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28. CHAPTER XXVIII.

GLOSSARY OF AERONAUTICAL TERMS.

Aerodrome.—Literally a machine that runs in the air.

Aerofoil.—The advancing transverse section of an aeroplane.

Aeroplane.—A flying machine of the glider pattern, used in contra-distinction to a dirigible balloon.

Aeronaut.—A person who travels in the air.

Aerostat.—A machine sustaining weight in the air. A balloon is an aerostat.

Aerostatic.—Pertaining to suspension in the air; the art of aerial navigation.

Ailerons.—Small stabilizing planes attached to the main planes to assist in preserving equilibrium.

Angle of Incidence.—Angle formed by making comparison with a perpendicular line or body.

Angle of Inclination.—Angle at which a flying machine rises. This angle, like that of incidence, is obtained by comparison with an upright, or perpendicular line.

Auxiliary Planes.—Minor plane surfaces, used in conjunction with the main planes for stabilizing purposes.

Biplane.—A flying-machine of the glider type with two surface planes.

Blade Twist.—The angle of twist or curvature on a propeller blade.

Cambered.—Curve or arch in plane, or wing from port to starboard.

Chassis.—The under framework of a flying machine; the framework of the lower plane.

Control.—System by which the rudders and stabilizing planes are manipulated.

Dihedral.—Having two sides and set at an angle, like dihedral planes, or dihedral propeller blades.

Dirigible.—Obedient to a rudder; something that may be steered or directed.

Helicopter.—Flying machine the lifting power of which is furnished by vertical propellers.

Lateral Curvature.—Parabolic form in a transverse direction.

Lateral Equilibrium or Stability.—Maintenance of the machine on an even keel transversely. If the lateral equilibrium is perfect the extreme ends of the machine will be on a dead level.

Longitudinal Equilibrium or Stability.—Maintenance of the machine on an even keel from front to rear.

Monoplane.—Flying machine with one supporting, or surface plane.

Multiplane.—Flying machine with more than three surface planes.

Ornithopter.—Flying machine with movable bird-like wings.

Parabolic Curves.—Having the form of a parabola—a conic section.

Pitch of Propeller Blade.—See "Twist."

Ribs.—The pieces over which the cloth covering is stretched.

Spread.—The distance from end to end of the main surface; the transverse dimension.

Stanchions.—Upright pieces connecting the upper and lower frames.

Struts.—The pieces which hold together longitudinally the main frame beams.

Superposed.—Placed one over another.

Surface Area.—The amount of cloth-covered supporting surface which furnishes the sustaining quality.

Sustentation.—Suspension in the air. Power of sustentation; the quality of sustaining a weight in the air.

Triplane.—Flying machine with three surface planes.

Thrust of Propeller.—Power with which the blades displace the air.

Width.—The distance from the front to the rear edge of a flying machine.

Wind Pressure.—The force exerted by the wind when a body is moving against it. There is always more or less wind pressure, even in a calm.

Wing Tips.—The extreme ends of the main surface planes. Sometimes these are movable parts of the main planes, and sometimes separate auxiliary planes.