Narrative:

The previous crew prepped the aircraft; including preflight. Upon arriving at the airport; I was briefed on weather and NOTAMS and did a walkaround inspection of the aircraft. I checked to make sure that the cowls were closed and fastened; fuel caps were secure and that all plugs and covers were removed. Upon reaching our cruise altitude; we noticed that the #2 engine oil pressure gauge was fluctuating slightly. A short time later the torque gauge also began fluctuating. A decision was made to abort the flight and return to our home base. Shortly after turning around; the 2 gauges began fluctuating erratically through an even wider range of indication; with the oil pressure gauge fluctuating from the green arc to just above the minimum redline. We decided to shut down that engine; declare an emergency and divert to a closer airport. Our nearest suitable airport had runway 15 available with winds from 210 degrees at 20 kts gusting to 30 kts. The next nearest suitable airport had runway 16 available with wind from 180 degrees at 15 kts. Both airports have crash fire rescue equipment; but only the latter had a control tower operating at the time. We elected to go to the latter airport. Weather was VFR with cavu. An uneventful; single engine visual approach and landing was conducted. Upon visual inspection of the engine; it was found that the oil dipstick was in the unlocked position; allowing more than half of the total engine oil to siphon out of the dipstick tube. If I had included an inspection of the engine oil level and security of the dipstick on my walkaround; I would have most likely discovered this problem before departing. Obviously; inspection of the dipstick security will be added to required items on the walkaround inspection. Also; we will be training all pilots in our department on improved preflight inspection procedures to include visually inspecting the security of the dipstick.

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Original NASA ASRS Text

Title: BE20 flight crew experiences fluctuating oil pressure and elects to shut down the engine and divert. A loose oil dipstick permitted oil loss.

Narrative: The previous crew prepped the aircraft; including preflight. Upon arriving at the airport; I was briefed on weather and NOTAMS and did a walkaround inspection of the aircraft. I checked to make sure that the cowls were closed and fastened; fuel caps were secure and that all plugs and covers were removed. Upon reaching our cruise altitude; we noticed that the #2 engine oil pressure gauge was fluctuating slightly. A short time later the torque gauge also began fluctuating. A decision was made to abort the flight and return to our home base. Shortly after turning around; the 2 gauges began fluctuating erratically through an even wider range of indication; with the oil pressure gauge fluctuating from the green arc to just above the minimum redline. We decided to shut down that engine; declare an emergency and divert to a closer airport. Our nearest suitable airport had Runway 15 available with winds from 210 degrees at 20 kts gusting to 30 kts. The next nearest suitable airport had Runway 16 available with wind from 180 degrees at 15 kts. Both airports have Crash fire rescue equipment; but only the latter had a Control Tower operating at the time. We elected to go to the latter airport. Weather was VFR with CAVU. An uneventful; single engine visual approach and landing was conducted. Upon visual inspection of the engine; it was found that the oil dipstick was in the unlocked position; allowing more than half of the total engine oil to siphon out of the dipstick tube. If I had included an inspection of the engine oil level and security of the dipstick on my walkaround; I would have most likely discovered this problem before departing. Obviously; inspection of the dipstick security will be added to required items on the walkaround inspection. Also; we will be training all pilots in our department on improved preflight inspection procedures to include visually inspecting the security of the dipstick.

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.