Adjusting Plane Or Adjusting Surface

A surface of small area for regulating lateral stability; usually located at the side edge or rear edge of a supporting plane. It is to be distinguished from an aileron (q. v.) in that it is capable of adjustment but not of independent movement by special operating devices.

Advancing Edge

See Entering Edge.

Advancing Surface

The forward supporting surface of a machine provided with supporting planes in tandem, as in the Langley aerodrome, or with superposed surfaces arranged in step formation.


Any arched supporting surface. The term has been proposed because few supporting surfaces are true aeroplanes. See also Aerofoil.


A term invented by the late Prof. Samuel P. Langley and used by him to designate an aeroplane flying-machine. Etymologically the term signifies " air-runner." It is more commonly used to designate a flying-course by analogy with " hippodrome." Mr. F. W. Lanchester and Dr. Alexander Graham Bell have sought to restrict the term to the use which Langley intended.


Langley's term for the science and art of flying with an aeroplane flying-machine.


The supporting surface of a flying-machine, coined, like Aerocurve, because the supporting surfaces of a flying-machine are not, strictly speaking, flat planes.


One who navigates the air.


The science of aerial navigation.


A term invented in France and introduced into English-speaking countries to designate any heavier-than-air flying-machine. The term is not much employed either in French or in English.


Any plane surface propelled through the air. The term was invented before it was discovered that curved surfaces are better than flat surfaces. Hence it is not strictly applicable to modern supporting surfaces.


A French word meaning " winglet," introduced into English to designate any freely swinging surface controlled by the aviator and designed to maintain lateral stability. Ailerons may be either tips hinged to the side edges or rear edges of the main supporting surface, or they may be small independent planes. See also Adjusting Surface, Balancing Plane or Surface, Stabiliser, and Wing-Tip.


A term originally employed to designate any aerial craft, whether heavier or lighter than air, but now restricted by the best writers to dirigible balloons.

Air Speed

The velocity of a machine in the air as distinguished from its velocity on the ground.


An aeronaut; one who navigates the air.

Alighting Gear

The wheels or skids or combinations of both on which a machine alights. See Skids.

Angle Of Attitude

See Angle of Incidence.

Angle Of Entry

The angle formed by a tangent to the entering edge with the line of motion.

Angle Of Incidence

The angle made by the main planes with the line of travel. Sometimes called " angle of attitude " and " angle of attack." The angle may be positive or negative, depending on the direction in which the plane is turned to the line of flight.

Angle Of Trail

The angle formed by a tangent to the rear edge with the line of travel in curved supporting surfaces.


Lanchester's term for a short, broad form of wing.


The downward curve or droop to the ends of supporting surfaces.


The top plan view of an aeroplane flying-machine.

Aspect Ratio

The ratio of the length to the width of a plane or curved supporting surface.


The suction produced by a current of air which strikes a curved supporting surface.


See Angle of Incidence.

Automatic Stability

See Stability.

Auxiliary Surface

See Supplementary Surface.


Flight with heavier-than-air machines as distinguished from ballooning.


The pilot of a heavier-than-air machine.


The maintenance of equilibrium by means of balancing surfaces. A distinction is sometimes made between Balancing and Stabilising (q. v.).

Balancing Plane Or Balancing Surface

A surface for establishing and maintaining equilibrium as well as to assist in turning. Such surfaces may be operated either automatically or by hand; they maintain both longitudinal and lateral balance.


A periodically recurring movement in a propeller blade or in a wing of a flapping-wing machine.


A flying-machine with two superposed supporting surfaces.


See Fuselage.


A kite invented by Hargrave and provided with two parallel vertical and two parallel horizontal surfaces in the form of an open box.


A compression member.


The curve of a supporting surface measured from port to starboard.


A small wheel of the alighting gear, so pivoted that, like the caster of a chair, it automatically suits itself to the direction of the flying-machine's motion on the ground.


An apparatus by which air is charged with a hydrocarbon so that it will either burn or explode. In the gasoline flying-machine motor it serves the purpose of mixing the gasoline vapor with air in the right proportion to form an explosive when ignited.


The under framework of a flying-machine.


An open box-like unit. Its parallel vertical and parallel horizontal surfaces serve to maintain stability.

Centre Of Effort

The point in which the effect of an axially exerted force is theoretically concentrated, as, for example, the thrust of a propeller.

Centre Of Gravity

A point in which the weight of a flying-machine is theoretically concentrated.