The ATSB has determined that an unfeathered prop on the failed right engine of a Beech Duchess led to a forced landing that substantially damaged the aircraft.
Duchess VH-BDS was on a night VFR flight from Coonamble to Cessnock, NSW, in June last year when the right engine failed. The pilot found he was unable to maintain altitude to clear terrain and elected to carry out a forced landing near Ravensworth. All three people on board evacuated the aircraft and none were injured.
During the accident investigation, the ATSB discovered that the propeller on the failed right engine was not feathered, which meant the climb performance of the aircraft was hindered.
"Given the aircraft's weight and [the] ambient conditions at the time of the engine failure, the aircraft's operating handbook indicated the aircraft should have been capable of maintaining altitude with the propeller of the failed engine feathered," the ATSB report released last week states.
"The pilot recalled that after the engine failure, he conducted the propeller feathering actions, but did not confirm that the propeller had feathered. He did not attempt to unfeather the propeller or restart the engine after this time."
The report notes that the ATSB did not conduct an investigation of the engine or the feathering system.
The ATSB stated that the most likely cause of the engine failure was carburettor icing, even though the pilot had applied carburettor heat, but the engine failed to respond. The report also recognises that another cause of the failure is possible given that the left engine seemed to unaffected even though it was operating in the same conditions at the same power setting.
The full investigation report is on the ATSB website.