Washington, DC - The National Transportation Safety Board today issued an urgent safety recommendation to the Federal Aviation Administration (FAA) in which it asked the agency to prohibit further flight of a type of a small airplane that has been involved in six in-flight structural breakups since 2006. The recommendations apply to the Zodiac CH-601XL, a low-wing, fixed-gear, single- engine, two-seat general aviation airplane designed by Zenair, Inc. In its urgent safety recommendation, the Board cited four accidents in the United States and two in Europe in which the CH-601XL broke up in-flight killing a total of ten people. Aerodynamic flutter - a phenomenon in which the control surfaces of the airplane can suddenly vibrate, and if unmitigated, can lead to catastrophic structural failure - is suspected in all of the accidents. The CH-601XL was certified as a Special Light Sport Aircraft (S-LSA) by the FAA in 2005. This type of certification does not require that the FAA approve the airplane’s design. Instead, the airplane model is issued an airworthiness certificate if the manufacturer asserts that the plane meets industry accepted design standards and has passed a series ground and flight tests. The Safety Board’s urgent recommendation to the FAA is to prohibit further flight of the Zodiac CH-601XL until they can determine that the airplane is no longer susceptible to aerodynamic flutter. The Safety Board’s investigations of the accidents that occurred in the U.S. point to a problem with the design of the flight control system, which makes the airplane susceptible to flutter.