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Aviation History
1958
1958-1- - 0252.PDF
256 FLIGHT CIVIL AVIATION . . . The Case for the Comet A Review of the Prospects for Britain's Jet Airliner By J. M. RAMSDEN ONE of the themes consistently running through D.H.'spromotional efforts behind the Comet 4 these last twoor three years has been: "A jet airliner of moderate size for routes of moderate traffic density." On a first assessment, thisstatement appears to be more a plain statement of fact than a telling sales-argument. Moderate size? But surely, one might ask,the historical trend of all airliner development to-date has exhibited increases in unit capacities—soon up to 150 seats—asthe classic way of moving increased traffic most profitably. Routes of moderate traffic density? Why buy a jet for such routes, whichcan surely be dealt with by less competitive equipment? Do not jets make the best sense on competitive routes, which by defini-tion tend to be routes of high traffic intensity? Whatever may have been the justification for such questions inthe past, they do not appear to be warranted today. By a combinationof good luck and good judgment, the Comet 4 today appears to be theright-sized jet at the right time. The word "moderate" when re-lated to size is of course relative to the capacity-standards of the Boe-ing 707 and the Douglas DC-8. The number of first-class passengersneeded by a Comet 4 to break even on a stage of, let us say, 2,500 miles,is probably about 25 or 30. By com- parison, the number required by anintercontinental DC-8 or 707 on the same stage is of the order of 40 or50. This suggests that, on routes of given traffic intensity, and assum-ing that each type of aircraft is scheduled at the same frequency, aComet will tend to achieve loads greater than those required to breakeven more often than its larger- capacity competitors. This argument does not necessarily hold good on routes wherethe traffic will stand large-capacity transports, where it might be found that the medium-sized Comet 4 was being operated at toohigh a load factor. In these circumstances more Comets might have to be scheduled to handle the given traffic volume and toavoid turning business away to competitors. Except on routes where higher frequencies are desirable—which is much less likelyon long-haul routes than on short-haul routes—two medium-sized Comets might tend to be a less profitable way of meeting the trafficdemand than one 707 or one DC-8. But there are clear signs that there are not all that many routes where traffic density is greatenough, or is likely for some years to be great enough, to justify exploitation by large-capacity vehicles. There are, in particular,two such signs which might now be considered. AFTER an elapse of four-and-a-half years the de Havilland Comet isabout to resume British jet transport operations. The new Comet, a complete revision of the original, twice as powerful and with twice thecapacity, will start operations during the next few weeks on the world's most highly contested route. This article takes a fresh look at theplace of the de Havilland Comet 4 family in world air transport. First, the rate of growth of world traffic, on the form of the pastyear or two—and especially so far in 1958—is not coming up to the expectations for which the vast big-jet orders of 1955 and 1956were placed. The average post-war rate of growth of world air transport upto 1955 was about 20 percent. In 1955 it was 16.6 per cent, in 1957 it was 14 per cent, and in 1958 the rate of growth will almostcertainly be less. The load factors achieved by the world's airlines COMET FAMILY STATISTICS .;- "Series Typical seating Static thrust (Ib)... Span (ft) ... :^*.,Length (ft) Heightf (ft) Wing area (Sq ft) Total tankage (Imp. gal Maximum weight (Ib) . Capacity payload (Ib) Max. still-air stage-length with full payload and reserve fuel (st miles)Normal cruising speed (m.p.h.) Average cruising altitude (ft) ... 1A (Ghost 50 Mk 1) 44 5,000 11593 28.5 2,027 6,906 115,000 11,800 1,770450 34,000 2 (Avon Mk 117) 44 7,300 11596 28.5 2,027 6.906 120,000 13,500 2,535480 38.000 2E (Avons Mk 504 and Mk 524) 44 7,300 _ _ Jana 10,500115 96 28.5 2,027 6,906 120,000 11,042 2,240480 38,000 3 (Avons RA.26 and Mk521) 56 10,000 115111.5 28.5 2,121 8,308 145,000 16,305 2,800500 38,000 4 (Avon RA.29) 74* • 10,500 115111.5 28.5 2,121 8,990 156,000 19,124 2.720500 36,000 4B (Avon RA.29) 89» 10,500 108118 28.5 2,059 7,890 156,000 22,454 2,240530 23,500 4C (Avon RA.29) 89" 10,500 115118 28.5 2,121 8,990 156,000 23,209 2,270500 35,000 Notes: Figures take full account of effect of noise suppressors on performance. 'Mixed class, f Mean values: max. is 29.5ft at light weight. during these years have also dropped (from 59.3 per cent in 1956to 58.3 per cent in 1957), clearly indicating the extent of over- scheduling even with today's piston-driven fleets. There are signsin 1958 of an even greater fall in load factor. A fall of two points is generally more than sufficient to erase airline profitability;what will be the position when the 150-seat big jets are in service, and when the full effect of the airlines' financing commitments isbeing felt? This question has been the subject of much cynical gloom-mongering in the past year or two; suffice it to note here,in submitting the case for the Comet 4, that the air transport committee of the International Civil Aviation Organization haverecently predicted a considerable surplus of capacity in I960 and 1961 (Flight, August 15). And this surplus is forecast on theassumption, which must surely be optimistic, of a continued 15 This map, based on an original by de Havilland, shows the main air traffic streams in an average week of 1957-58. Each stream is labelled (e.g., 2-1-60) according, respectively, to the number of carriers, number of return flights per week, and seats offered each way each week. Summer and winter schedules listed in the "ABC World Airways Guide" were used except for North Atlantic figures which were those pro- duced by l.C.A.O. for 1957, less those for the Polar routes, which are shown separately. Thickness of the arrows is proportional to seats offered. Significance of this map in relation to the Comet's prospects is discussed in the text on the next page. 613-800 SOUTH AFRICA INCLUDES:- MADAGASCAR S.RHODESIA
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