Incident Summary
During takeoff, after the landing gear was retracted, the flightcrew heard a loud wind noise. The annunciator panel, which includes a red CARGO DOOR warning light to indicate an unsecured door, showed no indications of any malfunctions. Upon checking the cabin, passengers informed the crew that the cargo door had come open. The aircraft subsequently returned to land without further incident.
Pre-Departure Procedures
The ramp agent responsible for handling the flight stated that, per company procedures, he checked that all doors were secured during the pre-departure check. He noted that he did not observe anything different and that all doors appeared closed when he released the aircraft for taxi.
Post-Accident Inspection
After landing, an inventory of the cargo compartment revealed that no baggage had been lost. During the post-accident examination, the aft cargo door locking handle was observed in the unlocked position when the door was swung down. A visual inspection of the aft cargo door locks, switches, and the annunciator cargo door warning system found no discrepancies with the aft cargo door or its indicating/warning system.