Primary finding
Probable cause
A partial blockage of the main fuel supply line to the engine, caused by improper manufacture of the fuel line by unknown maintenance personnel.
Investigator assessment
Analysis narrative
During takeoff from a 1,800-foot-long private airstrip, the engine sustained a partial loss of power. The pilot aborted the takeoff, and was unable to stop the airplane before overrunning the departure end. The nose wheel separated and the airplane nosed over. Inspection revealed a 60% blockage of the main fuel supply line to the carburetor. A flap of rubber protruded into the inner diameter of the fuel line from an end fitting. This line appeared to have been manufactured from aviation parts by an unknown mechanic.
Source record
Factual narrative
On September 2, 1997, at 1000 Alaska daylight time, a Cessna 150H airplane, N467SR, sustained substantial damage when it nosed over during an aborted takeoff from a private airstrip on the Akwe River, 30 miles southeast of Yakutat, Alaska. The private certificated pilot was uninjured. The flight was conducted under 14 CFR Part 91 as a personal flight, and was departing the Akwe River for Juneau, Alaska. Visual meteorological conditions prevailed at the time of the accident, and no flight plan was filed. The pilot stated that just after takeoff from the 1,800 feet by 50 feet sand airstrip, while accelerating in ground effect, the engine lost partial power and he was unable to climb. The pilot intentionally attempted to land back on the strip. He pulled the mixture control to idle cutoff, and turned off the magnetos and electrical master switch. The airplane was not stopped prior to the end of the strip, the nose wheel broke off, and the airplane nosed over. Postaccident inspection by an FAA airworthiness inspector revealed an internal blockage in the main fuel supply line to the carburetor. A flap of rubber material protruded from the point where the flexible line was joined to an end fitting. It was estimated by the FAA inspector, that this flap would intermittently block approximately 60% of the fuel line inner diameter, based on fuel flow. The fuel line and fittings appeared to be an assembly built from aircraft grade parts by an unknown mechanic, but not of factory construction. Review of the aircraft and engine logbooks did not reveal when this assembly was installed. -