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Aeroplane Monthly - Airplanes glossary Category: Travel and Transportation > Airplanes Date & country: 14/12/2007, UK Words: 962

Bora
A cold, squally wind which blows in the winter from the North-East on the northern shore of the Adriatic and Aegean Seas.

Boss
Used only with a fixed-pitch propeller, is a collar with flanges which fits on to the propeller shaft and on to which the hub of the propeller fits. Should not be confused with a propeller hub which, in a fixed-pitch and in a controllable pitch propeller, is the central portion on to which the roots of the blades are attached.

Boundary Layer
The thin layer of air immediately surrounding the surfaces of an aeroplane or airship. This layer is slowed down in flight by the friction exerted on the surface as it moves through the air and represents an important element of drag.

Boundary Light
A light, of which there are usually a number, arranged round the limits of an aerodrome. It marks the extent of the landing area.

Bracing
A system, usually consisting of struts and/or wires, by which a compound structure is made rigid.

Brake Horsepower
(Abbreviated b.h.p.) The Horsepower available at the propeller shaft of an aero engine. It differs from the Indicated Horsepower by the power needed to overcome the internal friction of the engine. The term is derived from the convenient method of measuring the horsepower developed at the propeller shaft by running the engine against a calibrated b…

Bubble Sextant
A sextant used in air navigation in which a bubble level is provided to afford an artificial horizon for determining the altitude of a celestial body.

Buffeting
An irregular oscillation of any portion of an aeroplane distinct from 'flutter', because it is produced and maintained by the eddying wake behind some other part of the aeroplane, whereas 'flutter' is an unstable oscillation in a normal airflow. Buffeting can occur in the tailplane of a low-wing monoplane when it is literally buffeted by the wake o…

Bulkhead
A solid partition which is used to isolate one part of a structure from another. Used particularly with regard to the Fireproof Bulkhead behind an aero engine.

Bump
A colloquial term used to denote and sudden vertical or lateral movement of an aeroplane caused by thermal or eddy currents. Often erroneously referred to as 'air pockets'.

Bunt
The first half of an inverted or outside loop in which an aeroplane dives past the vertical into an inverted position and then returns to a normal attitude by a half roll or through half a normal loop. In a bunt the forces tend to throw the pilot from his seat and to break the wings downwards. Because of the abnormal stresses put upon an aeroplane …

Buran
(pronounced Boorarn). A strong wind from the north-east in Russia and Central Asia.

Cabane
The term for a tripod or similar arrangement of struts, usually at the centre-section of a biplane. Sometimes called a pylon.

Cabin
An enclosed compartment in an aeroplane or airship for housing the crew and passengers (if any).

Calm
The absence of any appreciable wind.

Camber
The curvature of the surface and/or centre line of an aerofoil section which causes lift. A heavily cambered aerofoil is usually a high-lift section. A slightly cambered aerofoil is usually a high-speed section.

Camera Obscura
A darkened enclosure which has a lens in the roof designed to throw the image of an aeroplane or cloud on a horizontal screen. Sometimes used for determining the speed of an aeroplane.

Canopy
The large envelope of a parachute which, when opened, offers resistance to motion through the air and so slows up the fall of the parachutist.

Cant
To tilt or to incline at an angle.

Cantilever
A term for a structural member held at one end by a rigid support, and free from any external bracing members. The term is often used with reference to wings or undercarriage legs which have no external bracing.

Captive Balloon
A balloon secured or towed by a cable.

Carburetter
A device which, with the aid of a draught of air, converts the fuel supply of an aero engine from a fluid into a vapour which is mixed with an appropriate amount of air and introduced into the combustion chamber as an explosive mixture.

Cartridge Starter
A means of starting an aero engine in which a cartridge is electrically fired in a cylinder and forces down one piston, thus rotating the crankshaft.

CAS
Chief of the Air Staff.

Cascades
Blades of aerofoil section set vertically, after the style of baffles, in a return-flow wind tunnel, to turn the airstream smoothly round a bend in the closed section.

Castoring Nosewheel
A nosewheel of a tricycle undercarriage which is not directly steerable but is free to swivel.

Castoring Tailwheel
A small wheel at the tail of an aeroplane which is free to swivel to assist manoeuvring on the ground.

Catapult
A mechanism for assisting the take-off of an aeroplane by giving an initial acceleration in addition to the normal thrust from the aero engine.

Ceiling
The maximum height to which an aeroplane can climb. The Absolute Ceiling is the height at which the rate of climb is zero and at which the aeroplane has only one possible flying speed. Absolute ceiling is sometimes called the theoretical ceiling. The Service Ceiling is the height at which the rate of climb of any aeroplane has dropped to 100ft. per…

Centre of Buoyancy
The point through which the entire upward thrust of an aeroplane, glider, gyroplane, balloon or airship, or the hull or floats of a seaplane may be assumed to act.

Centre of Gravity
The point in a body through which the sum of the weights of the parts which make up that body may be assumed to pass whatever the attitude of the body.

Centre of Pressure
An imaginary line along the span of an aerofoil along which all the aerodynamic forces on the aerofoil affecting lift may be assumed to act. The centre of pressure of an aerofoil is normally about one-third of the way back from the leading edge, but in certain flying attitudes and with flaps extended it may vary greatly and may even move right off …

Centre-Line (of an aerofoil)
A line drawn through an aerofoil from leading to trailing edges. Each point of this line is equidistant from the upper and lower surfaces of the aerofoil. In aerofoil design the curvature of the centre line is used for designation of the type of wing section.

Centre-line Camber
The ratio between the chord of an aerofoil and the maximum height of the centre line above the chord line. A measure of the amount of curvature between the leading and trailing edges.

Centrifugal Supercharger
A supercharger in which air or the ready mixed charge is compressed by centrifugal action.

Centripetal Force
The equal and opposite of centrifugal force. It is the force acting on the body and maintaining it in the curved path.

Chart Board
A table carried in most long-range aeroplanes on which the navigator can work. There is usually provision for attaching a map and parallel motion arms carrying a protractor.

Chassis
An archaic term often applied to the undercarriage of an aeroplane.

Chili
A dry southerly wind which blows in Tunis. Similar to the Sirocco.

Chine
The line which runs along the side of the hull of a flying-boat or a float, parallel to the keel and marks the change in angle between the side plating and the planing bottom.

Chinook
A warm dry wind which blows from the West on the eastern side of the Rocky Mountains. Similar to the 'Foehn' in Europe.

Chock
A wedge placed in front of the wheels of an aeroplane on the ground to prevent it from moving forward when the engine is run up.

Chord
The width of an aerofoil section, usually the wing, measured in a straight line from leading to trailing edge.

Cirro-cumulus (mackerel sky)
High clouds, usually found above 20,000 ft. and composed of ice crystals. Appears like ripples in the sky resembling sand on the sea shore or in groups and lines. Cirro-cumulus is invariably white and flaky.

Cirro-stratus
High clouds usually seen in a thin whitish veil which does not blur the outline of the sun or moon but sets a halo around them. Like Cirro-cumulus, is composed of ice crystals and found around 20,000 ft.

Cirrus (mares' tails)
High cloud around 20,000 ft. which appears in detached and fibrous wisps. Usually dead white and silky looking.

Clinometer
An instrument for indicating the lateral attitude of an aeroplane.

Closed-jet Wind Tunnel
A wind tunnel in which the air stream passing over the body under test is enclosed by rigid walls.

Cloud Amount
The proportion of sky obscured by cloud. Usually expressed in tenths of the sky covered. Thus 10/10ths indicates complete overcast. Also expressed in eighths or 'oktas'.

Cloud Base
The height at the bottom of a towering cloud.

Cloud Height
The height of the cloud base above the ground at the point indicated.

Clouds
Clouds, like fog, are caused by condensation of water vapour in the air when it is cooled.

Cockpit
The portion of a fuselage, hull or nacelle designed to accommodate the pilot and/or crew.

Col
With reference to a weather map, a region of weather between two areas of relatively high pressure and two areas of relatively low pressure. A col is usually associated with light winds, with thunderstorms in Summer and fog in Winter.

Cold Front
The boundary line between a mass of advancing cold air and a mass of warmer air under which it pushes.

Combustion Starter
A device to start an aero engine by the firing of a charge within a cylinder.

Commercial Load
That part of the disposable load of, an aeroplane from which revenue is derived. (Passengers, mails or freight.) Usually termed 'Payload'.

Compass
An instrument which consists essentially of a magnetic needle free to swing and which, subject to correction for conflicting magnetic fields, always points to the magnetic North. It thus indicates the angle in the horizontal plane between the magnetic North and the longitudinal axis of the aeroplane.

Compass Base
A circular area, usually on the edge of an aerodrome, marked with magnetic bearings upon which aircraft may be orientated for the compensation of errors in their compasses.

Compass Course
The angle between the: longitudinal axis of an aeroplane and the compass needle, measured clockwise from the compass needle between 0 degrees and 360 degrees.

Composite Cooling
(Usually termed Evaporative or Steam Cooling.) A cooling system for aero engines which makes use of the latent heat of evaporation by allowing the cooling fluid to boil, then passing the vapour to a condenser and returning the resultant liquid to the cylinder jackets. An example of the steam-cooled engine was the Rolls-Royce Goshawk of 1932.

Compressed Air Starter
A device for starting an aero engine by making use of the expansive energy of compressed air to push down a piston in a cylinder.

Compressed Air Wind Tunnel
(Sometimes called the Variable Density wind tunnel.) A wind tunnel in which the pressure of the circulated air can be increased so that the small scale of the models tested can be offset by the compensating factor of higher pressure.

Compressibility Drag
The great increase in drag, which arises when a body is moving at speeds around the speed of sound (770 m.p.h. at sea level decreasing steadily to 660 m.p.h. at 36,000ft., after which it is constant).

Compressibility Stall
The sudden loss of lift of a wing which is moved through the air at such a speed that the air flow over its upper surface reaches the speed of sound.

Compression Ignition Engine
An engine in which the ignition of the explosive charge is produced by the heat of compression alone without any electric spark. CI engines usually run on oil fuel and work on the Diesel cycle.

Compression Ratio
The ratio of compression, in the cylinder of an aero engine. Determined by the formula (r + R)/r, where 'r' is the compression space in the cylinder when the piston is at Top Dead Centre and 'R' is the volume swept by the piston in the cylinder.

Condensation
The conversion of a fluid from vapour into a liquid state. This happens when air is cooled below its dew point. Near the ground or sea this produces fog. When rising air is cooled, cloud forms.

Coning
The upward angular displacement of the rotor blades of a gyroplane or helicopter under the influence of lift. The Coning Angle is the angle between the rotor blades and the plane normal to the axis of the hub.

Connecting-rod Assembly
The complete assembly of two or more connecting rods of an aero engine working on one crankpin.

Constant-speed Propeller
Propeller in which the pitch of the blades is varied automatically by a governor so that the aero engine preserves a set, constant speed of rotation, whatever the load.

Consumption
The quantity of fuel or oil consumed by an aero engine or engines, defined in gallons per hour.

Contact
A colloquial term used to announce that the switch of an aero engine is on and the pilot is ready for the engine to be started. Largely a relic now from the days when propellers swung by hand.

Contours
In maps, the imaginary line joining points of equal height above sea level.

Contra-rotating Propeller
Two propellers mounted one in front of the other on concentric shafts and designed to rotate in opposite directions. By this method twice the horsepower is absorbed by a given diameter propeller and propeller torque is cancelled out. This method was used by the Italians on the 2,500hp Fiat A.S.6 motor of the Macchi Castoldi 72 racing seaplane of 19…

Control Column
The lever, sometimes surmounted by a wheel, by which the elevators and ailerons are operated. Sometimes called the Control Stick or Joystick, the control column is pulled back to raise the elevators and depress the tail to put an aeroplane into a climb. It is pressed forward to lower the elevators, raise the tail and so promote a dive. Movement of …

Control Surface
A surface, movable in flight, to control the motion of an aeroplane about its axes. The three principal control surfaces are the elevators, the rudder and the ailerons.

Controllable Pitch Propeller
(Abb. 'c.p. prop'). Propeller, the pitch of the blades of which can be changed, within previously determined limits during rotation.

Convection
In meteorology the transference of heat by the movement of vertical currents in the atmosphere.

Coolant
The liquid which is made to flow around the walls and head of the cylinders of a liquid-cooled engine and then passed through a radiator to disperse the excess heat from the engine. Coolant is usually water or glycol or a mixture of both.

Cooling Drag
The part of the drag of an aeroplane which is caused by the cooling system of the engine. For a liquid-cooled engine this is the drag of the radiator. For an air-cooled engine it is the drag caused by the air passing over the finned cylinders of the engine. The cooling drag needs on an average about 3 per cent of the total horsepower to overcome it…

Corrosion
The destruction of the surface of a metal by the chemical action of the fluid in which it is immersed. This takes the form of rust in steels and pitting in light alloys. Corrosion is caused particularly through the action of sea water. Various chemical treatments such as anodising are used to combat corrosion.

Course
In air navigation, the direction of the horizontal longitudinal axis of an aeroplane with reference to the angle it makes with a specified datum. The course is set on the verge ring of the compass and includes both the bearing of one's destination and an allowance for the effect of wind and the consequent drift.

Course and Distance Calculator
A navigational device used for the solution of the triangle of velocities. Sometimes called the Course and Speed Computor. With this instrument the air navigator, knowing wind speed and direction, the bearing of his destination and his own cruising speed, can read off the true compass course which must be flown and the distance in 'air miles.' Any …

Course and Drift Indicator
A device for measuring the angle between the longitudinal axis of an aeroplane and any other object and between that axis and the line of travel. Sometimes called a 'Bearing Plate'.

Cowling
A metal cover enclosing the whole or part of the power unit of an aero engine.

Cracked Spirit
The fuel obtained by high temperature distillation of crude oil. Petrol of high octane value is prepared by this process.

Crew
Persons carried in an aeroplane who are actively engaged in its pilotage, navigation, maintenance and in other duties connected with its commercial or military purposes. The crew varies from one in a fighter up to about ten in a large bomber or flying-boat.

Cross-bracing
Wires, cables or girders used in certain forms of construction to keep the structure of wings or fuselage rigid.

Cross-level
An instrument used to indicate the direction of the resultant force, or apparent direction of gravity, in a transverse plane. Sometimes called the Lateral Climometer.

Cross-section
A section of the fuselage, hull, float or ring of an aeroplane perpendicular to the longitudinal axis.

Crosswind Axis
The straight line through the centre of gravity of an aeroplane perpendicular to the axes of lift, drag and thrust.

Crosswind Force
The component of the resultant force on an aeroplane along the cross-wind axis, caused by the relative air stream. This force is zero except when the aeroplane is yawed or side-slipped.

Cruising Speed
The normal operating speed of an aeroplane. This may vary widely according to circumstances. An aeroplane normally cruises at about 85 percent of its top speed at any particular height.

Cumulo-nimbus
Heap clouds formed of heavy masses, which may rise to a great height. The tops of these clouds pile up like mountains and appear to have a fibrous texture.

Cumulus
Thick clouds of a woolly type, usually with flat base low down and rising up to cauliflower tops.

Cyclogyro
A flying machine which is supported in the air by power-driven rotors, which rotate about a horizontal axis, like the paddle-wheels of a steamboat. These paddle-wheels replace the normal wings. Each paddle-plane consists of long thin aerofoils, which are feathered at the turn. Machines of this type have been designed by Rohrbach in Germany and Plat…

Cyclone
A tropical revolving storm with winds of hurricane force, circulating anti-clockwise in the northern Hemisphere and clockwise in the Southern hemisphere. In temperate latitudes a cyclone is properly a Depression. In the West Indies a cyclone is called a hurricane. In the China Seas it is known as a typhoon. In Australia it is called a 'Willy-Willy'…

Damping Factor
With regard to the stability of an aeroplane, the rate of change in the violence of any movement from the level path.

Damping Moment
The moment of the force which tends to resist movement when damping is positive.