Narrative:

During this day we had a main and scavenge oil filter impending bypass indicator activated. We did follow the manual and at one point with the scavenge filter we found a step that required a patch check; when I asked for the materials and tools and we did not have them in stock. The manual requires the patch check results in order to determine if the engine should be returned to service or may need other maintenance actions. See fault isolation figure rgb scavenge oil filter impending bypass indicator activated. I did not find on this chart nor at the oil system -- inspection/check an approval data to release the engine without the results. I was told by mr X and mr Y that the aircraft was good to fly and that it did not require any other maintenance action other than filter replacement. They said that it should be carbon deposits and that it was not a concern. I told them that how we were going to track this condition until the patch check results were available; being this is the normal procedure on other situation where lab results are sent out and waiting for results. This is an example of this that I copy pasted from the manual and it is clear that the engine can be returned to service pending the results. 'If the debris is allowable; clean and install filters; strainer; chip detector strainer(south) and chip detectors. Record category; type and origin of debris. Send debris to an approved lab. The engine can be returned to service; pending the results of the laboratory analyzed debris.' I couldn't find a reference like this one for the filters and I think that the manual is inconclusive. Mr X called engine manufacturer and we had conservation with one of the engine manufacturer representatives and he said that the engine should be checked regularly until the lab results were available; but no data was given in writing. I think the manual should be revised and or the company should get some data with the help from the engine manufacturer in order to clarify this step. I think that management should stop pushing us to release something that is inconclusive. We had a huge engine failure during flight due to carbon deposits.callback conversation with reporter revealed the following information: reporter stated when only one engine oil filter bypass indicator pops; then he would have felt less concerned; because oil filter bypass indicators do occasionally pop with only normal wear deposits in the filter screen. But; in this case; both engine oil filter indicators had popped. So he was concerned about releasing the ATR-72 with both engines possibly indicating deteriorating conditions. Reporter stated he wanted to apply a maintenance inspection follow-up time table to recheck the oil filters downline again; especially since the maintenance manual seems to instruct mechanics to 'wait' for the lab test results of the oil filter deposit analysis prior to aircraft being returned to service. But; he was told that procedure was not required. If he wrote-up the bypass indicators in the logbook; there would not be any engine history readily available to maintenance or downline stations after 15-20 days because the logbook pages are pulled and sent to maintenance records. Reporter stated his carrier does not have a computerized electronic maintenance history program they could access and keep track of these kind of maintenance issues.

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Original NASA ASRS Text

Title: A LEAD MECHANIC EXPRESSES CONCERN ABOUT RELEASING ONE OF THEIR ATR-72 ACFT WITH POPPED ENG OIL FILTER BYPASS INDICATOR BUTTONS. THE MAINT MANUAL IS ALLEGEDLY INCONCLUSIVE ABOUT DETERMINING ACFT SERVICEABILITY IN THIS CIRCUMSTANCE.

Narrative: DURING THIS DAY WE HAD A MAIN AND SCAVENGE OIL FILTER IMPENDING BYPASS INDICATOR ACTIVATED. WE DID FOLLOW THE MANUAL AND AT ONE POINT WITH THE SCAVENGE FILTER WE FOUND A STEP THAT REQUIRED A PATCH CHECK; WHEN I ASKED FOR THE MATERIALS AND TOOLS AND WE DID NOT HAVE THEM IN STOCK. THE MANUAL REQUIRES THE PATCH CHECK RESULTS IN ORDER TO DETERMINE IF THE ENGINE SHOULD BE RETURNED TO SVC OR MAY NEED OTHER MAINT ACTIONS. SEE FAULT ISOLATION FIGURE RGB SCAVENGE OIL FILTER IMPENDING BYPASS INDICATOR ACTIVATED. I DID NOT FIND ON THIS CHART NOR AT THE OIL SYSTEM -- INSPECTION/CHECK AN APPROVAL DATA TO RELEASE THE ENG WITHOUT THE RESULTS. I WAS TOLD BY MR X AND MR Y THAT THE ACFT WAS GOOD TO FLY AND THAT IT DID NOT REQUIRE ANY OTHER MAINT ACTION OTHER THAN FILTER REPLACEMENT. THEY SAID THAT IT SHOULD BE CARBON DEPOSITS AND THAT IT WAS NOT A CONCERN. I TOLD THEM THAT HOW WE WERE GOING TO TRACK THIS CONDITION UNTIL THE PATCH CHECK RESULTS WERE AVAILABLE; BEING THIS IS THE NORMAL PROC ON OTHER SITUATION WHERE LAB RESULTS ARE SENT OUT AND WAITING FOR RESULTS. THIS IS AN EXAMPLE OF THIS THAT I COPY PASTED FROM THE MANUAL AND IT IS CLEAR THAT THE ENG CAN BE RETURNED TO SVC PENDING THE RESULTS. 'IF THE DEBRIS IS ALLOWABLE; CLEAN AND INSTALL FILTERS; STRAINER; CHIP DETECTOR STRAINER(S) AND CHIP DETECTORS. RECORD CATEGORY; TYPE AND ORIGIN OF DEBRIS. SEND DEBRIS TO AN APPROVED LAB. THE ENGINE CAN BE RETURNED TO SVC; PENDING THE RESULTS OF THE LABORATORY ANALYZED DEBRIS.' I COULDN'T FIND A REF LIKE THIS ONE FOR THE FILTERS AND I THINK THAT THE MANUAL IS INCONCLUSIVE. MR X CALLED ENG MANUFACTURER AND WE HAD CONSERVATION WITH ONE OF THE ENG MANUFACTURER REPRESENTATIVES AND HE SAID THAT THE ENGINE SHOULD BE CHECKED REGULARLY UNTIL THE LAB RESULTS WERE AVAILABLE; BUT NO DATA WAS GIVEN IN WRITING. I THINK THE MANUAL SHOULD BE REVISED AND OR THE COMPANY SHOULD GET SOME DATA WITH THE HELP FROM THE ENG MANUFACTURER IN ORDER TO CLARIFY THIS STEP. I THINK THAT MGMNT SHOULD STOP PUSHING US TO RELEASE SOMETHING THAT IS INCONCLUSIVE. WE HAD A HUGE ENG FAILURE DURING FLT DUE TO CARBON DEPOSITS.CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED WHEN ONLY ONE ENG OIL FILTER BYPASS INDICATOR POPS; THEN HE WOULD HAVE FELT LESS CONCERNED; BECAUSE OIL FILTER BYPASS INDICATORS DO OCCASIONALLY POP WITH ONLY NORMAL WEAR DEPOSITS IN THE FILTER SCREEN. BUT; IN THIS CASE; BOTH ENG OIL FILTER INDICATORS HAD POPPED. SO HE WAS CONCERNED ABOUT RELEASING THE ATR-72 WITH BOTH ENGINES POSSIBLY INDICATING DETERIORATING CONDITIONS. RPTR STATED HE WANTED TO APPLY A MAINT INSPECTION FOLLOW-UP TIME TABLE TO RECHECK THE OIL FILTERS DOWNLINE AGAIN; ESPECIALLY SINCE THE MAINT MANUAL SEEMS TO INSTRUCT MECHANICS TO 'WAIT' FOR THE LAB TEST RESULTS OF THE OIL FILTER DEPOSIT ANALYSIS PRIOR TO ACFT BEING RETURNED TO SERVICE. BUT; HE WAS TOLD THAT PROC WAS NOT REQUIRED. IF HE WROTE-UP THE BYPASS INDICATORS IN THE LOGBOOK; THERE WOULD NOT BE ANY ENGINE HISTORY READILY AVAILABLE TO MAINT OR DOWNLINE STATIONS AFTER 15-20 DAYS BECAUSE THE LOGBOOK PAGES ARE PULLED AND SENT TO MAINT RECORDS. RPTR STATED HIS CARRIER DOES NOT HAVE A COMPUTERIZED ELECTRONIC MAINT HISTORY PROGRAM THEY COULD ACCESS AND KEEP TRACK OF THESE KIND OF MAINT ISSUES.

Data retrieved from NASA's ASRS site as of May 2009 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.