Narrative:

During an IFR flight from alliance, northeast, to rockford, il, I experienced loss of oil pressure on the left engine of an small aircraft. I immediately requested vectors to the nearest airport which was sac city (ski). During the descent to landing, the oil pressure dropped to red line on the left engine so I shut it down and feathered the propeller. I experienced no other difficulties during the flight. The next day (I waited for daylight to inspect the cause), the mechanic and I discovered that the throttle cable was resting against the oil filter. It appeared that, over time, engine vibration had caused the throttle cable to rub a hole in the oil filter causing the loss of pressure when it finally broke through. The mechanic replaced the filter and secured the throttle so it wouldn't occur again. This problem could not be seen during a preflight because it requires removing the cowling to see the filter and throttle cable. I believe this problem would never have occurred if the mechanic that performed the previous 100 hour inspection had properly secured the throttle cable instead of allowing it to rest on the oil filter.

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Original NASA ASRS Text

Title: AN SMA TWIN SHUT DOWN AN ENG DUE TO OIL LOSS. IT LANDED SAFETY ENRTE.

Narrative: DURING AN IFR FLT FROM ALLIANCE, NE, TO ROCKFORD, IL, I EXPERIENCED LOSS OF OIL PRESSURE ON THE L ENG OF AN SMA. I IMMEDIATELY REQUESTED VECTORS TO THE NEAREST ARPT WHICH WAS SAC CITY (SKI). DURING THE DSCNT TO LNDG, THE OIL PRESSURE DROPPED TO RED LINE ON THE L ENG SO I SHUT IT DOWN AND FEATHERED THE PROP. I EXPERIENCED NO OTHER DIFFICULTIES DURING THE FLT. THE NEXT DAY (I WAITED FOR DAYLIGHT TO INSPECT THE CAUSE), THE MECH AND I DISCOVERED THAT THE THROTTLE CABLE WAS RESTING AGAINST THE OIL FILTER. IT APPEARED THAT, OVER TIME, ENG VIBRATION HAD CAUSED THE THROTTLE CABLE TO RUB A HOLE IN THE OIL FILTER CAUSING THE LOSS OF PRESSURE WHEN IT FINALLY BROKE THROUGH. THE MECH REPLACED THE FILTER AND SECURED THE THROTTLE SO IT WOULDN'T OCCUR AGAIN. THIS PROB COULD NOT BE SEEN DURING A PREFLT BECAUSE IT REQUIRES REMOVING THE COWLING TO SEE THE FILTER AND THROTTLE CABLE. I BELIEVE THIS PROB WOULD NEVER HAVE OCCURRED IF THE MECH THAT PERFORMED THE PREVIOUS 100 HR INSPECTION HAD PROPERLY SECURED THE THROTTLE CABLE INSTEAD OF ALLOWING IT TO REST ON THE OIL FILTER.

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.