pneumatically controlled canopy hydraulic ac- tuator opens and closes the canopy. A canopy- lock pneumatic actuator moves the canopy to the locked or unlocked position. The canopy is locked in  the  closed  position  by  locking  hooks  that engage latches on the cockpit sill. An inflatable rubber seal in the canopy frame forms a pressure- tight enclosure when the canopy is closed and locked. Three rearview mirrors are mounted on the pilot’s forward canopy frame and one on the naval  flight  officer’s  (NFO)  forward  canopy frame.  The  canopy  can  be  jettisoned  for  an emergency on the ground and during the ejection sequence. The  clamshell  canopy  pneumatic  system provides  normal  opening  and  closing  of  the canopy. The system is controlled with the canopy control handle at each crew station or with the external canopy control handle on the fuselage left side.  Pneumatic  pressure  from  externally  serviced reservoirs  supply  the  power  for  the  different modes of canopy operation. The canopy can also be manually opened and closed. A reference mark is painted on the fuselage and canopy, and when the canopy is closed and locked, the marks are aligned. SYSTEM  OPERATION The F-14 aircraft uses the clamshell canopy system. This pneumatic system is operated by setting  any  one  of  the  three  canopy  control handles, This action positions valves within the pneumatic  control  module  to  route  pneumatic pressure  to  or  from  the  system.  The  modes  of operation that can be selected are normal opening mode,  holding  mode,  normal  closing  mode,  boost closing  mode,  and  auxiliary  opening  mode.  The function of all three control handles is the same. Normal  Opening  Mode Figure 2-2 (a foldout at the end of this chapter) shows a schematic of the F-14 pneumatic canopy system. Setting the pilot canopy control handle to open pulls the lock lockpin and positions valves No. 1,2, and 6 within the control module to direct nitrogen at 325 psi through the C 1 and C3 ports of the module, to the timer check valve, and to the  unlock  port  of  the  canopy-lock  pneumatic actuator. Simultaneously, the shutoff valves in the open  and  close  modules  of  the  canopy  hydraulic actuator are vented to the atmosphere through the C5  port  of  the  actuator,  through  the  canopy pneumatic  timer,  and  through  valve  No.  3  in  the control module. The lock port of the canopy-lock pneumatic  actuator  is  vented  overboard  through the pneumatic timer. The piston of the actuator extends and, by means of a torque tube, cranks, and links, moves the canopy aft to unlock it from the sill locks. When the extending piston reaches the end of its stroke, ball locks engage to hold it  in  that  position.  The  extended  piston  also actuates the timer check valve, which directs the 325-psi nitrogen to the C1 port of the canopy hydraulic actuator. The nitrogen that enters the hydraulic actuator acts against the piston of the open  transfer  cylinder.  This  pressure,  acting against the piston, causes the hydraulic fluid on the opposite side of the piston to extend the ac- tuator. The extending actuator rotates the canopy on the aft hinge to open the canopy. As the ac- tuator extends, fluid displaced from the close side of the actuator acts against the piston of the close transfer cylinder. The nitrogen on the opposite side of this piston is vented overboard through the C2 port of the hydraulic actuator and through valve No. 4 of the control module. Pulling the lock lockpin at the beginning of the opening cycle closes the canopy switch, which provides 28 volts from  the  essential  dc  No.  2  bus,  through  the CAN/LAD   CAUTION/EJECT   CMD   IND circuit breaker, to the canopy caution indicator light  on  the  pilot  and  NFO  caution  advisory indicators. Holding Mode The HOLD position stops canopy motion at any desired opening. Valve No. 3 in the control module directs 325-psi nitrogen through the C5 port of the module, through the pneumatic timer, to  the  C5  port  of  the  hydraulic  actuator.  The nitrogen that enters the C5 port closes the shutoff valves in the open and close modules. The closed shutoff valves trap hydraulic fluid on the open and close side of the actuator piston, stopping piston travel. Normal Closing Mode Setting the control handle to CLOSE positions valves No. 1, 2, 4, and 5 in the control module 2-2