It appears a DRS failure, when the rear-wing flap failed to close as usual under braking, pitched Ericsson into his frightening accident when the Sauber smashed into the barriers and then barrel rolled down the side of the track.
Ericsson was able to walk away from the shunt and doctors in the medical centre gave the Swede the all-clear.
http://www.skysports.com/f1/news/124...ad-of-mercedes