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

Lateral Stability
That quality which tends to correct any disturbance out of the plane of symmetry (that is in side-slipping or rolling). An aeroplane is laterally stable when its wings are not easily tilted sideways by external forces.

Lay Off
A term used in hull and float construction. It means to transfer the design of the hull or float lines from scale drawings to full size on the mould loft floor.

Leading
The extent to which a rotor blade of a gyroplane is displaced forward from its normal position relative to the rotor head.

Leading Edge
(1) The forward edge of a streamline body or aerofoil. (2) The structural member at the leading edge of such a body or aerofoil.

Leading Sweep
As applied to a propeller blade, a general curvature of the blade towards the leading edge.

Leading-edge Radiator
A radiator built into the leading edge of a mainplane.

Leak Detector
An instrument, used in airships, which detects the presence of hydrogen and other gases in the air. It is used to find leaks in an envelope or gas bag.

Leakage
The loss of gas from the envelope or gas bags of an airship or balloon.

Leakage Drag
The drag caused by the leaks in the structure of an aeroplane. This only becomes important at high speeds. In modern fast aeroplanes leakage drag is an important component of the total drag. Experiments, chiefly carried out by Wing Commander Sidney Cotton, showed that a worthwhile increase in maximum speeds of existing aeroplanes can be achieved by…

Leste
(pronounced Lestey): A hot, dry, southerly wind in Madeira and Northern Africa in front of an advancing depression.

Levanter
An easterly wind experienced in the Straits of Gibraltar. This wind is stronger in winter than in summer. When of moderate force it causes a cloud to appear over the Rock. This phenomenon is known as the 'Levant.'

Leveche (pronounced Levetchey)
A hot, dry south-west wind in Spain which occurs in front of an advancing depression.

Life Line
A feature of certain designs of parachute. The flexible connection between the rigging lines and the harness when these are not directly connected.

Lift
(1) The component in a vertical, upward direction in straight and level flight of the resultant force created by the relative wind acting on the lifting surfaces of an aeroplane. (2) The total buoyancy of an airship.

Lift Axis
An arbitrary line through the centre of gravity of an aeroplane, which is vertical in straight and level flight.

Lift Wires
Wires or cables the principal function of which is to transfer the lift of non-cantilever wings to the main structure.

Light Aeroplane
An aeroplane having a total all-up weight of less than 1,200lb.

Limit of Proportionality
In effect this is the elastic limit of a material. The load applied is proportional to the extension it produces up to this limit. Beyond this point the material stretches far more rapidly for a given increase of load, and when the load is removed the material remains partly stretched.

Line Squall
A squall advancing on a wide front caused by the replacement of a warmer by a cooler body of air. The passage of a well-developed line squall is usually marked by a sudden or very rapid change of wind direction; heavy rain, hail or snow, thunder and lightning; rapid rise in barometric pressure; a sudden fall of temperature; and violent vertical dis…

Link Trainer
A device which was widely used for ground instruction in instrument flying. It resembles a small aeroplane built round an exact replica of an aeroplane's cockpit. The cockpit is provided with a hood so that 'blind' conditions can be reproduced and is fully equipped with all the normal controls and instruments of an aeroplane. These are ingeniously …

Load Factor
The ratio of the load at which a member or structure fails to the assumed working load under specified conditions of flight. The load factor of an aeroplane, when no conditions are specified, is that existing in flight with the centre of pressure in its most forward position. Load factor should not be confused with Factor of Safety, which is the ra…

Load Ring
A ring on which the basket suspensions and the net of a free balloon are secured.

Load Water Line
A horizontal line on a seaplane hull or float, marking the level of the water when in the fully loaded condition.

Loadings
(1) Power loading. The loaded weight of an aeroplane divided by the total power of the engine(s). (2) Span loading. The loaded weight of an aeroplane or glider divided by the square of the wing span. (3) Surface loading. The mean force on unit area carried by an aerofoil under specified aerodynamic conditions. (4) Wing loading. The loaded weight of…

Londitudinal Axis
The straight line through the Centre of Gravity parallel to a line which would join nose to tail.

Longeron
A main longitudinal strength member of a fuselage or nacelle.

Longitudinal Axis
A line fore and aft through the centre of gravity of an aeroplane and parallel to the line of flight.

Longitudinal Divergence
The pitching motion of an aeroplane which precedes a dive or a stall.

Longitudinal Stability
That quality which tends to correct any disturbance in the plane of symmetry (that is, in pitching). An aeroplane is longitudinally stable when it resists any external force tending to raise or lower the nose.

Loop
A manoeuvre consisting of a complete revolution in flight in a vertical plane. The upper surface of the aeroplane or glider performing the manoeuvre is on the inside of the circle.

Loop Aerial
A radio aerial consisting of one or more turns of a conductor, either self-supporting or in a protective covering. Loop aerials are mounted on the fuselage and may be of three types. (1) The fixed-loop aerial. A loop aerial permanently fixed with respect to the centre line of an aeroplane and used with a homing receiver. (2) Rotatable-loop aerial. …

Louvre
A movable vane for controlling an opening for the flow of cooling air.

Low
A meteorological term used to denote a region of low pressure, or depression.

Low Clouds
Clouds which have an average height below 7,000ft. They are:

Lubber Line
A line fixed to the forward end of a compass bowl. It corresponds to the nose of an aeroplane and enables the pilot to determine the direction in which the aeroplane is heading at any time.

Maestro
A North-Westerly wind experienced in the Adriatic. It occurs most frequently in Winter and Spring; when it blows in the Summer it is followed by fine weather.

Magnetic Course
The angle (measured in a clockwise direction) between the course of an aeroplane - that is, the direction steered - and Magnetic North. It is measured on a map from the nearest magnetic meridian.

Magnetic Track-angle
The angle (measured in a clockwise direction) between the track of an aeroplane - that is, its path over the ground - and Magnetic North. It is measured on a map from the nearest magnetic meridian.

Main Float
The principal watertight body of a floatplane which provides the necessary buoyancy on the water.

Main Step
A discontinuity in the under surface of a float or hull designed to help the seaplane 'unstick' from the water.

Mainplane
A complete main lifting surface of an aeroplane or glider.

Malleability
The property which allows a material to be permanently deformed, without fracture, when beaten or rolled.

Maneton
The detachable short end of the crankshaft in a rotary or radial engine.

Manoeuvrability
The ability of an aeroplane to change its attitude under the influence of its controls. Manoeuvrability and control are two conflicting requirements. The former is particularly desirable in fighters in which it can be developed at the expense of the stability. In bombers and transport stability is more important, although in some such machines a hi…

Maps
Four main types of air map were recognised internationally before the Second World War: (1) Basic Maps. These cover the whole World in 24 sheets and are intended for the planning of routes and to give general aeronautical information. (2) Route Maps. Drawn to a small scale, these are intended for navigational use on long journeys. (3) Local Maps: T…

Marine Distress Signal
A pyrotechnic device for use by aircraft in distress after landing on water.

Marshal of the Royal Air Force
The highest rank in the RAF, equivalent to an Admiral of the Fleet in the Navy and a Field Marshal in the Army.

Martensite
A hard, brittle, constituent of carbon steel. It is formed when the steel is cooled rapidly by quenching.

Mask Microphone
A microphone mounted in a face mask used for radio and intercommunication transmission in flight.

Mass Balance
A weight set forward of a control surface designed especially to prevent flutter.

Master Connecting Rod
In a radial aero engine the large connecting rod linking one of the pistons to the crankshaft. Articulated rods are connected to the big end of the master rod and transmit the power from the other pistons.

Master Pilot's Certificate
The highest grade of commercial pilot's certificate. This certificate is awarded to 'B' license pilots who have at least five years' experience and have satisfied other stringent requirements.

Maximum Flying Speed
The lowest speed at which an aeroplane or glider can be maintained in level flight.

Maximum Permissible r.p.m
The number of revolutions per minute of the crankshaft of an engine which must not be exceeded or maintained beyond a specified time - usually five minutes.

Maximum Power
The power developed by an aero engine at maximum permissible r.p.m. (see above)

Maximum-Power Altitude
The lowest height at which full throttle is permissible at maximum rpm for level flight. With a supercharged engine it is also the greatest height at which maximum boost pressure can be maintained in continuous climbing flight.

McKee Trans-Canada Trophy
A trophy awarded annually to the Canadian pilot who does most towards the sound advancement of Canadian Aviation. It was presented in 1926 by the late J Dalzell McKee, who made the first aeroplane flight across Canada.

Mean Chord
The total area of an aerofoil divided by the span.

Medium Clouds
Average height between 8,000ft and 20,000ft. They are: (a) Alto-cumulus. A layer of small masses of cloud arranged in groups, lines or rolls. (b) Alto-stratus. A grey fibrous cloud resembling a veil, through which the sun or moon shows vaguely without the halo effect which occurs with cirro-stratus cloud.

Mesh Wiring
A wire network which prevents the gas bags of a rigid airship chafing against the longitudinals of the hull structure.

Meteorograph
An instrument which records two or more of the basic meteorological conditions of pressure, temperature or humidity.

Mid-Wing Monoplane
A monoplane in which the mainplane is located approximately midway between the top and bottom of the fuselage.

Millibar
The thousandth part of a bar, a bar being a unit of barometric pressure equal to 750·1mm (29·531in) of mercury at 0°C in latitude 45°.

Mist
a slight fog caused by condensation of moisture.

Mistral
A cold, dry wind from the North or North-West, common on the Mediterranean coast of France.

Mixture Control
A device embodied in the carburettor of an aero engine for reducing the quantity of fuel supplied to the cylinders as height increases so as to maintain a constant ratio of fuel to air.

Monocoque
A method of construction in which the skin carries the whole or the greater part of the main loads; applied particularly to fuselages.

Monoplane
An aeroplane or glider with a single mainplane.

Mooring Area
An area of water reserved as a place for the mooring of seaplanes.

Mooring Mast
A relatively short mast to which airships are moored by a quick-release attachment in the nose. Great Britain originated the mooring mast and developed it into the mooring tower. The Americans use a mobile motor-driven form of mast for all types of airship. This has the advantage that it can be used for manoeuvring the airship while on the ground.

Mooring Tower
An elaborate high mast for mooring rigid airships. Mooring towers provide a means of entry to the airship from a platform near the top across a gangway let down from the airship. A lift runs from the foot of the tower to the platform, as do fuel and water ballast pipes.

Mortar Signal
A signal flare which after reaching a height of about 1,000ft burns steadily for part of its descent.

Mountain Breeze
A local wind caused by the downward flow of cold air off high ground at night or in Winter.

Multiplane
An aeroplane or glider with two or more mainplanes one above the other. There have been several quadruplanes and many triplanes.

NACA
The National Advisory Committee for Aeronautics in the United States of America - a body specially concerned with research and experiment (superseded by NASA - National Aeronautics & Space Administration - in 1958).

Nacelle
A body accommodating crew, load or engines of an aeroplane, glider or airship.

Navigation (Avigation)
The science of determining and plotting the position of an aircraft and of determining the courses to steer to reach any required destination.

Navigation Flame-Float
A pyrotechnic device dropped from an aeroplane on to water for determining the drift-angle by night.

Navigation Flare
A pyrotechnic device dropped from an aeroplane on to land for determining the drift-angle by night.

Navigation Light
A light on an aeroplane to reveal its presence and direction of motion at night. A complete set of navigation lights comprise a red light on the port (left) wingtip, a green light on the starboard (right) wingtip and a white light at the tail.

Neck
A tube at the base of a balloon through which the gas is passed during inflation and through which it can escape when it expands.

Nimbo-stratus
A low, rainy layer of cloud, grey in colour.

Nitralloy
A steel that can be surface-hardened by the Nitriding process.

No-Lift Direction
That direction of the airflow over an aerofoil in which no lift is generated.

Non-Induced Drag
The total drag of an aeroplane or glider less the drag which results from the lift of the wings. More often called the parasitic drag.

Non-Rigid Airship
An airship without a rigid keel and depending on the pressure of the gas within the envelope to retain its shape.

Nor' Wester
A disturbance of the line-squall type associated with thunderstorms and experienced in Bengal and Assam.

Normal Axis
A line passing through the centre of gravity of an aerodyne which is vertical in straight and level flight.

Normal Axis
The straight line through the Centre of Gravity at right angles to the lateral axis and the longitudinal axis. When an aeroplane is flying so that the longitudinal axis and the lateral axis are horizontal the normal axis is vertical.

Normal Flight
All manÅ`uvres needed in ordinary flying, such as level climbing and gliding flight, turns and side-slipping, but excluding aerobatics.

Normalising
The object of normalising is to relieve the stresses and refine the crystal structure after it has been coarsened by previous hot working.

Normally Aspirated Engine
An aero-engine the cylinder charge of which is normally taken in at the existing atmospheric pressure and temperature.

Norte (pronounced "nortey")
A cold, dry wind from the north over the Gulf of Mexico.

Nose Cap
A hub fairing fitted to the front of the boss of a fixed-pitch one-piece propeller.

Nose Radiator
An aero-engine radiator installed in the nose of a fuselage or nacelle.

Nose Rib
A rib between the front spar and leading edge of a main plane, tailplane or control surface.

Nose Slot Cowling
An aero-engine cowling in which the cooling air is discharged in the low-pressure area near the nose.

Nose-Dive
A steep descent with the nose of the aeroplane down. More correctly, simply 'dive'.

Nose-heaviness
The tendency of an aeroplane to lower its nose of its own accord when flying.

NPL
The National Physical Laboratory - an official centre of scientific research in Great Britain