What happened
On 15 November 2003, a Pilatus PC-6 (registration ZS-IHB) was conducting commercial parachuting operations departing from Carltonville Aerodrome. While climbing toward a target jump altitude of 11,000 ft AMSL, the aircraft entered a cumulus cloud at approximately 10,000 ft.
Upon entering the cloud, the aircraft encountered extreme turbulence. Passengers on board reported violent buffeting and significant fluctuations in altitude. The intensity of the gravitational forces was so severe that passengers were unable to move or reach the aircraft door. During this period, the aircraft entered a nose-down attitude and began spinning. The aircraft lost approximately 3,100 ft of altitude in roughly 23 seconds before the pilot successfully recovered the aircraft and leveled off after exiting the cloud layer.
The investigation
SACAA AIID investigators examined the flight details and the pilot's actions following the encounter with instrument meteorological conditions (IMC). The investigation established that the pilot, who held a valid commercial license but lacked an instrument flying rating, executed a steep descending turn and reduced throttle to exit the cloud.
Data indicated that the descent rate during the event reached approximately 8,086 ft per minute, a rate significantly exceeding the standard descent capabilities of the aircraft type. The incident was brought to the attention of the authority three weeks after the occurrence by a passenger. Following the report, the aircraft was grounded to undergo a mandatory structural integrity inspection.
Findings
- The primary cause of the incident was the pilot's inadvertent entry into cloud cover while flying without an instrument rating.
- The attempt to exit the cloud resulted in the aircraft entering an unusual attitude and a spin.
- The aircraft experienced extreme turbulence and high G-forces, which incapacitated the movement of the passengers temporarily.