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.
Efficiency--Output
Input
Efficiency (of an aeroplane as distinct from engine and propeller)--
Lift and Velocity
Thrust (= aeroplane drift)
Efficiency, Engine--Brake horse-power
Indicated horse-power
Efficiency, Propeller-- Thrust horse-power
Horse-power received from engine
(= propeller drift)
NOTE.--The above terms can, of course, be expressed in foot-
pounds. It is then only necessary to divide the upper term by
the lower one to find the measure of efficiency.
Elevator--A controlling surface, usually hinged to the rear of the tail-
plane, the operation of which turns an aeroplane about an axis
which is transverse to the direction of normal horizontal flight.
Empennage--See ``Tail-plane.''
Energy--Stored work. For instance, a given weight of coal or petroleum
stores a given quantity of energy which may be expressed
in foot-pounds.
Extension--That part of the upper surface extending beyond the
span of the lower surface.
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