TM 55-2840-241-23 5-14           Change 19 (11)  Adjust the aircraft linkage as outlined in the applicable Aircraft Maintenance Manual. (12)  Test the engine as outlined in Chapter 10. (13)  Make appropriate entry relative to governor replacement in the engine log. 5-14.  Double Check Valve.    a.  Removal.   CAUTION Do not torque through the double check valve  or  accumulators,  internal  damage could result, use adjacent hexagonal sur- faces for turning. When the double check valve or accumulators are removed, use extreme care to prevent foreign materials from entering the pneumatic lines, valve, or accumulators. (1) Hold union (60, figure 5-3) and disconnect air hose (15) from accumulator (58). (2) Hold elbow (61) and remove left accumulator (58). Discard preformed packing (59). (3) Remove nut (53), washer (54), spacer (55), and bolt (57) securing clamp (56) to the firewall shield. Remove the clamp from the check valve. (4) Hold   right   accumulator   (58)   and   remove double check valve (62). Remove elbow (61) and union (60)  from  the  double  check  valve.  Discard  preformed packing (59). b.  Inspection.      Inspect  general  condition  of  valve and check associated tubing for cracked coupling nuts and  chafed  surfaces.  If  crack  in  coupling  nut  is  sus- pected,  refer  to  TM  1-1520-254-23,  Technical  Manual Aviation Unit Maintenance (AVUM) and Aviation Inter- mediate Maintenance (AVIM) Manual Nondestructive In- spection Procedure for OH-58 Helicopter Series. c.  Installation.   (1) Install elbow (61, figure 5-3) and union (60) with new preformed packing (59) in double check valve (62). Tighten the elbow and union to 55-80 in. lb. (2) Place a new preformed packing on right ac- cumulator (58). Do not lubricate the preformed packing. Screw check valve (62) onto the accumulator. Hold accu- mulator (58) with a  backup wrench and tighten the check valve by turning on the narrow hexagonal surface adja- cent to the accumulator. Tighten to 40-65 in. lb. (3) Install clamp (56) on the double check valve. Attach  clamp to firewall shield with bolt (57), spacer (55), washer (54), and nut (53). Tighten the nut to 35-40 in. lb. (4) Place a new preformed packing on left accu- mulator (58). Do not lubricate the O-ring. Screw the accu- mulator into elbow (61). Hold elbow (61) with a backup wrench and tighten the accumulator by turning on the narrow hexagonal surface adjacent to the elbow. Tighten to 55-80 in. lb. (5) Connect air hose (15) to the accumulator and tighten to 80-120 in. lb. Figure  5-9.  Carbon Buildup on Fuel Nozzle   (6) Perform a fuel system pneumatic leak check. (Refer to paragraph 5-8.) 5-15.  Fuel Nozzle.   a.  Removal.   (1) Disconnect the fuel hose at the fuel nozzle (6, figure 5-3). CAUTION Care  must  be  taken  when  removing  the nozzle from the outer combustion case to prevent damage to the nozzle spray tip. If the spray tip is damaged, the nozzle must be replaced. (2) Remove   the   lockwire      and   unscrew   the nozzle from the outer combustion case. Carefully extract the nozzle from the combustion case. NOTE To preclude the possibility of the combustion chamber  becoming  misaligned,  do  not  re- move the fuel nozzle and the spark igniter at the same time. b.  Cleaning.   (1) Check for carbon deposits on the spray tip. Figure 5-9 shows the condition of a typical fuel nozzle removed  from  an  operational  engine.  A  nozzle  in  this condition  should  be  cleaned,  if  possible,  before  being reinstalled.