What happened
On November 29, 2001, at approximately 12:30 hours, a Hiller UH-12-E helicopter, registration EC-ETG, was performing aerial spraying operations over a lettuce field at Finca «Los Martínez» in Los Martínez del Puerto, Murcia. The aircraft was conducting a low-level application of liquid product when the landing skids struck the terrain.
The impact caused the helicopter to roll onto its right side. During the rollover, both the main rotor blades and the tail rotor blades made contact with the ground. The pilot was able to exit the aircraft uninjured, and no fuel leaks or fires were reported following the incident.
The investigation
The investigation focused on the flight conditions and the pilot's maneuvers during the application process. The pilot, a commercial helicopter pilot with over 15,000 total flight hours, reported that a strong tailwind gust occurred during one of the passes. This gust caused a sudden, uncontrollable descent. Despite the pilot attempting an emergency power reduction/discharge, the altitude loss was too rapid to prevent the skids from hitting the ground.
Investigators noted that for effective crop treatment, the aircraft was flying at an extremely low altitude, approximately 40 to 50 cm above the ground, as the crops were only about 20 cm high. This proximity to the terrain left virtually no margin for error or recovery during atmospheric disturbances.
Findings
- The primary cause of the incident was a tailwind gust that reduced the translational lift of the main rotor, leading to an instantaneous loss of altitude.
- The aircraft was operating at an altitude so low that the pilot had no-margin for corrective action once the descent began.
- The impact resulted in significant damage to the aircraft, including the destruction of the right skid, the main rotor blades, the tail rotor blades, and the spraying booms.