During 1958 the West German government caused some disappointment to the British and French aircraft industries by failing to order British or French interceptors for the re-established German Air Force. Instead they ordered the American Lockheed F-104 Starfighter. Even so it was well known beforehand that whatever aircraft were ordered would be regarded as interim equipment, against the day when a very high-speed vertical take-off aircraft became available—if ever.
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A step towards this ideal interceptor seems to have been taken. It has just been reported that the Ministry of Defense in Bonn has awarded "a secret development contract to a French firm for a new type of vertical take-off fighter"—the coleopter.
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Basically, tile Coleoptere is a jet engine, adapted to run in a vertical position while sitting on its tail, with a small cockpit on the top. Several aircraft of roughly this form have been flying for some time in the United States, but the Coleoptere is unique in that it has an annular wing; the aircraft stands inside it like a salt cellar inside a napkin ring. What is stopping the Coleoptere becoming a successful vertical take-off aircraft? The first difficulty has been to develop a precise and reliable method of balancing the aircraft on the column of air from its jet pipe during take-off and landing and, more particularly, during manoeuvres out of the vertical.
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Another control difficulty was that of overcoming the torque imparted to a vertical engine by its own rotating compressor and turbine wheels.
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A sensitive pilot can control the height of a unit such as this by careful operation of the throttle, so that the thrust of the jet balances its weight, but it would take a Superman to control pitching and rolling forces at the same time; automatic stabilisation has therefore to be introduced. This consists of a system of gyroscopes and gyrometers which sense the aircraft's movements and operate the jet steering system, the directional nozzle unit which counteracts tilting, and auxiliary air jets which compensate for any tendency to rotate.
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Nevertheless, before a successful coleopter can be achieved it must be shown that the Atar Volant with an annular wing can make the transition from vertical to horizontal flight, that the annular wing can support the aircraft in horizontal flight, and also that the much more tricky transition from horizontal flight back to a tail-first landing can be successfully made. The C.400 P.3 has accordingly been built as a full-scale coleopter to carry out the appropriate test programme. No doubt we can look forward to seeing it in flight at the International Paris Air Salon, which will be held in June this year at Le Bourget.
A. The engine produced by SNECMA engineers to overcome these problems was a straightforward turbojet in their "Atar" series, and in the logical French way it became known as the Atar Volant or C.400 P1. It was encased in a simple fairing which contained fuel and remote-control equipment. As the complete unit weighed 5600 pounds and the engine could produce a thrust of 6200 pounds, vertical lift was obviously feasible.
B. The MiG-21 proved itself over and over as a formidable dogfighter against the heavier American fighters which was another reason for the success of the MiG-21. Its reliable engine, easy maintenance, rough field capabilities, and save flight characteristic made it the most successful jet aircraft of all times.
C. Vertical take-off implies virtually indestructible air bases, because any piece of road or any field would serve for take-off. A fast climb to height is required since West Germany could expect only the shortest warning of an attack from the east.
D. I was privileged to inspect the test rig in October 1956, but even that experience was no preparation for the fantastic impression created by the second Atar Volant (the C.400 P.2), which stole the show at the international air display at Le Bourget in June 1957. At that time the P.2 surmounted by Auguste Morel, the test pilot, rose in a cloud of dust, stalked across the main runway, tilted about 20 degrees, danced back and forth, spun rapidly on its vertical axis, shot up to about 500 feet and then withdrew, leaving a sophisticated audience gasping. On the face of it the aircraft seemed distinctly unsafe but, of course, the very fact that these manoeuvres were even possible, and in rapid succession, was a considerable achievement.
E. SNECMA had already had experience of directional control of high-speed airflow by mechanical means—that is, metal spoilers inserted into the jet efflux. This method inevitably generated a delay of several seconds before an alteration of the controls by the pilot could be fully effective on the aircraft. This delay is unacceptable when the aircraft's stability depends entirely on the airflow from the engines. SNECMA therefore devised a directional nozzle unit consisting of a number of auxiliary jets of low output, bled from the engine compressor and sited round the outlet of the main jet. These deflect the main jet in order to steer the machine.
F. Work on this very interesting project has been going on in France for the past six years. The "firm" concerned is the Societe National d'Etude et de Construction de Moteurs d'Aviation (SNECMA), working in conjunction with Nord-Aviation, both organisations being integrated parts of the nationalised French aircraft industry. The aircraft should make its first flight this spring.