Incident Overview
While maneuvering at low altitude, the pilot of an open cockpit experimental airplane heard a loud pop, followed by a change in flight control feel. The pilot reduced engine power to idle and activated the ballistic recovery system (BRS). Moments later, the airplane struck trees and came to rest suspended near the ground. The pilot evacuated the airplane without assistance.
Wreckage Examination
Post-accident examination revealed that the left wing rear strut threaded eyebolt had separated from the threaded barrel of the wing strut. The engaged thread length measured 5/32 of an inch, with approximately 16 threads exposed beyond the barrel. According to the manufacturer's assembly manual, the minimum required thread engagement was 5/8 of an inch, leaving about three and a half threads exposed.
Sequence of Events
The failure occurred during a turn, likely subjecting the strut to increased loads. The audible pop and subsequent control feel change indicated a structural loss. The pilot's decision to activate the BRS suggests an awareness of the compromised airframe.
Investigation Findings
No other pre-impact anomalies were noted. The discrepancy between the measured and specified thread engagement indicates the eyebolt was insufficiently threaded into the barrel at the time of assembly or maintenance. This condition reduced the connection's strength, leading to its separation under load.