领域：学术论文 · 应用学科

1.5.1 Boeing 787 Dreamliner
The Boeing 787 Dreamliner (Fig. 1.5A) is a family of long-range, midsize wide-body, twin-engine jet airliners that can seat 242–335 passengers in a typical three-class seating configuration. This aircraft, the world’s first major commercial airliner to use composite materials as the primary material in its airframe, is Boeing’s most fuel-efficient airliner [11]. The Boeing 787 maiden flight took place on December 15, 2009 and completed flight testing in mid-2011. Final Federal Aviation Administration (FAA) and European Aviation Safety Agency (EASA) type certification was received in August 2011 and the first 787-8 model was delivered to All Nippon Airways in September 2011.

The Boeing 787 aircraft is 80% composite by volume. By weight, the material contents is 50% composite, 20% aluminum, 15% titanium, 10% steel, and 5% other [11]. Aluminum is used for the wing and tail leading edges; titanium is used mainly on engines and fasteners, with steel used in various areas.

Each Boeing 787 aircraft contains approximately 32,000 kg of CFRP composites, made with 23 t of carbon fiber [11]. Composites are used on fuselage, wings, tail, doors, and interior. Boeing 787 fuselage sections are laid up on huge rotating mandrels (Fig. 1.6A). AFP and ATL robotic heads robotically layers of carbon-fiber epoxy resin prepreg to contoured surfaces. Reinforcing fibers are oriented in specific directions to deliver maximum strength along maximum load paths. The fuselage sections are cured in huge autoclaves. The resulting monocoque shell has internal longitudinal stiffeners already built in (Fig. 1.6B and C). This highly integrated structure requires orders of magnitude less fasteners than the conventional built-up airframes. Similar composite manufacturing techniques are applied to the wings.

5.5.3 Technical contribution to performance
Air-vehicle performance is technology-based, and as technology evolves so performance is improved. This links to a gradual change in airliner design criteria, and while aircraft configuration has been relatively static, the shape of airliners has changed subtly in recent decades. It could change remarkably over coming years as new performance demands are made by customers.

A new structural material having the most influence is carbon-fibre reinforced plastic (CFRP). The Airbus A380 uses some all-CFRP components and has a large proportion of the fuselage manufactured using a unique aluminium/reinforced-plastic sandwich (trade name ‘Glare’), while the newer Boeing 787 Dreamliner and its even newer Airbus equivalent aircraft, the A350, will use carbon-fibre extensively. The Boeing design is in a more advanced state of development and is anticipated to have an almost all-CFRP fuselage shell and CFRP wings. Airbus A350 plans are based on a similar technological basis.

CFRP offers durability and is relatively light. The designers have to exploit the potential weight saving with care. For the 787 Dreamliner Boeing has allied airline requests for fuel efficiency improvements with a desire stemming from other areas of concern in the airports and airspace environments to offer more flexibility in operations. This is an early indication of the needs of the air transport system as a whole taking a part in the debates that range outside their direct area of interest. Boeing believe that the 787 will offer better fuel efficiency over a wide combination of payload and range values, and they also believe that being a smaller aircraft than most current long-haul types it will offer the opportunity for more point-to-point operations. The analysis of route networks in Chapter 1 has shown that airline hubbing is often the reason that some airports become congested, while others see their direct-route possibilities diminished. The 787 is being marketed as an aircraft capable of making hubs a thing of the past and opening more direct routes. The converse solution is to offer more capacity per movement at hubs, which is where the 600-800-seat A380 will be exploited. The reality will be, surely, that both types will make their mark.

Where the 787 is particularly significant is that the design is using the new technology adroitly. The aircraft wing is very flexible and in its detail it is indicative of a push to achieve a higher aerodynamic efficiency (a higher lift- to-drag ratio). This will reduce fuel-burn, and will be improved by using engines that are achieving better fuel-burn performance than earlier generation engines. The combination of aerodynamic and propulsion system improvements should set a new benchmark, and on preliminary performance data released by Boeing (at September 2005), the fuel efficiency at the maximum payload-range point was shown to be 33% improved on the 777-200LR. There is probably some optimism in this figure.

This has been achieved in one generation (there was an interval of about 15 years between the launch of 777 and 787 as projects), and exemplifies not just commitment by the manufacturers and their major suppliers to achieving significant environmental improvement but also in exploiting technology. In so doing, they do not minimise the cash-flow on their programmes and the risks they take are considerable. Most major companies involved in airliner design and suppliers such as aeroengine companies all delicately tread the lines that delineate technical and financial risk.

Aircraft efficiency is measurable in many ways. Some tabulated data regarding leading features of some significant aircraft types that have been introduced over the last 40 years are presented in Table 5.5 to exemplify briefly how some intuitive, and sometimes counter-intuitive, developments have taken place. Behind each of the strides that has been made in the evolutionary tale there is always also a tale of risk management on a grand scale.

Fuel fraction is a measure of the maximum fuel load as a proportion of the maximum take-off weight and is often quoted as a measure of technical efficiency. In the course of their life, short-medium-haul aircraft tend to complete more flights than long-haul aircraft and are more robust in terms of their construction. The consequence is that the fuel fraction is always lower than that of long-haul aircraft. (The differentiation is not so clear-cut, and the Boeing 757–200 and 767–400 are aircraft capable of trans- Atlantic operations and their fuel fraction is noticeably higher than other aircraft in their category.)

Listing the selected types in date order emphasises the fact that fuel fraction is not tending to rise, although it was expected that it would as lighter-weight structural materials became available. The observation is that as more fuel-efficient engines have been developed, the necessary range performance has been attained with smaller and less heavy aircraft.

The tendency for the key aerodynamic efficiency indicator, the wing aspect ratio, to rise with time is evident, albeit the rate of increase is slow. There are always exceptions to the rule. The A380 has a relatively low aspect ratio, which is attributable to the need to provide a given wing area but to fit into an apron stand ‘footprint’ that is 80 metres square. Hence aerodynamic efficiency has been compromised in order to make the aircraft compatible with modern airports.

翻译考点：
考点1：“All Nippon Airways”需译为“全日空航空”，译为“全日本航空”算错误
考点2：“titanium”推荐译为“钛”
考点3：“robotically”推荐译为“自动”
考点4：“longitudinal stiffeners”推荐译为“纵向加劲肋”
考点5：“The designers have to exploit the potential weight saving with care”推荐译为“设计师在挖掘其减重潜力时，必须十分谨慎。”
考点6：“payload”推荐译为“有效载荷”
考点7：“making hubs a thing of the past”推荐译为“打破枢纽束缚”
考点8：“flexible”推荐译为“柔韧”