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Aviation History
1989
1989 - 0156.PDF
FffiESPRAY The report on the 1985 Boeing 737 fire at Manchester will be released shortly. Kieran Daly examines the future of the systems designed to prevent such tragedies. Dramatic tests with a burning Trident airliner at Teesside Airport, England, last year, suggested that the Save company's water-mist cabin fire suppression system could be invaluable in saving lives in a post-accident fire. That immediate impression was supported by other tests and more detailed analysis, and now the project is developing the sort of momentum needed to see a revolutionary system into widespread airline service. Further ground trials in the UK and USA are planned, including work on a widebody hull. The UK Civil Aviation Authority (CAA) has taken the unusual step of issuing estimated costs of installing and maintaining a production system, and is asking the aviation industry for its views on the detailed technical questions thrown up by the tests carried out to date. Save (Safety (Aircraft and Vehicle) Equip ment) itself is seeking a buyer to inject the sort of finance needed to take the concept to production, and at least one competing system is under development. Most importantly, there is a growing acceptance that, if the system is proved technically practicable, the cost:safety benefit ratio will make purchase difficult to resist on economic grounds. Three CAA tests on the Teesside Trident showed that, as well as keeping cabin temperatures survivable during a fully- developed fire, the spray significantly hindered fire penetration through the wetted aircraft structure. In each case a pool of jet fuel was allowed to burn under the rear fuselage for three minutes. Test and test again In the first test (Flight, March 19, 1988) on the intact aircraft with the rear baggage hold full of baggage, the skin and structure were severely damaged but the fire did not penetrate the cabin. The skin was crudely repaired for the second fire, and the baggage hold refilled. Flames quickly destroyed the repairs and luggage so that the tail section dropped off aft of the rear pressure bulkhead, but the fire still did not penetrate the cabin. Finally, the spray system was removed from the toilets and last four seat rows for the third test. Even though flames rapidly entered the cabin, the sprayed portion was undamaged by fire and, as in the previous instances, the temperature remained survivable. The CAA says, however, that significant carbon monoxide levels were produced in all cases, and that this needs further investigation. Encouraged by early results, the CAA is arranging further research on both sides of the Atlantic. It is buying a Boeing 707 fuselage, which will be sited at Cardington, near Bedford, England, for work to deter mine the optimum layout and nozzle design to absorb toxic gases. In the USA the Federal Aviation Administration (FAA) will use CAA-supplied equipment to examine fire- spread rates with and without spray systems in a DC-7 at Atlantic City this spring, and in a widebody hull, possibly that of a DC-10, in the autumn. Primitive prototype The only Save systems in existence are fairly primitive and the company itself is under administration by accountants. Founder and system inventor Jim Steel died suddenly last year, and unpaid chairman Harold Hill called in the administrator when it became clear the company could not continue trading. At the time of writing, adminis trators Spicer and Oppenheim were negotiating with several potential buyers. Hill says that patent applications have been lodged in the United Kingdom, USA, Canada, India, and European countries on the grounds that this is "the first system to kill fire, cool temperatures, wash air, and maintain visibility". "We have been challenged," he adds, "but the challenges are dropping by the wayside." British Petroleum claims to have devised its own prototype system at Sunbury, near London. The CAA is also to examine the project, on which BP says it has been working for 18 months. BP is revealing little about it, but a major difference from the Save system is that it uses a water/compressed air mixture in the spray, rather than just water, as with Save. Save already has close contacts with British Airways, which is cautiously enthu siastic about the project, and Boeing. With a possible mandatory requirement for the equipment in the West, however, further competition seems certain to emerge. The resources already allocated to research by the CAA and FAA are a clear W indication of their hopes for the system. Fire services are also favourably impressed, but airlines, who will bear the brunt of imple mentation costs, are more cautious. British Airways says it will "provide all the necessary input" for research but would stop short of installing a prototype in an aircraft at its own expense. However, it is prepared in principle to allow the CAA to install a system in an operational BA aircraft, provided remaining safety questions are cleared up. "We would be prepared to risk drenching the passengers, provided the effects on the aircraft systems are acceptable," it says. BA describes the likely costs to the indus try as "substantial", but accepts that carriers "will have to meet them" to attain the resultant higher safety standard. Ultimately, success depends on the system's life-saving potential justifying its cost. The CAA proposes a computer analysis of past accidents, where sufficient data is available, to determine the probable benefit of water spray. The model would include cabin survivability, evacuation rates, and the likelihood of successful system operation. Accident analysis A preliminary CAA analysis of the 1966 to 1985 period revealed the following: 42 FLIGHT INTERNATIONAL, 21 January 1989
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