Downloaded from https://www.everyspec.com FM 1-509 CHAPTER 1 HYDRAULIC SYSTEMS FUNCTIONS Hydraulic systems perform a variety of functions in Army aircraft. They are used in fixed-wing aircraft to change the propeller pitch and operate the landing gear, wing flaps, wheel brakes, and shock struts. Also, they are used in helicopters to start engines and operate brakes, shock struts, dampers, flight control systems, loading ramps, folding pylons, winch hoists, and hydraulic clutches. ADVANTAGES A hydraulic system has many advantages: It is almost 100 percent efficient. The slight loss of efficiency (a fraction of 1 percent) is due to internal friction in the system machinery.
Moving parts of a hydraulic system are lightweight and can quickly be put into motion or brought to rest. The valves in a hydraulic system quickly start or stop the flow of fluid under pressure; very little effort is needed to operate them. For these reasons, the system Is easy for the operator to control. Hydraulic lines can be routed almost anywhere. Unlike mechanical systems which must follow straight pathways, the lines of a hydraulic system can easily be bent around obstructions. Also, major parts of hydraulic systems can be located in a wide variety of places. Since components of a hydraulic system are smaller than those of other systems, the space requirement is small.
Most of the parts of a hydraulic system operate in a bath of oil, making the system practically self-lubricating. USE OF LIQUIDS AND AIR Liquids. Characteristics. The aircraft hydraulic system transmits engine power to distant points in the aircraft. The force is carried by a liquid (oil) confined in-a system of tubes. To understand this system, certain characteristics of liquid must be understood; the primary one is fluidity. Fluids--substances that flow--can be liquids or gases, but the two differ 1-1