WPR11LA291

The pilot and the flight instructor were in the process of starting the climb after takeoff in the airplane that the pilot had recently purchased. As they started to turn toward the practice area, the airplane’s water-cooled engine suddenly began to overheat. The pilots therefore initiated a turn back toward the airport, but the engine started losing power. Because it appeared that they would not be able to make it to the airport, the flight instructor took over and landed the airplane in a nearby soft field covered with a crop of wheat. During the landing roll, the airplane nosed over and a fire began, which eventually consumed much of the airframe structure and engine components. Although the engine cooling system was missing a mandatory cooling system vent line, the teardown examination did not reveal any evidence of overheating or component seizure in the engine’s top end. The investigation also determined that the failure of the crankshaft to rotate after the accident was due to the postaccident melting and subsequent solidification of the phenolic MAG bearing cages due to the postimpact fire. The investigation was unable to determine the reason for the loss of engine power.

On June 27, 2011, about 0930 Pacific daylight time, an experimental Richard Challenger II, N9103L, nosed over during a power-off forced landing on soft vegetation covered terrain about one-half mile west of Moses Lake Municipal Airport, Moses Lake, Washington. The flight instructor received serious injuries, and the private pilot received minor injuries. The airplane, which was owned and operated by the private pilot, sustained substantial damage. The local 14 Code of Federal Regulations Part 91 instructional flight, which was taking place in visual meteorological conditions, departed Moses Lake Municipal Airport about two minutes prior to the accident. No flight plan had been filed. According to the Federal Aviation Administration (FAA) inspector who responded to the scene, the private pilot had recently purchased the airplane and was getting checked out in it by the flight instructor. During the first flight of the day, the owner made two takeoffs and two landings, and the flight was then terminated so that the owner and the instructor could discuss the next phase of the checkout, which was to take place beyond the traffic pattern. The owner, accompanied by the instructor, then took off for the second flight, and just after passing the end of the runway and starting to climb out in the direction of the planned practice area, the engine started overheating. They therefore elected to return to the airport, but as they started to turn back, the engine started losing power. Since it appeared that they were not going to be able to make it back to the airport, the instructor pilot took control of the airplane and attempted a landing in a soft agricultural field of tall wheat. Although the touchdown was successful, during the initial part of the landing roll, the airplane nosed over onto its back. After it flipped over, a fire broke out, which eventually consumed a majority of the airplane's structure. The initial postaccident examination of the airplane determined that portions of the airframe and engine systems had been destroyed by the fire. A further examination of the engine, which was monitored by the Federal Aviation Administration, found two anomalies. The first was that there was no engine cooling system vent line installed. This line, which is required by section 11.3.6 of the Rotax Installation Manual, was necessary on this specific installation because the engine was installed inverted (cylinder heads down). Instead, all venting holes were closed off with threaded plugs. But a further teardown of the engine did not reveal any evidence of any unusual wear, seizure marks, lack of lubrication, or signatures indicative of overheating on the pistons, piston rings, cylinder walls, or connecting rods; which is the area the cooling system is meant to extract heat from. The second anomaly was that the propeller and crankshaft could not be turned by hand. Therefore the crankcase halves were separated for further examination. The separation of thecrankcase revealed that both the inner and outer crankshaft MAG bearings would not rotate and that their phenolic bearing cages were melted. Therefore, the crankshaft assembly, to include the bearings and connecting rods, was sent to the NTSB Materials Laboratory for further examination. There it was determined that the phenolic bearing cage material, which when tested, melted at about 400 degrees Fahrenheit, had all flowed toward one side of the bearing assembly. It was also determined that there was a congregation (ganging) of the bearing balls on the same side that the phenolic cage material had flowed to, and that there was no indication of crankshaft rotation at the time the phenolic material melted. It was also noted that the melting of the phenolic cages was not uniformly consistent around their entire circumference, but was greater on one side than on the other. There was also no indication of bearing failure or incipient failure, and all corrosion found on the internal engine parts was consistent with postaccident exposure to moisture. At the completion of the examination process, no preimpact anomaly or malfunction had been found that would have contributed to a loss of engine power.