What happened
On 30 August 2008, a RotorWay Executive 162 F helicopter, registration ZU-RAT, was conducting a private flight from Aviators’ Paradise Aerodrome to Rustenburg Aerodrome. While cruising at approximately 800 feet AGL, the aircraft suddenly experienced a sharp leftward yaw. The pilot attempted to correct the heading using right rudder, but the input was ineffective. To regain control, the pilot reduced engine power, which stabilized the aircraft's heading.
Recognizing the emergency, the pilot initiated an autorotation landing. While searching for a landing site, the pilot had to navigate around trees and power lines, eventually selecting an open field. During the run-on landing, the helicopter's left skid struck a small mound of soil, causing the aircraft to nose over and land on its left side. Although the pilot successfully evacuated through a broken windscreen, the helicopter was destroyed by the impact and a subsequent fire in the surrounding dry grass. There were no injuries to the pilot.
The investigation
SACAA AIID conducted a desktop investigation into the incident. Examination of the wreckage revealed that the center tail rotor drive belt had suffered a catastrophic failure, with the broken belt found entangled in the center pulley.
Investigators reviewed the maintenance history and found that while the aircraft had been maintained by an approved person, there were discrepancies in the logbook certification. Crucially, the investigation established that the aircraft was still fitted with Gates brand tail rotor drive belts. The manufacturer had previously issued service bulletins warning that these specific belts were prone to premature failure and recommending they be replaced with Bando brand belts.
Findings
- The primary cause of the loss of directional control was the failure of the tail rotor drive belt.
- The pilot's decision to perform a run-on landing resulted in the aircraft touching down short of the intended zone.
- The aircraft's nose-over was triggered when the left skid impacted a 350 mm mound of soil.
- The aircraft was operating with non-compliant components, as the service bulletin regarding the Gates brand belts had not been implemented.
Safety action
- It is recommended that the manufacturer provide enhanced training for owners on using belt tensioning tools and performing effective visual inspections.
- The investigation suggested that the service bulletin regarding tail rotor drive system updates should be investigated for conversion into a mandatory airworthiness directive.
- A recommendation was made for the manufacturer to contact all operators using the identified Gates brand belts to ensure immediate replacement.