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Aviation History
1964
1964 - 0653.PDF
"""*3 378 FLIGHT International, 12 March 1964 .mwm A-11 . . . This photograph of an A-11 was taken at Edwards AFB, Califor- nia, where these aircraft are at present based the giant aircraft is now expected to fly in May. But this slippage by more than two years behind the original schedule has significantly reduced the lead-time between the generation of research data by the B-70 and the hardening of design details of the chosen American SST. It now appears certain that the latter will be designed for a Mach number much nearer to three than to two. Such a Mach number is ambitious enough for a military aeroplane, but for a civil transport it would be ambitious to the point of being foolhardy without the backing of very considerable flight experience on which to base the design. Since 1956 the United States has flown several types of supersonic aircraft in addition to those already mentioned. The General Dynamics B-58 bomber has frequently flown at Mach numbers greater than 1.5 for well over an hour at a time, and has demon- strated its ability to cover intercontinental distances at average speeds of the order of 1,000 m.p.h, despite the penalty of having to descend to subsonic speed at reduced altitude in order to take on fuel. McDonnell's outstanding F-4 Phantom family has demon- strated sustained flight at Mach 2.5 in full fighting trim. Perhaps most important of all, North American's X-15, which breaks entirely new ground in structures, propulsion and systems, has explored a performance boundary which has been progressively extended with improvements to the aircraft. The highest Mach number so far reached is 6.059 (over 4,100 m.p.h.), and a vast amount of valuable data has been recorded over a wide range of Sight conditions. But the X-15 cannot provide the answers to all the questions posed by the SST in the field of sustained highly supersonic flight during 60 per cent of a lifetime of perhaps 50,000hr. The only vehicle which will be able to duplicate an SST mission is likely to be another SST. It is against this background that the technological importance of the A-l 1 may be judged. But it is extremely doubtful that thea new aircraft was developed merely to provide answers in support of a possible SST programme. According to President Johnson, the project began in 1959. It was probably in this year that the Eisenhower Administration authorized the US Central Intelligence Agency to conduct "overflights" across the Soviet Union by Lockheed U-2 reconnaissance aircraft. The U-2 was designed under conditions of great secrecy by a special staff reporting directly to Kelly Johnson at a restricted building—known as the "Skunk Works"—at Burbank, California. But gradually reports of the high-flying, sailplane-like aircraft began to appear in public, and on May 18, 1956, this journal reported an official statement by Dr H. L. Dryden, then director of the US National Advisory Committee for Aeronautics (now NASA), admitting the existence of the U-2 and describing it as being em- ployed for such harmless types of upper-atmosphere research as plotting jet streams, counting cosmic-ray particles and measuring the concentration of ozone. In fact, of course, the U-2 was then already regarded as a potentially very valuable instrument in the Cold War, in that its ability to cruise at an altitude of some 70,000ft—later raised to perhaps 90,000ft by employing the larger J75 engine, with special modifications—appeared likely to enable it to be flown with impunity across any territory in the world. Hence the overflights, with NASA forced into the role of the accomplice providing the cloak of respectability. On July 6, 1956, this journal published a leading article entitled "U-2 ... can be a Top Security Chief" in which, for the first time, the cloak-and-dagger activity of this aircraft was set forth publicly. By 1959 Kelly Johnson and his special team had virtually finished with the U-2. They knew that before long it would become vulner- able to surface-to-air and air-launched missiles, and there now seems to be little doubt that they began to draft a proposal for a completely new aircraft capable of flying at least as high as the U-2 and approx- imately four times as fast. Their proposals were obviously accept- able to the Eisenhower Administration, and the "Skunk Works" got busy again—on the "U-3," now called the A-11. At least one newspaper has suggested that the entire programme was funded by the CIA, not one cent of whose expenditure is made public. But according to Pierre Salinger, the White House Press Secretary, the A-11 was "funded and managed by the Air Force in the normal manner for a classified project." The total programme cost must by now be at least 1300m, and if the money has indeed come from the Air Force appropriation it will have been included in the massive totals which have made Lockheed Aircraft the leading US defence contractor in both 1962 and 1963. It is worth commenting that in December 1959, along with the cutback in the B-70 programme, the USAF completely terminated the F-108 already mentioned. The reason given was lack of money; and in view of the obvious similarity between the F-108 and the A-11 it may be that the F-108 appropriation was simply diverted 18 miles further north to get the A-11 programme going at Burbank. According to the US Government the A-11 "was designed as a long-range intercepter, but has a potential reconnaissance capa- bility." Credence to this belief is lent by the fact that the A-11 has from the outset been matched with the complete armament system originally scheduled for the defunct F-108. This system has been developed by Hughes Aircraft, and comprises a search/lock-on radar of exceptional power and discrimination plus the AIM-47A (formerly GAR-9) air-to-air missile. But the powerplant is entirely different from that of the F-108. The A-11 is the only aircraft ever built around the Navy-funded J58 (JT-11) turbojet developed by Pratt & Whitney Aircraft at the division's Florida Research and Development Center at West Palm Beach. The J58 is a single-shaft engine (see diagram) of moderate pressure ratio, designed for Mach 3 and having a thrust "in the 30,0001b class." This is a sea-level static rating with reheat, and it can be exceeded at Mach 3 at the tropopause. Hamilton Standard provide the control system governing the fully variable intake, main and reheat fuel, and ejector-type variable nozzle. Kelly Johnson's team have chosen an overall configuration for the A-11 quite unlike that of previous US aircraft. It is remark- able that the wing plan should so closely resemble that of the Swedish Draken, since the latter was designed for a Mach number between 1.5 and 2. Lockheed claim their double-delta wing "elimi- nates the need for horizontal tail surfaces, flaps, slots, or other high-lift devices." The wing itself is closely related to that used in the Lockheed CL-823 SST, but there the resemblance ceases. Overall length of the A-11 is of the order of 110ft. The root chord of the wing extends over some 90 per cent of this distant and it would extend further still were it not cropped at the front (possibly to improve pilot visibility in a downwards direction). The thickness/chord ratio is probably less than 3.5 per cent. The for-
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