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Aviation History
1975
1975 - 0912.PDF
818 AIR TRANSPORT Boeing 747SP roll-out The 747SP, designed to fill the gap between the 707 and 747-200B and to fly further, higher and faster than all other subsonic airliners, was due to be rolled out of the Everett plant on May 19 before guests from the customer airlines. The seventh version of the 747 appears at a time when the market for airliners is looking decidedly soft, but Boeing expects to more than hold its share of the market in 1975. ANDY HOFTON examines the Special Performance 747 which Boeing claims will provide lower aircraft-mile costs than the 747-200B while maintaining a seat-mile cost advantage over the wide-body trijets. T HE 747SP will make its maiden flight in mid-July and certification, using the first three aircraft off the production line, is planned for the end of the year. Deliveries to Pan American will follow in early 1976, less than 2*2 years after the launching order placed in September 1973. Boeing expects Mr William T. Seawell, chairman and president of PanAm, together with senior representatives of Iran Air and South African Airways, to attend the official roll-out ceremony scheduled for Monday of this week, May 19. The order list for the Special Per formance 747 now stands at 13, comprising five for PanAm, three for Iran Air, three for South African Airways, and two for Syrian Arab Airlines. It is something of an oversimplification to describe the 747SP as a "cut-back" 747-100 although this is what it looks like. The performance has been reoptimised, drag has been reduced, the structure redesigned to cut weight and the systems revised to match the requirements of the new role. Overall length has been reduced by 48ft 4in to 176ft 9in and typical mixed-class passenger capacity from 385 to 281. About 42,0001b will have been trimmed from the operating empty weight (see table) and Boeing tells Flight that weighed "actuals" are coming out very close to predictions. The wing structure, for example, at 39,9161b is just 12 per cent up on predictions and is offset by cor responding sE'ings or other components. Boeing has never been the sort of company to stand by and watch other manufacturers selling aircraft in a sector of the market that could be filled with a product from Seattle. With the introduction in 1971 and 1972 of the wide-bodied trijets, in particular the Series 30/40 long- range version of the DC-10, Boeing began to feel the need for an aircraft larger than the 169-seat 707, but smaller than the 380-seat 747. The much heralded 7X7 family, which might have provided a 200-plus-seater, was still some way off, the American SST had been cancelled and the airlines were entering a period when a replacement aircraft was needed for the older 707s and DC-8s on "long, thin" routes. Suggestions by some pundits that Boeing 747SP CHARACTERISTICS Taxi gross weight (lb) Landing weight (lb) Zero fuel weight (lb) Operating empty weight (lb) Engines Thrust (lb) (ideal nozzles) Fuel volume (gal) Field length at max weight, sea level, 16° F (ft) Range with full passengers (n.m.) Seats Noise level at max weight (EPNdB) 747-100 738,000 564,000 526,000 357,100 JT9D-7A 46,950 47,210 10,200 4,960 385 103-5 747-200B 778,000 554,000 526,000 365,800 JT9D-7A(W) 48,750 51,430 10,600 5,280 385 1040 747SP 663,000 450,000 410,000 315,000 JT9D-7A 46,950 47,210 8,050 5,700 305 101-5 FLIGHT International, 22 May 1975 might adopt the TriStar, the child of near-bankrupt Lock heed, were not seriously considered in Seattle. PanAm, which had been the launching airline for the 707 and 747-100 and had always been an important Boeing customer, began to eye the McDonnell Douglas DC-TO-30. It was said at the time that McDonnell Douglas was willing to offer any version of the DC-10 as long as it had three engines in order to secure the PanAm contract. After a hard-fought sales battle, however, PanAm ordered tea examples of the new Special Performance version of the 747 and Seattle gave the project an unconditional go-ahead. Maximum take-off weight of the new aircraft was set at 660,0001b. Six 747 variants The SP is the newest in a family of six commercial models of the 747 based on the original 747-100. After successive improvements, the 747-100, which was launched with a maximum gross weight of 710,0001b, became the 747-200B weighing 775,0001b. This derivative, now available at weights of up to 800,0001b led to the 747-200F with a nose door, the 747-200C convertible freighter, also with a nose door, and the 747 Advanced Freighter with a maximum weight of 820,0001b. At the other end of the weight and range scale, Boeing sold Japan Air Lines the short-range 747SR in 1972 to be operated at weights of up to 520,0001b with 527 passengers on routes of less than 1,000 n.m. JAL normally flies the 747SR with 498 seats but the aircraft is basically a 747-100 beefed up to increase the fatigue life when used on short sectors. It retains the original tankage and can be flown with 385 passengers on more "normal" 4,500 num. routes. Boeing lists four main design objectives for the SP: to provide aircraft-mile costs competitive with the trijets with minimum impact on, 747-200 seat-mile costs; to retain handling and flight characteristics; to retain operational and maintenance commonality and the benefits of five years' operating experience and to provide range, take-off, initial cruise altitude and speed performance superior to the competition. PanAm was obviously impressed by argu ments of commonality and all that means in terms of spares holding and crew and ground-staff training. It was the financial pressures on the airline rather than any doubts about performance which resulted in a cutback in the order to five and negotiations to lease rather than buy the aircraft. Iran Air and Syrian Arab do not have 747s and bought the aircraft because of its attractive economics on long, thin routes; SAA needed an aircraft to fly non-stop to London out of Johannesburg's hot and high runway (London-Johannesburg non-stop, following a less demanding take-off, is within the capabilities of the 747-200B). All the existing customers have specified the 46,9501b-thrust JT9D-7A, although the 48,0001b-thrust JT9D-7F is available as an option. There is no commitment to offer the CF6 (which is an option on the 747-200/300) on the SP but this could be a possibility; the prospect of Rolls- Royce power now hangs in the balance (see Flight for May 1, page 691). Boeing says it "is talking to quite a number of airlines" who are potential customers but appears to be unwilling to comment on the suggestion that the Russians, who are interested in the 747, are more inclined towards the SP than the -200B. Structural alterations Because little of the basic 747 fuselage is parallel- sided, the cut in fuselage length from the 225ft 2in of the 100/200 to the 176ft 9in of the SP has required rather more than simply removing plugs. Portions have been removed forward of the front spar, aft of the trailing edge and forward of the pressure bulkhead (see illustration). The centre section has been modified to reduce weight, and a new section added to mate with the aft fuselage and thei tail cone. The tail section is now some 38in lower and has been rotated up one degree compared with the 747-100. Additional stiffeners and soundproofing have been added to the upper lobe. As the fin arm has been reduced, the tip has been extended 60in and a double-hinge rudder sub stituted for the basic single-hinge design and, according to Boeing, the SP has a higher yawing-moment capability than the basic aircraft. The strength of the fin torque box
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