The space inside housing 1 of the gyroscope unit, mounted on the airplane, is evacuated, the vacuum being produced by vacuum pump 2. The stream of air admitted through port a drives the rotor of gyroscope 3, which has a vertical axis. Rigidly attached to the gyroscope is a shutter (not shown) approaching either of two nozzles 4 to which air is delivered that is drawn in through capillary inlets d on the two sides of membrane 5 of the pneumatic relay. Owing to the great difference in the cross sections of the capillary inlets and the nozzles, the same vacuum is produced on the two sides of membrane 5, which is, in this case, in its central position. When the airplane deviates from horizontal flight, the vacuum in the right-hand compartment of the membrane chamber increases and the left-hand compartment is connected to the atmosphere. Membrane 5 is bent to the right, shifting valve spool 6, which admits hydraulic fluid from pump 10 to the right end of power cylinder 7. The fluid moves piston 8 to the left, moving the elevator as required. Fluid from the left end of cylinder 7 is discharged through the valve of spool 6 to the tank. As piston 8 travels, it pulls cable 9, attached at one end to its rod and at the other to nozzles 4. This turns the nozzles with respect to housing 1 so that the left nozzle moves downward and the right nozzle upward. Piston 8 continues to travel until both nozzles are covered to an equal degree by the shutter of the gyroscope. Since the elevator is still inclined downward, the nose of the plane drops and housing 1 turns. At this, the left nozzle is covered and the right nozzle is opened. Piston 8 moves to the right, returning the elevator to its middle position. Then the feedback cable turns the nozzles again so that they are covered equally by the gyroscope shutter. If the airplane flies horizontally, the fluid delivered by pump 10 is discharged through valve 11 to the tank. The speed of travel of piston 8 can be regulated by setting flow-control valve 12. The autopilot is switched off with valve 13. Excess pressure is prevented by relief valve 14 which by-passes fluid from one end of cylinder 7 to the other.
$4225$CHP,Rg$