Table 3-1.--Nitrogen Pressure Depletion
NORMAL CLOSING MODE
Setting the control handle to CLOSE positions
N2 Pressure (psi)
Time
valves no. 1, 2, 4, and 5 in the control module to vent
Charged at 3,000
Initial time 0
both transfer cylinders and the unlock port of the
1,000
After 1 minute
canopy-lock pneumatic actuator overboard. The weight
of the canopy closes it; pneumatic power is not
800
After 2 minutes
required. The closing time, approximately 10 seconds
600
After 3 minutes
from the fully open position, is controlled by the flow
regulators in the open and close control modules of the
500
After 4 minutes
hydraulic actuator, unlatching the ball locks. The
actuator piston retracts and, by means of a torque tube,
AUXILIARY OPENING MODE
cranks, and links, moves the canopy forward to engage
the canopy hooks in the sill locks. With the canopy in its
The auxiliary opening mode is used to unlock the
fully forward position, the lock pin engages and
canopy when normal pneumatic system reservoir
prevents aft transition of the canopy. The final motion
pressure drops below 225 psi. To prevent further
of the lock pin opens the canopy switch, breaking the
depletion of nitrogen pressure in the normal system, a
circuit to the canopy caution indicator light on the
low-pressure sensor repositions valves no. 5 and 6 in
CAUTION ADVISORY indicators; the lights go off.
the control module. The canopy must be unlocked by
activating the auxiliary opening mode. When the
BOOST CLOSING MODE
control handle is set to AUX OPEN, the auxiliary
unlock pneumatic release valve releases pressurized
To close the canopy under high-headwind
nitrogen from the auxiliary pneumatic reservoir.
conditions, the canopy control handle must be moved to
Nitrogen pressure from the reservoir flows through a
BOOST. Valve no. 4, in the control module, is
760 30 psi pressure reducer through the release valve
positioned to direct 790 psi nitrogen through the C2
and pneumatic unlock shuttle valve, to shift position of
port of the canopy hydraulic actuator to the close
the unlock shuttle internal spool. This directs nitrogen
transfer cylinder, and through the lock actuator check
pressure to the unlock port of the canopy-lock
valve to the P5 port of the pneumatic timer. This
pneumatic actuator, unlocking the canopy. Valve no. 1
nitrogen, acting against the transfer cylinder piston,
in the control module directs reservoir pressure to open
causes the hydraulic fluid on the opposite side of the
the transfer cylinder of the hydraulic actuator. This
piston to retract the actuator, closing the canopy. The
low-pressure nitrogen, acting against the transfer
final closing motion of the canopy actuates the
cylinder piston, counterbalances the weight of the
pneumatic timer, directing 790 psi nitrogen to the lock
canopy. The canopy can then be opened and closed
port of the canopy lock pneumatic actuator; this
manually with nominal effort; the canopy cannot be
unlatches the ball locks. The system functions in the
locked closed under these conditions. To return the
same manner to complete the locking action as in the
system to normal operation, the control handle must be
normal closing mode. The other valves in the control
set to OPEN. The release valve eccentric cam must be
module are positioned as when CLOSE is selected. The
manually reset to block auxiliary nitrogen pressure
flow regulators in the open and close control modules
flow to the shuttle valve and to vent the pressure in the
of the hydraulic actuator also control the closing time
canopy-lock pneumatic actuator.
for this mode of operation. After completion of boost
mode operation, the canopy control handle shall be
Q3-11.
How many modes of operation are there for
positioned to NORMAL close position; otherwise,
the F-14 canopy system?
depletion of nitrogen pressure from the canopy
Q3-12.
In what mode can the canopy stop at a desired
pneumatic reservoir will occur as shown in table 3-1.
opening?
3-5
