Incident Involving Pilatus PC-6 (Porter) ZS-IHB at Carltonville Aerodrome

Incident Overview and Aircraft Details On 15 November 2003, a Pilatus PC-6 (Porter) with registration ZS-IHB was operating a commercial parachuting activity from Carltonville Aerodrome (FACR). The aircraft carried one pilot and eight parachutists. The pilot-in-command held a valid commercial pilot's license without an instrument flying (IF) rating and had 37 total flying hours, with 382.6 hours on type. ## Sequence of Events Following take-off, the pilot began climbing toward a jump altitude of 11,000 ft AMSL. According to a parachutist's statement, the aircraft entered a cumulus cloud at approximately 10,000 ft. The aircraft then experienced violent buffeting, rising and falling alarmingly. The parachutist observed rain on the windshield and reported that gravitational forces increased to a level where she feared occupants might become unconscious. Jumping was not possible because occupants could not lift their arms or move to open the door. The parachutist next observed the aircraft exiting the bottom of the cloud in a nose-down attitude, spinning toward the ground. Within seconds, the pilot recovered the aircraft from the unusual maneuver and leveled off. The parachutist measured a loss of 3,100 ft in 23 seconds using a ProTracks altimeter. The pilot then climbed back to jump altitude, and the parachutists exited without further incident. ## Pilot Statement and Technical Findings The pilot stated that he inadvertently entered cloud and experienced severe turbulence. He closed the throttle and executed a steep descending turn, exiting the cloud in control of the aircraft at least 5,000 ft AGL. The altitude lost corresponded to a descent rate of 8,086 ft per minute, substantially higher than the normal descent rate for the aircraft type. ## Reporting and Aircraft Status The incident was reported to the South African Civil Aviation Authority (SACAA) three weeks after it occurred by a parachutist on board. Following the report, the aircraft was grounded pending a structural integrity inspection. The last mandatory periodic inspection prior to the incident was certified on 2 September 2003 at 5,234.0 airframe hours; an additional 50.0 hours were flown after that certification. ## Probable Cause The non-instrument-rated pilot inadvertently entered cloud (instrument meteorological conditions [IMC]) and, in an attempt to exit the cloud, the aircraft entered a spin. The pilot recovered the aircraft from the unusual attitude/maneuver once clear of cloud, losing 3,100 ft in altitude in the process.