What happened
During a descent at approximately 1820, the right engine of VH-BDS, a twin-engine aircraft, experienced a power loss. The environmental conditions at the time were consistent with the development of serious carburettor icing when operating at the chosen power setting without the use of carburettor heat. Following the engine failure, the pilot attempted to feather the propeller; however, the propeller did not reach the feathered position.
As the aircraft continued its descent, the pilot determined that the terrain between the aircraft's position and the airport could not be cleared safely. Consequently, the pilot executed a forced landing with the landing gear in the retracted position. The impact resulted in substantial damage to the aircraft.
The investigation
The investigation examined the performance of both engines during the descent. While the right engine failed, the left engine continued to operate normally at full throttle despite being subject to the same environmental conditions and power levels. This discrepancy suggests that while carburettor icing was a possibility, the power loss in the right engine might have stemmed from an unidentified source.
Furthermore, the investigation looked into the propeller's failure to feather. While the pilot performed the necessary actions, post-accident visual evidence confirmed the propeller remained unfeathered during the landing. The investigation could not rule out a mechanical fault that prevented the propeller from being selected into the feathered position, as the aircraft's systems were not physically examined.