TM 55-2840-241-23 Change 19          4-16.1 4-3.   Power Loss, N₂ Droop or Flameout Parameter Maintenance Check Procedures.  See applicable air- craft Maintenance Test Flight Manual (MTF). Check  maintenance  procedures  for  OH-58  aircraft when a power loss, N₂ droop, or flameout occurs. N₂ droop may occur during a normal flight maneuver requir- ing a rapid increase in power (i.e., rapid collective and or tail  rotor  inputs,  high  G  turn,  steep  turn).  If  N₂  droop occurs  but  low  RPM  warning  is  not  activated  and  N₂ recovers  to  100  percent  on  OH-58C,  and  further  N₂ droop is not experienced, no maintenance action is re- quired. NOTE For  all  maintenance  actions  notes  below, pneumatic  line  fittings  are  to  be  torqued  to specified values utilizing a torque wrench. All lines  are  to  be  installed  so  that  there  is  no preload or deformation of the in accordance with applicable TM's. a. When a power loss, N₂ droop, or flameout occurs (in parameters other than those established in paragraph above), check/inspect to determine the reason/reasons in accordance with the troubleshooting charts in table 4-1. b. If a reason/reasons for power degradation can- not  be  established  using  the  procedures  specified  in paragraph above, request assistance from AVIM Mainte- nance and proceed with the maintenance actions noted in paragraphs (1) through (5) below. If this is a second occurrence of power degradation on this aircraft/engine and  the  maintenance  actions  listed  below  have  been complied  within  the  last  100  flying  hours,  replace  the engine. (1) Check  engine  controls  for  proper  rigging. Check throttle angle on fuel control at idle detent for the pilot's and co-pilot's twist grip. Maximum allowable varia- tion   between   the   pilot's   and   co-pilot's   twist   grip   is 5/64-inch as measured on the fuel control sector. Re-rig controls if not within specifications per TM 55-1520-228-23 and per this TM for OH-58C. (2) Remove  engine  fuel  and  pneumatic  lines. Replace     engine     fuel     filter     P/N     6895177,     NSN 2915-01-040-2607 on OH-58C aircraft. Inspect fittings and lines for cracks, scratches, dents and improper seat- ing on sealing surfaces. If cracks in fittings or lines are suspected, refer to TM 1-1520-254-23, Technical Manu- al; Aviation Unit Maintenance (AVUM) Manual Nonde- structive Inspection Procedure for OH-58 Helicopter Se- ries. Inspect lines and fittings for contamination. Clean all lines per applicable TM's. Inspect lines for chafing, check compressor bleed valve. Correct any discrepancies. In- spect     and     clean     PC     filter     P/N     687458,     NSN 2945-00-231-8065 (OH-58C only) On OH-58C replace fuel nozzle P/N 6890917, NSN 2915-01-039-4730 and check valve P/N 6895171, NSN 4820-01-045-0205. Re- install pneumatic lines and filter. Leak check pneumatic system in accordance with TM 55-2840-241-23. Check compressor bleed valve for proper operation. (3) Remove all hoses, fittings and valve includ- ing fuel shutoff valve from the fuel boost pump to the engine. Clean and inspect all for damage and restric- tions. Reinstall or replace as applicable. Bleed the fuel system in accordance with the appropriate TM. With air- craft fuel shutoff valve open, start boost pump and check all accessible fuel lines, connections, and fittings outside the  fuel  cell  for  leakage.  Inspect  and  lubricate  starter generator splines. Check calibration of dual tachometer (N₂ and rotor RPM). (4) Check main and tail rotor systems for proper rigging and pitch angle, and re-rig as necessary. (5) Start    engine    and    perform    deceleration check. If deceleration check is not in limits, replace fuel control P/N 6895672 NSN 2915-01-034-4671; N₂ gover- nor P/N 6895673, NSN 2915-01-034-4317 and double check valve P/N 6876557, NSN 4820-01-047-2796 on OH-58C aircraft. Repeat deceleration check, if satisfac- tory, perform test flight in accordance with established procedures. c. Aircraft are restricted from NOE contour, low lev- el, and night flight for 10 hours after completion of the preceding procedures and must be flown at an altitude to allow safe autorotation as defined in TM 55-1520-228-10. After completion of the 10-hour restric- tion, repeat deceleration check. If satisfactory, perform test flight in accordance with established procedures. No further flight restrictions are imposed. d. After  completion  of  power  loss,  N₂  droop,  or flame  out,  parameter  maintenance  check  procedures, make an entry on engine DA Form 2408-15 citing date the inspection was performed and engine hours at the time inspection was performed. 4-4.   Engine Performance Check.    See applicable air- craft Maintenance Test Flight Manual (MTF).