Lacking the authority to ground aircraft itself, the National Transportation Safety Board (NTSB) has urged the FAA to ground the Zodiac CH-601XL light sport aircraft (LSA) made by Zenair, citing six in-flight breakups from 2006 to 2009.
The NTSB cited four accidents in the United States and two in Europe in which catastrophic structural failure due to aerodynamic flutter is suspected. All the accidents were fatal, killing a total of 10 people. NTSB investigators believe they have found a problem with the design of the flight-control system that makes the aircraft susceptible to flutter.
“The NTSB does not often recommend that all airplanes of a particular type be prohibited from further flight,” said NTSB Acting Chairman Mark V. Rosenker. “In this case, we believe such action will save lives. Unless the safety issues with this particular Zodiac model are addressed, we are likely to see more accidents in which pilots and passengers are killed in airplanes that they believed were safe to fly.”
An FAA spokesman said the FAA looked into the design of the CH-601XL after the first accident in 2006 and didn’t find design problems at that time. But due to the number of accidents since then, the FAA in February formed a special review team of experts to look into issues of the design and manufacturing of the aircraft, and plans to coordinate its review with the NTSB, British aviation authorities, and Dutch authorities.
“We haven’t made a decision [on whether to] ground it yet. We will formally respond to the NTSB, and we have formed a review team,” FAA spokesman Les Dorr said.
The FAA reference to Dutch and British authorities refers to aviation authorities in The Netherlands grounding the aircraft last year following an accident. Under a reciprocal agreement, British and German aviation authorities followed suit. But German aviation authorities later retracted the grounding.
Sebastien Heintz, president of Zenith Aircraft in Mexico, Mo., said he was surprised by the NTSB letter. Zenith Aircraft makes a kit model of the CH-601XL that is similar in many respects to the light sport model.
“We want to seriously look at all the NTSB concerns and address them individually. For quite some time we have looked at issues relating to flutter and it does not seem to be an issue if the aircraft is maintained properly,” Heintz said. Heintz is the son of the founder of the company, Chris Heintz. The light sport models of the CH-601XL are built by Aircraft Manufacturing and Design (AMD) in Georgia.
Matthew Heintz, brother to Sebastien, is manager of Zenair in Canada and has built subassemblies for the light sport CH-601XL and other Chris Heintz designs near Toronto, Canada. He said the CH-601XL is no longer manufactured and has been replaced by a new model, the Zodiac CH-650 light sport aircraft. It is basically the same as the CH-601XL.
“I just got the report and need to analyze it. It’s surprising, since the NTSB investigated an accident at Yuba City, Calif., and issued a final report that said nothing about manufacturing or flutter. The cause of that accident was found to be overloading of the airframe, and there was no mention of flutter.”
The NTSB listed the fatal breakups in its report: On Feb. 8, 2006, near Oakdale, Calif., a CH-601XL crashed after its wings collapsed (two fatalities). On Nov. 4, 2006, a CH-601XL broke up in flight while cruising near Yuba City, Calif. (two fatalities). On Feb. 5, 2008, a CH-601XL crashed near Barcelona, Spain, after its wings folded up during a descent shortly before landing (two fatalities). On April 7, 2008, a CH-601XL broke up in flight near Polk City, Fla. (one fatality). On Sept. 14, 2008, a CH 601XL crashed in the Netherlands (two fatalities). On March 3 this year, a CH-601XL broke up in flight while cruising near Antelope Island, Utah (one fatality).
LSAs are certified once the manufacturer presents documentation to the FAA that it has met the industry-agreed-upon ASTM standards. The NTSB urged the FAA to work with the ASTM organization to tighten LSA requirements. It sent a copy of its recommendations to ASTM.