Los Banos, CA, USA
N642KC
Schweizer 269C
The pilot and aircraft maintenance technician were performing a post maintenance test flight when a vibration occurred, followed by a total loss of engine power. The commercial certificated helicopter pilot made a forced landing in a muddy field, during which the helicopter received structural damage. Post accident examination revealed a failed exhaust valve in the number 3 cylinder, and that two exhaust spring seats had been installed, one on top of the other, causing excessive spring/valve pressures. The engine had been overhauled about 1.5 service hours prior to the loss of engine power.
On December 18, 2002, at 1521 Pacific standard time, a Schweizer 269C, N642KC, experienced a total loss of engine power and rolled over during a forced landing in a muddy field at Los Banos, California. The helicopter was operated by the pilot under 14 CFR Part 91. The commercial pilot and one passenger were not injured. The helicopter was substantially damaged. Visual meteorological conditions prevailed, and no flight plan had been filed. The flight originated at Los Banos about 1500. The pilot and aircraft maintenance technician were performing a post maintenance test flight when a vibration occurred followed by a total loss of engine power. Post accident examination revealed a failed exhaust valve in the number 3 cylinder. Further examination revealed two exhaust spring seats had been installed, one on top of the other, causing excessive spring/valve pressures. The operator had just overhauled the engine; the failure occurred about 1.5 hours after the overhaul.
The improper engine overhaul by other maintenance personnel, which resulted in an exhaust valve failure and a total loss of engine power while in maneuvering flight.
Source: NTSB Aviation Accident Database
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