FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1996
1996 - 2211.PDF
Wm7 DESCRIPTION Alien the re-winged 737-X, as it became mown, was selected (mainly for commonality easons), die definition of die wing became one if the first priorities. The new wing was designed for flight at peeds of up to Mach 0.82. An economical raise speed of Mach 0.79 at a ceiling of 41,000ft 12,500m) is more likely in service, compared o around Mach 0.74 at 3 7,000ft for the current- ;eneration 73 7. lb help gain a few more knots, loeing has designed a raked, low-drag wingtip imilar to die much larger tip of the 777. Wing area is increased to 125m2 (1,345ft2), irimarily through a 5.4m stretch in span which s faired into the existing tip chord, and an ntirely new wingbox. The longer-range mis- ion required more fuel capacity, so the rear spar /as moved aft to provide extra volume. The icreased span also meant newly designed xtended spars and redesigned fuel and surge mks. Each wing contains 4,9001itres of fuel, iking total fuel volume (including a 16,2 3 Olitre entre tank) to 26,0361itres — giving roughly ,660km (990nm) of additional range (see sys- •ms description). Chord is increased by 43 0mm which, togeth- r widi the new aft-camber cross-sectional pro le, gives a lower thickness-to-chord ratio than I the 1960s-vintage design of today's 737. Despite the bigger wing, the designers main lined maximum commonality with the current iselage by keeping to the same side-of-body tin location. Arevised, low-drag aft wing-body amposite fairing fits around the wing root. O LEAKS oeing took advantage ofthe wingbox redesign ) address some nagging manufacturing and laintenance headaches with the traditional ing, such as leaking fuel tanks. New in-spar ans, stiffeners and ribs were designed and pro- iced from improved aluminium alloy used for le first time on the 777. The new design also ved weight. "All the in-spar ribs are fully achined, as opposed to being built-up. We ved literally thousands of fasteners [and] parts id weight, and we also saved on the tooling," ys Caton. The new tooling was designed ling an improved version of the Dassault ATIA computer-aided design and manufac- ring system. The tooling allows improved anufacturing tolerances and, in doing, cuts e risk of fuel leaks. Some weight was also unexpectedly saved in e wing-design process as late as 1996, when ore sophisticated flutter-analysis techniques :came available. The analysis showed that ing-skin thickness could be reduced aft ofthe igine pylon and part of the mass transferred itboard to an area near the tip. "It came out of where and we saved up to 801b [36kg] on the 00 design, around 1201b on die -700, and I01b on the -600," says Caton. Alcoa's new 155 alloy (which is also used on die 777 wing) used for its high compression-resistance in e upper wing surface, stiffeners and in-spar ribs. A 2000-senes alloy, 2324, is used for the lower surface skin which is subjected to high tension loads. REDESIGNED SLAT The leading edge ofthe new wing is modified with a new Kruger flap and an additional slat out board. The slat is based on a simpler design made up of fewer parts and is expected to stand up bet ter to corrosion, particularly around the trailing- edge wedge of the slat on die upper surface. There are two leading-edge flaps inboard of each engine and four leading-edge slats outboard. "We've retained the same basic leading edge, because it was the simplest solution," says Caton. "However, because it is the aerodynam- ically most critical part ofthe wing, we are now building it differently, to improve the finished product and reduce variability. In the past, this has almost been hand-made, but now we are building it straight on to the front spar. It used to be a separate subassembly that was loaded on later. We have eliminated a whole part of the assembly process and therefore reduced cycle time," he adds. Simplicity is also the key to die trailing-edge redesign, in which the complex triple-slotted Low-speed windtunnel testing for the new 717 was carried out by the UK Defence Research Agency flap mechanism of die current wing is replaced with a more straightforward double-slotted design. "Again, we're talking about reduced parts and lower maintenance costs with this design," says Caton. A hydraulic motor drives a flap power-drive gearbox to operate all the trailing-edge flaps via a torque-tube drive to ball-screw actuators. If the normal hydraulic systems fail, the flaps can be operated using electrical power. A load-relief system is built in to protect the trailing-edge flaps from excessive airloads. This will move the flaps up by one position if airspeed exceeds a set limit when the flaps are at 30o-40°. Flap tracks, enclosed in new fairings, are made from stainless steel instead ofthe corro sion-prone high-strength carbon steel tradi tionally used. Composite ailerons are increased in span by 510mm, along wim a proportionately increased trim tab. The new-generation 7 3 7 has a similar engine nacelle/pylon design to that of the 777, for which Boeing has overall responsibility. As a result, the engine is supported at the wing by an attachment known as the Rl fitting, rather than being attached to die front and rear spars as on the current 737. "This helped us eliminate a fairing on the upper surface," Caton comments. The dorsal fin and vertical stabiliser have been lengthened, and the span of die horizontal stabiliser increased to cope with the additional power ofthe CFM International CF/M56-7B turbofans. Overall fin height off the ground has grown to 12.5m, compared widi 11.1m for die current aircraft. The area ofthe vertical stabilis er increases to around 26.4m2, some 5.5m2 greater than that of the -300. The dorsal panels and fin trailing-edge fixed panels are of a honey comb-sandwich construction, fabricated using a glassfibre-reinforced-plastic (GFRP) epoxy prepreg cured at 121 °C The tailcone panels are also made out of a honeycomb sandwich using GFRP epoxy prepregs cured at 176CC. Horizontal-stabiliser span, meanwhile, has grown from 12.7mto 14.3m, while the area has IGHT INTERNATIONAL 28 August - 3 September 1996 63
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
