Seven months after being asked by the US National Transportation Safety Board to do so, the Federal Aviation Administration has effectively grounded two factory-built light sport aircraft (S-LSA) models from the same manufacturer, Aircraft Manufacturing and Design (AMD).

The 7 November action came at the conclusion of a special airworthiness investigation launched by the FAA in April to study the Zenair CH601XL and CH650, similar aircraft both designed by Zenith Aircraft and available through AMD as factory-built or kit aircraft.

The FAA says structural failure accidents of the CH601XL date to 2005, and include five in-flight structural failures in the USA and several abroad. A sixth structural failure appears to have occurred in the USA on 6 November, the day before the grounding, killing the lone pilot on board. The FAA included the CH650 in the investigation, given the similarity of the airframes.

Findings from the review include a "non-conservative" for wing strength for bending loads "and basic static strength" that "does not appear to meet the intent of the ASTM standards for a 600kg [1,320lb] airplane, given the current flight envelope in the pilot operating handbook".

Although the FAA does not have a direct means of grounding light sport aircraft, the regulator reminded owners of their "regulatory obligation" to comply with a 7 November directive issued by AMD "in accordance with the ASTM International consensus standards safety directive process". AMD is assisting owners with several modifications to the design.

Source: Flight International