Primary finding
Probable cause
A loss of total engine power when a failed flapper valve in the air box blocked the flow of air through the carburetor throat.
Investigator assessment
Analysis narrative
The homebuilt accident airplane lost engine power during initial climb from takeoff. It collided with trees and terrain during a forced landing. The pilot described how he had been flying about 45 minutes and had done two landings and takeoffs. During the third takeoff the airplane had climbed about 75 to 100 feet when the engine lost power. Examination of the carburetor air box revealed a flapper valve in the air box had broken. The valve plate was free to move about in the space between the shaft and the carburetor air intake. The plate had been secured to the shaft with two spot welds. The surface of the broken welds appeared dull except for a small portion on one weld where the break appeared shiny. The carburetor air box had been purchased from an aircraft salvage operator for installation on the airplane.
Source record
Factual narrative
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