Narrative:

Climbing through 14;000 ft on vectors from ATC to join the 197 degree radial; I was alerted to a low oil pressure light on the annunciator panel for the left engine. I verified the pressure was indeed dropping. I called ATC; told him I had a low oil pressure warning and that pressure was dropping on the left side; and requested to return. The controller gave me vectors for a heading back and an altitude to descend to.about 3 minutes later; the oil pressure was continuing to drop and I decided to shut down and secure the left engine to prevent damage to both myself and the aircraft from an engine seize. I shut down the left engine while ATC gave me vectors for the right downwind. I completed the engine out; engine shutdown; descent; and before landing checklists. I then made a visual approach (right traffic) to the runway. Upon a successful landing; I declined further assistance from ATC and stated that I could taxi on my own. I was told to squawk 1200 and then I was given a taxi route to the south cargo ramp where I had originated from with emergency equipment following me to ensure a safe arrival.a company mechanic came out to inspect the left engine after I had parked and secured the aircraft. It was discovered that the oil dipstick had not been secured. The oil had leaked out through the dipstick tube and into the cowling; gear well; and out the upper and lower portions of the aft cowling attachment to the wing.I then completed and submitted a company irregularity report and notified the company director of ops; and all 3 chief pilots of the incident described above. Corrective actions were discussed and implemented to ensure this doesn't happen again.

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Original NASA ASRS Text

Title: BE99 pilot experiences low oil pressure on the left engine during climb out and advises ATC. Vectors back to the departure airport are received and the engine is shut down. Post flight revealed that the oil dipstick had not been secured and the engine oil was going overboard through the dipstick tube.

Narrative: Climbing through 14;000 ft on vectors from ATC to join the 197 degree radial; I was alerted to a low oil pressure light on the annunciator panel for the left engine. I verified the pressure was indeed dropping. I called ATC; told him I had a low oil pressure warning and that pressure was dropping on the left side; and requested to return. The controller gave me vectors for a heading back and an altitude to descend to.About 3 minutes later; the oil pressure was continuing to drop and I decided to shut down and secure the left engine to prevent damage to both myself and the aircraft from an engine seize. I shut down the left engine while ATC gave me vectors for the right downwind. I completed the engine out; engine shutdown; descent; and before landing checklists. I then made a visual approach (right traffic) to the runway. Upon a successful landing; I declined further assistance from ATC and stated that I could taxi on my own. I was told to squawk 1200 and then I was given a taxi route to the south cargo ramp where I had originated from with emergency equipment following me to ensure a safe arrival.A company mechanic came out to inspect the left engine after I had parked and secured the aircraft. It was discovered that the oil dipstick had not been secured. The oil had leaked out through the dipstick tube and into the cowling; gear well; and out the upper and lower portions of the aft cowling attachment to the wing.I then completed and submitted a company irregularity report and notified the company director of ops; and all 3 chief pilots of the incident described above. Corrective actions were discussed and implemented to ensure this doesn't happen again.

Data retrieved from NASA's ASRS site 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.