Accident Overview
A private pilot-owner was providing aerobatic instruction to another private pilot. The purpose of the flight was to demonstrate proper nose position during an aileron roll. The student pilot placed the airplane into inverted flight at full power and high RPM, as directed by the instructor.
Sequence of Events
After the aircraft was established in an inverted attitude, the instructor told the student to roll out of inverted flight. The student pilot responded by pulling aft on the control stick, executing a split-s maneuver. During the ensuing descent, the airspeed exceeded the never-exceed speed (VNE). The instructor noted that he was aware of the overspeed because he had previously flown above that speed to familiarize himself with the associated sounds.
As the pilot began the recovery from the dive, the right wing separated from the airframe. This component was the first to appear along the wreckage trail. The left wing was the second item found, mangled and twisted.
Examination Findings
Post-accident examination of the left wing revealed a fatigue striation pattern through approximately 90 percent of the aft leg of its main wing strut attach fitting. Additionally, fatigue cracking extended through about 25 percent of the forward leg of the same fitting.
The right wing's condition was consistent with an in-flight separation prior to ground impact. The exact cause of the right wing separation was not determined from the available information.