What happened
On 11 December 2021, a Bell 206L-3 helicopter, registration ZS-HXG, departed from Ultimate Heliport in Midrand, Gauteng, bound for Plettenberg Bay. The flight included a planned refueling stop at New Tempe Aerodrome. Shortly after takeoff, an eyewitness noticed smoke emerging from the engine compartment. After being alerted via radio by the observer, the pilot initiated a 18-degree turn to perform a precautionary landing back at the heliport.
During the approach, the pilot heard a loud bang and experienced an aggressive yaw to the right. The helicopter lost altitude rapidly and struck the ground just short of the helipad embankment. The impact caused the main rotor blades to strike the terrain, leading to substantial damage to the aircraft. The pilot sustained minor injuries, while the passenger remained uninjured.
The investigation
SACAA AIID investigators examined the wreckage and engine components to determine the cause of the power loss. CCTV footage from the heliport confirmed that smoke was visible during startup and intensified after takeoff, and also showed a significant oil spill on the helipad surface. The investigation also reviewed maintenance records following a compressor replacement that had occurred in April 2021.
Findings
- The engine failure was triggered by oil starvation caused by a damaged engine oil pressure supply hose.
- The engine oil pressure hose had been chafing against the rotating rotor brake disc.
- The engine's Number 6 and 7 bearings suffered thermal destruction due to the lack of lubrication.
- This thermal damage led to the decoupling of the spline coupling from the compressor drive shaft and a subsequent internal clash of rotating parts, which ultimately caused the turbine wheel to burst.
- The engine oil hose was not properly secured with the required P-clamps as specified in the maintenance manual.
- The aircraft was utilizing an older version of the oil hose that the manufacturer had recommended replacing with an updated part number.
- The investigation also noted the use of an unapproved bladder-type fuel tank in the cabin without proper regulatory or manufacturer approval.
Safety action
- The investigation highlighted the need for Maintenance Organisations (AMOs) to strictly adhere to manufacturer-prescribed assembly and installation procedures.
- It is recommended that AMOs implement annual maintenance training to reinforce safe practices.
- Operators are advised to use only manufacturer-approved components and to obtain proper regulatory approval for any modifications, such as the use of additional fuel tanks.