Downloaded from https://www.everyspec.com FM 1-509 mechanical advantage. The aircraft hydraulic system uses this principle because it is a system that transmits engine power to distant points in the aircraft where power is needed. This is done by multiplying the input effort (or force) enough to do the required job--in other words, gaining a mechanical advantage. In hydraulics, the mechanical advantage is the ratio between two pistons with regard to the factors of area and force. Figure 1-4 illustrates this principle; note the difference in the areas of the small and large pistons. This difference in size is how the mechanical advantage is obtained.
When a 50-pound force is applied to the small piston, the fluid pressure shows 25 psi on the gage; however, 25 psi acting on the large piston gives an upward force of 250 pounds. This gain in force (from 50 pounds to 250 pounds) is attained by increasing the surface area of the output piston. This 5-to-1 ratio does not change if the pounds per square inch change. For example, if the input force is limited to 20 psi or raised to 30 psi, the forces involved would obviously chanqe, but the ratio between the forces would still be 5 to 1. - - 1-7