Polymorphs for Passengers
By OLIVER STEWART HOSE who want to fly at 2,000 or 3,000 1 miles an hour will eventually be asked to choose between two different kinds of air vessel: the efflux box and the polymorph. The signs are that, for carrying passengers over great distances at great heights and speeds, polymorphs —that is, variable geometry aircraft with wings which can be swept back at different angles to give the shape best suited to any required speed —are to be the choice of the future. Lord Tedder referred to their great potentialities in the House of Lords the other day and the Ministry of Aviation has sponsored a design study.
For military applications, the efflux box, con- iisting of a cabin or cockpit which lifts itself on jets having fixed or vectored thrust lines and hen sits on them, may be preferred. It uses vestigial wings for cruising and top-speed flight, but it is primarily a large lump of undiluted horsepower unlikely to be well received by passengers.
Terminologically, a jet-lift craft is a loco- motive engine, while a polymorph is a flying nachine. Between them comes the conventional aeroplane with slots or boundary layer control which, if it is to be supersonic, needs the help tf an enormous runway to get off and to land.
Polymorphs should be both safer and quieter ban either conventional supersonic aeroplanes tr than jet-lift craft. After total power failure, 'or instance (and four engines have been known o pack up all together), a polymorph, in the fully spread configuration, can glide relatively slowly and so have a chance of bringing its passengers down alive. It cannot take off or land vertically and it cannot hover, but it can have a wide enough speed range to enable it to reach top speeds of more than three times the speed of sound with a landing speed below those of existing, subsonic air-liners. Aeronautical engineers have known of these advantages for many years and, to find out why there has been so little useful development, the same old questions that arise whenever British air policy is under examination must again be asked. Unfortunately the same old replies must be given.
In Britain the polymorph has been the pre- ferred subject of certain engineers and in- ventors for at least fifteen years, but the inability of successive Ministers (of Supply and of Aviation) or of their technical advisers ac- curately to appraise advanced designs has obstructed progress. Note the date of the 'design study' announcement—April, 1962—and then take a look back at history.
In its modern form variable sweep dates from the early 1940s. Britain was well in front when the first radical patents were taken out by L. E. Baynes in this country in 1949 and in the US, Canada and France in 1950. Baynes began work in 1947 and his patents show how stability and control as well as speed range can be obtained by reaching forward and back with wings and. tail surfaces. Wind-tunnel trials confirmed this inventor's claims and indicated a speed range of ten to one. (Boeing 707 about four to one.) In 1950 Baynes asked the Ministry of Supply for permission to read a paper on his invention before the Royal Aeronautical Society. Permis- sion was not given.
Then came the more widely publicised work of Dr. Barnes Wallis. It was in 1952 that the public heard of his ideas. If ever there was a novel aircraft design which deserved enthusias- tic, all-out national backing, it was the Wallis 'arrowhead' polymorph. The man himself was proved. Not only had he invented the weapon which breached the Moline and Eder dams and the 'earthquake' bomb, but, more important in this context, he was the man who had invented a new and successful method of aircraft con- struction, the 'geodetic' construction used in the Wellesley and Wellington bombers. In 1938 the Wellesley improved on the world's absolute distance record by no fewer than 870 miles. Here was no 'mad inventor' of the kind government technical men like to sneer at, but an engineer with more proved original work to his credit than any other man living.
Wallis did not, however, ask for government support for an idea. He sustained his claims for the polymorph in every manner known to prac- tical engineering. He did wind-tunnel trials, he made a series of free-flight model tests at an aerodrome in Cornwall, he subjected his wing pivot (for the mechanical difficulties here are formidable) to extended fatigue tests in a 120-ton rig at Weybridge.
I saw these tests and with many others in aviation I believed that Wallis had found the way to build an aircraft capable of top-speed bursts of over 3,000 miles an hour and cruising speeds of over 1,600 miles an hour with global range capabilities and good safety qualities. In May, 1952, and again later, Sir Harry Legge- Bourke, who knew the details of the polymorph, raised the matter in the House of Commons. It was raised repeatedly. Nothing was done until eventually the worst thing possible was done: the Wallis plan was handed to the Americans on a plate. After being temporarily put off by the crash of their Bell variable-sweep research air- craft, the Americans returned to the subject.
Whatever is done abroad, the most advanced theoretical, design, wind-tunnel and practical ,work has been done in this country, and it is ironical that the Government should authorise a 'design study' thirteen years after the Baynes patents.
The matter has wider policy implications. Mr. Thorneycroft has persuaded the French to allow Britain to put money and work into a French design of supersonic air-liner, It is not certain that the engineer in charge, M. Servanty, has decided on the ogival wing plan form shown in a model last year, but it is certain that he will not be using variable sweep. The French design —and in spite of denigratory grunts from the Farnborough direction it is wholly French—is a brilliant concept, but it will be exigent of run- way length.
Our resources are to be spread between a 'design study' of something our engineers have known a great deal about for a great many years and the building of a French supersonic air-liner. If the polymorph could be made to work it would make conventional air-liners obsolete. The French Super Caravelle may be looked on as an insurance against the failure of the polymorph. But the timidity of government officials in matters aeronautical (the Rotodyne and the mixed-power Saunders-Roe are examples) en- sures that if they are given an escape road from the riskier main circuit, they will always take it. While cold feet afflict our aviation policy- makers we shall not reap benefits from the bright ideas of our inventors. Lord Caldecote gave the regretful verdict of aviation people when he said recently (April 5) that the Ministry of Avia- tion, of which he had expected so much, had failed.
Previous page
