Accident Details
On 29 July 2002, at approximately 19:00 local time, an Air Tractor AT-802, registration EC-GHL, suffered an engine stoppage while in cruise flight near the town of Cardona, in the province of Barcelona, Spain. The aircraft was engaged in a forest firefighting mission. Earlier that day, the aircraft had departed Sabadell Airport at 13:00 with two people on board (pilot and operator), landed at Igualada Aerodrome to drop off the operator and load water, then continued aerial surveillance. After additional water drops on a fire in Nova de Segre (Alt Urgell region), the pilot made a technical stop at La Seu d'Urgell Aerodrome, then resumed firefighting with two more drops. En route back to Sabadell Airport for refueling, the engine stopped.
The pilot attempted to restart the engine but was unsuccessful. He identified a harvested cereal field and initiated an emergency landing. The aircraft struck the tops of pine trees adjacent to the field, then touched down hard, bouncing across the terrain. During the bounce sequence, the tail skid broke, and the pilot lost control. The aircraft crossed the field diagonally until the right wing impacted a pine tree, causing the aircraft to yaw right and eventually stop when the left wing struck other trees. The aircraft sustained serious damage to both wings, tail skid, elevator, propeller, and main landing gear. The pilot was not injured.
Aircraft and Pilot Information
The aircraft was an Air Tractor AT-802, built in 1996, powered by a single Pratt & Whitney PT6A-67AG engine. It held a valid airworthiness certificate until 28 April 2003. Two days before the accident, on 27 July 2002, the aircraft had undergone type B, E200, and E300 maintenance checks.
The pilot, aged 46, held a Commercial Pilot License valid until 28 December 2005, with ratings for single-engine piston landplanes and AT502/AT802. He had accumulated 3,420 total flight hours. In the 15 days preceding the accident, he had flown 23 hours and 5 minutes; the day before, he completed three flights totaling 4 hours and 10 minutes.
Fuel System Description
The Air Tractor AT-802 is equipped with two fuel tanks, one in each wing, which feed a central header tank. Fuel flows freely between the wing tanks and the header tank, allowing migration from one wing tank to the other. This design can cause fuel imbalance under certain conditions. If one wing tank becomes empty, the header tank may also empty, leading to engine stoppage due to fuel starvation. The manufacturer issued Service Letters #178 (8 April 1999), #178A (18 June 1999), and #219 (15 March 2002) addressing this issue, providing information on common causes of imbalance (e.g., refueling only one tank, sustained slips or skids, always turning in the same direction during water drops, blocked vent lines, clogged wing strainer, parking on an incline) and recommendations to minimize migration. The accident aircraft had not incorporated any of the recommended modifications.
Inspection Findings
After the accident, the propeller blades showed evidence that the engine was not rotating at impact. Fuel system inspection revealed the right wing tank was completely empty, while the left wing tank contained approximately 200 liters. This was consistent with fuel migrating by gravity from the right tank to the left, as the left wing was lower at the accident site. Flexible hoses connecting the header tank to the low-pressure fuel pump contained virtually no fuel; they appeared in good condition with no obstructions or dirt. The electric fuel pump, selector valve, and fuel filter were all found in perfect condition.
The engine was removed and sent to the manufacturer for inspection. Damage included: small nicks and rubbing on compressor turbine blades, with some blades broken and missing profile; first-stage power turbine blades showed impact damage; moderate carbon contamination was found on the outer surface of the rear housing. No damage was noted forward of the gas generator section, indicating the damage was not caused by foreign object ingestion. The likely sequence was initial failure of gas turbine blades, with fragments then damaging the power turbine section. The inspection concluded that the damage was not severe enough to substantially affect engine operation, though it likely reduced performance. It is possible the damage existed before the engine stopped.
Conclusions
Probable cause: A fuel imbalance developed between the two wing tanks, resulting in one tank and the header tank becoming completely empty, leading to engine stoppage due to fuel starvation.