the T.
Tender – A light motor lorry.
Throttle Lever – Controls the amount of explosive mixture entering the engine.
Ticket To Take – To pass an elementary flying test, and thus be registered as a certified aviator.
Torque Engine – The reaction of a propeller which tends to cause the machine to turn about its longitudinal axis in a direction opposite to that in which the propeller is revolving.
Tractor – A machine in which the propeller is fitted in front of the main planes.
Trailing Edge – The rear edge of the wing.
Trestle – Wooden frames or scaffolds designed to support the tail or wings of a machine when repairs are being carried out.
Triplane – An aeroplane with three pairs of wings, set one above the other.
Trueing Up – Adjusting the rigging of a machine so as to correct its balance in the air.
Turnbuckle – A fitting used to adjust the tension of wires to which it is attached. Also called a strainer.

Undercarriage or Underchassis – That part of a machine which carries the weight of the aeroplane on the ground, and also takes the shock of landing.

Veer – To A change of wind in a clockwise direction, i.e., from N. to E.
Vertical Bank – A loosely-applied phrase referring to any bank over 45 degrees.
Very’s Light – A coloured light fired as a signal from a special form of pistol.
Volplane – A glide.

Warp – The yarn running lengthwise in aeroplane fabric.
Warp To – To move the control lever sideways so as to increase or decrease the incidence on a wing with a view to raising or lowering it.
Wash In – An increasing angle of incidence of a wing towards its wing tip.
Wash Out – A decreasing angle of incidence of a wing towards its Wing tip.
Weft – The yarn running crosswise in aeroplane fabric.
Windscreen – A transparent screen mounted in front of the pilot and passenger to shield them from the rush of air by the machine in motion.
Wind Speed – The speed of the wind.
Wind Up – To be frightened of going into the air.
Wing – The main supporting surface of an aeroplane.
Wing Tip – The right or left-hand extremity, of a wing.
Wing Tip Skids – Semi-circular,pieces of bamboo placed under the wing tips to take the shock off the wings, should the machine heel over on the ground.
Wire Compensating or Balancing – The wire connecting opposite ailerons of top or bottom planes.
Wires Control – See ” Control Wires.”
Wires Drift – Used to transmit the head resistance set up by the wings to the main body of the machine.
Wires Flying Drift – Internal bracing wires of a wing connected from the front spar to the rear spar diagonally outwards in each cellule.
Wires Flying or Lift – Used to transmit the weight of the machine to the wings. They lie upwards and outwards.
Wires Landing – Used to take the weight of the wings when the machine is on the ground. They lie downwards and outwards.
Wires Landing Drift – Internal bracing wires of a wing connected from the front spar to the rear spar diagonally towards each cellule.
Wire Snake – Fine wire twisted round other wires to prevent the latter fouling the propeller, should they break.
Wires Warp – Wires used to warp the ends of the wings to control the machine laterally.

Zoom To – ascend very steeply after flying level at full speed.

Principal source of terms: Practical Flying. Complete Course Of Flying Instruction
By “A Flight Commander” – (W.G. McMinnies. R.N.)