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Aviation History
1997
1997 - 3325.PDF
UDZJfJX 777-300 MTOW of 299,600kg and 436kN engines. General Electric's GE90-92B, rated like the other -200IGW engines at dirust levels of up to 409kN, therefore became a candidate for the - 3 00, as did Pratt & Whitney's PW4090 and Rolls- Royce's Trent 892. In response to urgings from Korean Airlines, which particularly wanted the higher MTOW variant, P&W also agreed to commit to a 436kN engine for die -300, die PW4098. By late 1997, GE's reluctance to commit to a higher-thrust version of the GE90, and strong competition from P& Wand R-R, led to the US engine maker dropping its powerplant as an option on the -300. The remaining two, mean while, continued to study higher-thrust options for the proposed -200X ultra-long-range and - 300X extended-range 777 variants. Cathay Pacific Airways, one of the original partners in the "working-together" group which was instrumental in die 777 design, was a staunch champion of the stretch concept and was among the initial launch customers when the -300 was given the go-ahead at the Paris air show in June 1995. Other customers which, together with Cathay, placed $3.1 billion-worth of launch orders for 31 aircraft, included All Nippon Airways, Korean Airlines and Thai Airways International. By December 1997, two months after the first flight of the -300, the order tally had grown to 51, with Asiana Airlines, Japan Airlines and Malaysia Airlines joining the exclusively Asia-Pacific-based cus tomer group. With many early 747s coming up for retire ment, or conversion into freighters, Boeing believes that more than 170 777-300s could be delivered by 2006, and has outlined plans to make as many as 2 8 a year by 2002. To Boeing 777-300 changes from 777-200 Source: Boeing 20% passenger- capacity increase Forward fuselage stretched by 5.3m plug (ten frames) Ground-manoeuvre camera system Tail skid Ground-manoeuvre camera system Increased MTOW. MZFW and MLW Structure designed for MTOW of up to 299,600kg and 436kN-thrust engines Type A door and escape slide Strengthened: Fuselage sections Nose and main landing gear Inboard wing FLIGHT create the 777-300 from the -200, Boeing has inserted two plugs into the fuselage and redesigned the overwing area known as Section 44. The forward stretch involves adding 5.3m, or ten frames, to Section 43, while the aft-fuse- lage Section 46 has been extended by nine frames, or 4.8m. In theory, with the relatively tall main gear of the basic -200, the airframe was capable of even further stretching, but Boeing stuck to the 10.1m extension to maintain ade quate lift margin and minimise handling prob lems at airports around the world. NINE-FRAME STRETCH "The decision on a nine-frame stretch for the aft section was based on lift margin, because that was the point where take-off speeds and rota tion margin came together. That allowed us to use the same-length landing gear," says 777- 200X/300X and former -300 programme man ager Jeff Peace. As the size of the aft extension was finalised, so die proportionate length ot the forward plug was settled for centre-of-gravity and balance considerations. The longer aircraft cannot be rotated as steeply as the shorter -200 can, so die -300 needs more acceleration to create the same amount of lift for take-off at equivalent weights. In its efforts to launch the proposed -300X (which has J'»nniM a higher MTOW of around 324,600kg), the company is studying a "semi-lever" main gear to help reduce the take-off run for the same reason. The semi-lever, or articulated gear, offsets this limitation because actuated linkages attached to the oleo and forward end of die gear truck hold the aft end of the bogie on to die runway. "This effectively increases die lcngdi of die gear," says 777 preliminary-design chief project engineer Mike Burtle. "This increases the effective rota tion angle of die aircraft, which lowers the take- offspeed." The driving principle behind the structural changes to the fuselage was ".. .to keep a neutral position from the loading point of view", says body-Structures senior principal engineer Scott Tomkins. "The plug in front is designed to keep the frame stations the same forward or the front spar of die wing. It is not a true plug.. .it is real ly a new length of constant section because of the interface at the front spar." Tomkins describes the nine-frame aft stretch as "a real plug attached to Section 46". While much attention was given to stretch ing the fuselage, most of the design effort went into re-working Section 44 and the keel area beneath, called Section 45. "All die major struc tural changes were made in 44, which has now got a pretty thick skin," says 777 body-struc tures unit chief engineer Jack Donnan. Approximate - maximum • FLIGHT INTERNATIONAL 3 - 9 December 1997 37
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