Accident Sequence
The accident occurred moments after takeoff from runway 29 at Darwin Airport, Northern Territory. The flight was intended to revalidate the command instrument rating of the pilot under check, with a training and checking captain in command occupying the copilot's seat. The takeoff included a simulated engine failure. Data from the aircraft's flight recorders revealed that the pilot in command (PIC) retarded the left power lever to flight idle to simulate an engine failure, which introduced a simulated failure of both the left engine and its propeller autofeathering system. The increased drag from the windmilling propeller raised the control forces needed to maintain the aircraft's flightpath.
The pilot under check allowed the airspeed to decrease and the aircraft to bank toward the inoperative engine. He also increased power on the right engine and engaged the yaw damper in an attempt to stabilize the aircraft. These actions increased his workload and made control more difficult. The PIC did not restore power to the left engine to discontinue the manoeuvre. The few seconds available before the aircraft became uncontrollable were insufficient for troubleshooting and deliberation.
Probable Cause
The official findings identified several factors contributing to the accident: the PIC initiated a simulated left engine failure just after becoming airborne at a speed that did not allow adequate margin for error; the PIC simulated the failure by selecting flight idle instead of zero thrust, thereby simulating a simultaneous failure of the left engine and its propeller autofeather system; the pilot under check operated the aircraft at a speed and bank angle that, when uncorrected, resulted in loss of control; the pilot under check increased his workload by increasing torque on the right engine and selecting the yaw damper; and the PIC probably became preoccupied and did not abandon the simulated engine failure after the heading and speed tolerance for the manoeuvre were exceeded and before control was lost.