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Figure 12-8. Landing Gear Emergency Extension System.
Figure 12-10. Hydraulic System Flow Diagram, Raise Cycle.

Fluid Power - Intro to Hydraulics, Pneumatics, and how it all works
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aft doors’ cylinders and the shuttle valve on the nose  gear  cylinder  to  close  off  the  normal  port and operate these cylinders. The nose gear cylinder extends; this unlocks the uplock and extends the nose gear. The nitrogen flowing into the aft door cylinders opens the aft doors. Fluid on the close side  of  the  door  cylinder  is  vented  to  return through the actuated dump valves. Nitrogen from another bottle actuates the shuttle valves on the uplock  cylinders.  Nitrogen  flows  into  the  uplock cylinders  and  causes  them  to  disengage  the uplocks. As soon as the uplocks are disengaged, the  main  gear  extends  by  the  force  of  gravity. Fluid  on  the  up  side  of  the  main  gear  cylinders is  vented  to  return  through  the  actuated  dump valves,  preventing  a  fluid  lock. JET BLAST DEFLECTORS Jet  blast  deflectors  (JBD)  onboard  aircraft carriers   are   raised   and   lowered   by   hydraulic cylinders  through  mechanical  linkage.  Two hydraulic cylinders are attached to each JBD panel shaft  by  crank  assemblies.  (See  fig.  12-9.)  The shaft  is  rotated  by  the  push  and  pull  operation of the hydraulic cylinders. Shaft rotation extends or retracts the linkage to raise or lower the JBD panels. This operation is designed so that in the event of a failure of one of the hydraulic cylinders, the  other  one  will  raise  or  lower  the  panels. Figure  12-10  is  a  diagram  of  the  hydraulic control  system  of  a  JBD  during  the  raise  cycle. Hydraulic  fluid  from  the  catapult  hydraulic  supply system is supplied to the JBD hydraulic system through an isolation valve and a filter to the 4-way control valve assembly. (The 4-way control valve assembly   consists   of   a   pilot-operated   control valve,  a  direct-  or  solenoid-operated  control  valve, and  a  sequence  valve,  which  is  not  shown.) To  raise  the  JBD,  solenoid  B  of  the  4-way control  valve  assembly  is  energized.  The  spools of  the  4-way  valve  assembly  shift,  allowing medium-pressure hydraulic fluid to flow into port A of the hydraulic cylinder. The cylinders extend, Figure 12-9.—Operating gear assembly (panels raised). 12-10







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