A double spool valve device is employed to control the elevator of aircraft. It consists of valve spool 4, connected by links 9, 8 and 7 to auxiliary valve 5. This valve contains piston 1 with hollow rod 6. Movinhg in hollow rod 6 is piston 2, connected by flexible tie-rod 3 to the spindle of a gyroscope. Compressed air is admitted through a passage in the body of auxiliary valve 5 from where it passes through openings a and d, regulated by screws, into the upper and lower ends of valve 5. From these ends, the compressed air can pass through passages in piston 1 to the upper and lower ends of hollow rod 6. In the neutral position of piston 2, both air input passages into hollow rod 6 are blocked off. Upon motion of the gyroscope spindle, piston 2 moves inside hollow rod 6 and connects one of the ends of valve 5 to the atmosphere. At this, piston 1 and rod 6 are moved by the compressed air. Their motion is transmitted through links 7, 8 and 9 to valve spool 4 which controls the elevator. The motion of piston 1 continues until piston 2 blocks off the passages in piston rod 6.
$3917$LHP,FC$