Mosinee

During cruise flight, the pilot reported to an air traffic controller that the airplane was having engine fuel pressure problems. The controller advised the pilot of available airports for landing if necessary and asked the pilot's intentions. The pilot chose to continue the flight. GPS data recorded by an onboard avionics system indicated that the engine had momentarily lost total power about 20 seconds before the pilot reported a problem to the controller. About 7 minutes later, when the airplane was about 7,000 feet above ground level, the engine lost total power again, and power was not restored for the remainder of the flight. The pilot attempted to glide to an airport about 10 miles away, but the airplane crashed in a field about 3 miles from the airport. GPS data showed a loss of fuel pressure before each of the engine power losses and prolonged lateral g forces consistent with a side-slip flight condition. The rudder trim tab was found displaced to the left about 3/8 inch. Flight testing and recorded flight data revealed that the rudder trim tab displacement was consistent with that required to achieve no side slip during a typical climb segment. The GPS and flight data indicated that the lateral g-forces increased as the airplane leveled off and accelerated, indicating that the automatic rudder trim feature of the yaw damper system was either not engaged or not operating. The recorded data indicated autopilot system engagement, which should have automatically engaged the yaw damper system. However, the data indicated the yaw damper was not engaged; the yaw damper could have subsequently been turned off by several means not recorded by the avionics system. Testing of the manual electric rudder (yaw) trim system revealed no anomalies, indicating that the pilot would have still been able to trim the airplane using the manual system. It is likely that the pilot's failure to properly trim the airplane's rudder led to a prolonged uncoordinated flight condition. Although the fuel tank system is designed to prevent unporting of the fuel lines during momentary periods of uncoordinated flight, it is not intended to do so for extended periods of uncoordinated flight. Therefore, the fuel tank feed line likely unported during the prolonged uncoordinated flight, which resulted in the subsequent loss of fuel pressure and engine power. The propeller and propeller controls were not in the feathered position, thus the windmilling propeller would have increased the airplane's descent rate during the glide portion of the flight. The glide airspeed used by the pilot was 20 knots below the airspeed recommended by the Pilot's Operating Handbook (POH), and the reduced airspeed also would have increased the airplane's descent rate during the glide. The flight and GPS data indicated that the airplane had a gliding range of about 16 nautical miles from the altitude where the final loss of engine power occurred; however, the glide performance was dependent on several factors, including feathering the propeller and maintaining the proper airspeed, neither of which the pilot did. Although the POH did not contain maximum range glide performance data with a windmilling propeller, based on the available information, it is likely that the airplane could have glided to the alternate airport about 10 miles away if the pilot had followed the proper procedures.

Pilot was cleared for an ILS approach at his destination, and requested to report altitude of 3,000 feet on the approach. This was the last radio transmission received from the pilot. Aircraft was found in soft field six miles from the airport. Landing gear was up, flaps were down. Fisherman nearby reported hearing the aircraft maneuvering at low altitude. He reported that the engines sounded fine, but the sound was changing in pitch and intensity. He reported that got quiet just a few seconds before he heard the impact. The investigation revealed that there was evidence of a fire in the nose baggage compartment. The cabin heater is located in the nose baggage compartment, and had a recent history of discrepancies. The pilot, sole on board, was killed.

The on-demand air taxi airplane collided with trees and terrain during a third attempt at an ILS approach. The airplane crashed approximately two miles beyond the airport on the extended centerline of the landing runway. In an interview the pilot related that on his first approach to the airport he saw the runway and observed vehicles on the taxiway as he performed his missed approach. When he was asked the reason for the second missed approach he said it was because of instrument fluctuations on his course direction indicator. During this period he asked that the lights be set to high intensity because he could not see them. The lights were verified as being set for high intensity. He did not remember anything of the third approach after he passed the outer marker. Snow removal operations were in progress during the period the accident airplane was making approaches to the airport.

The pilot received numerous weather briefings/updates before takeoff, which included two pilot reports of windshear by aircraft on the approach into Appleton. Shortly after takeoff convective sigmet 1E was transmitted by the radar controller on the same frequency he was working N87163. This sigmet called for embedded thunderstorms. About 10 minutes later, while being vectored for the approach into Appleton, the pilot was given heading deviations because of weather. The aircraft crashed 1/2 mile from the approach end of the runway. A witness whose residence is located between the OM and MM for the ILS approach reported a 'huge downpour' with 'very strong winds' at the time of the accident. Wreckage examination revealed that all power controls for both engines were in the full forward position, and that the left and right main landing gear mounting trunnions were displaced upward into the wing fuel tanks. The pilot, sole on board, was killed.