What happened
On September 13, 2021, an EUROCOPTER AS 332 L2, registration EC-NBT, was engaged in aerial firefighting operations in the Sierra Bermeja region of Málaga, Spain. The aircraft was tasked with transporting 19 members of two forest fire brigades to a specific location within a firebreak to assist in combating an active wildfire.
Prior to landing, the crew performed a reconnaissance flight of the designated area. During this pass, they noted the presence of an excavator, which suggested the potential for significant dust accumulation upon landing. Despite the risk of a "brownout"—a phenomenon where rotor wash kicks up dust and obscures the pilot's vision—the crew decided to proceed with the approach.
As the helicopter descended, the rotor wash began to lift dust from the ground. Flight data and cockpit voice recordings indicate that at approximately 51 feet above the ground, the co-pilot warned of rising dust. As the aircraft continued its descent, the dust cloud enveloped the helicopter, causing a loss of lateral visual references. At approximately 22 feet AGL, the aircraft's trajectory drifted significantly to the right. Upon touchdown, the main rotor blades struck a nearby tree, causing severe damage to the rotor system. While all 21 occupants (two crew members and 19 passengers) escaped without injury, the aircraft was subsequently destroyed when the advancing wildfire reached the site hours later.
The investigation
The CIAIAC investigation examined the flight data recorder (FDR) and cockpit voice recorder (CVR) to reconstruct the final moments of the flight. The analysis focused on the crew's decision-making process regarding the deteriorating visibility and the impact of the terrain and environmental factors on the landing maneuver.
Investigators reviewed the operator's Standard Operating Procedures (SOP), which specifically mandate that pilots should plan for landing with reduced visibility and be prepared to execute a missed approach (go-around) if a brownout occurs. The investigation also analyzed the physical wreckage, noting that the damage to the main rotor blades was consistent with an impact against the branches of a tree.
Findings
- The crew was aware of the potential for a brownout due to the presence of disturbed earth and machinery in the landing zone.
- The crew maintained the landing approach despite the co-pilot providing multiple warnings regarding the rising dust.
- The loss of lateral visual references prevented the crew from maintaining the correct flight path, leading to the drift to the right and the subsequent strike with the tree.
- The continuation of the landing maneuver despite the lack of lateral visual references was the primary cause of the accident.