Narrative:

Descending through FL180; received both EICAS 'left engine low oil pressure' and observed indicated oil pressure dropping rapidly. PF reduced left engine thrust setting to idle while PNF complied with QRH procedure. Performed controled shutdown of left engine in-flight and accomplished all single-engine procedures. Declared emergency with center and received expedited vectors into ZZZ; which was the nearest suitable airport. Also notified company flight control and maintenance. Landing was uneventful and passenger did not seem overly alarmed. Maintenance reported that they found an oil inspection port cap had come loose and was missing.

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Original NASA ASRS Text

Title: A CL65 FLT CREW EXPERIENCED LOSS OF OIL PRESSURE IN L ENG. THEY DECLARED AN EMERGENCY AND LANDED AT NEAREST SUITABLE AIRPORT.

Narrative: DSNDING THROUGH FL180; RECEIVED BOTH EICAS 'L ENG LOW OIL PRESSURE' AND OBSERVED INDICATED OIL PRESSURE DROPPING RAPIDLY. PF REDUCED L ENG THRUST SETTING TO IDLE WHILE PNF COMPLIED WITH QRH PROC. PERFORMED CTLED SHUTDOWN OF L ENG INFLT AND ACCOMPLISHED ALL SINGLE-ENG PROCS. DECLARED EMER WITH CTR AND RECEIVED EXPEDITED VECTORS INTO ZZZ; WHICH WAS THE NEAREST SUITABLE ARPT. ALSO NOTIFIED COMPANY FLT CTL AND MAINT. LNDG WAS UNEVENTFUL AND PAX DID NOT SEEM OVERLY ALARMED. MAINT RPTED THAT THEY FOUND AN OIL INSPECTION PORT CAP HAD COME LOOSE AND WAS MISSING.

Data retrieved from NASA's ASRS site as of January 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.