Light sport aircraft manufacturer Zenair appears to be baffled by this week's plea by the US NTSB to ground the company's CH 601 XL two-seater. NTSB claims the aircraft exhibits a tendency to break itself apart in flight due to an aerodynamic resonance, aka "flutter", linked to the ailerons. The NTSB says flutter appears to be a factor in six accidents that have killed 10 people in the US and the Europe since 2006.
Zenair, apparently blindsided by the NTSB barrage on Tuesday, says "each accident discussed in the NTSB memo occurred under different circumstances" and that some of the accidents are still being investigated.
"We continue to believe wing flutter will not occur if the control cables are adjusted properly," says the company. "Nonetheless, we are carefully considering the points raised in the memo, including whether the Zodiac CH-601XL is susceptible to wing flutter."
"Zenith Aircraft will communicate with the FAA about the issues raised in the NTSB memo," they continue. "We will provide more information after we thoroughly consider the issues raised in the NTSB memo and we have spoken with the FAA about those issues."