AMERICAN CHAMPION AIRCRAFT 8KCAB near Oshkosh, WI — 2012-07-26
- Date
- 2012-07-26
- Location
- Oshkosh, WI, USA
- Airport
- OSH
- Aircraft
- AMERICAN CHAMPION AIRCRAFT 8KCAB
- Registration
- N60GK
- Category
- Airplane
- Highest injury
- None
- Fatalities
- 0
- Phase of flight
- Maneuvering
Probable cause
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.
NTSB narrative
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.
Analysis
- Primary failure mode
- Mechanical failure
- First missed decision gate
- Ensure seat assembly conformed to production type certificate before flight.
NTSB coding
- Sys/Comp malf/fail (non-power) · Maneuvering-aerobatics
Evidence available
- 5 docket documents
Docket documents5
- Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1form
- Statement of Party Representatives to NTSB Investigationinterview
- Miscellaneous - American Champion Aircraft Corp. Detail Response E-Mailother
- Miscellaneous - American Champion Aircraft Corp. Service Letter: 437other
- Miscellaneous - Communication Summary with an American Champion Representativeother