What happened
During the cruise phase of the flight, the crew observed the illumination of both propeller secondary low pitch stop (SLPS) lights. This indication suggested that the SLPS system was preventing both propellers from moving below the low pitch hydraulic mechanical stop. The failure occurred sequentially, with the right propeller light activating first, followed by the left light roughly one minute later. Attempts to follow emergency procedures to resolve the issue were unsuccessful.
During the flight, the right propeller feathered. While the aircraft was operating on a single engine, the crew encountered further issues with the propeller governor. Due to the mechanical situation, the crew decided to divert to a nearby airport with shorter runways, located approximately 3.2 nautical miles northwest, instead of continuing to a larger air carrier airport 8.5 nautical miles away.
During the approach to runway 35, the captain executed a close-in right base leg at a speed of 155 knots, which was 51 knots above the single-engine reference speed. The aircraft transitioned to final approach with the landing gear and flaps in the retracted position. The aircraft subsequently overshot the 2,688-foot runway, contacting a taxiway near the departure end of the runway. The aircraft then struck several obstacles before coming to a stop at a residential house. A fire following the impact destroyed the cockpit, the cabin, and portions of both wings. There were 0 fatalities reported in the provided text.
Findings
An investigation of the engines, propellers, and airframe showed no signs of mechanical failure or malfunction prior to the impact. While the cause for the simultaneous SLPS light illumination remains undetermined, the investigation noted that the aircraft was operating significantly above single-engine reference speed during the approach.