Standard procedure calls for takeoff Self_motion to continue after V1 , and the pilots initially followed such ; however , the vibration severely worsened upon rotation , and so , not knowing Know the cause of the vibration , the captain aborted Process_end the takeoff , despite having passed Motion_directional Vr .

The crew aborted Process_end the takeoff Self_motion at a speed below V1 at 800-900m down the runway .