The November 2006 fatal crash of the Grob G180A SPn prototype was caused by failure of the twinjet’s horizontal stabilizer, which “suffered an in-flight breakup due to aerodynamic flutter,” according to the final report issued by the German Federal Bureau of Aircraft Accident Investigation (BFU). While the cause of the flutter was
not determined, investigators considered a retrofitted elevator mass balance a possible culprit, as well as prior damage to the elevator horn. The company’s chief pilot was killed in the crash, which occurred while the SPn was performing a demonstration flight with low ceilings. Company policy dictated a “reduced flight display”–speed below 200 knots and a cloud-base minimum of 1,500 feet–but the aircraft was flying at up to 270 knots.