What happened
On 10 August 2022, a Thruster T600N 450, registration G-CBIR, was conducting a private flight at Causeway Airfield, County Londonderry. During the flight, the instructor initiated a simulated engine failure by closing the throttle at an altitude of approximately 100 to 200 feet. Following a previous incident during the same flight where the student reacted incorrectly to a power reduction, the instructor attempted a second demonstration of the necessary nose-down pitch procedure.
As the instructor reduced power and began to move the control stick forward, the student applied a firm backward pull on the shared control stick. This input overrode the instructor's attempt to pitch the nose down. Simultaneously, the student also pushed the stick forward, resulting in a steep nose-down attitude. To maintain enough airspeed for elevator authority during the flare, the aircraft had to maintain this high rate of descent. The aircraft subsequently made a heavy impact with the ground, causing the main landing gear to fail. The nose wheel dug into the surface, causing the aircraft to become inverted and resulting in fuel leaking from the tank vent.
The investigation
The investigation established that the flight's purpose was not initially intended to include additional circuits, and the student was not fully aware that engine failure practice was being conducted. Additional evidence revealed that after a previous landing, the instructor had taken off again for a circuit. During this second circuit, the instructor closed the throttle and prompted the student regarding their response to an engine failure. The student, perceiving a stall, reacted by pushing the stick forward while simultaneously resisting the instructor's inputs.
Findings
- The primary cause of the accident was the conflicting control inputs from the student and the instructor on the single shared control stick.
- The student's reaction to the simulated power loss involved simultaneous nose-up and nose-down inputs that overrode the instructor's commands.
- The aircraft landed with excessive vertical speed, leading to structural damage to the landing gear, propeller, and pod.
- The instructor performed the engine failure demonstration at an altitude that did not allow for a safe recovery given the student's interference.