Narrative:

Previous flight in aircraft (by another pilot) had resulted in large amount of oil loss. Cause was determined by a&P to be a loose oil filler neck. After tightening and safety wiring, oil was replenished and engine was ground run for several mins with no leaks and normal oil pressure. I departed with a flight instructor to practice commercial pilot maneuvers. Monitored oil pressure, checked normal. After approximately .6 hours flight, propeller oversped. I checked oil pressure, it was now almost 0 psi. Instructor told me to fly to nearest airport, where a normal (although rushed) landing occurred. After removing cowling, engine was again inspected and it was determined that an oil hose to the oil pressure gauge was loose at the fitting, and had probably allowed oil to escape. The oil had been changed by another a&P 3 hours prior to the flight, and the hose in question is in a position where inspection of the oil screen would be difficult without its removal. It appears that after servicing the screen, the hose was replaced but not tightened. Lessons learned: 1) following any maintenance, a test flight in the vicinity of an airport, VFR, is a must. 2) do not assume that just because a probable cause of some problem is discovered that it is the only cause -- carefully inspect all components, system, etc.

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Original NASA ASRS Text

Title: A BEECH SIERRA LOSES OIL PRESSURE DURING FLT AND MAKES AN IMMEDIATE LNDG WITH NO OIL PRESSURE. NO ACFT DAMAGE.

Narrative: PREVIOUS FLT IN ACFT (BY ANOTHER PLT) HAD RESULTED IN LARGE AMOUNT OF OIL LOSS. CAUSE WAS DETERMINED BY A&P TO BE A LOOSE OIL FILLER NECK. AFTER TIGHTENING AND SAFETY WIRING, OIL WAS REPLENISHED AND ENG WAS GND RUN FOR SEVERAL MINS WITH NO LEAKS AND NORMAL OIL PRESSURE. I DEPARTED WITH A FLT INSTRUCTOR TO PRACTICE COMMERCIAL PLT MANEUVERS. MONITORED OIL PRESSURE, CHKED NORMAL. AFTER APPROX .6 HRS FLT, PROP OVERSPED. I CHKED OIL PRESSURE, IT WAS NOW ALMOST 0 PSI. INSTRUCTOR TOLD ME TO FLY TO NEAREST ARPT, WHERE A NORMAL (ALTHOUGH RUSHED) LNDG OCCURRED. AFTER REMOVING COWLING, ENG WAS AGAIN INSPECTED AND IT WAS DETERMINED THAT AN OIL HOSE TO THE OIL PRESSURE GAUGE WAS LOOSE AT THE FITTING, AND HAD PROBABLY ALLOWED OIL TO ESCAPE. THE OIL HAD BEEN CHANGED BY ANOTHER A&P 3 HRS PRIOR TO THE FLT, AND THE HOSE IN QUESTION IS IN A POS WHERE INSPECTION OF THE OIL SCREEN WOULD BE DIFFICULT WITHOUT ITS REMOVAL. IT APPEARS THAT AFTER SVCING THE SCREEN, THE HOSE WAS REPLACED BUT NOT TIGHTENED. LESSONS LEARNED: 1) FOLLOWING ANY MAINT, A TEST FLT IN THE VICINITY OF AN ARPT, VFR, IS A MUST. 2) DO NOT ASSUME THAT JUST BECAUSE A PROBABLE CAUSE OF SOME PROB IS DISCOVERED THAT IT IS THE ONLY CAUSE -- CAREFULLY INSPECT ALL COMPONENTS, SYS, ETC.

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.