pump connected in parallel to the normal hydraulic
system, a ram air turbine actuator, and a turbine-
retract control valve. You can pull the release handle,
located in the cockpit within easy reach of the pilot, to
operate the system. A mechanical latch releases the
turbine assembly into the airstream.
spring-loaded turbine actuator initiates extension of
the turbine assembly, and the airstream force
completes the extension.
During starting and
acceleration of the turbine, the turbine blades remain
at a constant setting until near maximum rpm. At this
point, the governor senses the shaft rpm and begins to
vary the blade angle to prevent excessive turbine
speed. At this speed, the pump is delivering its
maximum amount of fluid. As the turbine slows
down, usually due to a decrease in airspeed, the fluid
delivery from the pump will also decrease. This type
of system allows the aircraft to be controlled in flight
by supplying the necessary hydraulic and electrical
The turbine is maintained in the fully extended
position by a hydraulic lock in the turbine actuator.
When the RAM AIR TURBINE RETRACT button
switch is depressed, electrical power is supplied to the
solenoid-operated turbine retract control valve.
Hydraulic pressure from the hydraulic power system
is ported to the retract side of the turbine actuator
(fig. 7-42) through a restrictor, which controls the
retract speed. As the turbine door reaches the closed
position, the spring-loaded hook-type lock is caromed
up until it drops over the roller, locking the door
closed. When the button switch is released, electrical
power is removed from the control valve and the
retract side of the actuator is repressurized, thus
completing the retract cycle.
Two types of pneumatically operated emergency
systems are currently used in naval aircraft. One type
consists merely of one or more storage cylinders, a
control in the cockpit for releasing the contents of the
cylinders, a ground charge valve, and the connecting
lines and fittings.
This type of system must be
serviced with compressed air or nitrogen.
Figure 7-42.Ram air turbine-control system schematic.