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Aviation History
1957
1957 - 1589.PDF
677 FLIGHT, 1 November 1957 AIRLINERS OF THE WORLD OEING 7O7 Boeing Airplane Company, Seattle, Washington FORTY years of aircraft manufacture, much of it devoted topioneering the next step forward in transport design, formsthe backdrop to the construction of Boeing's 707 jet trans- port—the aircraft that, perhaps more than any other, has cometo be symptomatic of the "jet age." Development of the KC-135s and the 707 prototype (the"Dash-80") has provided invaluable in-flight experience for the larger production versions of the 707 now under construction.Flight control systems, stability and control characteristics, sys- tems engineering and structural integrity will all have been well-proven by the time the first 707 is delivered (to PanAm) in December 1958; the aircraft is due to be rolled-out this monthprior to its first flight in December 1957. The Boeing 707 is not one but a whole family of aeroplanes,each scaled up or down in size and power to meet the specific needs of various airlines. The "Dash-80" prototype is thesmallest and lightest of them all, and is not truly representative of production 707s. The KC-135 is larger and heavier, and theairframe is much more nearly representative of the commercial 707. Offered now are a slightly confusing array of commercial707s, having three different fuselage lengths, two sizes of wing, and three engine alternatives. The first version, for domestic use,is the 707-120, with Pratt and Whitney JT3C-6 (J57) engines of 12,500 1b thrust (without water injection). A second 120 version—as shown in the cutaway drawing—has a longer fuselage (144ft 4in instead of 134ft 6in) and a greater basic operationalweight, but is otherwise similar. For example, both 120s have the same 2,433 sq ft ("small") wing. The same basic airframe can be matched to the increasedpower of the Pratt and Whitney JT4A-3 (J75) engine, when it is designated the 707-220 (the "hot-rod," so called, as ordered byBraniff), or to 16,500 lb s.t. Rolls-Royce Conway 505 engines, when it becomes the 707-520. (So far, no 520s have been bought.) The "Intercontinental," or overwater, Boeing 707s, intendedfor non-stop Atlantic operations, are altogether larger and heavier, with a larger, redesigned wing (2,892 sq ft) giving in-creased tankage, a maximum take-off weight of 295,000 lb (for taxying a gross weight of 296,000 lb is permitted), and the higherpowers applied to the 220. Suffix variations to the 707 Inter- continental are indicative of the type of powerplant installed:thus the 707-320 is powered by JT4A-3s and the 707-420 by Conways. As with the 120 and 220 there is, in addition, a similarchoice of two fuselage lengths; the shorter is dimensionally simi- lar to the longer fuselage of the 707-120. All fuselages are 148inin diameter, 4in more than the KC-135. BOEING 717 Originally known as the 707-020, the 717 is dimensionallysimilar to the short-fuselage 707-120. But operationally the air- craft are very different. The 717 has been designed to operateover short- and medium-length stages (200-1,500 miles), and the tankage has been drastically reduced from the 707 capacity to8,403 gal.; the maximum range with full 130-passenger payload is now 2,400 miles. A painstaking engineering programme, in-cluding the reduction of some skin gauges and the use of lighter undercarriage forgings, has resulted in a corresponding reductionin structural weight, and the performance will hence probably be slightly better than that of the 707-120 with the same JT3(J57) engines, although General Electric J79 engines are also contemplated. The take-off weight is 185,000 lb. This versionwas developed to compete with the Convair 880. The price— about $3.7 million—is some $500,000 less than the 707-120. AIRFRAME The structure is largely conventional, andstress levels have been kept on the conservative side. Little use is made of spot-welding or (unlike the 707's DC-8 and Convair880 competitors) of titanium, although integrally milled skins are widely used throughout the wing. Considerable use is made ofcrack stoppers and alternative load paths in what is essentially a fail-safe design. Fuselage The fuselage is built in four sections. The firstextends from the front pressure bulkhead to behind the forward entry door on the starboard side. The next and largest is atubular section which terminates at the wing trailing edge; the third section (sub-contracted to Ryan) tapers back to the rearpressure bulkhead, and the final piece is the extreme tail, which is independent of the tail unit. Most of the structure is identicalto that of the KC-135, although the upper bubble diameter has now been extended on all versions to 148in, 4in larger than thetanker. All the frames and stringers are of various riveted, angle or channel sections, and skin joints are made along strong longi-tudinal members reinforced with doubling strips. Much heavier frames are used at the wing spar stations; these are extrusionswhich are attached to the spars by forgings. At the intersection of the upper and lower bubble radii, transverse tie-booms formthe basis of the conventional floor structure, except over the wing, where the floor is built as part of the wing structure. There aretwo main doors on the port side, opposed by slightly smaller service doors or emergency exits to starboard; all are of the plugtype and are wider and deeper than their frames. The upper and lower edges of each door can be folded inwards and downwardson parallel linkages to reduce the effective depth, and the door, pivoting on the ends of hinged arms, can then slide out edgewaysthrough its opening. Under-floor freight and service compart- ments are provided with doors on the starboard side only whichpush in and slide sideways on rails. An optional feature which several airlines have ordered is the provision of glass-fibre bag-gage containers which can be pre-loaded with about 1,500 1b of
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