N915X

On July 2, 2004, at 1330 eastern daylight time, a Grumman G-164A, N915X, operated by Downstown Airport, Inc. was substantially damaged during a forced landing, shortly after taking off from a gravel airstrip in Chatsworth, New Jersey. The certificated commercial pilot was not injured. Visual meteorological conditions prevailed, and no flight plan had been filed for the local aerial application flight, conducted under 14 CFR Part 137.

According to a written statement submitted by the pilot, the departure to the south was normal until about 100 feet, when the engine began to lose power. The pilot made a "slight" right turn to align the airplane with the wind and a cranberry bog. The pilot also began dumping the 800-pound load of fertilizer that was onboard the airplane. After touchdown, the airplane nosed over in the bog.

The engine was disassembled and examined under the supervision of a Federal Aviation Administration (FAA) inspector at a maintenance and repair facility. The oil pump was removed and appeared to be normal, and the oil screen appeared to be clean.

The blower (supercharger) section of the engine was also examined. Several impeller blades were damaged or missing, and the remaining portions of the impeller exhibited signs of melting and breakage. The impeller shaft was bent, and its surface was discolored from heat and exhibited signs of rotational scoring. The impeller shaft bushings were worn and "oversize", and the blower shaft attach nut also exhibited heat discoloration.

Further examination of the engine revealed metal contamination in the engine cylinders.

According to the chief inspector at the facility where the engine was disassembled, the impeller shaft was supported by two bronze bushings that were lubricated by engine oil via a 1/8-inch hole in both of the bushings, and a 1/16-inch hole in one of the bushings. The 1/16-inch hole was found blocked. The inspector additionally stated that failure of the bronze bushing would cause the impeller shaft to "wobble," and permit contact between the blower and the rear case, which would then result in excessive damage to the impeller, impeller shaft, blower, and rear case.