Incident Overview
On 14 January 2014, a Robinson R44 II helicopter, registration ZS-RSO, was conducting a private flight in the Nelspruit area. The helicopter lost engine power within three seconds, accompanied by moderate to severe vibrations. The manifold pressure indicator increased above 25 inches, while oil pressure dropped to the red line, followed by a sudden engine stoppage. The pilot initiated an autorotation, identified a landing strip, and landed the helicopter safely. No occupants were injured, and the helicopter sustained no damage.
Aircraft and Personnel
The helicopter was a Robinson R44 II (serial number 10145), manufactured in 2003, with a total airframe time of 1,675.6 hours. The engine was a Lycoming IO-540-AE1A5 (serial L-32118-48A) with 470.4 hours since new and 48.7 hours since overhaul. The pilot, aged 22, held a private pilot licence with 161.2 total flying hours, including 60.0 hours on type. The flight was private, with one passenger on board.
Meteorological Conditions
Weather at the time was reported as CAVOK, with surface wind light and variable at 315°, temperature 25°C, and clear skies. Visibility was clear.
Investigation Findings
The helicopter was transported to an approved maintenance organization for examination. Visual inspection of the engine revealed no external leaks or damage. The affected connecting rod bushing had failed, resulting in a connecting rod failure and damage to the bottom of the engine casing. Metal particles were found in the oil sump. The investigation established that due to the fact that the connecting rod converts the pistons reciprocating motion into the rotational motion of the crankshaft, the failure could be attributed to undetermined overload during such conversion. Additionally, oil supply failure caused a drop in oil pressure.
Probable Cause and Contributing Factors
The probable cause of the incident was a successful forced landing following an engine stoppage or failure during flight. Contributing factors were connecting rod failure and oil supply failure, which caused a drop in oil pressure.