Why are airplanes coated with green material

Great idea! What happened to it?FlyBag is designed to protect against explosive air cargo

"We check the strength and elongation of the straps." Erik Wilhelm is a trainee textile laboratory assistant at the Saxon Textile Research Institute in Chemnitz. He clamps a fabric belt in a tensile testing machine several meters high. "We move the clamps together. We have 50 bar pressure on the clamps ... Now we're trying and ..."

The machine pulls the belt apart until it breaks. A diagram appears on a monitor. It shows that the belt did not stretch very much in the first few moments. Heike Illing-Günther is satisfied: "That means: This material is excellently suited for the application."

Like a big bulletproof vest

The application in this case is protection against terrorists. The researchers have developed bags made of high-strength material. On board airplanes, passengers could pack their suitcases in these sacks. If a bomb were stuck in one of the suitcases and exploded - the sack would withstand the explosion and thus protect the aircraft.

The material for the sack was developed here at the Textile Research Institute. It is aramid - the material that bulletproof vests are made of - and a plastic. The straps that have just been tested are designed to ensure that such a bag, called a FlyBag, does not expand too much in the event of an explosion. A simple idea, but not a particularly new one. In 2008 there was already the first EU-funded FlyBag project. On the side of the EU Commission, the project coordinator was quoted at the time: "We expect that in 2013 the first FlyBags will be in use on board commercial aircraft."

Problem: FlyBag is not fireproof

But that has not happened so far. Why not? The question goes to Samuele Ambrosetti from the Italian engineering company D'Appolonia, which coordinates the FlyBag project. "We had finished the first project and 2013 seemed like a good time to bring the first products out. But then we received funding for a new project and wanted to do more research and make a better product."

The FlyBags from the first project were good at containing explosions. If a bomb were to go off inside them, the FlyBags would hold back the expanding gases - i.e. the pressure wave - thanks to a special coating. The gas would then slowly escape through gaps in the FlyBag's particularly stable zip. Because of its high-strength material, the sack would also stop bomb fragments and thus protect the aircraft.

But the Flybags from the first project also had a huge weakness: "The biggest weak point was that the standard coating we used was not fireproof. And ultimately, if we want a sack that we can hang on an airplane, we need approval . And that assumes that I use non-flammable material, "explains Heike Illing-Günther from the Saxon Textile Research Institute.

FlyBag has been further developed

She and her colleagues solved this problem in the second research project. In addition, the researchers have now developed a whole range of products: There is now a small FlyBag for the cabin. The crew can put suspicious objects in there. "Then there is the clip-on fabric container for small aircraft. The third variant is the cover for a pallet that I can pull over a classic air freight pallet."

Finally, the fourth variant is an inlay. It can be placed precisely in a luggage container, as is standard in wide-body aircraft. The textile research institute has optimized the sacks so that they have as few seams as possible and can even be sewn together - after all, with their high-strength materials and up to 37 kilograms in weight, they are a challenge for the workers.

"Technically, we have solved everything. We are currently setting up a startup company and are looking for dealers. We have already had a few inquiries from companies in the USA, Russia, Singapore, France, Spain, Israel and the Middle East," says Samuele Ambrosetti.

Difficult search for partners

But commercialization is not easy. There are still no standards for equipment for explosion protection in aircraft. Samuele Ambrosetti wants to work this out with the European Aviation Safety Agency (EASA). In addition, the startup would be new to the aviation market, which is relatively conservative. Hence the search for partners who have already made a name for themselves in the industry. After all, you have to convince the airlines that the additional weight of the FlyBags is worth it.

If you ask Lufthansa, for example, you will learn that you have a functioning security system and you don't have to add another measure. Samuele Ambrosetti, on the other hand, says he receives weekly calls from interested airlines. And he has considered another application. Nowadays, lithium-ion batteries are often sent as goods by air freight. Normally there are clear safety rules for this, because the batteries can cause serious fires, but: "When private individuals send lithium-ion batteries - such as goods from Ebay sales - they do not always correctly declare them as dangerous goods."

And so the batteries sometimes fly unnoticed in cargo planes, says Samuele Ambrosetti. Since 2006 there have been at least eight cases in which such batteries have triggered fires in the cargo holds of passenger or cargo planes. If you believe the engineer, you could avert such dangers. This is done by packing unsafe charges in modified FlyBags as a precautionary measure, which not only can withstand explosions, but also enclose the burning batteries.