Incident Summary
During a flight, while maneuvering and descending to 1,600 ft mean sea level, the pilot banked the airplane to the left. He heard a brief whistle followed by a loud boom sound. Looking behind, he saw both portions of the right cabin door open. He returned to the departure airport without further incident. The airplane sustained substantial damage to the fuselage.
Pilot Actions
During preflight inspection, after a passenger had entered the airplane, the pilot ensured that the right-rear cargo portion of the right cabin door was secure. The right cabin door was a two-piece unit: a forward passenger door and a rearward cargo door combination, adjacent to the second row of passenger seats. The pilot did not close the right-front portion of the door because the passenger had secured it multiple times before. After completing the preflight inspection, the pilot entered the airplane and observed the passenger close and latch the forward portion of the right door. The pilot then saw the passenger, seated in the right rear passenger seat, struggling with the seatbelt which passed between the seat and the cargo door on the right. The pilot suggested the passenger switch seats, and the passenger moved to the left rear passenger seat and fastened his seat belt.
Postaccident Examination
Postaccident examination revealed red paint transfer on the forward portion of the door from the rear portion door latch. Both door sections could be opened if the latch for the rear door was open. The pilot reported that he believed the right rear passenger seatbelt must have pulled on the rear door latch enough to dislodge it. He added that the red paint transfer was not there before the flight. A postaccident examination video showed that the pilot was able to use the larger airbag section of the seatbelt to wedge open the rear cargo door latch. The pilot reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation. The "Rear Cargo Door Emergency Exit" placard in the airplane stated: "1. Open front cargo door as far as it will go. 2. Push rear door handle forward and force door open."