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Aviation History
2002
2002 - 0390.PDF
HEADLINES AIR TRANSPORT DAVID LEARMOUNT / LONDON NTSB warns pilots of tail fin danger Early analysis indicates that sideslip and rudder movement could have caused November's AA587 crash in New York The vigorous use of rudder in large aircraft under certain conditions can generate enough force to break off an undamaged vertical tail fin, the US National Transportation Safety Board (NTSB) is warning air lines. The alert is based on findings from the NTSB's investigation of the American Airlines Airbus A300- 600R crash last November. French tests, using different aerodynamic load calculation methods, have come up with similar results, says the NTSB. The NTSB has recommended to the US Federal Aviation Admini- More doubt is being cast on the future of the Boeing 777-200LR as sole customer EVA Air has re opened its ultra-long-haul aircraft studies and is considering an offer from Airbus for the rival A340-5O0. It comes as the carrier has agreed to lease two more Airbus A330-200s. Industry sources say EVA has been made a "very attractive" offer from Airbus for the A340-500 and larger -600 and may scrap its 777- 200LR/300ER commitments. EVA announced a deal in mid- 2000 for up to 15 longer-range 777s, ordering seven firm examples - three -200LRs and four larger -300ERs - for delivery from 2005. The carrier, however, is known stration that it should publish advice to all pilots of large trans port aircraft - not just those flying A300-600s - about the limitations on safe rudder use. The NTSB was due to reveal its findings as Flight International went to press. The NTSB says that, under certain sideslip conditions - which could be temporarily generated by slipstream vortices or windshear - vigorous rudder use could generate loads on the fin "high enough to cause con cern", and that in these circum stances rudder deflection limiters do not provide enough protection. to be unhappy about still being the only customer for the -200LR. Senior vice president Nieh Kuo Wei confirms there is uncertainty over the -200LR and confirms that EVA is considering an Airbus offer. "We are still in negotiation," he says. "We have not decided which aircraft we are going to purchase. The A340 offer is at a very attractive price." Nieh stresses that for now, however, EVA remains committed to the 777. Questions about the 777-200LR's future were raised in October, when Boeing said it had suspended the twinjet variant's development programme for up to 18 months due to poor market prospects. The tests, being carried out on A300s by the NTSB, have involved "wiggling the controls", measuring results, and projecting them mathe matically. The aerodynamic results indicated that loads strong enough to break a new tail could be gener ated by rudder use under certain circumstances involving sideslip. Meanwhile, working indepen dently, Canada's National Research Council believes that it may have discovered a contributory factor in the American Airlines accident. While researching the characteris tics of slipstream vortices, principal But it said that despite the sus pension deliveries to EVA would take place as scheduled from May 2006, and the first available slots would be available in 2005. It also said the more successful -300ER would go ahead as planned, with first deliveries next year. Boeing says it remains commit ted to the -200LR programme and is re-evaluating the major design release schedules. It says it plans to look at restarting the design config uration in mid-year to protect its first delivery commitment to EVA. The 777 was not EVA's first selec tion for ultra-long-haul operations, primarily to the USA. Late in 1997 the carrier signed a letter of intent research officer Dr Miroslav Mokry has discovered that wingtip vor tices can be strengthened by wind- shear. Because windshear with height was present when the acci dent occurred, Mokry believes that this could have been a factor. Applying recently researched mathematical models to the vor tices of the 747 ahead of the American aircraft as they would have been affected by the prevail ing meteorological conditions, Mokry found that the second of the wingtip vortices that the A300 hit would have been strengthened. for six firm and six optioned A340- 500/600s. Less than a year later it cancelled the tentative deal for the four-engined aircraft as the effects of the 1997-1999 Asian economic downturn began biting into profits. EVA, previously a loyal Boeing customer, agreed last year to lease six A330-200S from General Electric Capital Aviation Services (GECAS) and buy two from Airbus. The twinjets are due for delivery from early next year to replace Boeing 767-200/300S. Sources say EVA has agreed to expand its deal with GECAS and lease two more of the type, lifting its commitment to the A330-200 to 10, including the two on order from Airbus. Rudder movement to blame? The American Airlines Airbus A300-600 flew through the slipstream vortices of a preceding Boeing 747 while climbing away from New York Kennedy airport on 12 November. The flight data recorder (FDR) mea sured rudder movements. Almost immediately the fin detached and the aircraft crashed. The FDR measured side accelerations on the fin and rudder movements that followed them. The NTSB says that it may never be established whether the rudder movements resulted from pilot input because loads on the rudder pedals are not measured. Airbus and Boeing, however, have warned against heavy use of rudder in large aircraft except to counter asymmetric power at low speeds. The fin broke following rudder movement after hitting slipstream vortices AIR TRANSPORT NICHOLAS I0NIDES / SINGAPORE Boeing 777-200LR's future in jeopardy as sole customer EVA Air ponders Airbus A340 offer 6 12-18 FEBRUARY 2002 FLIGHT INTERNATIONAL www.fliqhtinternational.com
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