Several factors, including a wing structure that does not meet ASTM standards for light-sport aircraft, are indicated as causes for Zodiac CH601XL and CH650 aircraft in-flight accidents, according to a recently released Federal Aviation Administration report.
EAA had strongly recommended the FAA investigation to supply aircraft owners with comprehensive data to ensure safety of their airplanes. A series of in-flight structural failures led the agency to stop issuing airworthiness approvals on those Zodiac models in late 2009. The aircraft are available as fully constructed light-sport aircraft from Aircraft Manufacturing and Design Inc. (AMD) and as amateur-built kits from Zenith Aircraft.
“The FAA did an excellent job with this investigation and deserves credit for thoroughly exploring all possibilities,” said Earl Lawrence, EAA’s vice president of industry and regulatory affairs. “EAA had vigorously pushed for comprehensive data on these accidents. We wanted to see the data, so aircraft owners knew exactly what modifications were needed and why they were needed immediately.”
The FAA’s investigation did not indicate a single root cause for the in-flight failures, but implicated the potential combination of several design and operation aspects. An important finding in the FAA study was that the wing structure did not meet the approved ASTM International standards to handle the required loads and stresses for a 600-kilogram (1,320-pound) aircraft. The FAA report also identified issues with the airplane’s flutter characteristics, airspeed calibration, stick force gradients and operating limitations.
The aircraft manufacturers have developed modifications for the Zodiac wing structure and made them available to aircraft builders and owners. Airworthiness approvals had been suspended until modifications were made because of “known safety concerns,” in accordance with FAA regulations. EAA members were involved in many of the fatal accidents with the aircraft.
“Safety is always the top priority, and complete information is the best way to create and maintain the highest standard of safety,” Lawrence said. “Any aircraft accident is a tragedy, and EAA shares the sense of loss with the families and friends of the aviators affected. The FAA’s report contains excellent data and will enhance safety in these aircraft.” More information can be found at www.eaa.org