What happened
On 7 September 2013, a Robinson R44 Astro helicopter, registration ZS-RHX, was conducting agricultural spraying operations at the Ntomeni Sugar Estate in KwaZulu-Natal. While performing the first run of the spraying detail, the pilot identified electrical power lines positioned across the intended flight path.
To avoid a collision, the pilot executed an immediate climb and right turn. This sudden evasive maneuver caused a significant decay in both the aircraft's airspeed and main rotor RPM. In an attempt to recover these vital flight parameters, the pilot transitioned into a nearby valley. However, the terrain's slope prevented the recovery of sufficient airspeed and rotor RPM. With the aircraft's performance severely compromised, the pilot was forced to perform an emergency landing. The resulting hard landing on the sloping ground caused the helicopter to roll onto its right side, causing substantial damage to the aircraft and its spraying system. The pilot escaped without injury.
The investigation
An investigation by the SACAA AIID examined the flight history, aircraft maintenance, and weight calculations. The inquiry established that the aircraft was properly maintained by an approved organization and held a valid certificate of airworthiness. The pilot was a commercially licensed professional with significant flying experience.
Investigators also reviewed the aircraft's weight at the time of the incident. The total weight was calculated at 2,449 pounds, which was 49 pounds over the maximum certified take-off weight of 2,400 pounds. This discrepancy was attributed to a failure to perform an accurate weight and balance calculation prior to the mission.
Findings
- The primary cause of the accident was an unsuccessful forced landing.
- A major contributing factor was the pilot's failure to maintain a proper lookout for obstacles within the flight path.
- The aircraft was operating in an overweight condition, exceeding its maximum takeoff weight.
- The evasive maneuver to avoid power lines resulted in the main rotor RPM dropping below the minimum required for stable flight, rendering the aircraft unflyable and necessitating the forced landing.