Pierre

The pilot reported that before takeoff on the cross-country flight, the airplane contained 100 gallons of fuel, with 11 gallons in the header fuel tank, and the airplane’s automatic fuel transfer system was configured as per the checklist. No anomalies were noted during the engine start, takeoff, and initial climb. About 7 minutes into the flight and climbing through 12,000 ft mean sea level (msl), the engine sustained an abrupt loss of power that was confirmed by the loss of torque and engine compressor turbine rpm (Ng) speed. The pilot noted no cockpit warning or abnormal indications before the loss of engine power. The pilot declared an emergency and then executed a 180° turn back to the departure airport. The pilot attempted two engine restarts, and both were unsuccessful. Unable to make it back to the airport, the pilot executed an off airport forced landing. During the forced landing, the airplane sustained substantial damage to the fuselage and both wings. A postaccident examination of the airframe, fuel system components, and functional engine test revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. The fuel transfer pump switch was found in the manual position. The engine’s fuel was provided by the airframe header tank. Avionics data indicated that during the short flight, the header fuel tank quantity consistently decreased, and the airplane’s automatic fuel system did not continually resupply fuel to the header tank. Based on the available data, a functional engine test, and functional testing of the airplane’s fuel system, it is likely the pilot improperly configured the airplane’s fuel transfer system, which prevented the header fuel tank from automatically refilling during the flight and resulted in fuel starvation and total loss of engine power. Although the pilot reported that he had configured the airplane’s automatic fuel transfer system per the checklist, it is likely that the fuel transfer switch was in the manual or OFF position during the flight. In addition, the pilot did not properly monitor the header tank’s fuel quantity.

The airplane was on an instrument flight rules flight in night instrument meteorological conditions when the accident occurred. The airplane had been cleared for an ILS approach and the pilot elected to use a non-published procedure to intercept the final approach. After becoming established on the final approach, the airplane impacted the ground about 7 miles from the destination airport at an elevation approximately the same as the airport elevation. Flight inspections of the instrument approach performed prior to and subsequent to the accident revealed satisfactory performance of both the localizer and glideslope functions. The number one altimeter setting did not match the altimeter setting that was current at the time of the accident. Post accident examination of the altimeters revealed that the number one altimeter read 360 feet high. No determination was made as to whether the discrepancy existed prior to impact. However, the pilot did not report any pre-flight discrepancies with regard to the airplane's altimeters. No other anomalies were found or reported with regard to the airplane's structure or systems.

While cruising at FL240, a propeller (prop) hub arm on the left prop failed, releasing the prop blade, which struck a 2nd blade, breaking off its tip. This resulted in a severe engine vibration and shutdown of the left engine. The left engine was forced downward and inboard on its mounts. The cabin depressurized, possibly from blade contact. The flight crew made an emergency descent and received a vector to divert for an ILS approach to Dubuque. The airplane was incapable of maintaining altitude and descended in instrument conditions. Subsequently, it collided with a silo and crashed about 8 miles south of Dubuque. An investigation revealed the left prop hub failed from fatigue that initiated from multiple initiation sites on the inside diameter surface of the hole for the pilot tube. There was evidence that the fatigue properties of the hub were reduced by a combination of factors, including machining marks or scratches, mixed microstructure, corrosion, decarburization, and residual stresses. All eight occupants were killed, among them George Mickelson, 52, Governor of South Dakota.