What happened
On August 17, 2005, an Eurocopter AS 350B, registration I-AMNB, was conducting aerial firefighting operations near Sezze, Italy. The aircraft, operated by SAM s.r.l., was tasked with water collection from Lago delle Mole to combat a fire in the Piana del Quartaro area.
During the sixth and final water-refilling attempt, the pilot executed a steep approach to the lake surface. While attempting to transition into a climb following the dip, the aircraft experienced a rapid loss of altitude. The pilot applied collective pitch to increase lift, but the aircraft's skids became partially submerged in the water. During this maneuver, the tail rotor struck the surface of the lake.
Following the impact, the pilot managed to maintain control, cleared the water, and released the payload. The pilot noted the activation of the tail rotor chip detector light. After landing in a nearby field to check flight controls, the pilot returned to the mission area, but the chip detector light remained illuminated. The aircraft eventually landed at Piana del Quartaro, where the engine was shut down.
The investigation
The ANSV investigation focused on the sequence of the approach and the subsequent mechanical indications. Investigators examined the damage to the tail rotor blades, the tail rotor transmission, the pitch change rod, and the tail rotor drive shaft. The investigation also analyzed the activation of the chip detector, which indicated the presence of metallic particles in the lubrication system.
Findings
- The tail rotor blades, transmission, and associated components sustained significant damage.
- The activation of the tail rotor chip detector was likely caused by the release of metallic particles resulting from the physical impact of the tail rotor with the water.
- The pilot utilized a steep descent rate to avoid obstacles, including power lines and nearby structures, during the approach.
- The primary cause of the incident was the improper execution of the final steep approach, characterized by an excessive rate of descent that led to the tail rotor striking the water.