With the pump operating in the direction shown, the ship s rudder is thrown to the left, and the bow will swing to port. This operation shows how a small force applied on the steering wheel sets in motion a series of operations that result in a force of thousands of pounds. The swift, smooth power required to get airplanes from the hanger deck to the flight deck of a carrier is provided by a hydraulic lift. Figure 10-12 shows how this lifting is done. An electric motor drives a variable-speed gear pump.
Oil enters the pump from the reservoir and is forced through the lines to four hydraulic rams.
The pistons of the rams raise the elevator platform. The oil under pressure exerts its force on each square inch of surface area of the four pistons. Since the pistons are large, a large total lifting force results. Either reversing the pump or opening valve 1 and closing valve 2 lowers the elevator. The weight of the elevator then forces the oil out of the cylinders and back into the reservoir.