Citation II S2/Bravo (C550)
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 85; Flight Crew Total 22549; Flight Crew Type 383
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Returned To Departure Airport; Flight Crew Landed in Emergency Condition; General Flight Cancelled / Delayed; General Maintenance Action
Aircraft; Procedure
Shortly after take-off; we noticed a drop in oil pressure on the number 1 engine. We continued to monitor the oil pressure as it continued to drop. We notified ATC and requested a return to ZZZ. When the oil pressure reached its lower limits we proceeded to complete the engine shutdown per the engine shutdown checklist and [Requested Priority Handling] and made an uneventful landing. Maintenance discovered a crimped O ring which appeared to have been in an oil line since the last engine overhaul.
Citation 550 First Officer reported a loss of oil pressure caused an air turn back and emergency landing.