What happened
During a training flight involving a simulated hydraulic system failure, the pilot under instruction (P/UI) was performing a practice sequence in VH-BAA. The flight was intended to conclude with a specific landing technique prescribed by the rotorcraft flight manual (RFM), which mandates a flat approach into the wind and a slow run-on landing. However, the approach was planned for a right crosswind of 15-25 kt.
As the aircraft slowed, the variable crosswind became the dominant airflow, causing the helicopter to drift and experience unpredictable changes in pitch and yaw. CCTV footage indicates that the aircraft's airspeed decayed, leading to an unintended out-of-ground-effect hover. During this period, the aircraft lost positive control and yawed left, positioning the tail towards the wind and facing an active runway. Following an unidentified collective input that caused the aircraft to climb, the helicopter experienced a significant nose-down pitch and a left roll. The aircraft subsequently crossed the active runway, and control could not be recovered due to the proximity to the ground.
The investigation
Because the pilot under instruction could not recall most of the final stages of the flight, investigators relied on wreckage examination and CCTV footage to reconstruct the event. The investigation focused on the aircraft's behavior during the simulated failure and the effectiveness of crew coordination.
Investigators examined the deviation from the RFM, which requires landing into the wind to maintain manageable control. The analysis highlighted that the presence of a significant crosswind increased the pilot's workload and created unpredictable cyclic inputs. Furthermore, the investigation looked into the loss of control during the transition to a hover, noting that the aircraft entered a state where control was no longer assured. The investigation also addressed the entry into the active runway, concluding that the maneuver was likely an unavoidable consequence of the loss of controlled flight rather than an intentional runway excursion.
Findings
- The approach was conducted in a 15-25 kt right crosswind, contrary to the RFM requirement for an into-wind approach.
- The crosswind caused unpredictable changes in the magnitude and direction of control inputs as the aircraft slowed.
- The aircraft transitioned into an out-of-ground-effect hover, which increased the required control inputs and induced random aerodynamic perturbations.
- The failure to adhere to the prescribed landing procedure led to the aircraft departing controlled flight.