What happened
On April 9, 2016, a Cessna S550 Citation S/2, registered as EC-LQF, was performing a medical repatriation flight from Zurich to Valencia. The aircraft was carrying a crew of two and two passengers, including a patient and a doctor.
After departing Zurich at 11:50 UTC, the flight crew began a climb toward flight level 310. While passing through flight level 240, the pilots observed a slow but steady decline in oil pressure within the right engine. In response to this developing issue, the crew shut down the right engine as a precautionary measure and declared an emergency. The aircraft proceeded to divert to Geneva, where it landed safely on a single engine at 11:53 UTC. There were no injuries to the crew or passengers, and the aircraft sustained no damage.
The investigation
An inspection of the aircraft was conducted in Geneva on April 10, 2016. During the process of replenishing engine oil, investigators identified a leak between the oil pressure pump and the engine casing. The source of the leak was traced to a faulty seal on the oil pressure pump.
An examination of the oil filter revealed no abnormal debris or metallic particles. Because the sealing ring between the pump and the engine housing cannot be replaced individually on this specific model, the technician replaced the entire oil pressure pump assembly. Subsequent ground testing of the engine confirmed that the oil leak had been resolved.