SYSTEM  OPERATION Before   flight,   the   ejection   seat   safe/arm handle  is  kept  in  the  SAFE  position.  In  this position,  the  visible  portion  of  the  handle  is colored white and placarded as SAFE. When the aircraft is ready for flight, the pilot sets the safe and arm handle to the ARMED position. In this position,  the  visible  portion  of  the  handle  is colored  with  yellow  and  black  markings  and placarded as ARMED. The ejection sequence (fig. 6-19) starts when the pilot pulls the ejection control handle. The up- ward movement of the handle removes two sears from the seat initiator and fires two cartridges with the seat initiator. Firing Sequence Ballistic  gas  generated  by  the  right  cartridge within the seat initiator actuates the pin puller. The gas also activates the shielded mild detonating cord (SMDC) initiator. The SMDC then activates the aircraft identification friend or foe unit (IFF) and the canopy jettison system. Additionally, it activates  the  inertia  reel  cartridge  and  the 0.3-second delay initiator. Ballistic gas generated by the left cartridge within the seat initiator starts the   0.3-second   delay   initiator.   Ballistic   gas pressure from either 0.3-second delay initiators ignites  the  primary  cartridge  within  the  catapult. Catapult Firing and Initial  Seat  Movement Ballistic gas pressure developed by the cat- apult  primary  cartridge  causes  the  inner  and intermediate barrels within the catapult to rise and release the top latch mechanism. The secondary cartridges within the catapult fire progressively as the rising barrels are exposed to the heat and pressure of the primary cartridge gas. Progressive firing  of  the  catapult  secondary  cartridges provides a relatively even gas pressure during catapult  extension.  This  eliminates  excessive g-forces during ejection. As  the  seat  moves  upward,  the  emergency oxygen system is activated. A trip rod withdraws the firing link from the drogue gun and starts a 0.5-second   internal   timer.   Another   trip   rod withdraws the firing link from the time-release mechanism. Aircraft electrical power and personal services (oxygen and communication) between the seat and the aircraft are disconnected. At this point in the sequence, the leg restraint lines  are  drawn  through  the  snubbing  units  to restrain the pilot’s legs to the seat bucket. When the  leg  restraint  lines  become  taut,  the  upper portion of the leg restraint line shears from the lower  portion,  which  is  attached  to  the  floor bracket.   Forward   movement   of   the   lines   is prevented by the snubbing units. After  72  inches  of  catapult  extension,  the rocket motor initiator is fired by a cable that is attached to the drogue gun trip rod. Ballistic gas pressure  generated  by  the  cartridge  within  the rocket  motor  initiator  is  routed  to  a  pressure actuated  firing  mechanism  located  on  the  rocket motor. Flame and pressure ignite the rocket motor propellant  grain.  The  thrust  of  the  motor  is approximately 4,500 pounds and lasts for 0.25 second. Aircraft and Seat Separation Separation   of   the   seat   from   the   aircraft occurs  at  approximately  76  inches  of  catapult extension. At this point, the inner barrel separates from the intermediate barrel. The seat is now clear of  the  aircraft. The drogue gun primary cartridge fires after a  0.5-second  delay  to  propel  the  piston  from  the drogue  gun  barrel.  The  inertia  of  the  piston extracts the parachute flap closure pin and deploys the  22-inch  controller  drogue.  The  controller drogue,  in  turn,  deploys  the  60-inch  stabilization and retardation drogue. The 0.5-second time delay allows  the  seat  to  reach  its  maximum  altitude before  the  drogues  are  fully  developed.  The  seat will  stabilize  and  decelerate  because  of  the drogues, which are held to the seat by the scissor mechanism. If the drogue gun primary cartridge fails to fire, ballistic gas pressure will pass to the drogue gun  when  the  time-release  mechanism  (TRM) fires. This gas shears the firing pin retaining pin. The  firing  pin  then  strikes  the  secondary  drogue gun cartridge, which results in drogue deploy- ment. Should both the drogue gun primary and time-release  mechanism  cartridges  fail  to  fire, operation of the manual override handle will fire 6-26