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Aviation History
1987
1987 - 0857.PDF
that the significant majority of those sales will be A330s. A glance at these figures, even though it is obvious that you are not comparing apples with apples, plus a look at addi tional factors like the recent surge in 747 orders and a Boeing estimate that it will sell 400 high-gross-weight 767s, leaves you with the inescapable feeling that someone, somewhere has overestimated his share of the "long, thin" market. Either that, or the whole long-range market will be some what greater than 1,000 during the next 15 years or so, or the "long, thins" will take some of the 747's market. Taking some of the sales which might have gone to the 747 is indeed a possibility for the bigger "long thins" like the MD-11 and A340—indeed, Boeing concedes that this is so but cannot put figures on it. This would happen in areas where airlines might previously have bought the 747 purely because it was the only machine with the range for a desirable route, even though there might have been doubt about the ability to fill the aircraft. The changes which produce the MD-11 from its DC-10 base are not just minor adjustments: George Field is manager— design, MD-11 programme engineering, and he explains that where the DC-10 was born out of about 16,000 drawings, the changes which make the MD-11 consist of some 6,000 more plus the advantages of today's Cadcam (computer aided design and manufacturing). The changes start with stretching the DC-10-30 fuselage 18-6ft for the standard MD-11, pushing two-class seating up to 321 from 277. Maximum exit-limited capacity is 405. The extended range (ER) MD-ll's hull and seating are as for the DC-10-30. The MD-11 Combi can carry passengers/pallets in combinations of 120-214 passengers and six, eight, or ten pallets. A full pallet load is 26, and the MD-11F (freighter) can carry 90 tonnes of upper-deck cargo. George Field uses the term "super critical" somewhat liberally for the MD-11 wing, which is a DC-10 wing with its profile changed aft of the rear spar; aft- loaded would be a more appropriate description of its new profile. To have gone for an all-new wing design "would add $10 million a copy to the price of an MD-11", says chief customer engineer MD-ll/DC-10 Gary Smythe. That course of action would defeat the whole Douglas "low total ownership cost" approach. The addition of winglets as well, says Douglas, improves the aircraft's fuel efficiency by 3 per cent. There are a number of changes in the tailplane: compared with the DC-10's it is 30 per cent smaller, cambered, and contains 2,000 US gal of fuel which enables it to increase range and to give the aircraft e.g. control. The total effect of wing modification and e.g. control is to make the aeroplane some 7 per cent more fuel-efficient than its predecessor, and the new-generation engines (General Electric CF6-80C2 or Pratt & Whitney 4000) add a further 10 per cent to the comparative fuel efficiency figure. A stability augmentation system (SAS) will be fitted to compensate for the reduced natural stability which results from the smaller tailplane and the further-aft e.g., though Douglas says that handling without the SAS will be aceptable. Douglas says that it intends to use aluminium lithium floorbeams in MD-11 construction, which will give additional strength and weight saving. Alcoa has now 60 50 S 40 CD oa d (ton n o & 20 10 0 MD-11 DC-10-30 — - I I \ \ \ \ \ V \321 PSGR 277PSQR\ \ \ \ \ \ I I \ I \ 1.000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 Range (n.m.) MD-11 Max take-off weight 273-3 tonnes Max landing weight 1 95 tonnes Max zero-fuel weight 181-4 tonnes Fuel weight 117-5 tonnes Passengers maximum 405 2-class 321 3-class 276 Range (321 pax) 6,800 n.m. guaranteed the strength margins for pro duction batches, the manufacturer says. Cabin flexibility and underfloor cargo capacity are major MD-11 selling points, says Douglas. The fitment of modular galleys and lavatories means that a cabin change from a 270-seat three-class layout to a 400-seat charter configuration will be achievable within 12hr-18hr. The most radical changes possible, involving Combi realignment as well as seating density change, can be accomplished within 2\ days. Design for this degree of flexibility has been costly, according to senior staff engineer Joe Ornelas, because a sectioned air conditioning system and lighting and cabin address systems which would all accommodate change had to be pre- engineered into the MD-11 design. Under floor cargo capacity, says McDonnell Douglas proudly, is greater than that of a 747-400. The two-man-crew flightdeck tech nology promises to push ahead even of Airbus, with the radical change being in the electronic handling of what have tradi tionally been the engineer's tasks. "We have automated the flight engineer's function—we have put his book into a computer," says Field. "What Airbus has done," he continues, "is simply to minia turise the flight engineer's panel and put it in the overhead panel". At the heart of the "electronic flight engineer" concept are computers which handle all the aircraft's systems—fuel, electric, hydraulic, environmental, and miscellaneous. There are two computers per system. If one fails, the other takes over automatically, and if both fail, only then does control become manual, "and then the pilots handle it as they would in the Airbus", says Field with a smile. The computers handle the systems according to a checklist logic flow, then inform the pilots of the automatic corrective action and of its consequences. Long-lead items for the MD-11 were ordered some months ago, the mockup is nearing completion, and the assembly sequence for the lead aircraft begins in March next year. The certification programme starts in autumn 1988, and the first airline delivery will be made in April 1990. Production capacity by early 1992 is expected to be one aircraft a week. FLIGHT INTERNATIONAL, 13 June 1987 95
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