NTSB Identification: CEN12IA498
14 CFR Part 91: General Aviation
Incident occurred Thursday, July 26, 2012 in Oshkosh, WI
Probable Cause Approval Date: 05/09/2013
Aircraft: AMERICAN CHAMPION AIRCRAFT 8KCAB, registration: N60GK
Injuries: 1 Uninjured.
NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.
The pilot was performing at an air show and entered the aerobatic box with a 45 degree descending roll. At an airspeed of 150 mph, the pilot pulled up into a loop and then initiated a “snap-on-top-of-a-loop” maneuver. The pilot’s seat then broke, and the pilot and seatback fell backward onto the rear seat and rear control column, temporarily jamming the flight controls. The pilot was then able to recover the airplane to a “right-side-up” position with wings level. He flew away from the crowd to assess the situation and subsequently landed without further incident.
An examination revealed that the airplane’s seat bottom frame was not equipped with a required reinforcement truss stiffener. The manufacturer reviewed its production work orders and discovered that a batch of 10 seats were produced that were not constructed with the truss stiffener and, therefore, did not conform with the airplane’s production type certificate. As a result of this investigation, the manufacturer added steps to the seat production and inspection procedures to ensure proper seat assembly. Additionally, the manufacturer added to the seat welding fixture a locator (a visual cue) for the truss stiffener parts. Further, Service Letter 437 was published indicating that owners should perform a one-time inspection to ensure that the seat bottom frame contains the required reinforcement truss stiffener.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: The failure of the pilot’s seat bottom frame due to the manufacturer’s improper production, installation, and inspection of that seat bottom, which resulted in a temporary loss of control during an air show performance. Full narrative available
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