Zodiac Wing And Structure Problems Revealed

Zodiac CH601XL and CH650 models have, among other problems, a wing structure that does not meet ASTM standards for light-sport aircraft and were the causes of in-flight accidents, according to a comprehensive FAA report released Feb. 22.

Other factors also played a part, the FAA said, including “issues” regarding flutter characteristics, stick force gradients, airspeed calibration and operation limitations.

“FAA review of the in-flight failures did not indicate a single root cause, but instead implicated the potential combination of several design and operation aspects,” the FAA said. “Our preliminary assessments focused on the strength and stability of the wing structure.

“Further analysis during the special review found the loads the manufacturer used to design the structure do not meet the design standards for a 1,320 lb. airplane,” the FAA said in its report summary. “Static load test data verifies our conclusion.”

The EAA says it had strongly recommended that the FAA 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 of Mexico, Mo. (Read the full report at www.eaa.org/news/2010/Zodiac_Review_%20Report.pdf, or see the appendix at www.eaa.org/news/2010/ZodiacReportAppendix.pdf.

“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 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.”