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Aviation History
1955
1955 - 0192.PDF
192 FLIGHT FROM ALL QUARTERS More Britannias ? O harm has come of recent criticisms (direct or implied, andmostly unjustified) of the Bristol Britannia airliner and its progress. In fact, the answering of questions and the discussionof planning and progress have helped the aircraft and placed it in a stronger position in the public esteem. There now seems lessreason than before for B.O.A.C.'s proposal to order Douglas machines. Each additional large aircraft ordered from Americameans one fewer bought in this country, for it is not extra to the total of such machines which the airlines of the world can absorb. Present orders for Britannias—25, plus ten on option, forB.O.A.C., and six at letter-of-intent stage for Qantas—must now be increased if production is not to be interrupted later on. Thusa decision is likely to be announced in a day or two to order materials and proceed with the manufacture for an additionalbatch of Britannias. A small pilot order of perhaps two or three aircraft is likely to be placed by the Ministry of Supply, andthe Bristol Aeroplane Company and Short Brothers and Harland, Ltd., will show their faith in the Britannia by backing theremainder against new orders expected by the time the aircraft are taking shape. It will be recalled that in August, last year,Bristols acquired shares in Shorts, nominated two extra directors, and embarked on a programme of mutual collaboration. The Ministry's order for Britannias would no doubt be for theMk 250 L.R. for troop transportation. This is the type for which manufacturing plans are in hand at Belfast. In round figures, aBritannia, according to mark and without spares, costs between £650,000 and £850,000. Bell's Convertiplane "CARLIER this month, as we recorded last week, the Niagara*-> Division of the Bell Aircraft Corporation unveiled their vertical-jet-lifting prototype. On February 10th it was the turnof the company's helicopter division at Fort Worth, Texas, to reveal a wholly new development—in this case the Bell XV-3convertiplane. The company president, Larry Bell, visualized such an aircraftas long ago as 1943, but it was not until 1951 that the company was enabled to start actual design. In that year Bell was awardeda joint Army/Air Force contract for the development of a con- vertiplane for the Army. This machine has now materializedas the XH-33 or, as it is now designated, XV-3. Basically the Bell XV-3 is a combination fixed- and rotating-wing aircraft combining many of the advantages of the fixed-wing aircraft with those of the helicopter. It is powered by a singlePratt and Whitney engine (probably a Wasp) mounted just behind the small constant-section wing. The engine drives a gearbox andtransmission supplying power to a pair of airscrew/rotor units mounted at the wing tips. For vertical take-off the screws are used as rotors with theiraxes vertical, and the aircraft takes off and gains altitude in normal helicopter manner. It is then accelerated horizontally in the usualway and, at a given basic forward speed, the rotors are tilted forward through approximately 90 deg until they are acting asconventional airscrews. During this conversion process, which requires 10 to 15 seconds, the lift is transferred from the rotorsto the wing. In full forward flight the pilot changes the gear ratio between the engine and screws, thus making possible im-proved high-speed performance. It is claimed that there are no abrupt changes in attitude orflight characteristics during conversion from vertical to forward flight and that full control is maintained throughout. Transitionto forward flight can be stopped and reversed at any time and, in the case of engine failure, a return to helicopter configuration canbe made preparatory to an auto-rotative landing. The XV-3 is a four-seat aircraft which should be capable ofperforming a multiplicity of Army duties including all those at present undertaken by helicopters. The speed limitation of theXV-3 is predicted as greater than 175 m.p.h. and, in commercial use, Bell foresee the convertiplane (as a class) becoming supremeover stage-lengths from 100 to 750 miles. The XV-3, which measures 30ft in length and span and is 13ft high, is looked uponas a valuable prototype which may precede more advanced varia- tions on the same theme. The present prototype, which is illus-trated on page 202, is scheduled for exhaustive tied-down testing prior to flight testing in the spring. America and Air Superiority TFHREE pitfalls to be avoided in planning the maintenance of*- qualitative superiority in air weapons were enumerated by the Hon. Roger Lewis, U.S. Assistant Secretary of the Air Force(Material), in a speech at the recent honours night dinner of the Institute of the Aeronautical Sciences. The first, he said, waspoor conception, and by this he meant the technical results of inadequate military requirements. The second was indecision;here he referred to the absolute necessity of ruthlessness in ter- minating sterile or outdated projects. The third was unstableweapons planning and control; Mr. Lewis pointed out that the U.S.A. would never be ready for an emergency if planning wasdone on the basis of the ebb and flow of political events rather than on fundamental technical developments. The Assistant Secretary proclaimed his faith in the weapons-system concept, which he thought was an essential policy in view of the great complexity of modern weapons. He went on to saythat the rapid rate of change of the technical situation presented the greatest problem to defence planners, whose minds were con-tinually exercised by the possibility of unforeseen development. Pointing out the great difficulties of the rapid exploitation ofresearch, he quoted the example of the steam engine, the funda- mental concept of which was born in 1736 but was not appliedto locomotive traction until 1836 [In the United States—Ed.]. Jet engines were running on both the opposing sides in World War IIbefore the war began, yet effective jet aircraft were not in opera- tion until after the war was over; Germany's failure to exploither technical developments was one of the outstanding features of this war. Dealing with the present situation, Mr. Lewis pointed out thatthe United States possessed only seven per cent of the world's population and six per cent of the world's land mass, and said inthis connection that she must not fall into the error of taking comfort from an imagined technical superiority. National Wind Tunnels 'T'HIS country's largest supersonic wind-tunnel, with an 8ft x 8ftA working section, flexible walls, and absorbing some 80,000 h.p., should begin operation later this year. Designed for airspeeds upto Mach 2.7, it is located at the National Aeronautical Establish- ment, Bedford, which last week (for the first time) was open forinspection by the press. Among N.A.E.'s other facilities are a vertical spinning tunnel,of 15ft working-section diameter, which can be pressurized to four atmospheres; a 3ft supersonic tunnel which has been in use forthe last five years; and a 13ft x 9ft low-speed tunnel. Wind-tunnels at the R.A.E., Farnborough, were also visited.Here, one interesting development in progress was the modifica- tion of the 10ft x 7ft "high-speed tunnel" (used since 1942 forspeeds up to Mach 0.95) to form an 8ft x 6ft transonic tunnel capable of Mach 1.2.The highest speed attainable in the tunnels visited was Mach 4.8, approximately the limit ofconventional-type tunnels due to the liquefaction of air at those speeds. Tunnels capable of speedsup to Mach 9 (using air heated to 600 deg C) are now being designed, however, and shock-tubeand other techniques are expected to reproduce conditions of flight at Mach numbers of from10 to 20. A full description of the Farnborough and Bedford facilities will appear next week. BEDFORD BLOW-TUBE: Rising above the high-speed laboratory at N.A.E., Bedford, the new vertical spin- ning tunnel is typical of the establishment's impres- sive facilities (see "National Wind Tunnels").
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