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Aviation History
2003
2003 - 0011.PDF
AIR TRANSPORT DESIGN GUY NORRIS / LOS ANGELES BWB may lead to Sonic successor Tests show concept capable of operating at speeds up to Mach 0.93, offering alternative to ditched programme BOEING BWB AERODYNAMIC CONFIGURATIONS FLIGHT nmuuiuM GIUSEPPE PICARELLA Z0O3 Boeing has revealed preliminary results of another high-speed blended wing body (BWB) study that indicates a modified variant of the concept can operate feasibly at cruise speeds up to Mach 0.93, well above the baseline version's origi nal design speed of M0.85. The result could offer Boeing an alternative low-cost, high-speed option to the Sonic Cruiser, although the company says the higher speed of the BWB variant comes with a performance penalty. Insiders suggest, however, that since the Sonic Cruiser was axed, a MO.9 "sweet spot" discovered dur ing the evaluation could become the focus for future BWB efforts. Ironically, the high-speed study was launched as a direct result of the Sonic Cruiser programme and the company's "new emphasis on increased speed". Boeing says the natural area ruling of the BWB and its low wave-drag make the aircraft a good option for "performing at lower cost than a conventional air plane when increasing to higher subsonic speeds". Eight different BWB configura tions, all sized for 258 passengers, were studied using computational fluid dynamics (CFD) and Wing Multidisciplinary Optimisation design (WingMOD) covering Mach numbers of 0.85, 0.90, 0.93 and 0.95 and ranges of 13,875- 16,465km (7,500-8,900nm). Initial CFD design studies showed that wing planform changes were needed to reach the higher cruise speeds, and for the M0.93 case these included a 5° increase in leading Air Hong Kong is to be the launch customer for a new variant of the Airbus A300-600F freighter designed to handle general freight. The Cathay Pacific Airways and DHL Worldwide Express-owned all-cargo airline confirmed the expected deal last week, with an order for six new-build aircraft for delivery from 2004 and four options. It will be the launch customer for the A300-600F General Freighter, which differs from the existing A300-600F in that it has a cargo loading system and side door capable of handling both large items of general freight and small packages. Deliveries will be between mid- 2004 and early 2005. An engine selection has yet to be made between the competing power- plant offerings by General Electric and Pratt & Whitney. edge sweep across the entire span, plus an additional 3° increase in leading edge sweep for the inboard section. However, the WingMOD analysis revealed a balance problem with this design, so using this sec ond code, the BWB was further refined by reshaping the entire plan- form. The centre of gravity is further aft in the latest 13,875km design, dubbed BWB 6-250B, which increases the lift/drag ratio and improves fuel consumption. Take off weight also fell by almost 7% compared with the revised Mach 0.85 baseline design, while operat ing empty weight fell by 5.5%. The study revealed that aerody- namically, a M0.90 BWB configura tion "may be optimal" with a peak Mach number times lift to drag ratio occuring between M0.89 and 0.91. It adds that further CFD work will be required to quantify drag from propulsion-airframe interfer ence for all the high-speed options. Cathay originally planned to acquire used A300-600Fs for Air Hong Kong that were converted from passenger configurations, but decided recently to opt for new- build aircraft from Airbus (Flight International, 7-13 January). The order is part of a shift in focus for Air Hong Kong, which has traditionally operated larger Boeing 747 freighters. The switch to smaller aircraft is part of a plan to refocus operations on regional services rather than on long-haul flights, which Cathay has brought back into its own dedicated freighter operation. World Airline Directory Entries are closing for free inclusion in the Flight International 2003 World Airline Directory. If you have not replied, contact Air Transport Intelligence for a reply form, or click on the announcement box on the flightinternational.com home page. Tel: +44 (20) 8652 3859; fax +44 (20) 8652 3898; e-mail atidata@rati.com. ACCIDENT Elevator cited in 1900 crash An Air Midwest Beech 1900D twin turboprop pitched up to 52° before crashing out of control a few seconds after take-off from Charlotte Douglas Airport, South Carolina. National Transportation Safety Board (NTSB) member John Goglia says that an emergency call from the crew indicated "some sort of catastrophic event", and cited recent maintenance on the pitch control system as a subject that investigators would study quickly. Meanwhile, all 1900 operators are checking elevator control systems. The aircraft was operating a scheduled US Airways Express service to Greenville-Spartanburg, South Carolina, fully laden with two pilots and 19 passengers - all of whom were killed. During its take-off shortly before 09.00 on 8 January the aircraft (N233YV) rotated normally at first, says Goglia, but then "something occurred to drive that pitch angle to 52°". Manufacturer Raytheon Aircraft says normal rotate pitch is 7-10°, rotation to 20-22" is "robust" and any angle above 30° is unsustainable. The 1900 reached 400-500ft (120-150m) above runway 18R, then veered left as it went out of control, one wing hitting a hangar. "We do know that the elevator trim tab was replaced [on 6 January] and that would require cable tensions to be readjusted," says Goglia. "Those are significant events for the control system of this aircraft." The 1900 ele vator system is cable controlled, and both elevators have trailing edge trim tabs that are also mechanically controlled by cables. They can either be adjusted manually or by an electric motor. The flight data and cockpit voice recorders have been recovered, and indicate that the elevator occasionally moved erratically in the six flights since maintenance but had not shown such movement before. The distribution of the aircraft's load - which affects the aircraft's centre of gravity - is also going to be checked in the early stages of the investiga tion, says Goglia. CARGO Air Hong Kong to buy new A300 variant www.flightinternational.com FLIGHT INTERNATIONAL 14-20 JANUARY 2003 9
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