Narrative:

In cruise at FL410 I noticed a 20 KT drop in airspeed, looked at engine instruments and found left hand EPR gauge well past top of scale (top is 2.0 -- it read 2.09). All other engine gauges read what appeared to be idle readings. Thrust lever had not moved. I moved thrust lever fore and aft with no corresponding engine response. At first recognition of problem we requested and got a lower altitude. During descent we turned engine anti-ice on because of visible moisture. Conferred with maintenance -- no solutions. Approximately 8-10 mins after onset of incident engine came to life. Rest of flight uneventful. On ground, maintenance control told me they have a service bulletin addressing my exact situation, and this had occurred to this aircraft twice in the previous 2 weeks. Callback conversation with reporter revealed the following information: the aircraft was a B757-200 with the rolls royce rb-211 engines. The reporter stated that this was an 'in-flight idle' situation except that the throttle had not been at the idle position before the event, the throttle had not been moved from its cruise position. This was the 4TH event of this type in 4 weeks, same aircraft, same engine. The engine loss was very subtle, with no yaw and, of course, no warning associated with it. The reporter was angered by the fact that he had no prior information of this situation since the air carrier maintains only the previous day's page for the crew's information. The last event had occurred just 2 days before his flight. The company had an old maintenance service bulletin that only maintenance had access to, referencing an installation of a drain in the 'P1' sensing line to the fuel computer. When this plug gets dirty it plugs up. Prior to the air carrier maintenance department 'remembering' about the issuance of an old bulletin, the usual 'fix' or logbook comment from maintenance would be either a logbook note that the EPR sending unit was replaced, or 'unable to duplicate on the ground' or some information note that was not carried over in the log. Maintenance then 'remembered' the old bulletin and after associating the drain to the problem cleaned this drain and that fixed the in-flight idle events. It was, in essence, a 'liquid trap' problem. There is no in-flight checklist procedure for this event. Reporter thought it to be of interest that in each of the 4 cases, the crews had descended and turned on their engine anti-ice system. Again, in every case, within 8-9 mins the engine came to life again. The company knows about this, the pilot's union knows about it and the reporter hopes that other operators of the rb-211 as well as the manufacturer of the engine knows about it. The plane is fixed, the system isn't. The drain has to be kept clean.

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Original NASA ASRS Text

Title: A B757-200 FLC NOTES A LOSS OF AIRSPD AT FL410. THE L ENG PARAMETERS INDICATED AN INFLT SPOOL DOWN. PIC ASKS FOR LOWER ALT FROM ATC AND AFTER 9 MINS THE 'ENG COMES TO LIFE.' DURING EVENT AIRLINE MAINT WAS CONTACTED AND HAD NO SOLUTIONS FOR THE CREW. LATER INFO INDICATED THAT MAINT CTL HAD REF TO A SVC BULLETIN ISSUED FOR THIS SAME ACFT WITHIN THE PAST 2 WKS.

Narrative: IN CRUISE AT FL410 I NOTICED A 20 KT DROP IN AIRSPD, LOOKED AT ENG INSTS AND FOUND L HAND EPR GAUGE WELL PAST TOP OF SCALE (TOP IS 2.0 -- IT READ 2.09). ALL OTHER ENG GAUGES READ WHAT APPEARED TO BE IDLE READINGS. THRUST LEVER HAD NOT MOVED. I MOVED THRUST LEVER FORE AND AFT WITH NO CORRESPONDING ENG RESPONSE. AT FIRST RECOGNITION OF PROB WE REQUESTED AND GOT A LOWER ALT. DURING DSCNT WE TURNED ENG ANTI-ICE ON BECAUSE OF VISIBLE MOISTURE. CONFERRED WITH MAINT -- NO SOLUTIONS. APPROX 8-10 MINS AFTER ONSET OF INCIDENT ENG CAME TO LIFE. REST OF FLT UNEVENTFUL. ON GND, MAINT CTL TOLD ME THEY HAVE A SVC BULLETIN ADDRESSING MY EXACT SIT, AND THIS HAD OCCURRED TO THIS ACFT TWICE IN THE PREVIOUS 2 WKS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE ACFT WAS A B757-200 WITH THE ROLLS ROYCE RB-211 ENGS. THE RPTR STATED THAT THIS WAS AN 'INFLT IDLE' SIT EXCEPT THAT THE THROTTLE HAD NOT BEEN AT THE IDLE POS BEFORE THE EVENT, THE THROTTLE HAD NOT BEEN MOVED FROM ITS CRUISE POS. THIS WAS THE 4TH EVENT OF THIS TYPE IN 4 WKS, SAME ACFT, SAME ENG. THE ENG LOSS WAS VERY SUBTLE, WITH NO YAW AND, OF COURSE, NO WARNING ASSOCIATED WITH IT. THE RPTR WAS ANGERED BY THE FACT THAT HE HAD NO PRIOR INFO OF THIS SIT SINCE THE ACR MAINTAINS ONLY THE PREVIOUS DAY'S PAGE FOR THE CREW'S INFO. THE LAST EVENT HAD OCCURRED JUST 2 DAYS BEFORE HIS FLT. THE COMPANY HAD AN OLD MAINT SVC BULLETIN THAT ONLY MAINT HAD ACCESS TO, REFING AN INSTALLATION OF A DRAIN IN THE 'P1' SENSING LINE TO THE FUEL COMPUTER. WHEN THIS PLUG GETS DIRTY IT PLUGS UP. PRIOR TO THE ACR MAINT DEPT 'REMEMBERING' ABOUT THE ISSUANCE OF AN OLD BULLETIN, THE USUAL 'FIX' OR LOGBOOK COMMENT FROM MAINT WOULD BE EITHER A LOGBOOK NOTE THAT THE EPR SENDING UNIT WAS REPLACED, OR 'UNABLE TO DUPLICATE ON THE GND' OR SOME INFO NOTE THAT WAS NOT CARRIED OVER IN THE LOG. MAINT THEN 'REMEMBERED' THE OLD BULLETIN AND AFTER ASSOCIATING THE DRAIN TO THE PROB CLEANED THIS DRAIN AND THAT FIXED THE INFLT IDLE EVENTS. IT WAS, IN ESSENCE, A 'LIQUID TRAP' PROB. THERE IS NO INFLT CHKLIST PROC FOR THIS EVENT. RPTR THOUGHT IT TO BE OF INTEREST THAT IN EACH OF THE 4 CASES, THE CREWS HAD DSNDED AND TURNED ON THEIR ENG ANTI-ICE SYS. AGAIN, IN EVERY CASE, WITHIN 8-9 MINS THE ENG CAME TO LIFE AGAIN. THE COMPANY KNOWS ABOUT THIS, THE PLT'S UNION KNOWS ABOUT IT AND THE RPTR HOPES THAT OTHER OPERATORS OF THE RB-211 AS WELL AS THE MANUFACTURER OF THE ENG KNOWS ABOUT IT. THE PLANE IS FIXED, THE SYS ISN'T. THE DRAIN HAS TO BE KEPT CLEAN.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.