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One of the most spectacular and futuristic looking aircraft ever built was the C.450 Coleoptere (beetle), developed by the French Societe Nationale d’etude et de Construction de Moteurs d’Aviation in the late 1950s as a technology demonstrator for the vertical takeoff point-defense interceptor for France and Germany.
While there had been turboprop vertical-takeoff fighters developed in the United States by Lockheed Martin for the Air Force and by Convair for the Navy, SNEMCA, as an engine company, opted for a jet aircraft to provide the needed performance.
The company knew the first problem would be control of the aircraft, since it would be sitting on top of a column of jet exhaust. So, as the first step, SNECMA developed the C.400 Atar Volant series of remotely controlled and piloted research platforms to examine control and stability problems. These were nothing more than Atar jet engines mounted vertically on a tethered platform with a tubular four-wheel undercarriage.
In 1954, the company tested its first platform, the C.400 P.1, a remotely controlled vehicle using a jet exhaust deflection nozzle for directional control. The second platform, the P.2, had a pilot with an instrument panel and controls on top in an ejection seat. Directional control was still provided by deflecting the exhaust, and lateral control was provided by air jets located on the landing gear struts.
This second test platform looked particularly unsafe and it created a sensation at the 1957 Paris Air Show. Test pilot Auguste Morel took off in a cloud of dust, moved across the main runway, and began to rock back and forth in banks of about 20 degrees. After this demonstration, Morel quickly turned the C.400 P.2 on its vertical axis, shot up to about 500 feet and then roared away, leaving the audience stunned.
Performing these maneuvers in rapid succession showed that the SNEMCA vertical-takeoff concept was viable. Two more test platforms were produced, each with improvements from the previous designs. These platforms accelerated to speeds high enough to provide lift for an aircraft, so a wing could be added to the platform to make it an aircraft.
The airframe for the orignal aircraft was built by the NORD Aviation Company in 1958 and named the C.450. The fuselage was mounted inside a circular wing, a seemingly advanced wing design that had been designed by French aviation pioneer Louis Bleriot in 1906. While the wing did eliminate the influence of the wingtip vortices, it offered few other advantages other than reducing size. One wag described the C.450 as looking “like a salt shaker sitting inside a napkin ring.”
The C.450 had an Atar engine with over 8,000 pounds of thrust and had a thrust:weight ratio of 1.23:1. A thrust:weight ration greater that 1:1 is required for vertical takeoff. The C.450 began tethered flight tests in April 1959 and began its first free flights a month later.
The first tricky thing was vertical ascent and descent and control in the vertical. An automatic stabilization system of gyroscopes and gyrometers sensed the aircraft’s movements and operated the jet steering system to control pitching and rolling forces, and auxiliary air jets compensated for the tendency to rotate.
To help with landing, the pilot sat in an ejection seat that automatically tilted on descent up to 55 degrees so he was always horizontal, and he had a large window on the bottom of the aircraft to help him judge his distance above the ground.
The Coleoptere C.450 made nine vertical takeoff and landing flights and hovered for over five minutes. Then, on its tenth flight, when it was supposed the make the difficult transition from vertical to horizontal, as it approached the 50 degree point it began to suffer pitch and yaw oscillations that became uncontrollable. The pilot ejected successfully, but the crash ended the program. The tail sitter was not considered to be capable of undertaking a variety of missions, and the push for multirole fighters eliminated the idea of vertical takeoff point-defense interceptors.
