This first appeared as a Comment in the 10 September issue of Flight International.
There has always been a chance of fire on commercial transport aircraft, but the risk profile in today’s fleet is definitely changing, and probably increasing – yet nothing is being done to tackle this.
The reasons behind the change are many. Leading the list is the proliferation of lithium-chemistry batteries – a definable fire risk – in the personal electronic equipment of both passengers and crew. Their highly flammable nature has been blamed for the loss of at least one freighter aircraft, a UPS Boeing 747, which carried the lithium-ion cells among its cargo. And larger versions of those same lithium batteries have recently been deployed by aircraft manufacturers to power standby onboard equipment. In the case of the Boeing 787 they provide the ultimate back-up electrical supply.
The very latest airliners are also “more-electric” – electricity replaces hydraulic, pneumatic or mechanical power – resulting in an increase in the amount of electrical cabling. The proliferation of in-flight entertainment systems adds both batteries and yet more cabling. And the rapidly increasing use of composite materials for aircraft primary structures is changing the risk profile because composites have a different reaction to heat.
In the last three years, two freighters have been lost to onboard fires, but because they were not passenger flights public concern has remained dormant. The last catastrophic blaze that brought down a passenger aircraft was Swissair 111 in 1998. That is a long time ago, and it involved a Boeing MD-11, but nothing fundamental in terms of aircraft and cabin systems design has been changed as a result. Meanwhile estimates put the number of onboard smoke events today at one in every 15,000 flights. And cliché as it may be, where there is smoke, there is fire, be it real or potential.
One of the most remarkable facts about aircraft design for safety is that the only fire detection equipment on board commercial transport aircraft are in the engines, the freight bay and the lavatories. There are no detection systems in cockpits or cabins, so a fire that starts behind the panels because of an electrical short-circuit – like Swissair 111 – has a chance to take hold before its presence is noticed. And when smoke or fumes have betrayed its existence, there is no way of locating the heat source or directing extinguishant at it. This is simply unacceptable.
The Royal Aeronautical Society is leading a study into these risks. Action must follow it.