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Aviation History
1965
1965 - 0804.PDF
442 FLIGHT International, 25 March (?6' AIR TRANSPORT... THE DC-9 AND THE DEEP STALL THREE design changes made to the Douglas DC-9, followingwind-tunnel tests in an endeavour to avoid deep-stall problems such as those encountered on the BAC One-Eleven, are soon to be verified in the aircraft's flight-test programme. After preliminary evaluation by Douglas pilots, amounting to about lOOhr, the Federal Aviation Agency will begin certification flight testing. The first five DC-9s are expected to log about l,000-l,200hr in the overall flight-test programme, which originally was scheduled to result in FAA certification by January 1966. This date was based on a first- flight date of March 15; since the first aircraft flew on February 25 it is hoped that certification may now be achieved before the end of 1965. The first five DC-9s are expected to be flying by the end of June and a total of approximately 20 aircraft by the end of the year. First delivery is scheduled for December 1, 1965—to Delta Air Lines. Details of the Douglas approach to the deep-stall problem were given to Flight at the company's Long Beach plant in California two weeks ago by Mr John Brizendine, deputy general manager (DC-9) of the Douglas aircraft division. As executive head of the team responsible for producing the aircraft he is better known simply as "Mr DC-9." Relevant wind-tunnel tests continued for a period of over a year, Mr Brizendine said. Douglas was on to the deep-stall problem in the tunnels "at about the time BAC had their problem." The One-Eleven accident in October 1963 caused Douglas to intensify its efforts and investigate the subject in greater depth; wind-tunnel testing was completed about the middle of 1964 and, after analysis of the tests, the three changes were decided upon in October 1964. There was no formal interchange of technical information between BAC and Douglas on the question of the deep stall. Sir George Edwards cabled Mr Donald Douglas, Sr, offering in general terms to co-operate in working together on this problem; a polite acknow- ledgment from Mr Douglas agreed that this might be a good thing, but the suggestion was not formally followed up. One informal discussion did take place—at Seattle in November 1963—between Mr Kenneth Lawson, BAC aerodynamicist, Mr Brian Trubshaw, BAC test pilot and Mr George R. Jansen, the DC-9 test pilot. A leading role in the design of the DC-9 was played by Mr Harold W. Adams, whose experience at Douglas goes back to the hydraulics design on the DC-2. As assistant chief engineer (design) on the DC-9, he was the man who insisted in particular on the philosophy of simplicity (or, at least, of minimum complexity) that runs through the entire aircraft from basic concept to detailed subsystem and component design. First of the DC-9 design changes to stem from the wind-tunnel tests was a significant increase in tailplane area. Wings and tails for the aircraft are tooled and built by de Havilland Canada at Downsview, Ontario; in spite of the practical difficulties the change was effected in 84 days between the decision in October and the roll-out of the first aircraft in January. Second design feature confirmed by the tunnel tests was the introduction of an underwing fence known as a vortilon. This device, stated not to increase the drag at high cruising speeds, comes into effect at low speeds by causing vortices which tend to prevent the air from flowing out along the wings, and to delay separation up to higher angles of attack, thus obtaining higher lift co-efficients. A similar improvement in low-speed performance is in fact produced by the pylons of underwing podded engines. Although the vortilon contributed to the solution of the particular problem of the deep stall, its generally beneficial effect at low speeds would have made it an attractive feature in any case. Thirdly, a partial-demand system of power-assisted elevator control was added to effect a large nose-down movement when required. The normal aerodynamic tab loses effect at extremely high angles of attack; by pushing the control column further forward the pilot automatically obtains the hydraulically boosted control. Deep-stall tests will be carried out on the first two aircraft and also possibly on the third and/or fourth machines. The fifth aircraft will not carry test instrumentation but will be used in simulated intensive airline service to demonstrate functional reliability for FAA certification. Twelve pilots and 40 engineers have been assigned to the flight- test programme under the direction of Mr John C. Londelius, director of flight development, and Mr John P. Hann, flight-test project engineer. The four pilots who have flown the first aircraft to date are George Jansen, Paul Patten, Arnold Heimerdinger and Cliff Stout. The first two weeks of flight-testing included a number of stalls, but not at the extreme aft-c.g. loading and not in the "abused" conditions of the deep stall. The FAA certification programme should begin in about one month's time. For much of the time the flight-test DC-9s will be based at the NASA Flight Research Center, Edwards, California. In certain tests, including the deep-stall investigations, telemetry data will be transmitted to the ground at Edwards in addition to the automatic recording of instrument readings by film and tape equipment aboard the aircraft. Other tests not requiring the Edwards facilities will be made from Long Beach. FACING S8T FACTS MR BEVERLEY SHENSTONE, technical director of BOAC, will have some incisive things to say about the supersonic transport on the evening of March 31. He and Dr A. E. Russell will be opening an RAeS discussion evening on "The Difficulties and Advantages of Supersonic Civil Transport." This summary of Mr Shenstone's address is given in the March issue of the RAeS Journal:— The SST project is the largest, most expensive and most dubious project every undertaken in the development of civil aircraft. It is dubious because of the concern about the side effects of supersonic flying on a regular basis, the main one being the sonic boom. The project is unique in that in Europe it was instigated by and financed by the Governments for airlines and not by airlines. A similar pattern is followed in the USA. Another characteristic of the SST is that no airline has asked for it, but the project has tempted a few airlines to put in tentative orders, which has encouraged other airlines, out of fear, to put in other orders. The general run of technical unknowns is fairly well known, one of them being the heat caused by the friction of the air at the high speeds involved. Probably the greatest doubt lies in the improbability that the SST will be able to be profitable in operation. I agree that it is possible to make any given number of calculations on this matter, all with reasonable degrees of honesty, and half of them will show that airlines will make money and the other half will show the opposite. This is merely a measure of our lack of knowledge of these aircraft. Possibly the most irregular aspect of the SST is that it was not applied to military transport first but direct to civil transport. This in my view is absolutely the wrong method of approach. The RAF has been starved of modern military transport aircraft. At the present rate the only way it will get them will be when there is over-production in civil airliners, as an the case of the Comet, Britannia, and maybe the VC10. There seems no other way of equipping the RAF with really modern transports. There is a good case for such an experimental type of transport to be tried and proven by the RAF and the French Air Force. Airlines are not development organizations and there is no doubt that the SST will need a great deal of development, which means a great deal of flying, before it can go into service carrying the fare- paying public. Admittedly airlines could under contract do development flying but it would be expensive and require the diversion of specialized staff from other work. In the introduction of such machines into Transport Command the costs would not be so sharply defined and could be easily absorbed. RAF personnel would be only too glad to have some original work to do. It should not be forgotten that the USA projects which are intended to be faster than the Concorde are based essentially on the fact that the US Air Force will have two supersonic bombers in service before the civil aircraft are flown. The B-58 Hustler haf
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