NTSB Identification: WPR10CA398
14 CFR Part 91: General Aviation
Accident occurred Wednesday, August 04, 2010 in Lincoln, CA
Probable Cause Approval Date: 01/07/2011
Aircraft: Kirkpatrick Buzzard, registration: N84BS
Injuries: 1 Serious.

NTSB investigators used data provided by various entities, including, but not limited to, the Federal Aviation Administration and/or the operator and did not travel in support of this investigation to prepare this aircraft accident report.

The single-seat aircraft was registered with the Federal Aviation Administration (FAA) as an experimental, amateur-built aircraft. A week before the accident, the aircraft was assembled by a certificated aircraft mechanic. The pilot reported that he had previously flown the aircraft one time, for about 30 minutes. During the accident flight's takeoff roll, the pilot noticed that the aircraft did not "feel right," but he opted to continue. About 250 feet above the ground the outboard right wing "started to flutter in a violent way" and in response the pilot reduced engine power and aircraft speed. He then "lost all control." The aircraft impacted the ground in a field and seriously injured the pilot. About an hour after the accident skydivers noticed the wreckage and summoned emergency services to rescue the pilot. Examination of the wreckage by an FAA inspector revealed that the bolt that was supposed to attach an aileron pushrod to the outboard aileron bellcrank was lying loose in the bottom of the wing bay; neither the nut nor the cotter pin was recovered. Examination of the opposite aileron bellcrank revealed that the corresponding bolt and nut were not secured by a cotter pin, despite provisions for one. The mechanic who assembled the aircraft stated that he did not install cotter pins in either of the two noted bolts. The pilot stated that he did not inspect the aircraft after assembly or before the flight.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

A loss of control due to the mechanical disconnection of an aileron pushrod from its bellcrank as a result of the mechanic's failure to properly secure the pushrod attach hardware. Also causal was the pilot's inadequate preflight inspection.

Full narrative available

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