Investigators reviewed the performance of the flight crew after the engines separated. DFDR data revealed that the captain at times using full rudder pedal deflection, and control wheel deflections from 20 degrees to 60 degrees to the left, the report said. "The Boeing training manual states that in an asymmetric flight condition with two engines inoperative on one side, there should be enough rudder authority to allow the control wheel to be almost neutral up to MCT [maximum continuous thrust] at maneuvering speed," the report said.
During a flight in a B-747 simulator, "it was noted that with flaps up (which locks out the outboard ailerons) under the above-mentioned conditions and with maximum deflection, approximately 30 degrees left wing¬down control wheel deflection was needed to maintain straight flight," the report said.