Glossary

"Airplane" is now a household word. So is "airship." Careful households, capable of distinctions, use words correctly, do not confuse airplanes with airships. Aid is offered by the National Advisory Committee for Aeronautics Definitions:

Airplane: A mechanically driven aircraft, heavier-than-air, fitted with fixed wings.

Airship: An aerostat (lighter-than-air craft) with a propelling system.

Airship, nonrigid: An airship whose form is maintained by internal pressure in gas bags. . . .

Airship, rigid: Form maintained by a rigid structure.

Airship, semirigid: Form maintained by rigid or jointed keel, together with internal pressure.

Free balloon: An aerostat without a propelling system whose ascent and descent may be controlled by use of ballast or with a loss of the contained gas, whose direction is determined by wind.

Glider: Similar to an airplane, but without a power plant.

Ornithopter: Heavier than air craft, deriving support and propelling force from flapping wings.

Seaplane: An airplane designed to rise from and alight on the water.

Altimeter: An instrument for measuring elevation of aircraft above a given plane (usually sea level).

Ceiling, absolute: Maximum height at which a given airplane could maintain horizontal flight.

Control stick: The lever by which the longitudinal and lateral (up and down, sidewise) controls of an airplane are operated.

Fuselage: The structure (contains power plant, passengers, cargo, etc.) to which wings and tail unit are attached.

Pay load: That part of the load from which revenue is derived (passengers, freight).

Useful load: Crew and passengers, oil and fuel, ballast other than emergency, ordnance and portable equipment.

Taxi: To run an airplane over the ground, or a seaplane on the surface of the water, under its own power.

Wind tunnel: An elongated chamber (usually a tube) through which a steady air stream may be drawn or forced.

Zoom: To climb for a short time at an angle greater than that which can be maintained in steady flight, the airplane being carried upward at the expense of its kinetic energy.