When fluid is delivered by manual pump 1 through rotary directional valve 2 to the lower end of cylinder 3, the landing gear is retracted. The landing gear consists of wheels 4, strut 8 and links 9 and 7, which form the four-bar linkage ABCD. At this, piston 5 is moved upward by the fluid together with its rod 6, turning link 7 clockwise and strut 8 counterclockwise until the mechanism reaches the position shown by the dash lines. Cylinder 3 turns about fixed axis E; the second extreme position of the cylinder is not shown. Fluid from the upper end of cylinder 3 is discharged through valve 2 to the tank. When directional valve 2 is turned to the neutral position, the landing gear retraction mechanism is held in a definite position by the fluid in cylinder 3 on both sides of piston 5. Besides, valve 2 can be turned to the position in which fluid is delivered to the upper end of cylinder 3, moving piston 5 downward and lowering the landing gear.
$4281$CHP,AL$