The plane was too high and close in to land when it circled back to the airport. The captain was forced to continue circling Amsterdam until he could reduce his altitude to that required for a final approach to landing. During the second circle, the captain instructed the first officer to extend the wing flaps. The inboard trailing edge flaps extended, since they were powered by the number one hydraulic system, which was still functioning. However, the outboard trailing edge flaps did not extend, because they were powered by the number four hydraulic system, which failed when the number four engine was torn from the right wing. That partial flap condition meant that the plane would have a higher pitch attitude than normal, as the plane slowed down. The leading edge flaps (powered by the pneumatic system) extended on the left wing, but not on the right wing, because of the damage inflicted on that wing when the right engines were torn off. That differential configuration caused the left wing to generate significantly more lift than the damaged right wing, especially when the pitch attitude increased as the airspeed decreased. The increased lift on the left side increased the tendency to roll further to the right, both because the right outboard aileron was inoperative and because the captain elected to increase the thrust on the left engines in an attempt to reduce his very high sink rate. As the airspeed slowed, the ability of the remaining controls to counteract the right roll diminished. The Captain finally lost all ability to prevent the plane from rolling to the right. That roll continued until it reached 90 degrees, just before the impact with the apartment houses.