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Aviation History
1953
1953 - 0208.PDF
gftffMFf SSAHIFF AIRWAYS ONE OF 16 AIRLINES to have ordered the Convair-Liner 340 (the subject of the discussion below) is Braniff International Airways, which operates U.S. domestic and South American routes. Pictured here is the first of 20 Convair 340s on order by Braniff. CIVIL AVIATION THOUGHTS ON THE CONVAIR-LINER ONE reason for the belief that few, if any, orders have been lost to the British civil aircraft industry by reason of long delivery-dates may well be that a great part of the market has already been captured by American competitors. Many of our potential customers have quite recently placed orders for American transport aircraft which must be fully utilized for anything between five and ten years before their owners can think of replacing them with turbine-powered types. In the long- and medium-range categories most of the successful American machines are of war time or immediate post-war design, and the latest orders are for those versions developed to give better performance and payload capacity. A good example of these successful American designs is the Convair-Liner series for short and medium stage-lengths. The prototype Model 240 first flew in March 1947 and was certificated for civil aviation only eight months later. Altogether 175 Convair 240s were built—170 for the airlines. A larger, more powerful version, the Model 340, made its initial flight in October 1951 and received its C.A.A. certification in March 1952. Latest available figures show that the 340 has proved as attractive to operators as its predecessor, for over 20 orders have subsequently been placed for a total of at least 175 aircraft. Several have already been delivered and are in service with domestic operators. Assuming a unit value of £200,000 per aircraft (and this is con siderably less than the figure at present quoted for the 340), these combined orders for 350 Convair-Liners are worth £70 million— or some £35 million more than the total value of Britain's aircraft exports in 1952. About three-quarters of Convair's civil output is for domestic operators, the total export value of Model 240s delivered or 340s on order being in the region of £18 million. Details of Convair orders and the 32 operators responsible (in cluding 26 airlines) are as follows (excluding military contracts):— Airlines American Braniff Chicago and Southern Continental Delta Hawaiian Mid-Continent... National Northeast P.A.W.A. United ... Western Aero Argentina Aero O/Y (Fin land) Aeronaves de Mexico Central Air Transport Avensa (Vene zuela) C/fd. Model 240 79 S 5 5 15 10 5 6 130 Model 340 20 10 7 10 e 6 14 4 55 3 3 3 141 B/fd. Cia. Mexicana de Aviacion Ethiopian Garuda Indone sian ... K.L.M Orient ... Philippine Sabena ... Swissair T.A.A Corporations Aramco Executive Con vair-Liners ... Allison Div., G.M.C.» Mexico ... Texas Co. Pratt & Whitney •Turboliner. Model 240 130 2 8 12 3 6 4 5 4 1 175 Model 340 141 8 8 6 6 2 2 1 1 175 It will be seen that only five of the orders for 340s follow up previous purchase of 240s. The largest number of 340s will be operated by United Air Lines, with 55 aircraft; five of these were originally ordered by Pioneer Air Lines. Large numbers of the T-29 crew-trainer version of the 340 have been delivered to, or are on order for, the U.S.A.F., and an additional order for turbo prop variant (employing Allison T-38 turboprops and designated T-29E) was placed in October 1951. Yet another military version ordered in large numbers is the C-131 casualty-evacuation trans port. The Convair 240 is normally equipped to carry 40 passengers plus baggage. By comparison, the Model 340 has a longer fuselage providing standard accommodation for 44 passengers or additional freight; it also has higher aspect-ratio wings of increased span to permit the carriage of 500 gallons extra fuel (the 34o's two integral fuel tanks give a total capacity of 1,750 U.S. gallons). Numerous other refinements have been embodied. Basic comparative data for the two aircraft are as follows: Convair 240: length, 74ft 8in; span, 91ft 9m; wing area, 817 sq ft; weight empty, 30,3451b; take-off weight, 41,7901b. Convair 340 : length, 79ft 2in; span, 105ft 8in; wing area, 920 sq ft; weight empty, 32,3991b; take-off weight, 47,000 lb. Both types are pressurized and are powered by the same basic engine—the Pratt and Whitney R-2800; but the Model 340 has two CB16 engines which give a higher normal cruising power than the CAi8s powering the earlier machine. For short ranges the manufacturers quote maximum payloads of 10,155 lb (Model 240) and 14,100 lb (Model 340). One disadvantage common to both aircraft is that the relatively narrow internal cabin-width of 8ft ioin makes five-abreast seating an impossibility. In the 340, higher-density seating can only be achieved by installing extra pairs of seats in the fore or aft portions of the cabin and by decreasing the seat-pitching, in stages, from the normal 38m down to 34m. In this way, seating capacity can be varied between 44 and 56. According to the maker's figures, the Convair 340 can carry 13,500 lb payload over a 200-mile stage-length at a block speed of 210 m.p.h., assuming that 1,100 b.h.p. are being drawn from each engine at a cruising height of 10,000ft in still air; under the same conditions a payload of 10,000 lb can be carried by the 340 on a 1,000-mile stage at a block speed of 240 m.p.h. Convair's estimate of operating costs under U.S. domestic conditions shows a direct hourly cost of $138 and a corresponding figure of 67 cents per statute mile. These values assume a fairly high average utilization of eight hours daily, average journey length of 200 miles and speed of 207 m.p.h., with seven-year depreciation of capital investment. Corresponding figures for operating the CV-340 outside the United States show increases of some $60 per hour and 25 cents per mile, primary reasons for the increase being high fuel costs and lower utilization. In any case, such figures are probably optimistic and would vary greatly under different operating circumstances. The price of a Convair 340 with spares, according to the latest available estimate, is $700,000 (£250,000), making it more expen sive than the Viscount—which, as recent events have shown, is now capable of competing with the Convair on better than equal terms. In performance, structure weight and dimensions, the specifications of the two aircraft are remarkably close, but the British machine, being four-engined, is basically more costly to build in terms of man-hours and materials. Only high U.S. labour costs can be responsible for the un-
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