Accident Summary - continued

Additionally, the lock pins were not properly rigged to engage had the torque tube been properly rotated. The four lock pins on the lock tube were 1.6 mm short of the rear face of the restraining flanges. With the latch hooks not "over center" and the lock pins not engaged, the loads applied to the latch hooks from fuselage internal pressure were transmitted through the latching mechanism to the latch actuator support bracket, failing the two attachment bolts. When the two attachment bolts failed, the detached latch actuator enabled the latch hooks to slip off the latch spools, resulting in the sudden opening of the cargo door.

The sudden opening of the aft cargo door resulted in a rapid loss of pressurization in that compartment. The cabin floor was not equipped with pressure relief vents. Thus, the loss of the door caused the full differential pressure between the pressurized passenger cabin and the atmosphere to be exerted on the cabin floor over the compartment.

This loading failed the floor support structure and the cabin floor collapsed downward into the cargo compartment, sucking two rows of seats with passengers still strapped in them out of the opening.

The collapse of the floor resulted in the loss of use of the empennage control surfaces. The control cables from the cockpit to the empennage control actuators were routed through the cabin floor beams over this cargo compartment. The severed control cables made it impossible to control the aircraft pitch attitude.

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