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Aviation History
1975
1975 - 0916.PDF
822 AIR TRANSPORT FLIGHT International. 22 May (975 150 100 PAYLOAD (1000 LB At ranges above 5,700 n.m. the 747SP realty comes into its own. Performance is calculated for a standard sea-level take-off with inter national reserves. Take-off weights of the 747-100, 747-200b and 747SP are taken as 733,0001b, 805,0001b and 660,0001b respectively 50 plants has saved 4201b weight per engine. Spoilers and other controls have been tuned to meet the needs of the shorter aircraft but changes to the systems have been limited largely to adapting the plumbing to the new lengths. Overall, Boeing claims a SO per cent commonality of line-replaceable units between the SP and other 747 versions. The aircraft that emerges from the designers" surgery has a fuselage fineness ratio of about 8:1 (similar to that of the short-range 737). Compared with the 747-200B it has a lower wing loading (1201b/sq ft compared with 1401b/sq ft) and a higher thrust/weight ratio (0-285:1 compared with 0 25:1). But the introduction of simplified flaps has traded potential field-performance advantage for lower weight and cost. At a given take-off weight the SP has a slightly longer take-off requirement than the 747-200B and at a given landing weight the SP has slightly higher approach speeds and landing distances. The new aircraft scores, however, at ifls maximum take-off weight of 660,0001b when the take-off distance is some 2,500ft shorter than a 747-200B at 775,0001b and at maximum landing weights when the field requirement is some 600ft less. Boeing claims that the SP has better field performance for a given range than the wide-bodied trijets and that noise levels are comparable and all well below FAR Part 36. Boeing claims five per cent less cruise drag for the 747SP, brought about by the changed fuselage, a clean-up of the flap supports and modifications to a number of fair ings, and an initial cruise speed and cruise-altitude capa bility better than any other subsonic airliner. At maximum take-off weight, the 747SP will be able to achieve an initial cruise altitude at long-range cruise speed of over 37,000ft, or 1,300ft better than a 747-200 at the same brake-release weight and nearly 6,000ft better than a 747-200 or DC-10-30/40 following a maximum-weight take-off. Higher cruise altitudes, says Boeing, will avoid congestion and bring better fuel economy and a smoother ride. Unlike Concorde, the SP has not attracted any adverse comments about potential damage to the upper layer of the atmos phere as a result of exhaust pollution. A lower air-conditioning load and recent improvements to engine specific fuel consumption coupled with the lower drag, mean the SP will fly eight per cent more air miles per pound of fuel than the 747-200. At 5,000 n.m. range, the trip fuel required per passenger is the same for a 305-seat 747SP as that needed for the 385-seat 747-200, but at ranges above 5,700 n.m. the Special Performance aircraft begins to come into its own (see illustration). Both the SP and the 747-200B can carry 305 passengers 5,700 n.m. but at lower payloads the range of the 747SP is considerably better. At the fuel break point in the payload-range diagram, the SP has a range of 6,800 n.m. with a payload of 30,0001b (corresponding to approximately 150 passengers). Boeing says that this performance provides the capability to fly non-stop between city pairs that previously could not be connected by direct flights. It is also the kind of perfor mance which could provide an alternative to the super sonic Concorde, which would have to make a refuelling stop. The threat of competition from the proposed long- range A300B11 powered by four ten-tonne engines is not taken very seriously. It is one thing to make an aircraft that works techni cally, but quite another to convince the airlines that it will make money. It is difficult to make an economically viable cut-back aircraft, and some critics suggest that the MZFW = 410,000 LB 385 PASS. & BAGG. 305 PASS. & BAGG. 747-100 747-200B (JT9D-7FW) BASIC FUEL 8 2 3 4 5 6 7 RANGE (1000 NM) SP has one more engine than it needs, that the wing is too big and the fuselage too short. But Boeing made a success of the smaller revised 720/720B based on the 707, albeit designed for short ranges, and sold 154 examples. The company expects to sell between 150 and 200 SPs and claims seat-mile costs to be ten per cent better than the DC-10-30/40. Such factors as passenger preference, it says, will also work in the SP's favour. The fly-away prices of the SP and the 747-200B are similar at $31 million-$33 million and the SP is therefore more expensive on a cost per seat basis than the DC-10-30/40. The company does not disclose how much the 747SP programme will cost or what the break-even number will be. According to the annual report, however, the costs of long-term commercial programmes and US Government contracts not recovered from sales stood at $1,330 million at December 31, 1974, and much of this was accountable to the 747, which is being amortised over a production run of 400 aircraft. There had already been a steady decline in this "inventoried cost" from $2,798 million in 1969 to $1,326 million in 1973 and the slight rise in 1974 was perhaps attributable to the SP project. Boeing expects to sell at least 600 747s and the current order book stands at 292 with more than 250 delivered, making it the most success ful of the wide-bodies. The second 747SP is now in final assembly at Everett and will fly in August, Boeing tells Flight. The wing and centre section of the third aircraft are being joined. The first three aircraft, with the fourth as back up, will be used for some 400hr of certification flying, which should be fairly straightforward. The 747 factory at Everett has the capability of produc ing 7'2 aircraft a month, but is now running at two per month. At one time there were two production lines but the general slowdown in orders resulted in the East line being "deactivated." At present, however, new standard- body 747s are coming down the West line, and SPs and aircraft in for refurbishing on the East. Manpower assigned to the 747SP project reached a peak in early 1974. With work to do in other divisions—and on the 727-300—Boeing says that most of the personnel have been redeployed within the company. Below, the wing and fuselage of the first 747SP being mated at Everett; the sharp tapering of the rear fuselage is noteworthy
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