electrical canopy jettison device. Hydraulic power
the canopy open line to the canopy seal valve and
for operation of the canopy is from either the
hydraulically trips the seal valve. Thus, the air
combined hydraulic system or the hand pump
pressure in the canopy seal is dumped, allowing
system.
the seal to deflate. Pressure in the canopy open
When a canopy switch is in the CLOSE
line continues its flow through a flow regulator
position, it completes a circuit from the 28-volt
to the backhead end of the cylinder. This action
dc bus to a terminal on the isolation switch.
extends the cylinder, opening the canopy.
Hydraulic fluid in the opposite end of the cylinder
Current flows from the terminal, through the
returns through the canopy close line to the
closed contacts of the canopy switch, to solenoid
selector valve, across the valve, and into the
2 of the canopy selector valve. The selector valve
then energizes to the close position. Now,
combined hydraulic system. Fluid then returns to
hydraulic pressure from either the combined
the main reservoir of the system.
For canopy jettison (fig. 4-21), the emergency
hydraulic system or the hand pump system flows
canopy jettison switch, or either of the two
through the selector valve into the canopy close
line. Pressure through a flow regulator to the rod
emergency outside jettison switches initiates a
end of the canopy actuating cylinder causes the
firing circuit. Closing any of the three switches
piston and rod to retract closing the canopy.
completes the circuit to the electrically fired
When the canopy switch is in the OPEN
canopy jettison cartridge on the canopy cylinder
backhead end. The cartridge discharges through
position, power flows from the 28-volt dc bus
the canopy cylinder, causing the canopy to
through the control circuit breaker, the isolation
switch terminal, the opposite contacts of the
jettison.
canopy switch, to solenoid 1 of the canopy
PNEUMATIC POWER SYSTEM
selector valve. The selector valve energizes to the
The pneumatic power system supplies com-
open position, reversing the sequence of pressure
and return flow. Hydraulic pressure flows through
pressed air for various normal and emergency
Figure 4-21.-Canopy jettison.
