A Plane Without Wings: The Coleopter Story
In the 1950s, the French set aside conventional aircraft-building wisdom to design a plane unlike anything recognizable today. With a cylindrical wing, plans for ramjet propulsion, and the ability to take off and land vertically on its tail, this plane would lay the foundation for a new way to protect French air space. With planes that could take off from anywhere, rising to meet the enemy like a swarm of angry bees. Conventional airplanes need runways to get airborne. Accelerating until their wings generate enough lift to take off. One way to reduce the length of runway needed is to give the plane more power so it can get up to speed faster and lift off earlier. But in the 1950s, aircraft designers realized that with enough power, planes might not need runways at all. Instead of powering down a runway, they could be oriented towards the sky. And use engine power alone to lift off and accelerate until their wings generate lift.
The advent of more powerful engines gave rise to a new category of experimental aircraft called tail sitters. A configuration that could potentially revolutionize air forces. In any conflict, runways were going to be the first targets. And their destruction could render entire air forces inoperable. But tail-sitting planes wouldn’t need runways… they could instead be hidden or deployed to defend vulnerable targets. If engineers could get the configuration to work, tail-sitting planes promised to fundamentally change how and where aircraft could be used. In 1954, a French aerospace firm renowned for aircraft engines began developing wingless test rigs to prove the feasibility of the tail-sitting concept. Getting a tail-sitting plane to work would require more than just powerful engines. Entirely new control systems were needed to make vertical takeoff and landings possible. It was a daunting engineering challenge at the time. But the French weren’t the only ones perusing the idea. The Americans had also developed tail-sitting prototypes.
With each plane, they experimented with a different combination of propulsion, wing configuration, and flight control. But the French had something more radical in mind. The C.450 Coléoptère would barely even resemble an airplane, because its powerful turbojet engine would be surrounded by a ten-and-a-half foot diameter cylindrical wing. The highly unconventional wing promised greater efficiency by reducing wasteful wing tip vortices which occur on conventional wings And its compact shape would reduce the amount of space needed for takeoff and landings. But the French also theorized that the radical wing could eventually be engineered to function as a Ramjet, compressing incoming air, mixing it with fuel, and igniting it to power the plane to supersonic speeds beyond Mach 2.0. The wing would be a radical combination of a lifting device, airframe, and pulplusion, all in one. To control the aircraft during take-off and landings, thrust would be vectored using deflecting vanes in the engine’s exhaust. During conventional forward flight, triangular winglets would provide directional control. And to help transition back to horizontal flight, small retractable fins would deploy on the fuselage nose. But landing the Coléoptère would be challenging. With the pilot’s back to the ground, they’d have to look over their shoulder. So designers innovated a cockpit with a seat that could swivel 90 degrees to remain upright regardless of the aircraft’s orientation.
The Coléoptère would look straight out of science fiction. But as an aircraft being designed in the 1950s, long before computer simulations, daring test pilots would have to play just as much of a role as engineers in getting it to work. The Coléoptère began flight testing in April of 1959. First undergoing tethered evaluation before progressing to free flight. By May, the plane had proven its ability to hover for minutes on end and had even flown up to an altitude of 800 metres. The radical machine made waves throughout France and around the world. The Americans who had keenly followed the progress of the French from the very beginning, reached out to Aerospace firms to study cylindrical wings for themselves. But as with most novel designs, flaws soon emerged. Without the benefit of a conventional wing to counter rolling tendencies, the Coléoptère slowly spun on its axis during hover. Making control extremely difficult. And perched high on top of a vertically oriented plane, pilots struggled to judge just how far the aircraft was from the ground And in an emergency, conventional planes could still land without engine power.
Unlike the Coléoptère, which would always need its engine to land safely. But the French pressed on, confident that they could sort out the prototype’s flaws. By July of 1959, engineers were ready to tackle the more challenging procedure of transiting from vertical to conventional forward flight. It would be a pivotal moment for the program. On July 25th the Coléoptère lifted off vertically. but during its transition, it suddenly became too inclined and slow-moving to maintain altitude. The plane started tumbling back to earth, and the pilot struggled to regain control, only barely managing to eject in time. In an instant, the prototype was destroyed, and development suddenly ground to a halt. To continue, the program would need to secure additional funding to build a second prototype. But the funding would never materialize. Because the Coléoptère would be the last major effort at building a pilotted tail sitting plane. By 1960, the Amercians had abandoned development of their own tail-sitters. The configuration was a dead end. Simply too much of a compromise when it came to payload and range. And far too dangerous to pilot. And as it turns out, directing engine exhaust to lift the aircraft, instead of tilting an entire aircraft.. was a more practical and safer solution. The Coléoptère’s cylindrical wing also proved to be an elusive concept. With less induced drag, it was in theory more efficient than a conventional wing. But in practice, parasitic drag from the wing’s structure largely cancelled out benefits and introduced a host of other aerodynamic challenges. Setting aside conventional aircraft building wisdom often results in dead ends. But every so often, it leads to a breakthrough.
