catapults is controlled by a retraction engine control
valve (fig. 4-43).
Retraction Engine Control Valve
The retraction engine control valve directs the flow
of pressurized hydraulic fluid between the accumulator
and the operating chambers of the main hydraulic
cylinder. This valve consists essentially of a block
divided into seven chambers by a piston. The operating
chambers are connected to the cam-operated pilot valve
in the control console. This pilot valve operates the
retraction engine control valve. The low-pressure
chambers to the gravity tank, the two-way chambers
through connections to the operating chambers of the
main engine cylinder, and the high-pressure chamber
through a connection
to the retraction engine
accumulator are affected by the movement of the
piston.
The hydraulic fluid flow for the
retraction system is controlled by three
three-way valves which are shifted by
C-13 linear
two-position
air-operated
solenoid valves (fig. 4-44). They are the advance,
retract, and maneuver forward valves. Also included is
an electrically/manually operated four-way valve acting
as a three-way valve (maneuver aft), and the blocking
valve, which is also a two-position three-way valve.
The blocking valve is shifted to the ACTUATED
position by hydraulic pressure in the advance cycle, and
back to the NORMAL position by a predetermined air
charge in all other phases of operation.
Fixed orifices, of predetermined size, control the
advance and retract cycle times of all catapult linear
retraction engines.
Advancing the grab is accomplished by forcing
hydraulic fluid into the advance end of the retraction
engine cylinder. Power is transmitted to the crosshead
and through the cable system to advance the grab to the
forward end of the track, thus causing automatic
engagement of the grab with the shuttle. The advance
stroke buffer slows and stops the forward motion of the
grab, crosshead, and retraction engine piston at the end
of the advance stroke. After the grab has engaged with
Figure 4-43.—C-7/C-11 retraction engine control valve.
4-33
