What happened
Following the identification and repair of a fuel leak several days prior to the incident, the aircraft departed on its scheduled flight. Shortly after the takeoff phase, the crew detected smoke near the radio area and a faint odor within the cockpit. During an attempted return to the departure airport, the pilot of a nearby aircraft alerted the crew to visible flames on the left wing. In response to the developing fire, the pilot performed an emergency landing in a corn field. Although emergency responders arrived at the scene, muddy ground conditions hindered their efforts, allowing the fire to spread from the left wing to the fuselage and consume large portions of the airframe.
Findings
Investigations into the wreckage revealed that the fire originated in the aft lower section of the left wing, specifically between the inboard and outboard engines, near the fuel tanks. A post-accident inspection of the No. 1 main fuel tank showed that a C-channel, which had been installed during the recent repair, had partially separated. When the tank was tested with water, leakage was observed at the site of this separation.
- A longitudinal fatigue crack was discovered along the weld seam of the repair area.
- The crack was found to have progressed significantly since the repair was performed earlier in the week.
- The fatigue crack was a pre-existing condition that the recent repair attempt failed to resolve.
- It is believed that leaking fuel vaporized within the open wing structure, creating a flammable mixture that likely ignited upon contact with hot engine components.