Under normal operational conditions, gear pump 1 delivers hydraulic fluid through rotary directional valve 2 to the lower end of power cylinder 3. Piston 4 is moved upward by the fluid, retracting the landing gear of the plane. Fluid from the upper end of cylinder 3 passes through emergency valve 5 and is discharged by valve 2 to the tank. Valve 2 is turned to lower the landing gear. In case of a failure of the hydraulic system, emergency cartridge 6, included in the drive, is put into operation. By means of a firing pin, special substances are ignited in the cartridge and the evolved gaseous products of combustion are directed to emergency valve 5 where they force back piston 7 of the valve and are admitted into the upper end of power cylinder 3. The gases move piston 4 downward, lowering the landing gear.
$4277$CHP,AL$