the doped fabric from distorting the framework. [34]

=Serving=--To bind round with wire, cord, or similar material. Usually
used in connection with wood joints and wire cable splices.

=Slip, Propeller=--The pitch less the distance the propeller advances
during one revolution.

=Stream-Line=--A form or shape of detrimental surface designed to produce
minimum drift.

=Toss, to=--To plunge tail-down.

=Torque, Propeller=--The tendency of a propeller to turn an aeroplane
about its longitudinal axis in a direction opposite to that in which the
propeller revolves.

=Tail-Slide=--A fall whereby the tail of an aeroplane leads.

=Tractor=--An aeroplane of which the propeller is mounted in front of the
main lifting surface.

=Triplane=--An aeroplane of which the main lifting surface consists of
three surfaces or pairs of wings mounted one above the other.

=Tail-Plane=--A horizontal stabilizing surface mounted at some distance
behind the main lifting surface. _Empennage_. [36]

=Turnbuckle=--A form of wire-tightener, consisting of a barrel into each
end of which is screwed an eyebolt. Wires are attached to the eyebolts
and the required degree of tension is secured by means of rotating the
barrel.

=Thrust, Propeller=--See "Air-Screw."

=Undercarriage=--That part of an aeroplane beneath the _fuselage_ or
_nacelle_, and intended to support the aeroplane when at rest, and to
absorb the shock of alighting.

=Velocity=--Rate of displacement; speed.

=Volplane=--A gliding descent.

=Weight=--Is a measure of the force of the Earth's attraction (gravity)
upon a body. The standard unit of weight in this country is 1 lb., and
is the force of the Earth's attraction on a piece of platinum called
_the standard pound_, deposited with the Board of Trade in London. At
the centre of the Earth a body will be attracted with equal force in
every direction. It will therefore have no weight, though its mass is
unchanged. Gravity, of which weight is a measure, decreases with
increase of altitude.

=Web= (_of a rib_)--That vertical part of a rib which prevents it from
bending upwards. [37_a_]

=Warp, to=--To distort a surface in order to vary its angle of incidence.
To vary the angle of incidence of a controlling surface.

=Wash=--The disturbance of air produced by the flight of an aeroplane.

=Wash-in=--An increasing angle of incidence of a surface towards its
wing-tip. [38]

=Wash-out=--A decreasing angle of incidence of a