Downloaded from https://www.everyspec.com FM 1-509 Area is a surface measurement expressed in square inches. Length of stroke is a measurement of distance expressed in inches. The stroke length discussed in this manual refers to the distance a piston moves in a cylinder. If any two of the above factors are known, the third can be computed by using the equation in Figure 1-2. To apply this equation, multiply the two lower factors together to obtain the top factor, and divide the top factor by the known lower factor to obtain the unknown lower factor. For example, a piston having an area of 8 square inches moves a distance of 10 inches within a cylinder.
To find the volume of liquid moved, multiply A (8 square inches) times L (10 inches) to obtain V (80 cubic inches). Pascal’s Law. Practical applications of hydraulic principles are based on Pascal’s law: When external pressure (force) is applied to any confined fluid, the pressure is increased at every point in the fluid by the amount of external pressure (force). (Check the definitions of force and pressure.) An understanding of Pascal’s law depends on the interpretation of these terms. Pascal’s law applies to confined fluids only; it does not apply to fluids in motion, since moving fluid is not confined. Figure 1-3 illustrates how Pascal’s law applies in an aircraft hydraulic system.
When a force is applied to the piston in cylinder 1, it is transmitted to all portions of the confined fluid. For example, if the applied force is 5 psi, the pressure in cylinders 1, 2, and 3, and in the tubing will be 5 psi. But suppose a change takes place where a lack of resistance causes 1-5