The Aeroplane Speaks. Fifth Edition

=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. [37a] =Warp, to=--To distort a surface in order to vary its angle of incidence. To vary the angle of incidence of a controlling surface.