Narrative:

Part 135 flight with one passenger. I was the pilot flying. Normal takeoff avoiding thunderstorms after departure. 40 minutes into flight at FL380 M.76 we heard and felt two thumps and then constant vibration. The aircraft began to yawn a bit. I checked engine indications and found #1 engine oil pressure and N2 were rapidly decreasing. I completed the memory items for low oil pressure indication and closed the #1HP cock after confirming with the non flying pilot. I directed the non flying pilot to declare an emergency and request an immediate decent. The non flying pilot complied and requested a diversion to the nearest suitable airport. ATC responded ZZZ in 12 o'clock and approximately 40 miles. We were given a constant decent into ZZZ and completed the engine shutdown of failure in flight and then the one engine inoperative approach and landing checklists. As soon as the engine was contained the passenger was briefed on the situation. We discussed the possibility of an evacuation and what we would each be responsible for. Initially I requested to hold in order to reduce to maximum landing weight and the non flying pilot suggested we land overweight. I agreed and we asked to continue for the approach. We landed 390 pounds over maximum landing weight. We requested the fire trucks be in place and that they follow us to a stop on the runway. Landing was uneventful and we had no fire. After the condition of the aircraft was determined to be safe by the fire crew we requested to clear the runway and taxi to the FBO. The engine appeared to have not obvious physical damage and no loss of fluid. The chip detect was tripped. I contacted the acp on duty and debriefed.supplemental info from acn 832183: there was a loud clunk like the landing gear coming up. It was evident that the noise came from the left side of the aircraft. The captain flew the airplane while I proceeded with the engine shutdown or failure in flight checklist. During this time I also took off my headset and notified our passenger that we have had an engine failure and we are landing shortly. The passenger was calm and actually reading a paper.

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Original NASA ASRS Text

Title: Enroute at FL380 HS-125-900 flight crew felt two thumps from the left-hand side of the aircraft. Number 1 engine oil pressure and N1 were rapidly decreasing; engine was secured and an uneventful divert resulted.

Narrative: Part 135 flight with one passenger. I was the pilot flying. Normal takeoff avoiding thunderstorms after departure. 40 minutes into flight at FL380 M.76 we heard and felt two thumps and then constant vibration. The aircraft began to yawn a bit. I checked engine indications and found #1 engine oil pressure and N2 were rapidly decreasing. I completed the memory items for low oil pressure indication and closed the #1HP cock after confirming with the non flying pilot. I directed the non flying pilot to declare an emergency and request an immediate decent. The non flying pilot complied and requested a diversion to the nearest suitable airport. ATC responded ZZZ in 12 o'clock and approximately 40 miles. We were given a constant decent into ZZZ and completed the engine shutdown of failure in flight and then the one engine inoperative approach and landing checklists. As soon as the engine was contained the passenger was briefed on the situation. We discussed the possibility of an evacuation and what we would each be responsible for. Initially I requested to hold in order to reduce to maximum landing weight and the non flying pilot suggested we land overweight. I agreed and we asked to continue for the approach. We landed 390 LBS over maximum landing weight. We requested the fire trucks be in place and that they follow us to a stop on the runway. Landing was uneventful and we had no fire. After the condition of the aircraft was determined to be safe by the fire crew we requested to clear the runway and taxi to the FBO. The engine appeared to have not obvious physical damage and no loss of fluid. The chip detect was tripped. I contacted the ACP on duty and debriefed.Supplemental info from ACN 832183: There was a loud clunk like the landing gear coming up. It was evident that the noise came from the left side of the aircraft. The Captain flew the airplane while I proceeded with the engine shutdown or failure in flight checklist. During this time I also took off my headset and notified our passenger that we have had an engine failure and we are landing shortly. The passenger was calm and actually reading a paper.

Data retrieved from NASA's ASRS site as of April 2012 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.