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Aviation History
1997
1997 - 0011.PDF
AIR TRANSPORT NTSB makes explosive fuel tank recommendations DAVID LEARMOUNT/LONDON THE US NATIONAL Trans portation Safety Board (NTSB) has proposed far-reaching recommendations to reduce the risk of explosion in fuel tanks. The safety board warns diat all airliner fuel tanks are vulnerable to explo sion under certain conditions. Suspicions about fuel-tank safe ty have existed for many years, admits the NTSB in a document based on concerns raised by the Trans World Airlines (TWA) Boeing 747-100 crash near Long Island, New York, USA, on 17 July, 1996, in which 230 people died. Fuel-tank explosions have been a factor in three odier fatal accidents, die NTSB reveals. Although it emphasises that the cause of the TWA centre-wing fuel-tank (CWT) explosion has not yet been determined, the NTSB gives details of an August 1996 flight-test replicating flight TWA800, and notes that the con ditions caused "...an explosive fuel- air mixture to exist in the tank ullage [the space in die tank not filled by liquid fuel]". In the TWA800 747's CWT, the temper ature was about 46°C, says the NTSB. Fuel-air vapour becomes potentially explosive as fuel-tank temperature is between about 45°C and the "auto-ignition" point of 226°C -temperatures which reduce with altitude. Given these condi tions, says the NTSB, all that is needed for explosion is "an energy source sufficient for ignition". The NTSB recommends that the US Federal Aviation Admini stration invoke measures "preclud ing the operation of transport category aircraft with explosive fuel-air mixtures in the fuel tanks". Although all die accidents quoted in die paper involve Boeings, the implication here and in the report's generic descriptions of the issue is that it involves all airliner types. The NTSB, however, has de clined to clarify the point, as has Airbus Industrie, saying that it has received no instructions on the subject. Boeing has warned the FAA that any action will have im plications for "the entire aviation industry".The FAA says diatitwill consider the NTSB's recommen dations carefully. These include: • incorporating systems for filling die fuel-tank ullage with an inert gas like nitrogen; • banning heat-generating equip ment from proximity to fuel tanks, or improving tank insulation. The safety board notes that heat-pro ducing air-conditioning units are situated close to 747 CWTs; • until such modifications can be incorporated, all available mea sures for loading cold fuel and keeping it cold should be adopted; • in the 747, an "appropriate" minimum amount of fuel should be kept in the CWT; • in aircraft with a heat-source near any fuel tank, tank-tempera ture should be displayed. The NTSB quotes accidents to support its argument, including : • the crash of an Iranian air force Boeing 747-100 approaching Madrid, Spain on 9 May, 1976: fol lowing a reported lightning-strike, there was an explosion and air borne separation of die right wing; I an accident to an Avianca 727 near Bogota, Colombia, on 27 November, 1989. A small bomb under a passenger seat exploded. The NTSB says: "The bomb explosion did not compromise the structural integrity of the aircraft [but] punctured the CWT and ignited die fuel-air vapours in the ullage," destroying the aircraft; • an 11 May Philippine Airlines 737-300 accident at Manila Air port, where die CWT exploded on the ground, killing eight people. The NTSB notes that the ambient temperature was 3 5°C and the air craft had been parked in the sun. • JAL plans new carrier JAPAN AIRLINES (JAL) plans to establish a new low-cost sub sidiary carrier in March, in the face of growing domestic competition. The new carrier hopes to cut air fares by up to 20% on trunk ser vices to Sapporo and Fukuoka, by using foreign crews and flight attendants and scaling back in flight services. It will operate two to three Boeing 737s, expanding to 12-15 aircraft by 2010. JAL's subsidiary, Japan Trans- Ocean Air QTA), in which it has a 51 % stake, is to take a 10% stake in the new carrier. JTA flies Boeing 737-200s, -400s and NAMC YS- 11s on domestic routes. • Egyptair introduces the A340-200 EGYPTAIR HAS BEGUN OPERATING the first of three Airbus A340-200s, alongside an existing A340-300 leased from Gulf Air. The 260-seat Airbuses were ordered in 1995, along with three General Electric GE90-powered Boeing 777s, to supplement its long-haul fleet and replace the airline's fleet of Airbus A300B4s and Boeing 767-200s. SAS takes a vital step towards free-flight target SAS HAS BECOME the first airline to install a certifiable example of one of the most impor tant items of equipment needed by die industry to achieve the goal of free flight. The MMI5000 cockpit display of traffic information (CDTI) was installed in a Fokker F28 for a cer tification flight, widi the Swedish civil-aviation authority on board on 14 December. Swedish suppliers Carmenta and I Iectronic provided die soft ware and hardware for the full- colour display seen on the centre pedestal. The F28 is also equipped with the Swedish-developed Global Navigation Satellite System (GNSS) Transponder which re ceives differential global-position- ing-system signals from a network of ground stations and datalinks the aircraft's position to odier air craft and air traffic control. The technique, known as auto matic dependent surveillance- broadcast (ADS-B), is the crucial technique which is expected to be at the heart of any free-flight sys tem of the future. The MMI5000, however, is more than just a CDTI — it also functions as a limited flight-man agement system complete with moving map and pop-up menus of navigation aids, airfields, flight plans and odier features. Its extreme accuracy, married to a database of airfield layouts allows it to be used as a surface-movement guidance system, displaying the positions of vehicles equipped with the GNSS Transponder, say its promoters. Under the north European ADS-B Network programme, 12 aircraft and some 30 vehicles at several airports are scheduled to be equipped with the transponder and/or the CDTI during 1997 in the world's biggest trial of the ADS-B system. The project also makes extensive use of die Swedish self-organising, time-division, multiple-access datalink which has emerged as a rival to die Mode-S datalink. • FLIGHT INTERNATIONAL 1 - 7 January 1997 9
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