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Aviation History
1958
1958 - 0474.PDF
490 FLIGHT "Flight" photograph "The first transport aeroplane of 'modern' design can be said to have been the Boeing 247 . . ." This is the first 247D, which had variable- pitch propellers and higher supercharging; it was third in the "speed" category of the 1934 England-Australia race. Origins of the Modern Airliner PART 1: SETTING THE PATTERN By PETER W. BROOKS, B.Sc, A.C.G.I., A.F.R.Ae.S. AIR transport as it is today was made possible by a type of/•% aircraft which first appeared 25 years ago. Indeed, the •*- •*• first transport aeroplane of "modern" design can be saidto have been the Boeing 247, which made its first flight at Seattle on February 8,1933. The Boeing was followed within six months—on July 1 of the same year—by the portentous DC-1 which began the famous series of Douglas transports, the descendantsof which, above all others, have made modern air transport possible. Before 1933, the aircraft used by the pioneer airlineslacked the technical and economic characteristics which events have shown are essential to an effective air transport industry. Today's airliner has evolved during the 25 years by gradualdevelopment and progressive refinement. There are surprisingly few radical innovations in the basic design of the modern propeller-driven transport aeroplane as compared with the Boeing 247 and DC-1. The Viscounts, Britannias, DC-7Cs and L-1649s oftoday are closely related in the engineering, operational and economic sense to the first transport aeroplanes of the "modern"era i.e., those which originally flew in 1933. In spite of the similari- ties, however—indeed, in some respects, perhaps because of them—cruising speeds have risen from 150 to 350 m.p.h., passenger capacities from ten to around 100, and operating stage-lengthsfrom about 500 to 3,500 miles. Most important of all, the total operating cost (in terms of today's money values) has been reducedfrom nearly a shilling per seat-mile to a figure in the region of fourpence and the safety of the vehicle (measured in fatalities per100 million passenger miles on the U.S. domestic routes) has been improved twelvefold so that, last year, the U.S. airlines achieveda level of safety comparable to that of the railways. This spectacular progress has been achieved with the same kindof airframe structure and without any radical advances in over-all applied aerodynamics, but steady improvements in the air-cooledradial piston-engine—in terms of output, power/weight ratio, specific fuel consumption and life between overhauls—have beena factor. Take-off powers have increased from about 500 to 3,500 h.p. and lives between overhauls from about 500 to 1,500hours. The recent appearance of the propeller-turbine is giving, and promises, still further benefits. It must be admitted that theuse of progressively larger aerodromes, and of longer and more expensive runways, has also played its part by making possiblehigher wing-loadings. These have increased from about 15 to about 85 lb/sq ft. At the same time, stalling speeds have increasedfrom 60 to 100 m.p.h. Nevertheless, the cantilever low-wing mono- plane, with riveted light-alloy stressed skin, retractable under-carriage, and engines (driving variable-pitch tractor airscrews) arranged in front of the leading edge of die wings, has remainedfundamentally unchanged from the days of the 247 and DC-1. There have, of course, been innumerable detailed improvementsand the aircraft have grown tenfold in weight. The aluminium alloys used as the main airframe structural material have beengreatly improved and steel and titanium have appeared alongside them in small quantities. Integrally machined structural com-ponents have come into limited use on some of the latest aircraft and metal bonding and spot-welding have also won some support;but, even so, airframes are still largely made up of riveted light-alloy sheet and extrusions and the actual structural techniques haveremained basically unchanged. The Boeing and Douglas companies set a pattern 25 years ago which has persisted in remarkable fashion. Aircraft type Boeing 200 Boeing 247 Boeing 247D Douglas DC-1 Douglas DC-2 Douglas DC-3 Lockheed L-10 TABLE I: CHARACTERISTICS OF THE Engines 1 xP.SW. R-1860-7 2 X P. & W. R-1340-SIDI 2 x P. & W. R-1340-53 2 X Wright R-1820-F3 2 X Wright R-182O-F3 2 x Wright R-1820-G2 2 x P. & W. R-985-13 Take-off power (b.h.p.) 575 2 x 550 2 X 600 2 x 710 2 x 710 2 X 1,000 2 X 450 Maximum take-off weight (Ib) 8,000 12.650 13,650 17.500 18,080 24,000 10,100 FIRST "MODERN-TYPE' Wing area (sq ft) 535 836 836 942 942 987 458 Wing span (ft in) 59 1i 74 0 74 0 85 0 85 0 95 0 55 0 1 TRANSPORT AIRCRAFT Length (ft in) 41 n 54 4 54 4 60 0 62 0 64 5± 38 7 Cruising speed (S0% T.O. power) (m.p.h.) 135 155 160 170 170 170 180 Stalling speed (m.p.h.) 57 59 60 59 61 64 65 Type of flaps nil nil nil split split split split Number of passenger seats 6 10 10 12 14 21 8
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