pneumatically operated systems. The compressed
adequate air supply to the compressor at all
air is held in storage cylinders in the actuating
altitudes. The air compressor is driven by an
systems until required by actuation of the system.
electric or a hydraulic motor. The system under
These cylinders and power system manifold
discussion in this chapter is hydraulically driven.
receive an initial charge of compressed air or
(See figure 4-22.)
nitrogen from an external source. In flight, the
The aircraft hydraulic system provides power
air compressor replaces the pressure and volume
to operate the hydraulic-motor-driven air com-
lost through leakage, thermal contraction, and
pressor. The air compressor hydraulic actuating
system operation.
system consists of a solenoid-operated selector
The air compressor receives supercharged air
valve, flow regulator, hydraulic motor, and motor
from the engine bleed air system. This ensures an
bypass line check valve. When energized, the
Figure 4-22.-Pneumatic system.
4-27