What happened
On 27 February 2016, a Robinson R22 Beta II helicopter, registration ZS-REW, was conducting a crop spraying operation near Killer Krankie, Margate, in KwaZulu-Natal. The flight, operated by Triple R Aviation, began with a takeoff from a private farm. Shortly after lifting off and transitioning to approximately 50 feet above ground level, the pilot observed the low rotor RPM warning light illuminate on the instrument panel.
Due to the low altitude, the pilot was unable to restore the necessary rotor speed. Consequently, an emergency forced landing was executed in a nearby sugar cane field. During the touchdown, the aircraft's left skid became trapped in a furrow in the uneven terrain. This caused the helicopter to enter a dynamic rollover, eventually coming to rest on its left side. The pilot sustained minor injuries, while the aircraft suffered substantial damage, including destruction of the main rotor blades, damage to the tail boom and mast, and the loss of the left skid.
The investigation
An investigation by the SACAA AIID examined the flight history, aircraft maintenance, and the sequence of the accident. The inquiry confirmed that the pilot held a valid commercial helicopter license and a current medical certificate. The aircraft, ZS-REW, was airworthy, with only 36.7 hours flown since its last mandatory periodic inspection.
Investigators analyzed the impact and wreckage, noting that the engine remained attached to its mounts despite the dislodged instrument panel. The investigation also reviewed the mechanics of low-inertia rotor systems, noting that the R22 is particularly susceptible to aerodynamic stalls when rotor RPM decays. The wreckage showed that the main rotor blades struck the tail boom and surrounding vegetation during the rollover sequence (as seen in Figure 8).
Findings
- The pilot failed to monitor and maintain the rotor RPM during the critical phase of takeoff.
- The decay in rotor RPM occurred at such a low altitude that recovery was not possible.
- The uneven surface of the sugar cane field contributed to the loss of control when the skid caught in a furrow.
- The aircraft was operating within its weight and balance limits, though it was near the forward center of gravity limit.