In a special report (PDF) released by the FAA this week, investigators said their review of a series of fatal in-flight accidents involving Zodiac CH601XL and CH650 aircraft “did not indicate a single root cause, but instead implicated the potential combination of several design and operation aspects.” The report says analysis during the special review found that the loads the manufacturer used to design the structure of the wing “did not meet the ASTM standard for a 1,320 lb aircraft.” The review also identified issues with the airplane’s flutter characteristics, stick force gradients, airspeed calibration, and operating limitations. In its recommendations, the review team suggests that a number of corrections, revisions, and clarifications be made to the ASTM standards. The FAA and the manufacturer are still working to modify and test the design. “Once the manufacturer has verified the new design through further testing and analysis … owner/operators can make the suggested modifications, and the CH 601 XL and CH 650 should be able to return to safe flight,” the report concludes.
“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.” Dan Johnson, president of the Light Aircraft Manufacturers Association, told AVweb his organization welcomes the FAA report. “LAMA has received feedback from individuals in the LSA community that indicates the FAA report is a factual and in-depth analysis of the CH601 accidents,” he said. Further, he said, “LAMA observes that AMD thoroughly researched the problem and designed a remedy fortheir airplane,which FAA has noted.”
