DAVID LEARMONT / LONDON
Aircraft should be purged of flammable materials, says Canadian Safety Board investigating Swissair MD-11 accident
Certification authorities must change rules which allow flammable materials to be used in parts of the aircraft which have no fire detection and suppression systems, the Transportation Safety Board of Canada (TSBC) has urged in the latest recommendations emerging from investigations into the 1998 Swissair Boeing MD-11 crash.
At the same time the TSBC report slams present US Federal Aviation Administration certification tests for electrical wiring flammability as totally inadequate, and states that the currently mandated inspection checks on the state of wiring in existing aircraft will inevitably fail to detect danger in most cases.
In December 2000 the TSBC stated that fire detection and suppression systems for cockpit and fuselage fires in all commercial transport aircraft were totally inadequate, and issued recommendations for improved fire safety systems. Now the agency has gone further and said that flammable materials should be eliminated.
"Because the most stringent fire tests today are reserved for seat cushions, wall panels and other materials located in cabin areas," says the TSBC report leading to the recommendation, "some of the most flammable materials in the pressurised portion of an aircraft tend to be located in hidden, remote or inaccessible areas. In these areas they have the potential to contribute to an uncontrollable aircraft fire."
The TSBC recommendation reads: "For the pressurised part of an aircraft, flammability standards for material used in the manufacture of any aeronautical product [should] be revised, based on realistic ignition scenarios, to prevent the use of any material that sustains or propagates fire."
On wiring standards, the TSBC recommends: "A certification regime be mandated that evaluates electrical wire failure characteristics under realistic operating conditions and against specified performance criteria." For example, says the Board, despite the fact that insulation material on wires in wiring bundles have been shown to become chafed, abraded or cracked in use, the tests are not required at present to show that a wire would be proof against ignition in the face of electrical arcing if the wiring in question suffers any damaged.
Finally, the TSBC recommends, all systems and subsystems within the pressure hull should be tested to ensure that they would not exacerbate a fire already burning. An example given was oxygen or ventilation ducting with flammable parts which, when fire-damaged, would worsen a fire by providing it with a supply of oxygen or air.
Source: Flight International
