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.