Distance Piece—A long, thin piece of wood (sometimes tape) passing through and attached to all the ribs in order to prevent them from rolling over sideways.
Displacement—Change of position.
Drift (of an aeroplane as distinct from the propeller)—The horizontal component of the reaction produced by the action of driving through the air a surface inclined upwards and towards its direction of motion PLUS the horizontal component of the reaction produced by the “detrimental” surface PLUS resistance due to “skin-friction.” Sometimes termed “head-resistance.”
Drift, Active—Drift produced by the lifting surface.
Drift, Passive—Drift produced by the detrimental surface.
Drift (of a propeller)—Analogous to the drift of an aeroplane. It is convenient to include “cavitation” within this term.
Drift, to—To be carried by a current of air; to make leeway.
Dive, to—To descend so steeply as to produce a speed greater than the normal flying speed.
Dope, to—To paint a fabric with a special fluid for the purpose of tightening and protecting it.
Density—Mass of unit volume, for instance, pounds per cubic foot.