CEN12FA534 · Beech G18 - S

The airplane had climbed to an altitude of about 11,000 feet mean sea level (msl) with 12 parachutists seated inside the airplane on two rear-facing "straddle benches." The airplane was flying at an indicated speed of 100 mph with the flaps retracted. The operator's written guidance for "skydiving jump runs" indicated that the airspeed should be maintained at 110 to 120 mph and that the flaps should be set at 30 degrees. As the airplane arrived at the planned drop location, the parachutists stood up, opened the door, and moved farther aft in the airplane to prepare for their jump. Five of the parachutists were positioned aft of the straddle benches and were hanging onto the outside of the airplane, several of the other parachutists were standing in the door, and the remainder of the parachutists were standing in the cabin forward of the door. According to instructions on the operator's skydiver briefing card, no more than four jumpers should be allowed to occupy the door area during exit. Several parachutists heard the sounds of the airplane's stall warning system, and the airplane then suddenly rolled and began to descend. All 12 parachutists quickly exited the airplane. Several witnesses reported seeing the airplane turning and descending in an inverted nose-down attitude and then appear to briefly recover, but it then entered a nearly vertical dive, which is consistent with a loss of control event as a result of an aerodynamic stall and subsequent entry into a spin.

Federal Aviation Administration (FAA) guidance indicates that the pilot-in-command (PIC) must know the weight and location of jumpers during each phase of the flight to assure that the aircraft stays within center of gravity (CG) limits and that the PIC must remain aware of CG shifts and their effects on aircraft controllability and stability as jumpers move into position for exiting the aircraft. Further FAA guidance indicated that, if a stall recovery is not promptly initiated, the airplane is more likely to enter an inadvertent spin, which can degenerate into a spiral. It is likely that the number of parachutists near the door area during exit shifted the CG aft and contributed to the aerodynamic stall/spin.

The pilot suffered a serious traumatic brain injury in September 2005 as a result of colliding with a truck while bicycling; however, he did not report that injury during all subsequent FAA medical certificate applications. Persons with an injury of this severity will likely have long-term issues with cognition, attention, executive functioning, sleep disturbance, and impulsivity. However, without the results of any postinjury neuropsychological testing, the status of the pilot's cognition and decision-making during the accident flight could not be determined.

Verbatim NTSB analysis and probable cause from the NTSB dataset