According to the season review, he spun trying to set a lap time after oil had been dropped by Grouillard.
I remember Brundle mentioning it in commentary once, where he thought Senna had tried to take the corner far too fast, knowing the line was just around the corner, and spun as a result. Irregardless, he'd lost too much time on the oil, so he was never going to beat Patrese, who'd set his time just before Grouillard had blown up.
Edited 1 time(s). Last edit at 07/17/2012 05:52PM by gav.