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Aviation History
1957
1957 - 0456.PDF
458 FLIGHT CIVIL AVIATION .;i; :.M THE FUTURE OF LONDON AIRPORT THE growth and development of London Airport have recentlybeen the subject of two papers by men who have lived close to L.A.P. since the war. In our November 16, 1956, issue, wesummarized the paper read before the Royal Aeronautical Society by Sir John D'Albiac (who, until he retired earlier this year, wasCommandant). Now Sir Alfred Le Maitre, Controller of Ground Services, M.T.C.A., has made a contribution in a paper read beforethe Royal Society of Arts on March 27. Although Sir Alfred did not refer to recent reports that "vast replanning of London Airportmay soon be needed" because of Government "miscalculations" of future traffic growth, he did say: "Few big projects end up asplanned, and London Airport is no exception. Aircraft grow larger and are more densely seated, so that turn-round times and there-fore stand-occupancy on the apron grow longer. Consequently, round the diamond we are growing short of apron space. More-over, I think we must accept that the early plans under-estimated the parking problem ... In addition, the use of outer standsinvolving a bus journey from terminal to aircraft, though logical, has never been popular with the public or the operator." To increase apron space and because present runway capacityshould be sufficient, it was now possible, Sir Alfred said, that one— or possibly two—runways would be put out of commission. Thenext step was to bring into the central area the long-haul inter- national operations at present at L.A.P. North, with resultantopportunities for experiments with the finger system. lns-.de a Britannia at Belfast representatives of Northeast Airlines are seen discussing contractual matters with (right) Mr. E. J. Stevens of Shorts. The Northeast engineers are, from left to right, Messrs. Meiss, Case and Splaine, the last-named being the representative at Bristol. THE MEDIUM-TRANSPORT COST CONTROVERSY 'T'HE interesting article by Mr. F. H. Robertson in Flight of-*• March 8 ("The Medium-range Transport") presents a clear- cut conclusion. This is always a happy state of affairs if it reallyis so, but one must regretfully come to the conclusion that the answer is not so clearly in favour of the turboprop as he haspresented it. Furthermore, this can be shown by studying the figures in his article. Firstly, in respect of the simplified cost formula, there is muchto be said for the cautious use of such a labour-saving device. To be simple it must leave out account of many factors, but thosewhich are included should be realistically assessed. Accepting the fact that crew costs and landing fees cannot easily be included,some of the assumptions which are used to arrive at the numerical coefficients are not in line with European operating experience;these are set out in Table 1: — TABLE 1 First cost of aircraft ... Fuel cost Robertson £9/lbNil 3,000 hr 24d/gal More realistic £14/lb 30% of first cost 2,250 hr 20d/gal The effect of using the more realistic figures is to alter theformula direct operating cost from: — W F1,000 — + 10,000 — pence/long-ton n.ml. VP PR to: — 1,780 — + 8,400 — pence/long-ton n.rhl.VP PR W (lb) is the weight of aircraft less fuel and payload. V (kt) is the true mean cruise speed. P (lb) is the payload carried. R (n.ml.) is the equivalent still air range. , ' •-. ' . F (lb) is the fuel carried.It will be seen that the second term (which is a measure of fuel consumption) has become relatively less important and thiswill tend to make the turboprop with its lower fuel consumption look less favoured. Applying the data of Mr. Robertson's Table 1to the above formulas, Table 2 is obtained : — TABLE 2 Aircraft Viscount 802 ..... Electra . Caravelie Comet 4A Convair 880 Boeing 707 Direct operating cost (pence/long-ton n.ml.) Robertson 16.7 13.0 12.8 16.5 15.1 16.5 15.2 More realistic constants 23.8 18.9 18.1 20.2 19.1 20.2 19.4 HERE is a further contribution to the popular controversy about therelation between jet and turboprop operating costs. Referring particu- larly to Mr. Frank Robertson's recent examination of the subject, itcomes from Mr. R. H. Whitby of B.E.A. The Viscount 802 is designed for large seating capacity inrelation to its weight payload, and in any comparison on a ton- mile basis it will appear at a disadvantage, so that it will befairer (and will incidentally favour Mr. Robertson's point of view) if in taking average values it is not included. ' TABLE 3 Aircraft Average of turboprops Average of turbojets ... Turbojet dearer than turboprop by Direct operating cost (pence/long-ton n.ml.) Robertson 12.9 15.8 23% More realistic constants 18.519.7 6% The cost difference is then quite well in line with the morelaboriously worked out data of Lord Douglas' Brancker Memorial Lecture—a tribute to the usefulness of Mr. Robertson's quickformula, provided more realistic constants are used! Turning now to the hypothetical turbojet and turboprops ofMr. Robertson's article these are most easily considered by W Fcomparing the parameters — and — for these aircraft with VP PRcurrent design practice. The first parameter is a measure of the lightness of the aircraft for a given "traffic delivery rate," whilethe second is a measure of the engine efficiency. TABLE 4 Turbojet Average for turbojets of Table 2... "Bristvikjet" Improvement assumed Turboprop Average for turboprops of Table 1 "Turbeuroprop" Improvement assumed W VP 0.0069 0.0057 17% 0.0081 0.0059 27% F PR 0.00089 0.00095 —7% 0.00047 0.00038 18% Weighting the separate improvements by applying them to the cost formula, overall Mr. Robertson has allowed an improvement above present design practice of about 3 per cent for the turbojet. On the other hand for the turboprop about 25 per cent has been allowed. It would be interesting to hear what developments he has in mind which would give this. Is it solely low-consumption turbines (which can benefit the turbojet as well) and large propeller diameter?
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