to  vent  both  transfer  cylinders  and  the  unlock port   of   the   canopy-lock   pneumatic   actuator overboard. The weight of the canopy closes it; pneumatic  power  is  not  required.  The  closing time, approximately 10 seconds from the fully open position, is controlled by the flow regulators in  the  open  and  close  control  modules  of  the hydraulic actuator. The final closing motion of the canopy actuates the pneumatic timer to direct 325-psi  nitrogen  from  valve  No.  2  of  the  control module  to  the  lock  port  of  the  canopy-lock pneumatic  actuator,  unlatching  the  ball  locks.  The actuator piston retracts and, by reverse action, moves  the  canopy  forward  to  engage  the  canopy hooks in the sill locks. With the canopy in its full forward positions, the lock lockpin engages and prevents aft movement of the canopy. The final motion  of  the  lock  lockpin  opens  the  canopy switch, breaks the circuit to the canopy caution indicator light on the caution advisory indicators, and the lights go off. Boost   Closing   Mode To  close  the  canopy  under  high  headwind conditions, the canopy control handle must be moved to BOOST. On aircraft not modified by AFC 95, the control handle must be rotated out- board to move the handle pasta stop to BOOST. Valve No. 4 in the control module is positioned to  direct  790-psi  nitrogen  through  the  C2  port  of the   canopy   hydraulic   actuators   to   the   close transfer cylinder. This nitrogen, acting against the transfer cylinder piston, causes the hydraulic fluid on the opposite side of the piston to retract the actuator.  The  other  valves  in  the  control  module are  positioned  the  same  as  when  CLOSE  is selected,   and   the   system   functions   in   the same  manner  to  lock  the  closed  canopy. The closing time for this mode of operation is also  controlled  by  the  flow  regulators  in  the open  and  close  control  modules  of  the  hydraulic actuator. Auxiliary  Opening  Mode The auxiliary opening mode is used to unlock the   canopy   when   normal   pneumatic   system reservoir   pressure   drops   below   225   psi.   To prevent  further  depletion  of  nitrogen  pressure  in the   normal   system,   a   low-pressure   sensor repositions valves No. 5 and No. 6 in the control module. The canopy must now be unlocked by activating the auxiliary opening mode. To set the canopy control handle to AUX OPEN on aircraft not  modified  by  AFC  95,  the  handle  must  be rotated  outboard  to  move  past  a  stop  (the handle will remain in the AUX OPEN position). When the control handle is set to AUX OPEN, the  auxiliary  unlock  pneumatic  release  valve releases pressurized nitrogen from the auxiliary pneumatic  reservoir.  Nitrogen  pressure  from  this reservoir flows through a 325-psi pressure reducer, through the release valve and pneumatic unlock shuttle valve, to shift position of the shuttle valve internal spool. This directs nitrogen pressure to the  unlock  port  of  the  canopy-lock  pneumatic actuator, unlocking the canopy. Valve No, 1 in the control module directs reservoir pressure to the open transfer cylinder of the canopy hydraulic actuator.   This   low-pressure   nitrogen,   acting against  the  transfer  cylinder  piston,  counter- balances the weight of the canopy. The canopy can then be easily opened and closed manually. The  canopy  cannot  be  locked  closed  under  these conditions.   To   return   the   system   to   normal operation,  the  control  handle  must  be  set  to OPEN and, on aircraft not modified by AFC 95, rotated outboard to move past a stop. The release valve eccentric cam must be manually reset to block  auxiliary  nitrogen  pressure  flow  to  the shuttle  valve  and  to  vent  the  pressure  in  the canopy-lock pneumatic actuator. SYSTEM   COMPONENTS The purpose of each of the major components of the F- 14 clamshell canopy system is presented in the following paragraphs. Refer to figure 2-2 to see how each component fits into the overall system. Canopy  Hydraulic  Actuator The  canopy  hydraulic  actuator  opens  and closes the canopy. It consists of a double-acting hydraulic cylinder, two transfer cylinders, and two hydraulic control modules. The transfer cylinders convert  pneumatic  pressure  from  the  canopy pneumatic control module to hydraulic power. The   hydraulic   control   modules   contain pneumatically   actuated   shutoff   valves   that 2-3