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Boeing 763 New Large Aircraft

In the mid 1990s airlines and aircraft manufacturers began discussing the future requirement for a new, larger aircraft capable of carrying between 500 and 1,000 passengers that, as a result, will weigh in excess of 1 million pounds. Deliveries of these types of aircraft were expected to begin in 5 to 10 years. Development of new large aircraft was explored by Boeing, McDonnell Douglas, and Airbus Industries. Each planned to develop its own family of "super-jumbo" jets. Many of the planned aircraft were larger derivatives of aircraft that are already flying. Other new aircraft, however, were based on completely new designs that are unlike anything currently in production. Announced specifications underwent continuous alteration with changes ranging from simple size adjustments to dramatic redesign of the entire aircraft. Some aircraft that were originally planned as a double-deck design were scaled down to traditional single-deck.

The average weight of commercial aircraft has increased consistently over the last thirty years. The trend in aircraft maximum takeoff weights for large aircraft introduced over the past 3 decades suggests that the upward trend in aircraft weight can be expected to continue to increase with the introduction of first and future generations of NLA. One trend is the weight characteristics of the larger transport aircraft used for long international flights. A second trend is the weight trend of the large transports used on shorter routes. These trends are parallel and are most likely to continue on the same track in the future. By taking these trends and their associated values into consideration, one can predict that the weights of future long route NLA will increase to 1.6 million in the next 20 years, while the shorter route NLA will also rise to 1 million pounds during the same period of time.

Commercial transport aircraft have also increased in wingspan length over the last several years. Many NLA will be classified in the largest airplane design group category, Group VI, recognized by the FAA. The largest wingspan included in this design group category is 262 feet. Current trends in aircraft wingspans indicate that they will continue to grow but may be curved to remain within the parameters of current design Group VI criteria. It is anticipated that it will reach a plateau and result in maximum values at or below 262 feet for two reasons. The first is that the development of higher efficiency wings will permit the carrying of more weight without an increase in size. The second reason, actually an unavoidable restriction, is that airports will be unable to fit aircraft that are much larger than 262 feet on their taxiways and runways without compromising the required separation standards for aircraft operating at the airport. The future demand for faster transport aircraft may also influence the trend in wingspan length, as they will most likely be equipped with swept wings for faster flight.

Other design characteristics of future NLA that can be predicted based on historical trends are the fuselage length, tail height, and landing gear wheelbase. These three elements, in general, are very closely related to each other. The wheelbase of the aircraft is typically a function of the fuselage length; the longer the fuselage, the longer the required wheelbase. Likewise, as the size of the aircraft increases, the height of the aircraft increases. Future derivatives of NLA are also expected to continue to grow in size and may be expected to have fuselage lengths upwards of 280 to 300 feet. As a result, they can also be expected to have wheelbase values upwards of 140 to 150 feet and tail heights over 80 feet.

Current FAA airport design standards provide reference and guidance for airport designers and forecasters relating to construction and configuration of all runways, taxiways, aprons, and terminals. The design of these items is based primarily on the size, approach speed, and number of aircraft the airport is expected to serve. The FAA established the Airport Reference Code (ARC) system to aid designers in properly determining the size of the runway, taxiway, or terminal that is needed at an airport. Advisory Circular AC 150/5300-13, Airport Design, defines ARC as "a coding system used to relate airport design criteria to the operational and physical characteristics of the airplanes intended to operate at the airport." The geometry of all surfaces at an airport is designed specifically for the largest aircraft or group of aircraft that will be operating at the airport. This assures that all aircraft will be provided with the proper obstacle clearance and separation requirements while maneuvering on the airport's paved surfaces. An airport's ARC includes both a letter and a number for the critical aircraft approach category and the airplane design group, respectively.

The Boeing NLA, or New Large Airplane was a 1990s concept for an all-new airliner in the 500+ seat market. Somewhat larger than the 747, this aircraft was similar in concept to the Airbus A380 and McDonnell Douglas MD-12. The 763 concept not only provided room for 450 to 550 passengers, but could be equipped with sleeping berths in an upper deck for longer intercontinental routes up to 9,000 nm (16,740 km). Boeing chose not to pursue development of this concept, focusing instead on updates to the 747.

763-241

The Boeing Large Airplane Product Development (LAPD) team evaluated the C-17, the high-wing military transporter developed by the newly acquired McDonnell Douglas company for the US Air Force. Although this was at first sight a strange model on which to base a potential LAPD, the Boeing team found intriguing possibilities with the design, particularly its excellent emergency evacuation layout. The team visited Lockheed Martin and researched the layout and structure ofthe C-5, and spent a day crawling over an Antonov An-124 that was visiting Seattle.

The result was a "C-17" look-alike design, designated the Model 763-241, with a high wing, four underslung turbofans and an enormous T-tail, 20.1 m to 21.3m high depending on configuration. The aircraft's span was 80m and length overall was 76.25m. The vast, ovoid-section fuselage was about 8.2m wide at the floor level ofthe single main deck, with five exits on each side. The main undercarriage, comprising a six-wheel main truck on the outer station and a four-wheel main truck on each inner station, was housed in streamlined fairings that were far less obtrusive than those on the current C-17. Windtunnel tests on a model showed the design was capable of Mach 0.9-plus cruise speeds.

Despite the design's promising operational aspects, the vast size ofthe tail and the height of the engines above the ground posed significant problems for ground support. Also, structural analysis revealed "lots of issues" with wing loading, and the structure of die fuselage needed to support the high-set wing box and the complex undercarriage bays.

763-246C

By 1998 Boeing began work on a design resembling a 777 with a four-engined low wing layout. The Boeing 763-246C concept aircraft was a 450-550-seat single-deck four-engined wide-body airliner that [as of 1999] could enter service as soon as 2006, if approved by the Boeing board. Current plans, however, are for continued development of 747-400 derivatives. Boeing performance targets for the 763-246C include costs as much as 10 percent lower than those of the Airbus A3XX-100 two-deck concept aircraft; a composite wing would be used.

After many alterations, the resulting design (one of which was the Model 763-246) showed a 14,300km range aircraft with seats for 454. An extended-range version of the design, which included innovative features such as a composite wing, revealed the range potential for 16,600km missions. The aircraft's 35 swept wing had a span of 80m, and a length of 73.5m for the standard version, and 80.2m for the stretch. MTOW ranged from 471,200kg to 532,500kg for the larger version.

A stretch was outlined which could seat up to 547, with optional overhead sleeping accommodation for 82. With three aisles instead of two, all passengers sat on one deck, but there was sleeping berths above the passenger deck. It was 75 Ft tall and around 270 feet long and could carry between 480 and 547 passengers.

The most significant advantage over the A380 would be revenue cargo volume. The design of the A380 called for a 25% capacity jump over the 747-400 (555 v. 416 passengers). However, nearly the entire jump is acheived through the addition of the full-length double deck. While this is a very effecient and convenient method of adding capacity while minimizing overall dimension growth, it had a severe draw back: it adds virtually nothing to the lower cargo holds. The 747-400 has a listed lower hold volume of 6,025 cu. ft. The A380 has a total volume of 6,045 cu. ft. - an increase of less than 0.5%.

The 763-246C design would have a cargo hold to match its extended width. Not only does it gain another passenger aisle, but also another row in the hold (3 LD-3's side-by-side). Also, the 763-246C would be significantly longer than the A380, further enhancing its cargo advantage. At 273' 5", the 763-246C would best the A340-600's current record by nearly 30' of total length. Considering the A340-600 (and likewise, the 777-300ER) has a monstorous cargo volume (7,331 cu. ft. for the former, 7,100 for the latter), its not hard to imagine the 763-246C having 50-75% more cargo volume than the A380.



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