Narrative:

On visual approach from IMC to the runway; we were unstabilized at 500 AGL and the captain; as pilot flying; initiated a go around. As the first officer placed the ctot [continuous torque on takeoff] switch to apr [automatic power reserve]; the right engine feathered and the crew noted the master warning and master caution annunciations and identified and verified that the right engine had auto-coarsened by observing the right prop oil pressure at zero. The right engine torque was at zero and the right engine prop RPM all confirmed the prop oil pressure indication.the captain then called for; and the crew executed; the QRH for engine failure which called for the crew to shut down and secure the engine. We notified ATC that we had lost the right engine and we would be extending our upwind and downwind and returning for landing on the runway. During the first officer's (captain briefed) PA announcement the captain declared an emergency with ATC and clarified our intention to land. ATC issued landing clearance and asked if assistance was needed.a normal twenty flaps landing was uneventful and the aircraft was slowed and taxied clear of the runway. ATC advised us that crash fire rescue equipment was going to follow us in. We acknowledged and completed the after landing checklist. The captain made a PA to reassure the passengers. We then proceeded to the gate and the captain called for the engine shutdown. The parking checklist was completed and the captain greeted the passengers as they deplaned. I do not have very much information as to the cause of this auto-coarsen/engine failure event. I did note that the first officer had unintentionally closed both lp [low pressure] bleed valves instead of the hp [high pressure] bleed valves during the original before landing checklist. The lp bleed valves were selected back on and the hp bleed valves were closed. It is my estimate that this occurred approximately forty five seconds before the auto-coarsen event which does not seem to be related due to the time frame; but I thought it would be worth mentioning since the bleed air pressure is a parameter of the auto-coarsen computer.

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Original NASA ASRS Text

Title: Following a go around due to an unstabilized condition at 500 AGL the flight crew of an SF340 experienced an unexplained auto-coarsening of the right propeller. Per the QRH; they shut down the engine and returned for an uneventful landing.

Narrative: On visual approach from IMC to the runway; we were unstabilized at 500 AGL and the Captain; as pilot flying; initiated a go around. As the First Officer placed the CTOT [Continuous Torque On Takeoff] switch to APR [Automatic Power Reserve]; the right engine feathered and the crew noted the Master Warning and Master Caution Annunciations and identified and verified that the right engine had auto-coarsened by observing the Right Prop Oil Pressure at zero. The Right Engine Torque was at zero and the Right Engine Prop RPM all confirmed the Prop Oil Pressure Indication.The Captain then called for; and the crew executed; the QRH for Engine Failure which called for the crew to shut down and secure the engine. We notified ATC that we had lost the right engine and we would be extending our upwind and downwind and returning for landing on the runway. During the First Officer's (Captain briefed) PA announcement the Captain declared an emergency with ATC and clarified our intention to land. ATC issued landing clearance and asked if assistance was needed.A normal twenty flaps landing was uneventful and the aircraft was slowed and taxied clear of the runway. ATC advised us that CFR was going to follow us in. We acknowledged and completed the After Landing Checklist. The Captain made a PA to reassure the passengers. We then proceeded to the gate and the Captain called for the engine shutdown. The Parking Checklist was completed and the Captain greeted the passengers as they deplaned. I do not have very much information as to the cause of this auto-coarsen/engine failure event. I did note that the First Officer had unintentionally closed both LP [Low Pressure] Bleed Valves instead of the HP [High Pressure] Bleed Valves during the original Before Landing Checklist. The LP Bleed Valves were selected back on and the HP Bleed Valves were closed. It is my estimate that this occurred approximately forty five seconds before the Auto-coarsen event which does not seem to be related due to the time frame; but I thought it would be worth mentioning since the bleed air pressure is a parameter of the Auto-coarsen Computer.

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.