the safe-and-arm seat ejection module for use if the  lanyard-operated  firing  mechanism  of  the module fails. As previously mentioned, during emergency ground egress, seat ejection, or ditching condi- tions, the canopy may be jettisoned by pulling either an internal or external canopy emergency jettison  initiator  handle.  During  emergency ground egress, without seat ejection, the explosive signal provided by the canopy jettison initiator is blocked from entering the SMDC lines of the seat ejection system by the one-way explosive transfers. Inert connectors joining the SMDC lines transfer  the  explosive  stimuli  through  bulkheads, straight  runs,  tee  connections,  and  90-degree bends. Explosive manifolds, within SMDC line runs,  allow  output  SMDC  lines  to  be  initiated from  one  SMDC  input.  This  assures  system redundancy  by  providing  dual-line  initiation  for the canopy-separation charge. Canopy Jettison Initiators Two  canopy  jettison  initiators  enable  the  air- crewman to jettison the canopy during emergency conditions, without initiating seat ejection. The canopy may be jettisoned by pulling the canopy emergency jettison initiator handle on either the pilot’s or NFO’s right instrument panel. Canopy  External  Jettison  Initiators Canopy  external  jettison  initiators  enable  the ground crew to jettison the canopy during ground emergency  conditions.  Each  initiator  is  manually actuated by pulling its canopy external jettison initiator handle. System  and  Backup  Initiators The system has two system initiators and one backup initiator. One system initiator is located behind  each  ejection  seat.  These  initiators  are actuated by pulling the face curtain or secondary firing  control  handle.  They  provide  the  initial explosive  signal  for  canopy  jettison  and  seat ejection. The backup initiator is on the cockpit turtle  deck.  This  initiator  performs  a  backup function  for  the  safe-and-arm  seat  ejection module. It is actuated by a lanyard attached to the canopy and the initiator sear linkage. As the canopy  is  jettisoned,  the  lanyard  actuates  linkage to remove the sear and fire the initiator, sending an  explosive  signal  through  a  1.1-second  time delay to the safe-and-arm module. 2-8 Canopy  Gas  Generator The canopy gas generator is attached to the lower  end  of  the  canopy  hydraulic  actuator.  The canopy  gas  generator  provides  high-pressure  gas to  the  actuator,  to  jettison  the  canopy. Inert  Connectors Inert  connectors  installed  throughout  SMDC line runs permit interconnection of the SMDC lines. Explosive  Manifolds Explosive manifolds installed within SMDC line  runs  incorporate  an  internal  explosive crossover that permits either SMDC to fire both output  SMDC  lines.  The  manifolds  also  provide structural support for mounting the SMDC lines to  the  aircraft  structure. One-Way  Explosive  Transfers One-way  explosive  transfers  installed  within SMDC line runs provide unrestricted explosive transfer  in  one  direction  only.  If  an  explosive signal is introduced in the opposite direction, it is  blocked. SLIDING CANOPY SYSTEM Learning Objective: Recognize the opera- tion, emergency jettison procedures, and components of the sliding canopy system. An example of the sliding canopy system is found  on  the  A-6  aircraft.  The  A-6  cockpit  is covered by a sliding canopy powered by a canopy system consisting of the components required for normal operation and emergency jettison of the canopy.  The  entire  system  is  hydraulically operated with the exception of the jettison device. The  A-6  uses  a  pneumatic  jettison  concept. Hydraulic power for operation of the system is furnished   by   the   combined   (both   engines) hydraulic   system   or   the   hand   pump   system (fig.   2-6). SYSTEM  OPERATION Hydraulic flow to open or close the canopy is  controlled  through  a  canopy  selector  valve, which is in the nosewheel well under the cockpit