Date: 201210
Local time of day: 0001-0600
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Light: Night
Aircraft: BAe 125 Series 800
Operator: Air Taxi
Operating under: Part 135
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Powerplant Lubrication System
Component problem: Malfunctioning
Reporter organization: Air Taxi
Reporter function: First Officer; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Other / Unknown
Anomaly: Aircraft Equipment Problem Critical
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Inflight Shutdown; Flight Crew Diverted; Flight Crew Landed in Emergency Condition; General Declared Emergency; General Maintenance Action
Contributing factors: Aircraft; Human Factors
Primary problem: Aircraft

Narrative: The plane was stabilized at FL400 and Mach 0.75 when the Captain noticed the oil indication [high] on the #1 engine.  He brought it to my attention as he began reducing power to try to keep the pressure within normal levels.  It was soon apparent that even at idle the #1 oil indications were still exceeding the limitations. The Captain transferred the flight controls to me and I coordinated a lower flight level with Center because the plane was not able to maintain a safe airspeed at our filed altitude.  As we descended the Controller asked what our problem was and I responded that we were monitoring an engine indication and were not declaring an emergency at this time; but would keep him advised.  During this time; the Captain was on the phone with Dispatch and Maintenance Control.  I'm not sure the names of the people he was talking to; but he had a frustrated tone in his voice.  Once he was off the  phone he informed me that Maintenance wanted us to continue to our destination.  This would not be a safe option to continue for over 2 hours single engine; at night with passengers; and a very likely engine shutdown.  As we continued to descend the oil pressure continued to rise and it became apparent we would indeed need to secure the engine.  We delayed shutting the engine down because all other indications  were normal; and we wanted to be below 20;000 feet so we could start the APU before we secured the engine.  After the Captain informed the passengers of our situation; we declared an emergency and diverted. The Captain took the controls and radios as I performed the engine shutdown procedures and single engine landing procedures per the QRH.  We were in VMC conditions the entire time; but got vectors from ATC to establish us on a base for landing.  After completing all checklists we made an uneventful landing and cleared the runway.  We taxied safely to the FBO and deplaned our passengers.[On a previous occasion] during a dual engine swap the mechanics did not hook up the air line off the #2 engine for the rudder bias.  This was not detected until a crew attempted to fly.  These same mechanics also failed to properly adjust an engine oil pressure part that resulted in the incident above.  I'm not a mechanic; but it would be prudent to do a proper test flight on a plane that had an engine change; much less two.  The plane should not have been released to fly passengers without a test flight verifying proper working order of the new engines.  Since Dispatch knew this plane was having new engines put on they should not have released the plane before a test flight was done and any additional mechanical issues dealt with.  Maintenance Control suggesting we fly a crippled airplane for over 2 hours so it would be closer to a more convenient facility is not appropriate.  Also according  to the Captain; the person had limited knowledge of the jet and didn't want to call to get answers due to the time of the day.  Maintenance should be someone we can trust to help and bring another view point to a situation to solve it quickly and safely.  They need to know they are a tool for us to use.  Maybe the old adage of; 'Would you put your spouse and kids in that airplane or not?' should be reviewed with them.




Synopsis: Hawker 850 First Officer experiences high oil pressure at FL400.  Maintenance indicates that the crew should continue two hours to destination.  When the oil pressure cannot be maintained within limits by reducing thrust the engine is shut down and the flight diverts to a suitable airport.