Promising results for bomb-proof bag in aircraft trial

A lightweight lining for aircraft holds that can withstand the force of explosions could help prevent terrorist attacks similar to the Lockerbie bombing, according to its international team of developers. The research is being led by Sheffield University, and was reported in The Engineer at the outset of the project. The team has now demonstrated the concept using retired aircraft at Cotswolds Airport, including a Boeing 747 and Airbus A321, and increasingly-powerful explosive charges. 

Dubbed Fly-Bag by the team, the lining is built up from layers of fabrics with high strength, heat and impact resistance, including woven aramid fibre, better known as Kevlar. The fibres in the lining are coated with shear-thickening fluids which, when subjected to a strong force such as an impact or explosive impulse, sharply increase their viscosity. This helps to dissipate the impulse by effectively stretching out the time during which it affects the fabric.

“Key to the concept is that the lining is flexible and this adds to its resilience when containing the explosive force and any fragments produced,” said research diector Andy Tyas of the Department of Civil and Structural Engineering at Sheffield, who is also a director of a university spin-out called Blastech. “This helps to ensure that the Fly-Bag acts as a membrane rather than as a rigid-walled container which might shatter on impact.” 

Fly-bag has to contain a shockwave that can move at up to 20,000mph and temperatures up to 3,000^oC, as well as resisting the inflation effect of the expanding gases frome combustion of the explosive and shrapnel formed by the hard parts of the luggage and any metallic pieces used by a bomb-maker. The team has developed their layered material so that it can withstand these conditions while being only 1.3mm thick. 

Although the structure has been tested already in isolation, the aircraft tests help the researchers understand how Fly-Bag might work in the conditions it is intended for; previous trials had shown it expands when something explodes inside it, but the team needed to be certain this expansion would not damage the aircraft. Tyas said the results so far have been ‘very promising.’

The consortium, which includes engineers from Greece, Spain, Italy, Germany, Sweden and the Netherlands, is aiming to produce a technology which is just as effective, but lighter and cheaper, than the hardened luggage containers that are currently available to deal with the threat of bombs hidden in luggage checked into the aircraft hold; these have been implicated in a number of terrorist attacks dating back to the early years of passenger flight, with the Lockerbie bomb in 1988 perhaps the most notorious today. 

The team envisages three different versions of Fly-Bag, all of which would need to be certified by aircraft regulators: a lining that would hang inside the entire luggage compartment of a narrow-bodied jet; a smaller version for the luggage crates that are used in wide-bodied jets; and a compact version that would be carried in the passenger compartment and used if cabin crew suspect a passenger has brought a bomb on board in their hand-luggage. Italian airline Meridiana is believed to have already shown interest in the technology.