Ligeti Stratos

The Stratos was an Australian single seat ultralight aircraft, developed by Charles Ligeti in the 1980s. It was notable for being a high-performance aircraft of radical design.

Design and development
Charles Ligeti was a Czechoslovakian industrial chemist with experience in mechanical engineering. He commenced design studies for a high-performance aircraft in the 1970s. He migrated to Australia in 1977 with design work then resuming in May 1983. Development included the building and testing of free flight models and a $1/4$-scale radio-controlled model.

The Stratos is designed to be stored and transported fully assembled, without any need for disassembly or dismantling. The aircraft was designed to comply with the Australian ANO 95-10 code for ultralight aircraft. Aerodynamically, the Stratos is a very clean design. The most notable feature is its closed wing configuration, with the sweptback foreplane and the high-mounted mainplane being connected at their wingtips by vertical fins. The pilot sits in a recumbent position in a streamlined nacelle. The engine is mounted at the rear and powers a three-bladed ducted fan. There is no empennage. The undercarriage consists of two non-retractable wheels arranged in tandem, with balancer wheels located under the wingtips.

Operational history
The prototype, piloted by Ligeti, first flew on 25 April, 1985, with him later reporting that the aircraft fulfilled or exceeded all expectations. The prototype was taken to the 1986 EAA Convention at Oshkosh, Wisconsin, where it flew every day for a week. Having returned to Australia, further flight testing was conducted with the prototype.

During testing at Penfield, near Sunbury, Victoria on 22 September 1987, Ligeti lost control of the aircraft, with the craft falling vertically to the ground. The aircraft was destroyed and Ligeti killed. An investigation by the Australian Transport Safety Bureau focused on a change made to the forward wings, so that they had full span elevators, affecting stalling and pitching behaviour.