Narrative:

Component check XXXX backup generator oil level and oil filter check revision date nov/thu/99. I was an assigned mechanic to accomplish this component check. I checked the center display control panel and it displayed that the right backup generator oil level required servicing. I opened the right fan cover on aircraft xyz and proceeded to service the right backup generator in accordance with component check XXXX. I misunderstood the component check and had realized I had performed the component check incorrectly. The way that the component check is written, I should have opened both engine fan cowls, and physically inspected the condition of the backup generators and the cowls need to remain open until a crew chief or inspector inspects the generators. It is my opinion that the fan cowls should only be opened when a backup generator requires servicing. Callback conversation with reporter revealed the following information: the reporter stated the component check is a check of the backup generator system on the B777 due to input shaft failure. The reporter stated the check is accomplished prior to departure of every extended range operation to detect a sheared input shaft on the variable speed constant frequency backup generators which are subject to shaft bending, wobbling and seal leakage. The reporter said the check starts with using the EICAS display on the maintenance page format chapter 24 which displays numerous electrical indications as oil temperature, oil level status and oil filter status. The reporter said the engine cowling is then opened and a visual check of the unit is accomplished looking at oil sight levels, checking for obvious leaks. The reporter stated the input shaft is not visible but a good clue to failure would be lack of oil and signs of leakage or discolored oil and/or a clogged oil filter. The reporter said a failed shaft cannot be detected using the EICAS maintenance page format and a visual check is required. The reporter stated the special item check job card was confusing because the card had a signoff block for the crew chief or inspector and it was thought this block required visual inspection by the crew chief or inspector. The reporter said engineering corrected this card signoff block to indicate the crew chief or inspector assured the check paperwork was correct and no visual inspection is required. The reporter stated the aircraft is pwred with 2 rolls royce trent 840 engines. The reporter said some improved shafts have been installed but the number is unknown and also seal problems still exist.

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Original NASA ASRS Text

Title: A B777-200 BEFORE EACH EXTENDED RANGE OP DEP, A COMPONENT CHK MUST BE ACCOMPLISHED TO THE BACKUP GENERATORS L AND R BUT THE JOB CARD CREATED CONFUSION ON INSPECTION REQUIREMENTS.

Narrative: COMPONENT CHK XXXX BACKUP GENERATOR OIL LEVEL AND OIL FILTER CHK REVISION DATE NOV/THU/99. I WAS AN ASSIGNED MECH TO ACCOMPLISH THIS COMPONENT CHK. I CHKED THE CTR DISPLAY CTL PANEL AND IT DISPLAYED THAT THE R BACKUP GENERATOR OIL LEVEL REQUIRED SVCING. I OPENED THE R FAN COVER ON ACFT XYZ AND PROCEEDED TO SVC THE R BACKUP GENERATOR IN ACCORDANCE WITH COMPONENT CHK XXXX. I MISUNDERSTOOD THE COMPONENT CHK AND HAD REALIZED I HAD PERFORMED THE COMPONENT CHK INCORRECTLY. THE WAY THAT THE COMPONENT CHK IS WRITTEN, I SHOULD HAVE OPENED BOTH ENG FAN COWLS, AND PHYSICALLY INSPECTED THE CONDITION OF THE BACKUP GENERATORS AND THE COWLS NEED TO REMAIN OPEN UNTIL A CREW CHIEF OR INSPECTOR INSPECTS THE GENERATORS. IT IS MY OPINION THAT THE FAN COWLS SHOULD ONLY BE OPENED WHEN A BACKUP GENERATOR REQUIRES SVCING. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE COMPONENT CHK IS A CHK OF THE BACKUP GENERATOR SYS ON THE B777 DUE TO INPUT SHAFT FAILURE. THE RPTR STATED THE CHK IS ACCOMPLISHED PRIOR TO DEP OF EVERY EXTENDED RANGE OP TO DETECT A SHEARED INPUT SHAFT ON THE VARIABLE SPD CONSTANT FREQ BACKUP GENERATORS WHICH ARE SUBJECT TO SHAFT BENDING, WOBBLING AND SEAL LEAKAGE. THE RPTR SAID THE CHK STARTS WITH USING THE EICAS DISPLAY ON THE MAINT PAGE FORMAT CHAPTER 24 WHICH DISPLAYS NUMEROUS ELECTRICAL INDICATIONS AS OIL TEMP, OIL LEVEL STATUS AND OIL FILTER STATUS. THE RPTR SAID THE ENG COWLING IS THEN OPENED AND A VISUAL CHK OF THE UNIT IS ACCOMPLISHED LOOKING AT OIL SIGHT LEVELS, CHKING FOR OBVIOUS LEAKS. THE RPTR STATED THE INPUT SHAFT IS NOT VISIBLE BUT A GOOD CLUE TO FAILURE WOULD BE LACK OF OIL AND SIGNS OF LEAKAGE OR DISCOLORED OIL AND/OR A CLOGGED OIL FILTER. THE RPTR SAID A FAILED SHAFT CANNOT BE DETECTED USING THE EICAS MAINT PAGE FORMAT AND A VISUAL CHK IS REQUIRED. THE RPTR STATED THE SPECIAL ITEM CHK JOB CARD WAS CONFUSING BECAUSE THE CARD HAD A SIGNOFF BLOCK FOR THE CREW CHIEF OR INSPECTOR AND IT WAS THOUGHT THIS BLOCK REQUIRED VISUAL INSPECTION BY THE CREW CHIEF OR INSPECTOR. THE RPTR SAID ENGINEERING CORRECTED THIS CARD SIGNOFF BLOCK TO INDICATE THE CREW CHIEF OR INSPECTOR ASSURED THE CHK PAPERWORK WAS CORRECT AND NO VISUAL INSPECTION IS REQUIRED. THE RPTR STATED THE ACFT IS PWRED WITH 2 ROLLS ROYCE TRENT 840 ENGS. THE RPTR SAID SOME IMPROVED SHAFTS HAVE BEEN INSTALLED BUT THE NUMBER IS UNKNOWN AND ALSO SEAL PROBS STILL EXIST.

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.