To close the cargo door, the door control switch that is located on the Control Panel is held in the CLOSE position. This provides power to the door actuator, closing the door. Closing the door removes power from the door actuator and provides power to the latch actuator, closing the latches and illuminating the lock light (Green), indicating the door is ready to lock. Then, the external door handle is rotated inward until secured by the trigger. This locks the latches, closes the vent door and turns off the door warning lights in the cockpit. Through the viewing port located just above a latch access door, a visual check of the lock pin can be made to verify that the door is properly locked.

The following illustration shows a typical aft cargo door with five latches. The aft cargo door on the accident airplane had four latches. The view is from inside of the aft cargo compartment looking forward.

The following illustration shows the aft cargo door latching/locking mechanism in its pre-accident open loop configuration

The following illustration shows the aft cargo door latching/locking mechanism in the post-accident close loop configuration.