Narrative:

My co-worker and I were handed a carbon seal part by our lead (X) and were instructed to replace the carbon seal for the starter generator on the #1 (left hand) engine. I got on top of the wing and I proceeded to remove the starter generator; while my co-worker remained on the ground. I opened up the inboard engine cowling and removed the aft inboard engine cowling and handed it to him. I removed the starter generator and handed it to him. He climbed on the ladder and he noticed a loose oil line and some residual oil in exhaust duct boot and he brought it to the attention of our second lead (Y); also on day shift. He and lead Y informed lead X about the oil line and he did come out and look at it. Lead X asked him if he had tightened up the oil line; which he responded that he did. He informed lead X that he suspected that this was where the oil leak was coming from and he asked lead X if he still wanted us to replace the carbon seal? Lead X said to go ahead and replace the carbon seal since we had already removed the starter generator; which we did. Upon reviewing the job card; there were different service bulletins relating to specific engine modifications (mods) in regards to carbon seal replacement. Being unsure of the effectivity of this aircraft; I asked my co-worker if he knew how I could go about finding which service bulletin went with this engine. He was not sure; so he went and asked another mechanic. That mechanic climbed up on the wing and said that I had to remove six nuts which held on the generator exhaust duct. I removed the exhaust duct and there was another seal which had to be removed before I was able to remove the carbon seal. I asked what the other seal was and my co-worker removed it easily with a flat head screwdriver. Once that seal was removed; I had access to the old carbon seal; which was held in place by three small nuts. I removed the old carbon seal and my co-worker had given me the new seal which he had already installed the o-ring. Before I installed the seal; I asked him if he had put any oil on the o-ring and he said that he did; but then he also wiped off some residual oil off the engine and applied it to the o-ring. I put the seal in place and I started each nut with my fingertips. Using a ratchet; my co-worker told me not to tighten each nut one at a time; but to turn each one just a little at a time; until all were snug. Once snug; the job card said to torque each nut to 35-inch pounds. While using the torque wrench; I proceeded to torque each nut; but before coming to final torque; the socket would slip off the nut. I informed my co-worker about it and he climbed the ladder and backed off the nuts a little bit and tried to do the final torque; but the ratchet still came off. I asked him if he had a smaller socket and he did not and he went to ask other mechanics if they had something smaller. He was unable to find a socket; but I had a wrench that fit each nut perfectly; so my co-worker just bumped (tightened) each nut. After that was done; I proceeded to reinstall the seal that was covering the carbon seal; the generator exhaust duct; and the starter generator; and closed all cowlings. Co-worker wiped off oil that was on the outside the cowling. When I was done; lead X and lead Y did a compartment wash of the engine and after that; they proceeded to run the engine. After running the engine; there was no oil on the cowling and there was no further oil found in the exhaust duct boot and there were no faults found. I was notified by my co-worker of the problem before I clocked out. I cannot explain how this happened; but I don't think that the nut was over-torqued; but if it was; I don't understand how this could be the result. The seal showed that it was bent where the o-ring sat; so I don't see how a 3/16 size nut could bend the seal. If the seal was that fragile; there should have been some indentation from the nut on the seal. I think the seal was replaced on the night shift. There being no short cuts in repairs to aircraft; events may occur. But there should be some type of access information to the mechanic stating which service bulletin applies to which aircraft and if our airline does have something showing this information; it should be made accessible to all mechanics. The effectivity of the aircraft should be readily available. From previous experience; all information relating to a particular aircraft; new and old models; and parts were readily accessible or stated on the work card.

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Original NASA ASRS Text

Title: A Mechanic reports about a Saab SF-340 aircraft requiring an air turnback after takeoff; for a left engine low oil pressure and quantity. Mechanics had just changed the Carbon Seal for the left engine starter generator.

Narrative: My co-worker and I were handed a carbon seal part by our Lead (X) and were instructed to replace the carbon seal for the starter generator on the #1 (left hand) engine. I got on top of the wing and I proceeded to remove the starter generator; while my co-worker remained on the ground. I opened up the inboard engine cowling and removed the aft inboard engine cowling and handed it to him. I removed the starter generator and handed it to him. He climbed on the ladder and he noticed a loose oil line and some residual oil in exhaust duct boot and he brought it to the attention of our second Lead (Y); also on day shift. He and Lead Y informed Lead X about the oil line and he did come out and look at it. Lead X asked him if he had tightened up the oil line; which he responded that he did. He informed Lead X that he suspected that this was where the oil leak was coming from and he asked Lead X if he still wanted us to replace the carbon seal? Lead X said to go ahead and replace the carbon seal since we had already removed the starter generator; which we did. Upon reviewing the Job Card; there were different Service Bulletins relating to specific engine modifications (mods) in regards to carbon seal replacement. Being unsure of the effectivity of this aircraft; I asked my co-worker if he knew how I could go about finding which Service Bulletin went with this engine. He was not sure; so he went and asked another Mechanic. That Mechanic climbed up on the wing and said that I had to remove six nuts which held on the generator exhaust duct. I removed the exhaust duct and there was another seal which had to be removed before I was able to remove the carbon seal. I asked what the other seal was and my co-worker removed it easily with a flat head screwdriver. Once that seal was removed; I had access to the old carbon seal; which was held in place by three small nuts. I removed the old carbon seal and my co-worker had given me the new seal which he had already installed the O-Ring. Before I installed the seal; I asked him if he had put any oil on the O-Ring and he said that he did; but then he also wiped off some residual oil off the engine and applied it to the O-Ring. I put the seal in place and I started each nut with my fingertips. Using a ratchet; my co-worker told me not to tighten each nut one at a time; but to turn each one just a little at a time; until all were snug. Once snug; the job card said to torque each nut to 35-inch LBS. While using the torque wrench; I proceeded to torque each nut; but before coming to final torque; the socket would slip off the nut. I informed my co-worker about it and he climbed the ladder and backed off the nuts a little bit and tried to do the final torque; but the ratchet still came off. I asked him if he had a smaller socket and he did not and he went to ask other Mechanics if they had something smaller. He was unable to find a socket; but I had a wrench that fit each nut perfectly; so my co-worker just bumped (tightened) each nut. After that was done; I proceeded to reinstall the seal that was covering the carbon seal; the generator exhaust duct; and the starter generator; and closed all cowlings. Co-worker wiped off oil that was on the outside the cowling. When I was done; Lead X and Lead Y did a compartment wash of the engine and after that; they proceeded to run the engine. After running the engine; there was no oil on the cowling and there was no further oil found in the exhaust duct boot and there were no faults found. I was notified by my co-worker of the problem before I clocked out. I cannot explain how this happened; but I don't think that the nut was over-torqued; but if it was; I don't understand how this could be the result. The seal showed that it was bent where the O-ring sat; so I don't see how a 3/16 size nut could bend the seal. If the seal was that fragile; there should have been some indentation from the nut on the seal. I think the seal was replaced on the night shift. There being no short cuts in repairs to aircraft; events may occur. But there should be some type of access information to the Mechanic stating which Service Bulletin applies to which aircraft and if our airline does have something showing this information; it should be made accessible to all Mechanics. The effectivity of the aircraft should be readily available. From previous experience; all information relating to a particular aircraft; new and old models; and parts were readily accessible or stated on the Work Card.

Data retrieved from NASA's ASRS site as of April 2012 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.