FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1989
1989 - 0524.PDF
• -.• •••'...'•. . Three sides of the cargo door aperture are intact United 747: cargo door suspected US accident investigators are concentrating on the forward cargo door as the possible source of the cabin structural failure suffered by a United Airlines Boeing 747-100. A bomb, fatigue failure, and corrosion have all been discounted. Nine people died in the rapid cabin decompression at 23,000ft caused when a 10ft by 20ft hole appeared in the starboard side. The National Trans portation Safety Board is not sure whether the cargo door failed first, or followed the fuselage panels. Last summer the Federal Aviation Admini stration issued an Airworthi ness Directive (AD) ordering airlines to inspect cargo-door lock systems on early 747s after one partial inflight fail ure. The United aircraft, N4713U, had apparently undergone inspection of its cargo-door locking systems, but modifications ordered in the AD had not yet been carried out. United Flight 811 from Honolulu to Auckland, New Zealand, carried 336 passengers and 18 crew. According to the crew, about 20min after take-off and 70 miles out the captain heard a thump passing through 22,000ft and the aircraft yawed to port, followed by number three engine failure. There was a fire in number four engine, and, after jetti soning fuel, the crew landed back at Honolulu just over an hour after take-off. United immediately announced a programme of detailed technical inspections of 747 door mechanisms. Additionally, the airline directed that a mechanic should inspect every 747 cargo door on arrival at destination and personally oversee the door closing for departure. The NTSB does not expect to recover the door involved, which is in 16,000ft of water. The 747 was the 89th built by Boeing and the sixth deliv ered to United in November 1970. It had accumulated 58,815hr and just over 15,020 cycles. Boeing says that a "high-time" aircraft of similar age to the United 747 would typically have registerd 79,000hr and 26,000 cycles. The United aircraft was built using the cold-bonding process which has been widely questioned following the massive Aloha Airlines 737 roof failure last year. The pro cess uses a cold-temperature adhesive to fasten over lapping panels of fuselage skin. Later experience indi cated that cold bonds tended to separate slightly and to suffer corrosion. Cold bond ing was replaced by hot bond ing for all Boeing aircraft after 1971, but the accident aircraft was one of 169 cold-bonded 747-100s. USA and UK reveal advanced STOVL plan by Julian Moxon in Washington D.C. The USA and UK have agreed the future direction of their advanced short take-off and vertical landing (ASTOVL) research. It is the first major result of the January 1986 agreement between the two countries to co-operate on future ASTOVL research. A bilateral government team studied four different propulsion systems proposed by industry teams in both countries (advanced vectored thrust, remote augmented lift, ejector augmented lift, and hybrid tandem fan). Its conclusions do not specifically favour any one concept, although the hybrid tandem fan was eventually rejected because it had "significantly higher risks" without offering enough performance gain. The team finds the best solu tion comes with a "mixed flow" engine (with core and bypass airflows mixed before exit at the nozzle) located in the traditional position for a supersonic fighter aircraft—at the rear of the fuse lage. One or more remote nozzles ducted off the engine would be used to balance the aircraft during vertical flight. "We were not striving for an unconventional concept," says Jack Levine, NASA's flight projects director, and co- chairman of the US/UK joint working group. "This is a super sonic fighter that has vertical landing capability. We have agreed on a simple, elegant solution arising from the need to balance the aircraft in jetborne flight." One concept, however, was selected for separate devel opment by Harrier II prime contractor McDonnell Douglas because it had "special merit". This is a version of the "four-poster" system used on the Harrier, in which fan and core flows are exhausted sepa rately through front and rear nozzles. McDonnell Douglas' proposed mixed-flow vectored- thrust idea combines both flows in a common plenum chamber before discharge. The next step will be to develop a joint US/UK programme to look at seven critical technology elements of the mixed-flow /remote-lift concept. The plan should be complete by the end of this year, and may, says Levine, include definition of an- experimental research aircraft. "There are very preliminary discussions in both countries" on a flying test vehicle, he says. The technology programme should culminate in 1995 with a technology base that would support a service requirement for an ASTOVL supersonic fighter. The US Air Force (which took part in the recent study) is developing its own research programme for a STOVL fighter to complement the Advanced Tactical Fighter early in the next century. The service had no comment on whether it would take advan tage of the UK/US research. The seven main elements are: • diverter valves and transfer ducts; • aircraft and ground environ ment; • hot gas ingestion; • aircraft controls and handling qualities; • propulsion controls; • nozzles; • STOVL augmentors. In assessing the various ASTOVL systems, the team noted that Harrier-type short- coupled propulsion systems located astride the aircraft e.g. "significantly compromise design flexibility from many points of view, particularly supersonic performance, manoeuvrability, and stores carriage". The great advantage offered by a remote-lift system, says Levine, is that it provides flexibility in engine location to allow for balance and volume distribution. A mixed engine flow for cruise flight was considered important because separate core and bypass nozzles are, accord ing to the study, "likely to lead to higher afterbody drag, and the core nozzle may subject parts of the rear of the aircraft to very hot, high-energy jets". Non-reheated mixed-flow supersonic fighter engines are 2 FLIGHT INTERNATIONAL, 4 March 1989
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
