Strain—Deformation produced by stress.
Side-Slip, to—To fall as a result of an excessive "bank" or "roll."
Skid, to—To be carried sideways by centrifugal force when turning to left or right.
Skid, Undercarriage—A spar, mounted in a fore and aft direction, and to which the wheels of the undercarriage are sometimes attached. Should a wheel give way the skid is then supposed to act like the runner of a sleigh and to support the aeroplane. [28]
Skid, Tail—A piece of wood or other material, orientable, and fitted with shock absorbers, situated under the tail of an aeroplane in order to support it upon the ground and to absorb the shock of alighting. [28a]
Section—Any separate part of the top surface, that part of the bottom surface immediately underneath it, with their struts and wires.
Spar—Any long piece of wood or other material.
Spar, Main—A spar within a surface and to which all the ribs are attached, such spar being the one situated nearest to the centre of pressure. It transfers more than half the lift from the ribs to the bracing. [29]
Spar, Rear—A spar within a surface, and to which all the ribs are attached, such spar being situated at the rear of the centre of pressure and at a greater distance from it than is the main spar. It transfers less than half of the lift from the ribs to the bracing. [30]