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Aviation History
1955
1955 - 1740.PDF
FLIGHT, 9 December 1955 EVOLUTION OF THE VANGUARD . . . but the company feel it is worth the expense to obtain such data,and it may be that a Vanguard airframe will be similarly examined! Ever since the 1953 decision to employ turboprop power, theVanguard project has centred around the Rolls-Royce RB.109 Tyne. When tailored to the needs of the earliest V.870, therequired output was in the order of 2,500 to 2,750 e.h.p.' but steady growth of the aircraft project has been reflected in corres-ponding increases in design power of the engine, and the initial figure for the Tyne is now no less than 4,020 s.h.p. or 4,470e.h.p. This power should be more than met for commercial ser- vice by the time that the Vanguard appears, and development ofthe engine makes provision for an increase to 4,750 and then 5,000 e.h.p., and the latter figure can be accommodated by theVanguard with no alteration to the structure. In the Vanguard, the Tyne will be installed as a quick-changepowerplant, with accessibility and general ease of maintenance even better than the level set by the Dart in the Viscount. Mostof the bulk of the Tyne is well forward around the double-helical reduction gear. Surrounding this gear is an annular intake whichfits closely behind the periphery of the airscrew spinner, and the actual circumference of the front of the engine is formed by theannular oil tank, with twin oil coolers above. The remainder of the cowling is tailored to the optimum profile for minimum drag,the Tyne itself being extremely slim in comparison. Most of the accessories will be mounted underneadi where they will be readilyreached from below. Owing to the size of airscrew required, the Tynes will be further from the ground than are the Darts in theViscount, and trestles will be necessary for engine servicing. Petal-type cowlings will be employed, with a subsidiary intake(Viscount-style) for the oil-cooler air. A low-drag design of nacelle has been evolved, with a reduction in cross-section acrossthe maximum thickness of the wing—a feature common to most fast transport aircraft and one which considerably reduces inter-ference drag. The inboard jet-pipes are carried back across the wing to exhaust above the trailing-edge, the pipe being separatedfrom the wing by a firewall. This arrangement provides for a clear run of flap and also greatly eases problems associated withretraction of the main undercarriage units. The latter do, how- ever, inevitably result in a considerable bulge on the undersideof the inner nacelles. Outboard jet-pipes are likely to pass under the wing; at least this is the arrangement on the models of theVanguard which have been publicly shown. Airscrew Considerations Airscrews for the Tyne have been developed by bothde Havilland and Rotol. Both units employ four solid forged, light-alloy blades fitted with electric de-icing and capable offeathering, reversing and going into automatic coarse pitch in emergency. Both types of airscrew will have a diameter of14ft 6in. This size is sufficient to absorb all the anticipated development of the Tyne, as also is the spacing of the engineson the wing of the Vanguard. Clearance between the inboard airscrews and the fuselage is ample (this is referred to later in aparagraph dealing with noise), although ground clearance has naturally been held to a minimum in order to keep the chassislength at the lowest possible value. This also affects such funda- mentals as the height of the door sills and the overall height tothe top of the fin, both of which can be of importance to the commercial operator. In the Vanguard fuselage Vickers have evolved what seems tobe one of the finest passenger-carrying bodies yet developed for stages of up to 3,000 miles. Chief dimensions were shown in ourOctober 21st issue, from which it can be deduced that the fuselage will be bigger than that of any four-engined transportyet made in Britain or America. Almost the entire length will be usable, and the overall geometry makes the evolution of anefficient interior relatively simple. The extreme nose contains a search radar installation, ahead ofthe front pressure bulkhead. The remainder of the nose section is occupied by an extremely roomy flight deck surrounded by large 863 and deep windows, of which the forward electrically heated panelsare sharply swept back, the width of the deck being sufficient to allow the pilots to get close to the screens. The nose entry isparticularly interesting and Vickers expect it to be exceptionally efficient at M = 0.6 cruising speed, as well as being quieter than anentry with sharp radii over the cockpit. Vickers have actually learned much from the development of the Valiant cockpit, thefenestration of which is not dissimilar, either in aerodynamics or geometry, to that for the Vanguard. The standard flight-decklayout makes provision for a flight crew of three or four, with radio and electronics conveniently mounted in racks on the walls.General equipment of the deck is being planned to suit world- wide operation. The remainder of the usable fuselage above the floor is com-paratively unobstructed, and can be used by an operator as he wishes, all furnishing and bulkheads being non-structural. Twomain entrance doors are provided on the port side, one forward and one aft, both of which have power-operated airstairs incor-porated. On the starboard side two smaller doors are fitted, one opposite each entrance door, to form servicing entrances for toiletsand to act as emergency exits. In addition to the four doors, the windows over the wing and adjacent to the entrance doors pro-vide emergency exits. This is in excess of either A.R.B. or C.A.A. requirements. Cabin Pressurization Design maximum cabin-pressure differential is 6i lb/sq in(the same as in the Viscount), providing for an 8,000-ft interior when cruising at 30,000ft. The latter is foreseenas the maximum cruising altitude in B.E.A. service, and lower altitudes would be employed on all but the longest stages. Abuilt-in oxygen system is provided for the flight crew, and portable oxygen sets will also be carried. The Tyne is designed toprovide air suitable for a pressurized cabin, from a large bleed port in the intermediate casing between the low- and high-pressurecompressors. Nevertheless, the Vanguard's huge hull will need a great deal of air and it is not normally good practice to tap offvery much from the main powerplant. Furthermore, it is still a moot point whether or not oil seals can be made foolproof, and oilcontamination in the cabin air would be disastrous. Consequently, the Vanguard will employ separate engine-driven blowers forfuselage pressurization, with complete duplication of output. A very capable heating and cooling installation will be provided,and this will be particularly important owing to the great capacity of the Vanguard and its ability to encounter widely varyingambient conditions in the course of a working day. In an outside air temperature down to minus 76 deg F (an exceptionally lowtemperature for altitudes below 30,000ft) the interior will be com- fortably maintained at 70 deg F; conversely, the refrigerationsystem will maintain the interior at the same temperature in ambient conditions of 95 deg F with 65 per cent humidity. The interior of the new transport should be exceptionally quietand, in fact, the noise requirement in the specification was more severe than the highly competitive level set by the Viscount. Asalready stated, there is to be generous clearance between the inboard airscrews and the fuselage, and the reduction gear ratioof the Tyne (0.061:1) is such that the cruising tip-speed will be comfortably low. Even the reduction gear itself has been speciallydesigned to minimize noise generated by the meshing of the teeth. Passenger windows, of which there will be 19 on each side, at 39inpitch, will be very similar to those at present employed in the Viscount. In all normal interior arrangements there will beneither passenger seats nor windows in the planes of the air- screws, which should markedly reduce the interior noise level. Under-floor space in the lower bubble will be divided by thewing into two large holds. Both will be fully pressurized and air- conditioned, and will provide unobstructed space throughout atotal usable length of 53ft 3 in. The interior will be fully lit, and stressed to accept heavy point loads, the maximum size of indi-vidual load that can be accommodated being limited solely by door size. The standard Vanguard freight door will measure 5ft 6inby 4ft 3in, considerably larger than any at present used on Alternative seating arrangements for BI.A. Vanguards: the five-abreast layout provides for 93 passenger seats while the four-abreast scheme accommodates 76 passengers in exceptional comfort. Impressions of the interior with both arrangements appear overleaf.
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