Thursday, the FAA froze the issuance of new airworthiness certificates for Zodiac CH-601XL series aircraft; Friday the NTSB released news of another Zodiac in-flight break-up and made an example of its earlier recommendations to the FAA. The FAA's most recent action forces operators seeking airworthiness certificates for the model to prove they've made specific modifications meant to prevent aerodynamic flutter. A Special Airworthiness Information Bulletin issued on November 7 by the FAA already effectively grounded some of the aircraft that were not in compliance -- and there's the catch. The Zodiac is available as a Light Sport Aircraft and an Experimental category amateur-built kit. So far, the FAA's actions do not require that modifications be made to the amateur-built planes. The aircraft involved in the most recent (November 6) fatal crash was amateur-built. In reviewing that accident, the NTSB noted recommendations it had previously sent to the FAA that, had they been implemented, may have prevented the latest fatal crash.
The NTSB stated Friday in an advisory that it called on the FAA in April of 2009 to ground the model, citing six accidents involving aerodynamic flutter that had so far killed ten. The Board says that the FAA responded at that time by saying it lacked "adequate justification" to impose a mandatory grounding of the entire fleet. Mandatory grounding aside, Zenith (manufacturer of the aircraft kits), the FAA and the EAA have all recommended that all Zodiac CH-650 and CH-601XL aircraft remain grounded until modified, regardless of their certification status.