for such a sophisticated aircraft like that to suddenly lose control on take off with 2 highly experienced pilots for no apparent reason makes no sense. Even if they where conducting EFATO drills this shouldnt happen. The Brasilia has gauranteed performance with one engine on T/O... Obviously Something terribly went wrong.This could not be pilot error. Without a doubt, mechanical failure!!! To me it sounds like the malfunction of the engine propeller control unit and this would allowed the propeller blade angles to go below the flight idle position if they where conducting EFATO drills. I am sure there are many other factors contributing to the accident as all accident have a chain of events to lead up to it.