What happened
During a training flight near Cowra Airport, an instructor initiated a simulated engine failure by moving the left engine mixture control to the idle cut-off position while the aircraft was at approximately 2,600 ft AGL. Following an instrument approach, the student pilot visually established the aircraft on final approach. At a low altitude above the runway, the instructor commenced a go-around. During this maneuver, the aircraft experienced a rapid leftward yaw and roll, leading to a loss of control. The Beechcraft E55 impacted the ground in a near-vertical, nose-down attitude and came to rest in an inverted position. Post-accident examination of the wreckage confirmed that the right engine was producing significant power at impact, while the left engine was not producing power.
The investigation
The investigation focused on why the left engine remained inoperative and why the go-around was attempted under asymmetric conditions. It was determined that the instructor used the mixture control to simulate the failure, a method used by the operator to render the engine inoperative. While the standard procedure intended for the instructor to eventually set zero thrust by returning the mixture to full rich, the left engine remained at idle cut-off with a windmilling propeller. This windmilling propeller created increased drag, contributing to the difficulty in maintaining directional control.
Data analysis showed that the student's flight path included significant deviations in airspeed and altitude, likely due to pilot handling rather than environmental factors. Furthermore, the investigation found that the crew did not perform a check to verify that the engine had been restarted and was producing power. The student had also deferred extending the landing gear, which may have interrupted the checklist flow. Because the student had already announced an asymmetric configuration, the crew was not prepared for the power demands of a go-around.
Findings
- The instructor likely failed to move the left engine mixture lever back to the rich position, leaving the engine inoperative.
- The instructor initiated a go-around at an altitude below the minimum air control speed while unaware that the left engine was still non-functional.
- The operator's training procedure for asymmetric flight involved using the mixture control to simulate failure without a confirmed restart, which increased the risk of undetected asymmetric thrust.
- The use of mixture control instead of throttle reduction to simulate engine failure created a risk of undetected asymmetric operation.