What happened
During a night VFR approach, the engine of VH-LCZ, a Cessna 172, experienced a power loss. The pilot noticed a reduction in propeller speed shortly after turning onto the final approach. While the pilot attempted to troubleshoot the issue by applying carburettor heat, the engine did not recover before the aircraft's altitude decreased significantly.
As the aircraft descended, the pilot attempted a forced landing in a large, unlit area. During this descent, the aircraft struck power lines and subsequently collided with the ground. The accident resulted in minor injury to the pilot and substantial damage to the aircraft.
The investigation
Investigators examined the engine to determine the cause of the power loss. While a post-accident examination of the engine was not performed, which meant a mechanical defect could not be entirely dismissed, the ATSB found that fuel exhaustion, fuel contamination, and maintenance issues were unlikely.
Evidence suggested that the pilot did not apply carburettor heat during the descent prior to the engine issues, which, when combined with weather conditions favorable for ice formation, made carburettor icing a likely cause. The investigation also noted that the pilot's position on final approach—approximately 1,500 m from the runway threshold at 500 ft—left insufficient glide distance to reach the runway once the power loss occurred.
Findings
- The engine power loss was likely caused by the accumulation of ice in the carburettor.
- The pilot's decision to maintain the optimum glide speed by pitching the nose down, rather than attempting to stretch the glide, prevented a low-altitude stall and helped maintain aircraft control.
- The selection of the landing site was complicated by the night conditions, which made it difficult to identify obstructions such as the power lines that the aircraft eventually struck.