Factual Information
On Tuesday, 15 August 2006, at 19:40 local time, an Air Tractor AT-802, registration EC-HNK, operated by FAASA, crashed near kilometer 21 of the AV-901 road in Ávila. The aircraft was engaged in aerial firefighting and had departed from La Iglesuela runway at 19:30 to combat a fire near Puerto de Mijares.
While climbing through a valley leading to the pass, the pilot determined that the rate of climb was insufficient to clear the ridges at the valley's end. Engine power, propeller revolutions, turbine temperature (ITT), and airspeed indications were normal. He increased torque and propeller pitch to improve climb gradient but realized the aircraft would not clear the pass safely. He decided to jettison the water load and turn around. According to his statement, he turned approximately 15–20 degrees right to approach the valley wall and initiated a left turn with the nose down to gain speed to 130–140 knots. After turning about 150 degrees, he felt a strong descent. Expecting imminent impact, he leveled the aircraft and aimed for a suitable area to minimize the collision's effects.
The aircraft struck a small wooded area of 15–20 trees, losing energy through successive impacts and leaving a debris trail until it came to rest. Shortly after the initial impacts, before the aircraft stopped completely, a fire began. The pilot, the sole occupant, jumped out through the left window before the aircraft halted.
The aircraft was destroyed by impact and subsequent fire, which also spread to surrounding vegetation. No evidence of pre-impact mechanical failure was found during the on-site inspection.
The pilot reported weather conditions as good visibility, no clouds, and strong wind (direction unspecified). The day before, he had flown through the pass three times, and on the morning of the accident he had also overflown the area. He held valid licenses, ratings, and medical certificate. His last recurrent training as an agricultural and forestry pilot was on 5 April 2006. Maintenance records showed the aircraft was maintained according to its approved program.
Analysis
The aircraft's final condition precluded detailed wreckage examination. The pilot did not report any pre-existing mechanical deficiencies, and instrument readings were normal for the flight conditions; therefore, a failure of the aircraft or its systems was ruled out.
Though some lee wind effects and downdrafts from uneven heating of valley slopes may have existed, they were considered not significant to the accident's development, as they would have been low-intensity and close to the ground. These factors may have had only a moderate influence in the final moments when impact was unavoidable. Similar conditions had existed during a previous flight that day without incident.
A more relevant factor might have been that the aircraft carried more load than in previous operations, possibly unnoticed by the pilot, but the weight difference would have had to be considerable to produce the observed climb performance reduction.
The distance from the impact point to the pass and the elevation difference made it unlikely to clear the valley end safely, even considering the aircraft was at a higher altitude before the turn, since altitude and speed were lost during the attempted turnaround.
The most probable scenario is that the aircraft entered the valley at a lower altitude than on previous occasions, preventing it from clearing the pass or executing the turn.