20130424012379A

Amendment to original report:

On July 25, 2013 the NTSB received a teardown report from covington aircraft in okmulgee, OK.

The supercharger unit was sent to and inspected by covington aircraft. The finding in the teardown report state that the rear bearing failed and was fragmented. The rear bearing balls were plasticized, the phenolic ring separated from the bearing and small fragments were noted throughout the blower. The outer race remained intact. The middle bearing phenolic ring was fragmented and pieces recovered in the immediate vicinity of the bearing. The flat spots consistent with rubbing were noted on the bearing balls. The outer race contained metal fragments. Both the inner and outer race remained intact. The front bearing contained metal and phenolic fragments between the outer race, phenolic ring, inner race, and the balls. The bearing would not rotate but was externally unremarkable. Based on this report no recommendation by the FAA iic are being considered at this time.

In an initial telephone interview the pilot stated that the "engine rolled back" at about 200-300 hundred feet above the runway surface. He landed in an unplowed crop field about 1500 feet past the airport/runway. The airplane rolled over on its back. The pilot stated that he was not injured. In a second phone conversation on the same day the pilot stated that the airplane was, at the time of the accident, being inspected for its annual inspection but wasn't finished. He said that he wanted to fly it around to warm up the oil before the oil change. In a face-to-face interview the pilot was asked how much gas the tanks had and he said he believed about 35 gallons. The gas was just put in the tanks so it wasn't from last year. The five days after the accident and after the airplane was relocated to a hangar on the airport the FAA iic looked in both wing gas tanks and saw gas in them. The pilot provided a written statement stating that "the airplane was washed. The engine was washed down and inspected". After 15 minutes of run time on the engine to warm it and the oil temps up he taxied to runway 31. The engine was run up to 30" manifold pressure, prop was cycled, magnetos were checked and the carburetor heat was checked before takeoff. At the first power reduction after takeoff the engine continued to lose power such that flight was not sustainable. The pilot chose to land straight ahead in a crop field. The field conditions were wet and soft. The landing wheels (both) broke off of the main gear struts causing the struts to dig into the earth and the airplane then flipped over coming to rest in an inverted position. The pilot secured the aircraft systems and then egressed without injury. In the follow up investigation the engine was rotated by hand and no firm compression from any cylinder was noted. An Air intake tube was then removed from a cylinder to look for metal debris. Metal shavings were found in the tube. The metal shavings are suspected to be from the supercharger unit. A determination of the actual failed component has yet to be determined as a teardown of the collector case and supercharger assembly has not been accomplished. The NTSB has arranged for a teardown inspection with an engine overhaul facility. Upon receipt from the NTSB of the results of the teardown inspection this report will be amended.

On December 20, 2013 a telephone conversation with ron hollis at covington aircraft engines was made to discuss their findings on the teardown inspection of the blower unit. Mr. Hollis stated they found the supercharger blower aft bearing to have failed . He confirmed that the bearing was an faa-pma part and he emailed a picture of the bearing as found. Upon questioning he stated that although it is not a frequent occurance he has seen these bearings failed in other engines. He also did not feel that the PMA bearing is a subpar part because of the frequency of failures.