Ex Swiss AF U-89. Built originally as a Bü133C, it was converted in 1970 with a Lycoming AI0-360 engine and was the sole example of this variant. While engaged in aerobatics on -5 January 1999, it struck a house at Abtwil, in St.Gallen canton. The aircraft burst into flames and was completely burnt out. The pilot was seriously injured and airlifted to hospital.