spout. A pipe or similar device used to carry a liquid from a container in a stream that is easy to control.
sprag clutch. A form of freewheeling clutch used in the rotor-drive system of a helicopter. The sprag clutch allows the engine to drive the rotor, but, when the engine power is reduced, the clutch allows the rotor to freewheel, and prevents it trying to drive the engine.
spray gun (cleaning tool). A type of maintenance tool used for cleaning parts. Compressed air is blown through the spray gun, and as it passes through a venturi, it produces a low pressure. This low pressure picks up a cleaning solution, such as varsol or naphtha, and sprays it out in the form of tiny drops onto the surface being cleaned. The combined solvent action of the cleaning solution and the force of the high-pressure air removes dirt, grease, or other contaminants from the surface.
spray gun (paint spray gun). A device that breaks a liquid finishing material, such as paint or lacquer, into tiny drops and blows them onto the surface being painted. Two basic types of paint spray guns are: suction-feed and pressure-feed guns. A suction-feed gun uses suction produced by venturi action inside the gun to pick up the finishing material from a cup attached to the gun. The material sprayed by a pressure-feed gun is forced into the gun by air pressure on the fluid stored in a pressure cup or pressure pot.
spray strip (water craft). Small strips of metal mounted on the side of a flying boat hull. Spray strips throw a spray of water out away from the aircraft.
spreader bar (aircraft floats). Horizontal structural members between the two floats mounted on an aircraft.
springback (aircraft control system). A method used to assure that the control arm of a device being controlled actually reaches its full-travel stop. There are stops on both ends of an aircraft throttle control. The stop on the carburetor must be contacted first, then the throttle control is moved farther until its stop in the cockpit is reached. This additional movement stretches the control mechanism, and when the throttle control is released, it springs back a slight amount.
Technicians often refer to this type of control adjustment as “rigging in the proper cushion.” Springback assures that the stop on the carburetor is contacted before the stop in the cockpit.
springback (sheet metal forming). Springback, in sheet metal forming, is the tendency of the metal to spring back and form an angle less than the angle bent in a brake or a forming block. When a 90° angle is to be bent, the metal must be bent through an angle of about 93° or 94° (depending upon the temper of the metal) so it will spring back to exactly 90°.

spring steel. High-carbon steel, a steel containing more than 0.5% carbon, that has been hardened and tempered to give it the maximum amount of elasticity, or the ability to return to its original shape after it has been deflected. Spring steel is hardened and then tempered to remove part of the brittleness by reheating until it turns a uniform dark blue.