What happened
On the afternoon of August 7, 2000, a PZL M18B Dromader, registration SP-ZUN, was engaged in aerial firefighting operations near Miranda do Corvo, Portugal. Operated by Aeronorte, the aircraft departed from Lousã airfield to drop fire retardant on a forest fire in the Vale de Boiças area.
During the mission, the pilot attempted a second drop of the retardant after an initial pass was unsuccessful. While executing a maneuver to turn left and climb following the drop, the aircraft entered a stall, followed by an autorotation. The aircraft entered a spin, striking trees and crashing into a slope of the Serra da Lousã. The impact and subsequent fire caused the total destruction of the aircraft. The pilot, the sole occupant, was killed.
The investigation
The GPIAAF investigation examined the flight history, environmental conditions, and the pilot's operational decisions. Investigators noted that while general weather conditions were good, the immediate area of the fire was characterized by intense smoke, heavy heat, and significant turbulence. Other helicopter pilots stationed in the area had already refused to participate in the mission due to these hazardous visibility and safety conditions.
Technical analysis of the wreckage showed that the engine was still operating at the time of impact, though not at maximum power. The investigation also reviewed the pilot's experience and the operator's management of flight and rest periods, noting that while recent flight times were within legal limits, records regarding rest periods were incomplete.
Findings
- The pilot failed to maintain active situational awareness regarding his three-dimensional position relative to terrain and obstacles.
- The pilot's focus on maintaining visual contact with the fire target led to an incorrect assessment of the aircraft's approach to the mountain.
- A false sensation of high airspeed, caused by the proximity of the terrain and exacerbated by a tailwind, contributed to the error.
- The lack of a visual horizon, due to reduced visibility from smoke and the aircraft's low altitude relative to the mountain peaks, prevented effective recovery.
- The pilot reacted abruptly to the sudden appearance of the terrain, initiating a climb that triggered the stall and subsequent spin.
- Environmental factors, including severe turbulence and wind shear caused by the mountain topography, created highly adverse operating conditions.
- The pilot's recent experience with the specific aircraft type and seasonal firefighting operations was insufficient for the high-risk environment.