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Figure 12-8. Landing Gear Emergency Extension System.

Fluid Power - Intro to Hydraulics, Pneumatics, and how it all works
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stroke piston will cause tilt to be put on the tilt plate,  and  the  A-end  will  cause  the  mount  to  train right. Figure  12-7  is  a  simplified  block  diagram showing the main element of the hydraulic power drive   system   under   automatic   control   for clockwise  and  counterclockwise  rotation. There   are   two   principal   problems   in   posi- tioning  a  gun  to  fire.  One  is  to  get  an  accurate gun-order  signal.  This  problem  is  solved  by  the director-computer   combination.   The   other problem is to transmit the director signal promptly to  the  gun  so  that  the  position  and  movements of the gun will be synchronized with the signals from  the  director. The   problem   of   transforming   gun-order signals  to  mount  movements  is  solved  by  the power  drive  and  its  control—the  indicator regulator.  The  indicator  regulator  controls  the power  drive,   and  this,  in  turn,  controls  the movement  of  the  gun. The   indicator   regulator   receives   an   initial electrical  gun-order  from  the  director-computer, compares  it  to  the  existing  mount  position,  and sends  an  error  signal  to  the  hydraulic  control mechanism  in  the  regulator.  The  hydraulic  control mechanism controls the flow to the stroke control shaft, which positions the tilting box in the A-end of  the  transmission.  Its  tilt  controls  the  volume and direction of fluid pumped to the B-end and, therefore,  the  speed  and  direction  of  the  drive shaft of the B-end. Through mechanical linkage, the  B-end  output  shaft  moves  the  gun  in  the direction determined by the signal. At the same time,   B-end   response   is   transmitted   to   the indicator  regulator  and  continuously  combines with  incoming  gun-order  signals  to  give  the error  between  the  two.  This  error  is  modified hydraulically,   according   to   the   system   of mechanical linkages and valves in the regulator. When  the  gun  is  lagging  behind  the  signal,  its movement  is  accelerated;  and  when  it  begins  to catch  up,  its  movement  is  slowed  down  so  that it  will  not  overrun  excessively. LANDING   GEAR   EMERGENCY SYSTEM If the landing gear in a naval aircraft fails to extend   to   the   down   and   locked   position,   the aircraft has an emergency method to extend the landing  gear.  This  text  will  cover  the  nitrogen system. The   nitrogen   storage   bottle   system   is   a one-shot  system  powered  by  nitrogen  pressure stored   in   four   compressed   nitrogen   bottles (fig. 12-8). When the landing gear control handle is  used  to  actuate  the  emergency  landing  gear system,  a  cable  between  the  control  and  the manually   operated   nitrogen   bottle   opens   the emergency gear down release valve on the bottle. Nitrogen  from  this  bottle  actuates  the  release valves  on  the  other  three  bottles  so  that  they discharge.   Nitrogen   flows   from   the   manually operated  bottle,  actuates  the  dump  valves,  and causes the shuttles within the shuttle valves on the Figure 12-7.—Operation of the hydraulic power drive. 12-8







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