Background
A line service technician disconnected an airplane from a battery charger and left the right access door open, which provided access to the fuel control unit, fuses, fuel line, oil line, and battery charging port, as was his routine. He then towed the airplane from the hangar and parked it in front of the airport terminal. Three passengers arrived first, followed by the pilot about 30 minutes later.
Accident Sequence
The pilot uploaded navigational charts, performed a preflight check which he described as normal, and started the engine. The taxi and engine run-up were also normal. The wing flaps were set to 10°. After liftoff, the pilot believed he retracted the landing gear and continued climbing. Shortly thereafter, the right cowl door opened partially and began "flopping" up and down 3 to 4 inches. The pilot reduced torque to prevent the door from opening fully. While turning onto the left crosswind leg to return to the runway, the right cowl door opened completely. The airplane could not maintain altitude even with full power, so the pilot lowered the nose. The airplane struck trees, pancaked, slid sideways, and came to rest in the front yard of an abandoned house.
Injuries
Two passengers received serious injuries. One of them was found out of her seat, unconscious on the floor shortly after the accident, and died 227 days later. The private pilot and one other passenger sustained minor injuries.
Investigation Findings
Examination of the wreckage found no evidence of preimpact failures or malfunctions of the airplane or engine that would have precluded normal operation. The right access door latches and clevis keepers were functional, with no overstress or deformation, indicating the door had not been closed and latched before takeoff. The battery charging port cover inside the compartment was not secured, suggesting the preflight inspection was incomplete. A checklist found by the pilot's seat, labeled "FOR SIMULATOR TRAINING PURPOSES ONLY," listed only one item under "EXTERIOR PREFLIGHT": "EXTERIOR PREFLIGHT…COMPLETE." The airplane manufacturer's pilot's operating handbook (POH) was found in a cabinet behind the pilot's seat, inaccessible from the pilot's station, and contained detailed preflight guidance. The landing gear was found in the down and locked position, with the handle still down, indicating the pilot had not retracted it as he thought. Recorded data showed the airplane climbed along the runway heading, then entered a left turn with a bank angle increasing to about 45° and angle of attack increasing to about 8°, causing airspeed to decrease below the stalling speed (about 20% higher due to load factor) until the airplane stalled aerodynamically. This indicated the pilot became distracted by the open door.
Probable Cause
The official probable cause was the pilot's inadequate preflight inspection and his subsequent failure to maintain airplane control, which resulted in an access door opening after takeoff, and the airplane exceeding its critical angle of attack and experiencing an aerodynamic stall.