What happened
On Saturday, June 26, 1999, at 14:35, two formations of five helicopters arrived at AD Biarritz for parking. The first formation landed successfully, with its leader managing the guidance for the group's positioning at the parking stands. The second formation, consisting of the helicopters registered SP-SUG and SP-SUH, was also being managed by its leader.
During the arrival of the second formation, the leader did not provide guidance for the parking maneuvers. The air traffic controller instructed the pilot of SP-SUH to park at stand number ten, an instruction which the pilot acknowledged. The controller then instructed the pilot of SP-SUG to park on the left side of the first aircraft. However, the pilot of SP-SUG responded by stating "stand number eleven." Despite the controller expressing concern that the aircraft would be too close, the pilot of SP-SUG proceeded toward stand eleven. As the aircraft maneuvered, the tips of the rotor blades on both PZL Swidnik W3 Sokol helicopters struck each other.
The investigation
The investigation focused on the radio communications between the air traffic controller and the pilots of the second formation. Investigators examined the sequence of instructions provided by the controller and the subsequent read-backs by the pilots. The investigation specifically looked at the transition of responsibility for aircraft guidance between the formation leader and the air traffic controller, as well as the clarity of the instructions regarding the positioning of SP-SUG relative to SP-SUH.
Findings
- The collision resulted in damage to the blade tips of both helicopters.
- The primary cause of the accident was a misunderstanding by the air traffic controller regarding the positioning instructions and the resulting pilot response.
- There was a lack of continuous guidance for the second formation, as the formation leader did not assume the role of guiding the aircraft to their stands, leaving the instructions to the controller.