What happened
On 1 July 2011, a Eurocopter AS350B3 helicopter, registration ZS-HDK, was conducting an aerial survey near Sishen Aerodrome in the Northern Cape. The flight crew, consisting of two pilots and a systems operator, was returning to the aerodrome to refuel after several hours of operation.
During the approach at approximately 1,200 feet, the pilot-not-flying (PNF) deactivated the accumulator test switch without the pilot-in-command's (PIC) permission, triggering a hydraulic warning. The crew then decided to use the situation as a training opportunity, initiating a simulated hydraulic failure procedure as outlined in the pilot's operating handbook. This involved deactivating the master hydraulic switch on the collective pitch lever.
As the helicopter descended toward runway 3 and approached ground level at roughly 3 to 6 feet, the PNF requested the reactivation of the hydraulic system. While the pilot flying (PF) complied with the request, the hydraulic system was not fully restored because the previously deactivated accumulator test switch remained off. This caused a sudden, intense leftward yaw that the pilot could not counteract with the rudder pedals. The aircraft's right-hand skid struck the ground, leading to a dynamic rollover that left the helicopter resting on its side.
The investigation
SACAA AIID investigators examined the wreckage and the flight crew's actions. While the crew initially reported a genuine mechanical failure, subsequent interviews revealed that the event was a self-induced training exercise. Post-accident inspections of the hydraulic system, including tests on the pump, belts, and pressure transmitters, showed no mechanical defects or failures.
The investigation also uncovered significant discrepancies regarding the pilots' training. Records indicated that one pilot had undergone conversion training at a facility that lacked proper classroom infrastructure and a standardized syllabus, and the regulator's audit reports showed inconsistencies regarding the compliance of the training organizations involved.