Power, Horse—One horse-power represents a force sufficient to raise 33,000 lb. 1 foot in a minute.
Power, Indicated Horse—The I.H.P. of an engine is a measure of the rate at which work is done by the pressure upon the piston or pistons, as distinct from the rate at which the engine does work. The latter is usually termed "brake horse-power," since it may be measured by an absorption brake.
Power, Margin of—The available quantity of power above that necessary to maintain horizontal flight at the optimum angle.
Pitot Tube—A form of air-speed indicator consisting of a tube with open end facing the wind, which, combined with a static pressure or suction tube, is used in conjunction with a gauge for measuring air pressures or velocities. (No. 1 in diagram.)
Pitch, Propeller—The distance a propeller advances during one revolution supposing the air to be solid.
Pitch, to—To plunge nose-down.
Reaction—A force, equal and opposite to the force of the action producing it.
Rudder—A controlling surface, usually hinged to the tail, the operation of which turns an aeroplane about an axis which is vertical in normal horizontal flight; causes an aeroplane to turn to left or right of the pilot. [22]
Roll, to—To turn about the longitudinal axis.