What happened
During the takeoff rotation of a flight scheduled for 0830 departure, a passenger seated in row 32 observed the rear cargo door open. The passenger notified a flight attendant, who then alerted the cockpit. The flight crew experienced audible bangs and airframe vibrations, leading them to declare an emergency. The aircraft returned to the airport and landed without incident. Upon the aircraft's arrival on the runway, airport fire personnel observed that the aft cargo door was open at a 90-degree angle, though the handle appeared to be in or flush with the door.
Investigations into the departure timeline revealed the aircraft arrived at the loading area at 0800, later than scheduled. The captain noted that the flight engineer was working quickly to complete duties prior to departure. During the final walk-around, which included a check of the cargo doors, the captain reported that no cargo door lights were illuminated on the annunciator panel.
Discrepancies were noted regarding the aircraft load. While the load manifest listed 172 passengers (with 168 initially on board and two late arrivals), the bag count presented inconsistencies. Ground handlers reported loading 202 bags, including 5-6 bags loaded just before departure, but a post-incident count revealed a total of 208 bags were onboard.
The investigation
Technical examinations focused on the cargo door mechanism and the aircraft's warning systems. Testing of the aft cargo door proximity switch revealed contamination between contact terminals, although investigators could not determine if this contamination caused an indication anomaly on the annunciator panel. Post-incident functional tests confirmed that the cargo door open warning light and its associated circuit were functioning normally. It was noted that when the handle is closed, the door does not sit flush with the doorframe.