What happened
On 2 July 2020, a Guimbal Cabri G2 helicopter, registration SP-NCA, was performing a training flight at the Nowe Miasto nad Pilicą (EPNM) aerodrome. The flight, conducted by an instructor and a student pilot, was intended to evaluate the student's ability to complete a pre-solo flight exam through a series of aerodrome traffic circuits.
During the ninth circuit, light rainfall began to fall, and weather conditions started to deteriorate. To avoid landing outside the designated flight area due to the weather, the instructor decided to perform the final circuit as an autorotation simulation, intending to terminate the maneuver with a hover and air-taxiing to the helicopter stand.
As the helicopter approached the ground at an altitude of approximately 8 ft, the aircraft unexpectedly yawed to the right. In an attempt to halt the descent, the instructor moved the collective dynamically to its maximum upward position. During the subsequent landing roll, the deceleration caused by the high angle of the main rotor disc led the rotating main rotor blades to strike the tail boom. The impact severed the rear part of the tail boom, including the fenestron, which was thrown several meters from the fuselage. The crew sustained no injuries.
The investigation
The PKBWL investigation examined the flight parameters, the aircraft's mechanical state, and the crew's actions. The investigation confirmed that the helicopter was airworthy, the weight and center of gravity were within limits, and both crew members were properly rated, rested, and not under the influence of any substances. The investigation also analyzed the weather conditions, noting the presence of clouds and rainfall at the time of the accident.
Findings
- The primary cause of the accident was an error in aircraft control, specifically the dynamic movement of the collective to its maximum upward position combined with a high angle of the main rotor disc inclination caused by pulling the cyclic to an extreme rear position.
- The decision to initiate the flare at an altitude higher than usual contributed to the occurrence.
- The crew's intention to end the exercise with a hover and air-taxiing, driven by a time deficit due to deteriorating weather, was a contributing factor.
- Concerns regarding an unintentional landing outside the flight area influenced the crew's decision-making.