LAX94LA299

On short final, the pilot experienced a total loss of engine power. The pilot made a forced landing in a field 25 feet short of the runway. The airplane collided with a berm and nosed over. An examination was performed of the airplane's maintenance history and engine. Evidence was found indicating that the operator had previously requested his contract maintenance to resolve earlier engine power loss events. On the accident flight, the airplane had been operated for about 2.7 hours since last receiving maintenance. The teardown examination revealed the engine's fuel control unit linkage had been manipulated such that it produced idle flow rates outside of required settings.

On July 27, 1994, at 0800 Pacific daylight time, a Schweizer G- 164B, N3627Q, operated by Sutter Butte Dusters, Inc., Live Oak, California, experienced a total loss of engine power on short final approach to the operator's private airstrip in Live Oak. The airplane touched down in a rice field about 25 feet short of the runway, collided with a berm, and nosed over. The restricted category airplane was substantially damaged, and the commercial pilot was not injured. At the time of the accident, the pilot was returning from an aerial application flight which had originated from Live Oak at 0730.

In the pilot's completed "Aircraft Accident Report," NTSB Form 6120.1/2, he reported that the airplane had a history of losing engine power. On July 12, 1994, the airplane had received a 400- hour inspection at 1,633.5 hours, and at 1,647.7 hours the airplane was provided to mechanics to ". . .find out what was happening."

Information received from the operator and from Pratt & Whitney Canada revealed that mechanics at a company named Yubba Sutter Aviation (which performed the last maintenance on the airplane at the request of the operator) had consulted with mechanics at Turbines Inc., and, thereafter, the high pressure fuel pump and the fuel control unit were replaced. The airplane was then returned to service. The pilot reported that the accident flight occurred at 1,650.1 hours.

Under the direction of the National Transportation Safety Board, the engine was shipped to Pratt & Whitney Canada, Inc., where it was examined under the direction of the Superintendent, Corrective Action, Transport Canada Aviation.

In summary, with one exception, the teardown examination revealed no indications of preimpact distress or operational dysfunction to any of the engine components examined (notwithstanding impact- related damage). The exception related to rigging of the fuel control unit.

The examination revealed the fuel control unit high-idle fuel flow had been set at 89 pounds per hour, and the fuel control unit input lever angle had been set approximately 8 degrees below the appropriate position for high idle. The low-idle fuel flow was found at 149 pounds per hour. According to Pratt & Whitney Canada, these flow rates did not conform to required values, and were ". . . well outside of any normal airframe specified setting." Pratt & Whitney Canada also concluded that these rates were ". . . indicative of manipulation of the fuel control unit high idle link adjustment."

Also noted in the teardown report was the fact that the compressor section including blades, disks, and spacers were observed coated with an accumulation of fine organic debris, oil, and a dirt film.