What was found
LT DUCT PRESSURE FLUCTUATES DURING DESCENT. ON DESCENT LT PACK FLUCTUATE 20-35 PSI. BLEED INOP. REPLACED LT ENG PRSOV IAW MM, NO HELP. REPLACED HI STAGE PILOT CONTROLLER & OVERTEMP SENSOR. ENG RUN ACCOMPLISHED & FAILED. ACCOMPLISHED HEALTH CHECK OF PRSOV & HPSOV. FOUND NORMAL PARAMETERS. REPLACED REVERSE FLOW CHECK CONTROLLER DUE TO DIAPHRAGM LEAKAGE. ENGINE RUN CHECK FOUND NORMAL. ACCOMPLISHED PNEUMATIC TEST ON NR 1 ENGINE. ALL RPMS, PARAMETERS WITHIN LIMITS IAW JRH & MATCHED WITH RT ENGINE, LOAD - NO LOAD. DUCT PSI FOLLOWS BLEED SWITCH, ON & OFF. NR 1 ENGINE, REVERSE FLOW PILOT VALVE HAS BEEN REPLACED FOR FLUCTUATIONS IN ENGINE PNEUMATIC PRESSURE. RUN ENG UP TO BLEED SHIFT 80+- 5 PERCENT FOR 2 MIN AND VERIFY ALL PARAMETERS ARE WITHIN JHR. AT ALL RPMS, PARAMETERS WITHIN LIMITS IAW JRH & MATCHED WITH RT ENGINE, LOAD - NO LOAD. DUCT PSI FOLLOWS BLEED SWITCH, ON & OFF. BLEED SHIFT OK SEVERAL RUNS.