P/Q

This glossary of historic aviation terms is reproduced from 'The Spotters Glossary' which appeared in 'The Aeroplane Spotter' from January 1940 onwards. 'The Aeroplane Spotter' was the first journal devoted exclusively to the study and practice of aircraft recognition.

We are pleased to have been able to reproduce the entire glossary from A-Z, offering a unique insight into aviation terminology (and therefore aviation history and technology) prior to and during the 1940s.

NB: In the interests of clarity we have substituted current equivalents where words and phrases used in the original publication have fallen from general use (eg, 'aero motor' has been replaced by 'aero engine').

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Pack: The canopy and shroud lines of a parachute packed within the pack cover.

Pack cover: A canvas covering which accommodates a parachute when folded.

Packing: The operation of folding a parachute and inserting it within the pack cover ready for use. Parachute packing is done by qualified specialists.

Pampero (pronounced "pampearaw"): Line squalls experienced in Argentina and Uruguay which are accompanied by rain, thunder and lightning, and a sudden change of wind to the South-West.

Pancaking: Landing an aeroplane in a stalled condition so that it has an abnormally high rate of descent or an abnormally low forward speed.

Panel: A section of a parachute canopy or gasbag.

Parachute: A collapsible device used to retard the descent of a falling body. Parachutes, which comprise a pack, a canopy, shroud lines and harness, may be of two basic types:-

(a) The Free Parachute: This type is used by aircrews and is a purely emergency device, although it was used for exhibition purposes before the Second World War. Free parachutes are operated by the wearer after he has left the aircraft.

(b) The Automatic Parachute: This type, known as the "Statichute" in the RAF, is used by parachute troops, and for dropping supplies. It is operated by a "static line" attached to the aeroplane which pulls the canopy out of the pack as the body falls clear of the aeroplane. Drops from very low levels are possible with this type of parachute.

The first successful parachute descent was made by André-Jacques Garnerin, who descended from a balloon over Paris on October 22, 1797.

Parachute Flare: A pyrotechnic flare attached to a parachute, which can be dropped from an aeroplane to illuminate the ground beneath it.

Parachute Troops: The parachute soldier was much in the news during the Second World War and with other types of airborne troops - carried in both aeroplanes and towed gliders - was considered to be of growing importance in the future. The Russians started training parachute troops in 1934, and were later copied by the Germans. British parachute units were formed in 1940 and were incorporated in the Army Air Corps on its formation on February 27, 1942.

Parachutist: A person using a parachute.

Parasitic Drag: The total drag of an aeroplane or glider less the drag which results from the lift of the wings. Sometimes called "non-induced drag."

Parasol Monoplane: A monoplane with the mainplane mounted above the fuselage on struts.

Parkerising: A process whereby a protective coating is applied to iron and steel parts to prevent rusting and corrosion.

Partially Evaporative Cooling: A cooling system for aero-engines in which the coolant (cooling liquid) is allowed to boil during part of its passage round the cooling circuit.

Patch: A piece of fabric sewn to the envelope of a balloon or non-rigid airship, to which the rigging lines are attached.

Payload: That part of the useful load of a civil aeroplane which can be devoted to paying load; that is, the weight of passengers, mails and freight that may be carried.

Performance: The essential flying characteristics of aircraft under standard atmospheric conditions. The figures obtained under any existing conditions are corrected so as to apply to a standardised theoretical state of the atmosphere.

Petrol: A trade name for the spirit consisting of a mixture of volatile fractions of the paraffin, napthene and aromatic series of hydrocarbons used in internal-combustion engines.

Phillips Entry: The form of dipping leading edge to a wing section which was patented in 1884 by Horatio Phillips, one of the British pioneers of heavier-than-air flight.

Pilot: The individual who operates the flying controls of aircraft.

Pilotage: The art of piloting aircraft safely and accurately from one place to another by means of map-reading and the recognition of ground objects.

Pilot Balloon: A small free balloon used to determine the direction and speed of the wind at various heights. The position of the balloon after given intervals of time is observed with a special type of theodolite. From the figures obtained in this way the speed of the wind at successive heights can be calculated.

Pilot Officer: A junior commissioned rank in the RAF corresponding to a Midshipman in the Navy and a Second Lieutenant in the Army.

Pilot Parachute: A small parachute connected to the main canopy of many types of free parachute to ensure its rapid and correct withdrawal from the pack cover.

Piston: A cup-shaped member of circular cross-section which slides up and down in the cylinder of an engine. It absorbs the expansion force of the fuel in the cylinder and transmits it via the connecting rod to the crankshaft.

Piston Ring: A ring inset into the piston of an engine intended to preserve a gas-tight seal between the piston and the cylinder wall.

Pitch: (i) The geometric pitch of a propeller is the distance that propeller would advance in one revolution provided there was no slip.

(ii) The angle by which the nose of an aircraft is inclined up or down from the horizontal.

Pitch Indicator: An instrument for indicating angle of pitch of an aeroplane in flight. Sometimes called a fore-and-aft level.

Pitching: The rotary motion of an aircraft about its lateral axis. That is to say, a motion in which its nose tends to rise or fall.

Pithio: A high carbon steel used for valve ends and similar parts of an aero-engine.

Pitot Tube: Parts of an airspeed indicator consisting of a tube with an open end exposed to the airstream. The compressed air in the pitot tube is conveyed by a length of tubing to the pilot's cockpit. There the pressure is shown by the airspeed indicator, which gives a reading in terms of miles an hour airspeed.

Plane: The complete wing of an aeroplane or glider. The term "plane" should not be used for "aeroplane."

Planing Bottom: A smooth surface on the underside of the hull of a flying-boat or of a float lying forward of the main step.

Polar Front: A meteorological term for the line of discontinuity which occurs under certain conditions between a mass of air coming from polar regions and another mass from more temperate zones.

Porpoising: The undulating motion in a fore-and-aft direction of a seaplane when taxying. It is a sign of bad hull design and was a common characteristic of early seaplanes.

Port: The left side (looking forward) of aircraft and ships. The port navigation light is red in colour.

Port Drift-angle: A navigational term for the angle between the true course and the true track when the bearing of the former is greater than that of the latter.

Position Error: The reading of an airspeed indicator differs from the true airspeed because of a number of errors. The error arising from the mounting of the pitot tube in a position where the airflow is disturbed by its proximity to the aeroplane is termed the "position error."

Pour le Mérite: An obsolete German decoration for military bravery which at one time ranked highest and was approximately equivalent to our own Victoria Cross, although it was more freely awarded. Most of the outstanding German fighter pilots of the First World War gained the Pour le Mérite. Its French name was derived from the fact that it was instituted by Frederick the Great, the founder of the German Empire, who spoke only French. It is better known today as the Blue Max.

Power: The time-rate of expended energy when work is done.

Power Jet: (i) A fuel jet in the carburettor of an aero-engine which comes into operation when the throttle is opened beyond the setting for maximum cruising conditions. (ii) A device for propulsion of aircraft as used by the Caproni-Campini C.C.2 jet-propulsion aeroplane.

Power Loading: The ratio of maximum loaded weight of an aeroplane to its total maximum power. That is to say, Power loading = loaded weight total power.

The power loadings of modern aeroplanes vary from about 5lb per h.p. for fighters to about 12lb per h.p. for heavy bombers. Power loading chiefly affects the take-off distance, rate of climb and stalling-speed with engine on.

Precipitation: A general meteorological term for the forms in which water may fall after condensation from the atmosphere. Precipitation may take the form of rain, drizzle, snow or sleet.

Precipitation Interference: Disturbance in radio reception caused by the impact of rain, snow, hail or sleet on the aerials of an aircraft in flight.

Pre-ignition: The ignition of the charge in the cylinder of an internal-combustion engine before it is fired by the sparking plug(s). Pre-ignition is caused by some overheated part, such as the sparking plug or exhaust valve or by incandescent carbon.

Pressure Gradient: The rate of change of pressure in an imaginary horizontal plane running between areas of high and low pressure on a weather map.

Pressure Head: A combination of pitot and static pressure tubes forming part of airspeed indicator installation.

Primer: A device for spraying fuel into the induction system or combustion chambers of an aero-engine to facilitate starting.

Profile Drag: The drag (that is to say total head resistance) of the wings of an aeroplane or glider excluding that caused by the vortices at the wing tips. In other words, profile drag is the sum of the drag caused by surface friction and the pressure drag.

Profile Drag Power Loss: The power expended in overcoming the profile drag of the blades of a propeller.

Projection: Geographically, a method whereby the outlines of features on the surface of the world may be represented on a map. As the world is spherical whereas the map is flat, the outlines on maps are only approximations to the true outlines on the world itself. Well-known projections include Mercator's, Cassini's Gnomonic, and Gauss Conformal.

Proofing: The treatment of fabric to render it gas-tight or water-resisting.

Proof Stress: The load for a given cross sectional area under which a material must not stretch permanently beyond a specified percentage of its length.

Propaganda Balloon: A small free balloon, sent up without passengers but with a device by which propaganda leaflets may be dropped at intervals. Propaganda balloons were suggested in the mid-19th Century and were used is the First World War. They were also employed to a small extent by the French during the early months of the Second World War.

Propeller: A device commonly used to convert the power of an aircraft piston or turboprop engine into propulsive force; each blade is essentially a rotating wing, twisted and varying in section from root to tip to achieve maximum efficiency, which produces lift in a forward direction, i.e. thrust. In the 1940s propellers were often referred to as airscrews.

Prototype: The first trial aeroplane built to a new design.

psa: Graduate of the RAF Staff College.

Pterodactyl: The name of a series of tailless aeroplanes designed by Captain G.T.R. Hill and built by Westland Aircraft Ltd. Captain Hill was aided in the design work by Major J.W. Dunne, the famous pioneer of this type of aeroplane.

Purity: Of the gas in an aerostat, the ratio of the volume of hydrogen or helium (depending on which is used) in the envelope to the total volume of gas contained.

Pusher Aeroplane: An aeroplane with pusher engine(s).

Pusher Engine: An aero-engine which drives a pusher propeller, that is to say, which propels the aeroplane forward by means of a propeller situated aft of the wing.

Pylon: The support or mast for the rotors of a gyroplane or helicopter. Pylons are also occasionally used to brace, from above, the wings of a wire-braced monoplane or to protect the pilot from injury in a crash should the aeroplane overturn.

Q

Qibli (pronounced "kibly"): A hot, dry, southerly wind experienced in Tripoli.

Quadruplane: An aeroplane with four mainplanes mounted one above another