FAA Doesn't Ground Zodiac CH-601XL

Special Review Team Investigates NTSB’s Recommendations
FAA Does Not Ground Zodiac CH-601XL

On April 14, 2009, the National Transportation Safety Board (NTSB) issued an urgent safety recommendation to the Federal Aviation Administration (FAA), asking the agency to prohibit further flight of the Zodiac CH-601XL. The low-wing, single-engine 2-seater designed by Zenair had been involved in six in-flight structural breakups since ’06. Aerodynamic flutter is suspected in all of the accidents.
     In response to NTSB’s recommendation, FAA put together a special review team consisting of FAA specialists from flight test, engineering, manufacturing and accident investigation. “The special review team will analyze the Zodiac CH-601 XL and its derivatives,” writes FAA administrator Randolph Babbitt in a July 13 letter to NTSB. “A design review for each version may suggest further FAA action.”
     It should be noted that there are four variants of the Zodiac CH-601 XL: a Special light-sport aircraft (SLSA), an Experimental LSA (ELSA), a European microlight model, and an Experimental amateur-built version. FAA noted that NTSB’s recommendation seemed to treat all the Zodiac derivatives the same, [but] mentioned two specific versions: the SLSA and the Experimental amateur-built models. “Data indicates the CH-601XL has a safety record similar to other SLSA and appears capable of safe flight and operation if maintained according to the manufacturer’s recommendations,” writes Babbitt.
     At this time, FAA “lacks adequate justification” to ground the CH-601XL aircraft.
     In the meantime, FAA’s special review team will investigate the following safety recommendations issued by NTSB: Make sure the CH-601XL has adequate protection from flutter, evaluate the wing and aileron system, communicate findings of the special review team, keep the Board informed on the progress of flutter requirements, decide on the appropriate action if a design characteristic is identified as a potential safety issue, make recommendations to the ASTM F37 committee if the special review team determines additional standards regarding stick force and controllability are necessary, clarify the standards for airspeed calibration, and work with the ASTM F37 committee to address proper airspeed calibration.
     Babbitt says he will keep NTSB informed of his agency’s progress on these safety recommendations, and expects to provide a further response by March 31, 2010.