The first of two prototypes flew on 22 December 1979, but testing showed that the Epsilon had poor handling and it was redesigned with a new swept back fin supplemented by a ventral strake and a larger tailplane, while the wing was fitted with elliptical tips increasing the wingspan from 7.40 m (24 ft 3 in) to 7.59 m (24 ft 11 in). The first prototype flew again with these changes on 31 October 1980, and it was soon found that the handling problems had been fixed.