What happened
On August 11, 2023, at 12:36 local time, a EUROCOPTER AS355NP helicopter, registration EC-MMF, operated by the Dirección General de Tráfico (DGT), was performing a landing in the municipality of La Mojon andnera, Almería. The flight had departed from Almería Airport for a scheduled stop at a private area near a restaurant to allow the crew to eat before continuing their mission.
The pilot initiated a visual approach to an unprepared landing site. While hovering at approximately 2 meters above the ground in ground effect, the rotor wash generated a significant cloud of dust. This phenomenon, known as brown-out, completely obscured the pilot's view of the terrain and all external references. During the period of zero visibility, the aircraft drifted backward. The pilot, unaware of the lateral movement, attempted to manage the descent, but the aircraft subsequently struck a tree with the tail rotor, causing the helicopter to overturn on its right side.
The investigation
The investigation examined the aircraft's flight path, maintenance records, and the circumstances of the landing. Investigators reviewed video footage from a witness, which confirmed that the aircraft was stable in ground effect before being enveloped by a dust cloud. The investigation also analyzed the pilot's experience and the organizational procedures of the DGT. It was noted that while the pilot had extensive experience, he had not received specific training for brown-out conditions or landings in unprepared zones. The investigation also confirmed that the aircraft's engines and flight controls were functioning normally at the time of the incident, and the primary issue was the loss of spatial orientation due to the dust cloud.
Findings
- The primary cause of the accident was the loss of visual references caused by a brown-out condition during the landing phase.
- The pilot's decision not to abort the landing immediately upon the onset of the dust cloud contributed to the emergency.
- The aircraft's tail rotor collided with a tree at an estimated height of 6-7 meters, leading to the subsequent rollover.
- The crew experienced a period of spatial disorientation where the backward movement of the aircraft went undetected by the pilot.
- The specialist camera operator attempted to warn the pilot of the backward drift, but there was insufficient time to prevent the collision.