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Aviation History
1961
1961 - 0125.PDF
FLIGHT, 27 January 1961 IR COMMERCE SOONER, SMALLER SUPER VC10 . . . Tm- sixteenth BOAC VC10 off the Vickers production line may; ffer substantially from its predecessors. Under discussionh £r"ecn corporation and manufacturer now is a new size of airc aft, larger than the VC10 but not so large as the Super VC10previously projected. It has been reported that this new aircraft triic- r have about 195 seats; there are a maximum of 150 at 34inpitcK'in the VC10 and 212 in the Super VC10. While there is no suggestion that BOAC's total order for forty-five VC10 seriesaircraft will be altered, it now seems likely that the Super may not be ot the capacity and length which previously characterized thisdevelopment. It will be recalled that while there is no difference in diameter between the VC10 and Super VC10 fuselages, thelength of the latter is stretched by just over 27ft; the new variant might therefore be 17ft longer, or of about 176ft length overall. Little information was available earlier this week from BOACabout these changes, the corporation's only comment being that "We are investigating with Vickers-Armstrongs whether theSuper VC10 can be brought in earlier in the programme of deliveries." If the basic VC10 can be phased-out earlier, thefifteenth aircraft is the natural place, this preceding the usual production break allowed for a step-up to a different modificationstandard. Materials provisioning, it is understood, has already been made for thirty-five VClOs of standard size. The nomenclature of the VC10 series has now become con-fusing. It is apparently the intention to introduce the suffixes A, B, C, D and so on, to distinguish aircraft of varying capacity;the between-size aircraft is possibly the VC10C. . . . AND QUIETER TOO? ""THERE has been some speculation whether one of the reasons••• why BOAC and Vickers have had a change of mind about the Super VC10 is the difficulty of designing a large aircraft that will;not exceed specified noise limits when taking off at full load. This is a reflection not only on the absolute noise-level of theiengine, but of the power/weight ratio of the aircraft, since this affects angle and rate of climb. Noise decreases with the square ofdistance from the source and a fast climb-out is the best of all noise-abatement techniques. In the case of the Super VC10, noise problems may not, in fact,much affect the issue now under discussion. Rolls-Royce say there is no connection between these reports and the noise-suppression problems of the larger Conways. But noise con- siderations do now figure largely in powerplant design. One ofthe conclusions of the lecture, Trends in Aircraft Propulsion (summarized in Flight last week), was that "reduction of take-offnoise by increasing by-pass ratio is largely fruitless because compressor and other noise will become a dominating source." It was the noise problem which dominated much of the dis- 125 cussion of this lecture at Southampton University last week,leading Mr Maurice Brennan to exclaim, "The whole engine seems to be designed around noise!" Mr A. N. Clifton asked if itwas likely that the additional power that engine manufacturers often had to make available to compensate for design growthwould result in engine by-pass ratios, and thus diameters, being increased solely for the purpose of maintaining noise levels withinspecific limits. The lecturer, Mr H. Pearson (chief engineer [performance and research] of Rolls-Royce), agreed that this wasprobably the case; increased temperature would put up noise. Another compressor stage could be added, in which case the noisewould go up in proportion to the thrust, but in general it would be better to increase the by-pass ratio. Mr Pearson went on to explain why compressor noise wasbecoming a troublesome problem. It has its origin in the pressure field generated forward of the rotating blades. Known as "near-field" noise, it is extremely loud. Its frequency is that of the number of blades passing a given point per second—the "discretetime," and the noise is compounded of different frequencies generated by several stages. This noise reduces exponentiallyfrom the source. The "whine" of a compressor is probably caused by eddies from the trailing edges of the compressor blades and istherefore a function of the efficiency—or rather the inefficiency— of the compressor. Compressor noise varies with mass flow andtemperature rise in the relationship (MAT)1-6. Another point made in the discussion concerned the competitiveaspects of noise suppression. If a designer is limited to a specific noise level, Mr Brennan asked, could not a march be stolen bya competitor who allowed noise to rise a few decibels? He under- stood that the additional 3,000ft that was being added at LondonAirport reversed the operating-cost advantage the VC10 pre- viously showed over the Boeing 707. Wg Cdr T. R. Cave-Brown-Cave asked how long were we going to go on with noise limits; was it not a psychological approach to airport residents that wasneeded? After all, it had been demonstrated that noise levels of less than 85db would do no physiological damage. It was a pity,he added, that so much publicity had been given to noise levels in the vicinity of airports; and should not residents fit doublewindows to keep out the noise? Mr Pearson, in reply, said that long-suffering humanity had tobe taken into account by engine designers. Competitive designers and airlines could pinch a bit from noise limitations, but thosewho did so might (like Delta Airlines at New York) find them- selves threatened with a veto on the use of the airport. Jet noisereached much higher levels than 85db, so that penalties had to be paid to suppress it; with higher by-pass ratios these were small. WHIRLING FROM (HEATHROW) TO (GATW1CK) BEA helicopter services may start again next year with a servicebetween London Airport and Gatwick or, more accurately, between London (Gatwick), BEA's helicopter base, and London(Heathrow). The service would initially be operated by Westland Whirlwinds, of which the corporation now have long experience,and these may be replaced by Westland 192Cs in 1963. These plans, now under discussion with the Ministry ofAviation and the Treasury, from whom a subsidy would have to be obtained, are an indication that the introduction of BEAhelicopter services has slipped another year. Originally it was intended to operate between Penzance and the Scilly Isles withVertol 107s, but after permission to "buy-American" had been refused by the Treasury the corporation decided that the 192Cwas not at a sufficiently developed stage to introduce it on an overwater route. Introduction of this service has again beenpostponed. The intention is to operate between London's airports on anhourly basis; the journey time would be about 20 minutes. Assum- ing a 12-hour operating day in the summer, BEA would thusoffer a capacity of about 100 seats a day next year, rather more than are available between Gatwick and London on the summer-only inter-airport coach. Demand last year was probably stifled by inadequate frequency, the buses operating the 75-minutejourney only twice a day. It remains to be seen whether anything like sufficient capacity per trip is offered by the 8-passengerWhirlwinds at peak hours. No fare has yet been decided although some revenue assumptions must have been made on which tobase a request for operating subsidy. About £5 one-way would not seem unreasonable in view of the few alternatives avaiiable,and although this is 4s per straight line mile, the taxi fare for one person is not substantially less. This artist's impression of the Boeing 727 in service shows well the ventral door which, a la Caravelle, is the main passenger entrance. Also noteworthy is the location of the centre P & W JT8D, which is much farther aft than the Trident's central Spey. Boeing soy that the first 727, a production aircraft, will be rolled out in August 1962, with the first flight due in November 1962. According to Mr John Steiner, 727 chief project engineer, Boeing expect to sell 300 727s by 1970
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