Date: 201509
Local time of day: 1201-1800
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Light: Daylight
Aircraft: Citationjet (C525/C526) - CJ I / II / III / IV
Operator: Personal
Operating under: Part 91
Flight plan: IFR
Mission: Personal
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Oil Filler Cap
Component problem: Improperly Operated
Reporter organization: Government
Reporter function: Enroute
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Situational Awareness; Workload
Second reporter function: Pilot Flying; Single Pilot
Anomaly: ATC Issue All Types; Aircraft Equipment Problem Less Severe; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control; Person Flight Crew
When detected: In-flight; Pre-flight
Result: Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance; Flight Crew Returned To Departure Airport; General Maintenance Action
Contributing factors: Aircraft; Human Factors
Primary problem: Ambiguous

Narrative: A C525 was level at FL400 and called me and told me that he just lost an engine and needed to return to his departure airport. He was originally going to the Midwest. I asked him if he could stay on his present heading for a moment because I knew he had traffic right under him at FL390. He said he should be able to. I just needed him to diverge from the FL390 traffic so I could start him down and turn him back to the east. I turned the FL390 traffic 20 left to get him out from under the C525 and that was when C525 advised that he was descending and couldn't hold altitude. I said Ok and turned the FL390 traffic 40 Left. I then cleared C525 to descend and maintain FL240. I also had to turn another southbound aircraft out of his way. I turned C525 to 190 heading and then once he was under the FL390 traffic I cleared him to this destination. C525 and the FL390 traffic did lose separation.Keep calling traffic the whole time.


Second narrative: Cruising in normal operations at FL400 when I got a Crew Alert System (CAS) message that there was low oil pressure on the right engine. Using the checklist I followed the instructions to first reduce N1 to 80% and see if the message extinguished. It didn't so the next procedure was a precautionary engine shut down. After securing the engine shutdown I contacted ATC to advise that I had lost an engine and I wanted to divert back to our airport of origin. She asked if I could maintain altitude I advised I could; but not long as I would not maintain a safe airspeed. When I was 30 KTS over Vref I advise ATC that I was in a 1;000 FPM descent. I maintained heading until I was given a vector and instructed to descend to FL250 which was 1;000 feet below my single engine ceiling. She asked if I wanted to divert to a large international airport and I said no the departure airport was better for me. I made this choice because of the high descent rate of series of 360 turns that would be required which I decided was unstable and inferior to my plan to go to my departure airport I continued my descent until about 40 miles from destination when I had to increase the rate of descent to make the altitude required and assigned. The nearby airport TRSA asked if I needed equipment at the airport and I replied negative just vectors to the ILS at my departure airport was fine. We were stabilized and under complete control. I taxied into the ramp without incident. The fault was the cap on the oil filler has become loose somehow and the fluid had leaked out slowly. I replaced the oil and did a static run with satisfactory results and did a short post maintenance review test flight with all systems and engines running and reporting fine and within appropriate limits.


Synopsis: A C525 pilot at FL400 reported a Crew Alert System (CAS) Low Oil Pressure light and requested clearance to their departure airport. The controller working the flight vectored another aircraft to allow an enroute descent. The pilot discovered a loose engine oil cap.