History of Flight
On 2 November 2021, a Bell 206L helicopter, registration ZS-HDX, operated by Henley Air (PTY) LTD, departed Rand Airport (FAGM) at 0925Z on a repositioning flight to Buffels Mine near Klerksdorp, North West province. The flight was conducted under commercial helicopter operations (Part 127) with a pilot and one passenger on board. Approximately 35 minutes into the cruise phase, the pilot observed an engine out warning light, followed by indications of zero oil pressure, torque, and gas generator (Ng). Rotor RPM (RRPM) and transmission oil temperature (TOT) gauges remained normal. Subsequently, a loud bang emanated from the engine compartment, and the low rotor RPM warning activated. The pilot entered autorotation, turned the helicopter into wind, and prepared for a forced landing. All pedal controls lost effectiveness, but the pilot executed a successful forced landing on a private farm 16 nm southwest of Fochville. After landing, he shut down the engine. A fire erupted in the engine bay, which the pilot extinguished using the portable fire extinguisher.
Injuries
Neither the pilot nor the passenger sustained any injuries.
Damage to Helicopter
The helicopter sustained substantial damage, including damage to the engine, cowling, fuselage, tail rotor drive shaft, and one main rotor blade.
Engine Examination
Metallurgical examination and analysis of the engine components determined that the engine failure resulted from separation of the gas producer bearing thrust plate anti-rotation tab. This separated tab traveled through the oil system and lodged between the oil pump scavenge gear and the wall. Consequently, the oil pump could not provide adequate lubrication to the number 6 and 7 bearings, which failed due to thermal damage. Subsequent damage occurred to other turbine parts.
Probable Cause
The probable cause, as stated in the investigation report, is engine failure due to loss of lubrication to the number 6 and 7 bearings caused by a separated thrust plate anti-rotation tab which lodged between the engine oil scavenge gear and the wall of the oil pump, preventing adequate flow of engine oil.