Narrative:

The captain and I picked up the aircraft at the maintenance hangar. The aircraft had a maintenance inspection that previous night. I did the normal preflight inspections. We taxied to the gate on both engines, performing the normal preflight checks. We shutdown the #2 engine en route. We boarded passenger, taxied out to the runway on #1 engine, starting #2 en route. Normal takeoff. Normal engine parameters. Climbing through 9000 MSL, we experienced a low engine oil pressure warning on #1 engine. We decided to shutdown the engine using the 'precautionary engine shutdown' checklist. We returned to cvg. Landing was uneventful. When we arrived at the gate maintenance was standing by. Maintenance found the #1 engine oil cap not properly installed. During preflight inspection both oil caps appeared to be installed properly.

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Original NASA ASRS Text

Title: AN LTT ACR CREW HAD TO SHUTDOWN 1 OF THEIR ENGS BECAUSE THE ENG'S OIL DRAINED OUT OF A LOOSE OIL TANK CAP.

Narrative: THE CAPT AND I PICKED UP THE ACFT AT THE MAINT HANGAR. THE ACFT HAD A MAINT INSPECTION THAT PREVIOUS NIGHT. I DID THE NORMAL PREFLT INSPECTIONS. WE TAXIED TO THE GATE ON BOTH ENGS, PERFORMING THE NORMAL PREFLT CHKS. WE SHUTDOWN THE #2 ENG ENRTE. WE BOARDED PAX, TAXIED OUT TO THE RWY ON #1 ENG, STARTING #2 ENRTE. NORMAL TKOF. NORMAL ENG PARAMETERS. CLBING THROUGH 9000 MSL, WE EXPERIENCED A LOW ENG OIL PRESSURE WARNING ON #1 ENG. WE DECIDED TO SHUTDOWN THE ENG USING THE 'PRECAUTIONARY ENG SHUTDOWN' CHKLIST. WE RETURNED TO CVG. LNDG WAS UNEVENTFUL. WHEN WE ARRIVED AT THE GATE MAINT WAS STANDING BY. MAINT FOUND THE #1 ENG OIL CAP NOT PROPERLY INSTALLED. DURING PREFLT INSPECTION BOTH OIL CAPS APPEARED TO BE INSTALLED PROPERLY.

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.