A SIMPLE idea could make flying much safer. Tests in the US have shown that
cooling fuel before it is put into aircraft prevents explosive fumes building up
in the fuel tanks.
The explosion of TWA flight 800 off Long Island in July 1996, which killed
230 people, is thought to have been caused by the ignition of fuel vapour in one
of the jet鈥檚 fuel tanks. The US Federal Aviation Administration has since been
looking at many ways of improving fuel tank safety, including eliminating any
potential sources of sparks.
But Terry Koethe, a Texan inventor, believes he has hit on a way of making
planes safer without the need for any expensive modifications to the world鈥檚
12 000 commercial jets. 鈥淲e do not alter the composition of the aviation fuel in
any way鈥攕o it meets all specifications as there are no magic additives,鈥�
he says. 鈥淎ll we are doing is cooling the fuel.鈥� The idea is to minimise
vaporisation, so there is no chance of an explosion even if static electricity
or faulty wiring creates a spark.
Advertisement
The temperature of the fuel delivered to an aircraft from an underground tank
or a tanker ranges between 15 掳C and 33 掳C, depending upon the ambient
temperature. But since the TWA 800 crash, industry research has revealed that
fuel can get far hotter than that before take-off, especially if a plane has
been sitting in the sun. And as an aircraft climbs, says Koethe, the drop in
pressure draws more fumes into the tank headspace. In such cases, he reasons,
safety will depend largely on the absence of sparks.
Koethe thinks it is better to severely reduce the formation of combustible
vapour. His company, Fuel Dynamics of Arlington, Texas, has developed a system
that cools fuel to 鈥�1 掳C or below before it is put into an aircraft.
鈥淭his is the ideal safety temperature, where we get fewer hydrocarbon vapours,
and keeps it out of the flammability range,鈥� he says. The system also injects
nitrogen gas during fuelling, flushing out oxygen and thus reducing the chance
of an explosion even further.
Last week, Koethe, an FAA observer and a team from the University of North
Dakota tested the Polarjet cooling system at an airbase in Fort Worth, Texas.
They loaded one wing tank of a Learjet with cooled fuel and the other with fuel
at a normal temperature. After the plane sat on the tarmac for an hour, the
university team found that there was only 20 per cent as much fuel vapour in the
space above the cooled fuel as in the other tank. Levels of hydrocarbon
pollutants escaping from the cooled tank鈥檚 vents were similarly reduced.
鈥淚 was sceptical about this cooled fuel approach, but the benefits are
significant,鈥� says Ted Aulich, project manager at the University of North
Dakota鈥檚 Energy and Environmental Research Centre. 鈥淵ou will be way below the
lower explosive limit of jet fuel vapours in air for a long, long period of the
flight.鈥� Tom Haueter, a safety expert with the US National Transportation Safety
Board, believes Polarjet is 鈥渁n interesting concept鈥� whose prospects the board
is currently considering.