P
Panel—Another name for [Curtain]—which see.
Parabola—The form outlined when a cone is cut by a plane parallel to a line drawn on its surface from its apex to its base. Declared to be the correct scientific curve for aeroplane surfaces, but not so proven, as yet.
Pilot—A term widely used for an operator, or driver, of any form of aircraft.
Pitch—The distance which a propeller would progress during one revolution, if free to move in a medium which permitted no [slip] (which see); just as the thread of a bolt travels in the groove of its nut.
Plane—Speaking with exactness, a flat spread of surface; but in aeronautics it includes also the curved sustaining surfaces of aeroplanes.
Polyplane—Another term for Multiplane.
Port—The left-hand side of an aircraft, as one faces forward. See [Starboard].
Projected Area—The total area of an irregular structure as projected upon a flat surface; like the total area of the shadow of an object cast by the sun upon a plane fixed at right angles to its rays.
Propeller Reaction—A force produced by a single revolving propeller, which tends to revolve the machine which it is driving, in the contrary direction. This is neutralized in various ways in the machines driven by single propellers. Where two propellers are used it is escaped by arranging them to move in opposite directions.
A pterygoid plane.
Pterygoid—That type of the wings of birds which is long and narrow—as distinguished from the apteroid type.
Pylon—A tower-shaped structure used as a [derrick] (which see); also for displaying signals to aeronauts.