Air Tractor 301 HK 4968 Emergency Landing on Roadway in Colombia (HK4968)

Incident Overview and Flight History On July 12, 2020, an Air Tractor 301 with registration HK 4968, operated by Fumigaray S.A.S., was scheduled for an agricultural spraying mission over the Monterrey 1 farm, located 12 nautical miles north-northeast of the company's main base at Los Almendros near Apartadó. The pilot started the engine at 05:25 local time, completed a 15-minute warm-up, and conducted pre-flight checks that showed normal parameters. After loading 70 gallons of fuel and 270 gallons of product, the aircraft completed its first mission without incident. For the second mission, the aircraft was loaded with 300 gallons of product and a full 70 gallons of fuel. Upon completing the spraying task, the pilot reported abandoning the area and returning to the base, switching to the company's radio frequency of 122.9. ## Engine Failure and Emergency Landing While climbing to 700 feet above ground level to return to the base, the pilot heard a loud noise accompanied by severe vibration, although the instruments initially displayed normal parameters. The vibration quickly became constant and extremely intense, making it impossible to read the instruments. The pilot declared an emergency. Although the Indira runway was approximately 4 nautical miles away, the aircraft's condition made it impossible to reach. The pilot observed smoke from the engine and oil leakage for about 30 seconds before the engine shut down. The pilot selected an emergency landing site on a roadway in the Currulao district, which had two-way vehicle traffic. The pilot approached and landed at minimum speed in a short, controlled manner. However, during the deceleration roll, the aircraft collided with a vehicle in front of it, causing both to veer off the right side of the road and come to a stop outside the roadway. ## Casualties, Damage, and Investigation When the aircraft stopped, the pilot shut down all systems and evacuated without injury. The vehicle driver was also uninjured. The incident occurred in visual meteorological conditions. Colombia's accident investigation authority, the Grupo de Investigación de Accidentes (GRIAA), was notified by the operator at approximately 10:15 local time and dispatched an investigator. Due to government biosanitary security regulations, the GRIAA applied a COVID-19 investigation procedure and relied on the air operator and other authorities for initial actions. The investigation determined that the serious incident was caused by an emergency landing on a roadway due to total engine failure, which resulted from the fracture of the master connecting rod due to material fatigue. This fatigue was a consequence of the operator's failure to comply with the engine maintenance program established by the manufacturer. Contributing factors included the operator's failure to comply with the manufacturer's maintenance manual by specifying engine repairs at 1,200 hours in its general maintenance manual, whereas the manufacturer stipulated that this service should be performed between 600 and 1,000 hours for agricultural aviation aircraft. Additionally, the operator's erroneous system for recording and calculating engine flight hours counted the time between takeoff and landing instead of the time between engine start and shutdown. Combined with the excessive total hours for major repair (1,200 hours), this resulted in the engines operating under deficient maintenance conditions. The investigation issued six operational safety recommendations.