15. Ailerons.—Movable auxiliary surfaces used for the control of rolling or banking motion. Other definitions are that they are for the lateral control or for maintaining equilibrium. When they are a part of the upper plane they are sometimes called wing flaps.
16. Landing Wires or Ground Wires (Single).—The single wires which support the weight of the panels when landing or on the ground.
17. Flying Wires, or Load Wires (Double).—The wires which support the body or fuselage from the planes when in flight.
18. Drift Wires.—The horizontal wires which lead from the nose of the fuselage to the wings and thus keep them from collapsing backward. For the same reason the wings have interior drift wires.
19. Diagonal Wires.—Any inclined bracing wires.
20. Skids.—(a) Tail Skid.—The flexible support under the tail of the machine.
(b) Wing Skid.—The protection under the outer edge of the lower wing.
(c) Chassis Skids.—Skids sometimes placed in front of the landing gear.
21. Horns, or Control Braces.—The steel struts on the controls to which the control wires are attached.
22. Struts; Wing Struts.—The vertical members of the wing trusses of a biplane, used to take pressure or compression, whereas the wires of the trusses are used to take pull or tension. There are also fuselage struts and chassis struts.