Throughout the 1950s, aircraft designers around the globe started developing a distinctive aircraft layout, named a tail-sitter. Dissimilar to the typical aeroplanes, tail sitting planes rested on their tails and utilized engine power only to raise off the ground before changing to vertical flight and coming back to land vertically once again on their tail. Despite the configuration, being technically difficult to develop, it would enable aircraft to function without runways, conventionally challenging how and where air forces could use their aircraft.
In the early 1950s, French aerospace firm SNECMA (Société Nationale d’études et de construction de moteurs d’aviation) started developing wingless test rigs to establish the logic of the tail sitting idea. At the time, American companies were also creating tail sitting prototypes of their own, but SNECMA would take it a step further by designing a tail sitting aircraft featuring a highly unfamiliar cylindrical-shaped annular wing.
The cylindrical wing ensured greater efficiency over a traditional wing by eradicating wing-tip vortices. It would also be more precise, further lessening the space required for vertical take-off and landings. French designers also hypothesized that a cylindrical wing could be engineered ultimately to operate as a ramjet engine, driving the aircraft in supersonic speeds.
The C.450 Coléoptère was built in 1958, with restrained flight testing starting in early 1959. By May, the unorthodox plane had accomplished its maiden successful unassisted hover, even attaining altitudes of 800 meters. Despite initial successes during flight tests, defects soon started surfacing in the aircraft’s design. The Coléoptère proved exceedingly challenging to pilot. An innovative pilot seat could turn 90 degrees, but pilots still attempted to figure out the aircraft’s distance from the ground during landing. Devoid of a regular wing to offer resistance, the Coleoptere also had a propensity to slowly spin on its axis.
On July 25, 1959, the Coléoptère conducted its 9th test flight. This time, the pilot had to shift the aircraft from vertical to horizontal flight, a tough procedure that would mark a huge milestone for the program. The Coléoptère lifted off successfully, but during the transition, it suddenly became too disposed and slow-moving to maintain altitude. The aircraft began tumbling back to earth as the pilot tried hard to regain control, hardly managing to eject at the very last minute. The Coléoptère was destroyed.
The second prototype of the Coléoptère would never be built. By the 1960’s it was imminent that the tail sitting configuration was a dead-end. It was actually too much of a compromise when it came to payload and range, and far too challenging to pilot. It was evident that vectoring thrust, allowing the aircraft to remain horizontal, was a more logical and safer remedy.