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Aviation History
1964
1964 - 0652.PDF
/• f LIGHT International, II March 1964 BY THE TECHNICAL EDITOR Iliffe Transport Publications Ltd 1964 It is remarkable how much an experienced artist can deduce from the photograph published overleaf. At the same time there remain one or two details in this sketch— notably the junction of the wing leading edge with the body and with the inner sides of the engine nacelles—which must be regarded as provisional I, compartment for second crew-member or instrumentation; 2, Hughes fire-control radar; 3, electronics and air-conditioning (entire nose may hinge downwards ahead of this bay); 4, nose gear; 5, fuel; 6, AIM-47A missile bay; 7, in/out intake doors; 8, all-moving fins; 9,intakes to con-di nozzle; 10, folding ventral fin; 11, conical-camber outboard leading edge; l2,J58engine; 13, fixed ventral fins A-11 Some Thoughts on a 2,000 m.p.h. Aircraft SINCE February 29, when the President of the United Statesdisclosed the existence of the Lockheed A-11 in a TV Pressconference, practically everybody interested in aviation has been asking "How do they do it ?" The question does not seek the answers to the technical problems of building a Mach 3 -j- aeroplane; it asks how it is that a country like the USA can authorize, finance, design, develop, manufacture and flight-test a dozen enormous 2,000 m.p.h. aircraft without a word of the programme leaking out. It would be diverting to consider this matter further; but this journal is concerned less with subterfuge than with flying machines, and the A-11 is the mostest flying machine we have yet seen. It is proposed now to discuss its characteristics as fully as the two releasable photographs allow. The first point to relate is that we were incorrect when we surmised last week that the A-11 has but one engine. In fact it has two, despite the fact that they are the most powerful air-breathing aircraft engines known. It is appropriate to begin by outlining the terms in which the US President announced the A-ll's existence. The official state- ment reads in part as follows :— ; "President Johnson has revealed that the United States has successfully developed an advanced experimental jet aircraft which has been test-flown at speeds exceeding three times the speed of sound. The President announced at a Saturday morning news conference that the performance of the plane, designated as the A-11, 'far exceeds that of any other aircraft in the world today.' He said the aircraft, now undergoing extensive tests at Edwards Air Force Base in California, has been tested in sustained flight at more than 2,000 m.p.h. and at heights in excess of 70,000ft. "Mr Johnson told newsmen that development of the A-11 'was made possible by major advances in aircraft technology, of great significance to both military and commercial application.' He said the tests are to determine the plane's capabilities as a long-range intercepter, but added that the development of supersonic com- mercial transport aircraft will also be greatly assisted by the lessons learned from this A-l 1 programme. 'One of the most important technological achievements in the development of the plane,' Mr Johnson said, 'has been the mastery of the metallurgy and fabri- cation of titanium metal which is required for the high temperatures experienced by aircraft travelling at more than three times the speed of sound.' " Before discussing the A-11 in detail it is desirable briefly to recapitulate the development of supersonic aircraft in the USA. The first aeroplane in the world to achieve sustained supersonic flight was the Bell X-l, and it did so on October 14, 1947. From the X-l were evolved several improved aircraft of substantially higher performance. The X-1A reached approximately Mach 2.5 at 70,000ft on December 16, 1953, and the swept-wing Bell X-2 exceeded Mach 3 in 1956. From 1955 until January 1957 remark- able progress was made by North American Aviation with the X-10. This was a large canard test vehicle for the XSM-64 Navaho missile, and despite the limited power of its twin J40 turbojets it exceeded Mach 2 on many occasions. This magic figure of Mach 2 was also exceeded as early as 1954 by the two prototype Lockheed XF-104 Starfighters. Designed by C. L. "Kelly" Johnson, vice-president for Advanced Develop- ment Projects of Lockheed Aircraft Corporation, the XF-104 demonstrated the progress which could be made up the Mach number scale by reducing thickness/chord ratios and achieving optimum matching between the air intake, engine and nozzle. Mach 2 was also exceeded before the end of 1956 by the North American F-107A and Republic F-105B. By this time work was well advanced at the Los Angeles Division of North American Aviation upon two exceedingly ambitious aircraft for the US Air Force: the F-108 Rapier, built to meet the requirement of Weapon System 202A for long-range interception, and the B-70 Valkyrie built to meet the requirement of Weapon System 110A for an intercontinental bomber. As originally conceived, the B-70 was to burn high-energy (ethyl-borane ^'pe) chemical fuel in the afterburners of its six General Electric J93 turbojets in order to achieve a "dash" per- formance of Mach 3. It was later found possible to achieve Mach 3 throughout the mission, and without the use of such exotic fuel. Nevertheless, on December 3, 1959, the decision was taken to abandon the programme as a bomber and to complete only three (since reduced to two) aircraft for flight-test purposes, additional to a static-test airframe. Moreover, the development programme of the XB-70A has been seriously delayed, largely owing to the extreme difficulty of welding together the stainless-steel sandwich panels which form the integral tankage, without leaving occasional pinholes through which the fuel leaks under the 201b/sq in nitrogen pressure in the tanks. After most painstaking research, a method of cutting back the welds and brazing along their edges was evolved to seal the tanks. As these words are written the new wing is almost complete, and
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