Narrative:

Upon arrival at work I found that the aircraft was in the hangar and not yet finished with a routine inspection. I spoke with the lead mechanic and he indicated it would be ready in about 45 mins. A while later I came back into the hangar and did a preflight inspection of the airplane. The engine cowlings were opened and I looked at the engines from ground level. I asked that I be allowed to check the oil levels in the engines prior to removing the aircraft from the hangar. The second mechanic, replied that the oil levels were fine, he had checked them himself. While it was being fueled I again checked the aircraft with particular attention to latches on the cowling and baggage doors. At about 5-10 mins in flight we observed a fluctuation in oil pressure on the right engine. We returned to the airport and did a precautionary shut down of the right engine in flight when the oil pressure appeared to be close to redline. The problem appears to be either a defective oil cap or the failure of the mechanic to properly secure the cap. The checking of the oil level is an item normally performed by the flight crew. In this case I was assured that the oil level was okay by the mechanic I had observed working on and inspecting the engine. His qualifications to make observations and comments regarding the condition and airworthiness of the engine are far superior to mine. I deferred to his judgement in this matter. After all, if you can't trust a mechanic, who can you trust?

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Original NASA ASRS Text

Title: COMMUTER SMT RETURN LAND DUE TO LOW OIL PRESSURE.

Narrative: UPON ARR AT WORK I FOUND THAT THE ACFT WAS IN THE HANGAR AND NOT YET FINISHED WITH A ROUTINE INSPECTION. I SPOKE WITH THE LEAD MECH AND HE INDICATED IT WOULD BE READY IN ABOUT 45 MINS. A WHILE LATER I CAME BACK INTO THE HANGAR AND DID A PREFLT INSPECTION OF THE AIRPLANE. THE ENG COWLINGS WERE OPENED AND I LOOKED AT THE ENGS FROM GND LEVEL. I ASKED THAT I BE ALLOWED TO CHK THE OIL LEVELS IN THE ENGS PRIOR TO REMOVING THE ACFT FROM THE HANGAR. THE SECOND MECH, REPLIED THAT THE OIL LEVELS WERE FINE, HE HAD CHKED THEM HIMSELF. WHILE IT WAS BEING FUELED I AGAIN CHKED THE ACFT WITH PARTICULAR ATTN TO LATCHES ON THE COWLING AND BAGGAGE DOORS. AT ABOUT 5-10 MINS IN FLT WE OBSERVED A FLUCTUATION IN OIL PRESSURE ON THE R ENG. WE RETURNED TO THE ARPT AND DID A PRECAUTIONARY SHUT DOWN OF THE R ENG IN FLT WHEN THE OIL PRESSURE APPEARED TO BE CLOSE TO REDLINE. THE PROBLEM APPEARS TO BE EITHER A DEFECTIVE OIL CAP OR THE FAILURE OF THE MECH TO PROPERLY SECURE THE CAP. THE CHKING OF THE OIL LEVEL IS AN ITEM NORMALLY PERFORMED BY THE FLC. IN THIS CASE I WAS ASSURED THAT THE OIL LEVEL WAS OKAY BY THE MECH I HAD OBSERVED WORKING ON AND INSPECTING THE ENG. HIS QUALIFICATIONS TO MAKE OBSERVATIONS AND COMMENTS REGARDING THE CONDITION AND AIRWORTHINESS OF THE ENG ARE FAR SUPERIOR TO MINE. I DEFERRED TO HIS JUDGEMENT IN THIS MATTER. AFTER ALL, IF YOU CAN'T TRUST A MECH, WHO CAN YOU TRUST?

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.