What happened
On July 16, 2015, at 15:05 UTC, an Eurocopter AS 350 B2, registration D-HCOL, was engaged in firefighting operations near S. Martinho das Amoreiras, Odemira, Portugal. Operated by Everjets, the helicopter was responding to a request from the Rescue Operations District Command (CDOS) to assist with a forest fire.
During the mission, the pilot identified a ground-based firefighting brigade and planned a water discharge ahead of their position. While performing a go-around and gaining altitude following the release of approximately 50/500 liters of water, the pilot noticed the proximity of electrical cables through peripheral vision. An immediate evasive maneuver with a sharp nose-up attitude was attempted, but the bottom of the water bucket struck the power lines.
Upon impact, the pilot instinctively activated the manual release mechanism for the bucket. However, instead of falling away, the bucket became entangled and wrapped around the helicopter's tail boom antennas. After being alerted by the ground crew that the bucket was stuck, the pilot utilized the aircraft's remaining maneuverability to perform an immediate landing approximately 300 meters from the impact site.
The investigation
The GPIAAF investigation confirmed that the flight was properly authorized and the pilot was fully qualified. The aircraft was found to be airworthy, with all documentation valid and maintenance programs up to date. The investigation established that the aircraft's mass and balance were within normal operating limits, noting that the weight had decreased immediately prior to the incident due to the water discharge.
Investigators examined the wreckage and the impact site, determining that the helicopter and the bucket sustained damage during the collision. The investigation also considered environmental factors, specifically the high atmospheric temperatures and reduced visibility caused by smoke.
Findings
- The primary cause of the incident was human factors, specifically the pilot's failure to identify additional electrical cables located beneath the primary lines previously identified during a reconnaissance flight.
- Poor visibility and heavy smoke from the active forest fire obscured the presence of these secondary cables.
- High atmospheric temperatures, reaching approximately 40°C, acted as a significant contributing factor, affecting aircraft performance and density altitude.
- The mechanical entanglement occurred because the bucket, upon release, rolled into the tail boom antennas rather than dropping vertically.