to all classes of
sustaining surfaces; strictly applicable only to flat surfaces.

Adjusting Surfaces--Commonly a comparatively small surface, usually at
the end of a wing tip, used to adjust lateral balance; preferably
restricted to surfaces capable of variable adjustment, but not of
movement by controlling devices. See "Stabilizer'" and "Wing tip" and
compare "Aileron."

Advancing Edge--The front edge of a sustaining or other surface.

Advancing Surface--A surface that precedes another through the air, as
in a double monoplane.

Aerocurve--A proposed substitute for aeroplane.

Aerodrome--A substitute proposed by Langley for aeroplane. Strictly
applicable to a course rather than to a vehicle.

Aileron (a'ler-on)--A small hinged or separated wing tip or surface
capable of independent manipulation for the purpose of maintaining
lateral balance.

Aviation (a-vi-a'shun)--Dynamic flight by means of heavier-than-air
mechanisms.

Aviator (a'vi-a-ter)--The operator or pilot of a heavier-than-air
machine.

Aerofoil--Term used to indicate lifting surface,

Angle of Incidence--The angle which a line drawn from the leading to the
trailing edge of the plane makes with the horizontal trailing angle
between the tangent to the trailing edge of the plane and the chord or a
line drawn from the leading to the trailing edge.

Arc--Any portion of a circle or other curve.

Aspect--The top or plan view of an aeroplane surface.

Automatic Stability--Applied to lateral or longitudinal stability
maintained by the action of suitable elements on mechanisms independent
of any control exercised by the operator. There is a tendency to
restrict the term to such stability secured by automatic manipulation of
controlling devices, rather than to systems in which balance is
maintained by the use of dihedral arrangements.

Biplane (bi'plane)--An aeroplane with two superposed main surfaces.

Balance--To maintain equilibrium by hand or automatic movement of
balancing surfaces, as opposed to equilibrium maintained by stabilizing.
See "Stabilizer."

Body--The center part of an aeroplane or other aerial vehicle, in which
the motor, fuel tanks, passenger accommodation, etc., are placed.

Camber--The camber of the ribs is the amount of curvature which is
imparted to them in the same way that a motor car spring or a road has a
camber or curvature.

Chassis (shas-see)--That part of the main framework of a monoplane to
which the main planes