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Aviation History
1960
1960 - 3094.PDF
1010 FLIGHT, 30 December 1960 Boeing's Trimotor BACKGROUND TO THE DEVELOPMENT OF THE 727 By ALASTAIR PUGH THE day after the Boeing 727 was announced, a "Flight" staff memberwho was in New York flew to Seattle to discuss at first hand the design and engineering background behind this challenging new short-haul jetairliner. Here, to follow our analyses of December 16, is his report. BOEING are already in business with the 727 in a big wayEngineering drawings are reaching the shops, at least twopartial mock-ups have been built in preparation for con- struction of the first aircraft, and aerodynamic and engineeringtesting has been in progress since June 1959. Purchasing of materials will start in March, component-purchasing followinga few months later. Before the first aircraft is rolled out in the late summer of 1962 some 5,000 people will be working solelyon the 727 programme. Many of those comprising this work- force have considerable previous experience of jet transport manu-facture, starting eight years ago with the -80 prototype. This air- craft, basis of the -120, -220, -320, -420 and 720 series is also beingused to develop the 727, notably the complex new flap. A podded JT8D on its short stalk is also shortly to be installed on the rearfuselage aft of the wing. The whole profile of the 727 has been mathematically lofted and is recorded on master magnetic tapesto which all manufacturing reference is made. The first Boeing 727 should fly in the autumn of 1962 andnearly the whole of the following year will be devoted to flight testing. At least three aircraft will be used. These dates are heredeliberately generalized; in practice Boeing have the month and day for each stage of the programme already fixed on their progresschan, although delivery of one aircraft each to Eastern and United is given as "at the end of 1963 or early in 1964." Anyone who doubts Boeing's ability to maintain this time-scalemight recall that, with the possible exception of BOAC's late- modified first 707-420s, the whole of the commercial jet familyplus about 430 KC-135s have all been delivered on or ahead of programme date. Why has there been a departure, in the 727, from the four-engined, underwing pod-mounted formula which has apparently served the remainder of the family so well? And, plagiarism aside,why does the 727 so very closely resemble the de Havilland Trident? What persuasive influence is there that so closely dic-tates short-range jet fashions on both sides of the Atlantic? Firstly, in designing the 727, Boeing were never trammelled bywhat had gone before. Work on a short-range jet started about 4i years ago and by August last year, not long after the work-forcehad been expanded to over 100 for the first time, some 65 different configurations had been studied. The emphasis at that time wasadmittedly on two- and four-engined layouts, in which under- wing-pod mounting was preferred for the four, and aft-mounting(a la Caravelle) for the twin. Before discussing the reasons for the latter, it is worth puttingon record Boeing's dislike of rear mounting per se. They do not subscribe to the "clean wing" concept in the belief that total dragcan be reduced or that the maximum coefficient of lift can be increased. Drag of the nacelle pods on the 727 is comparablewith the wing pods on the 707, and although it is true that by banishing the engines to the back-end flap (and foreflap) area andlift can be increased, Boeing say that the wing pod pylons make the tailoring of the stall a much easier job; fences do not have tobe over the whole top surface of a wing to do their work of controlling spanwise flow. What Boeing will not countenance is four engines across therear fuselage in a row. Their own experience is that, arrangement The 727-265 twin-engined project (a previous study, the -257, had an engine on each side of the fuselage above and behind the wing) was followed by the 727-264C, a twin with engines mounted on the aft fuselage and with speed capsules for increased Mach number. Next came the two projects illustrated opposite, the four shown being among the more interesting of over 60 drafted by Boeing since the summer of 1956 727-265 project 727-264C project
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