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.
Roll, to—To turn about the longitudinal axis.
Rib, Ordinary—A light curved wooden part mounted in a fore and aft direction within a surface. The ordinary ribs give the surface its camber, carry the fabric, and transfer the lift from the fabric to the spars.
Rib, Compression—Acts as an ordinary rib, besides bearing the stress of compression produced by the tension of the internal bracing wires.
Rib, False—A subsidiary rib, usually used to improve the camber of the front part of the surface.
Right and Left Hand—Always used relative to the position of the pilot. When observing an aeroplane from the front of it, the right hand side of it is then on the left hand of the observer.
Remou—A local movement or condition of the air which may cause displacement of an aeroplane.