Flight Background
The aircraft was conducting a sport parachute flight, carrying 24 parachutists to an altitude of 12,500 feet over a drop zone for a mass jump. The cabin was configured for cargo, with no passenger seats except for one jump seat. Twenty-four seat belts were attached to the floor of the cargo area. The cabin door had been removed, and an unapproved step and four handholds were installed outside and forward of the cabin door for parachutists.
Flight Sequence
The standard jump-run procedure involved slowing the aircraft to 95 to 100 knots, extending the landing gear and approach flaps, and reducing power on the left engine. Parachutists remained in position without using seat belts until approaching the drop zone, at which point two moved outside the aircraft while others moved close to the doorway. The first jumpers were unaware of any problem but observed the aircraft enter a steep bank, roll over, and spiral nose-down. Sixteen jumpers exited the aircraft; three of them struck the stabilizer. The aircraft subsequently crashed in a near-vertical descent.
Investigation Findings
Examination revealed that the aircraft's center of gravity was behind the aft limit for both takeoff and the jump. The elevator trim actuator was found in a position corresponding to full nose-up trim.
Probable Cause
The official investigation determined the loss of control occurred due to improper maintenance/modification, improper supervision by company/operator management, the pilot in command exceeding aircraft weight and balance limits, reduced airspeed, and an inadvertent stall by the pilot in command.