# How does EMAS reduce damage in case of an aircraft overrun?

As can be seen there is huge cracks and breaking of the runway but the plane was not damaged. According to twitter this is due to Engineered Materials Arresting System (EMAS). The FAA is adopting a plan to expand the use of this method for arresting overruns on runways that do not have enough land for a runway safety area (RSA).

I am interested to know how this system works. Is it similar to gravel runaway truck arrestors on the steep downhill roads? Do we have any specifications and test data?

EMASMAX® is the latest, most durable version of ESCO’s EMAS, developed with and technically accepted by the FAA. EMASMAX arrestor beds are composed of blocks of lightweight, crushable cellular cement material designed to safely stop airplanes that overshoot runways. - FAA Fact Sheet – Engineered Material Arresting System (EMAS)

So yes it's like gravel runoff areas, where the crushable material slows down the aircraft by providing resistance through the landing gear. The difference being this is a bit more engineered so you don't get bits flying up into the engines etc. like gravel would.

As for specs, the same link claims it can stop an aircraft going 80 mph but doesn't state a size of aircraft.

A standard EMAS installation can stop an aircraft from overrunning the runway at approximately 80 miles per hour. - FAA Fact Sheet – Engineered Material Arresting System (EMAS)

• Thank you @Notts90. One would like to see new research on material which would behave more like a very dense viscose liquid/plastic with self repairing and self leveling properties. I understand why use of gravel-bed is not practical but this system has its own limitations. – kamran Oct 28 '16 at 14:52
• A Piper Cub at 80MPH and an A380 at 80MPH are two very different propositions. I wonder toward which end of the spectrum that "80MPH" statement is aimed... – FreeMan Oct 28 '16 at 15:41
• @FreeMan I had the same thought. I really hope it's the A380 end! – Notts90 supports Monica Oct 28 '16 at 16:48
• @FreeMan The FAA AC on EMAS design (AC 150/5220-22B) says the design is for the aircraft using the associated runway that imposes the greatest demand upon the EMAS. - so basically the fattest pig they expect to land there, at maximum weight. It also notes that the design models don't work well for planes that have a max takeoff weight less than about 25,000 pounds - i.e. "They're not designed or intended for stopping a Piper Cub. You should be able to do that yourself." – voretaq7 Oct 28 '16 at 18:47
• @FreeMan, it is a huge difference in energy, but if you can get the same coefficient of friction, you'll get the same braking distance. And since the bigger aircraft has more wheels and higher pressure on each, it will crush more of the material and might get almost the same coefficient of friction. The design then mainly governs how thick the layer has to be so there is enough for the big aircraft to crush and impart the energy into. – Jan Hudec Oct 31 '16 at 21:39