What happened
While performing air sampling operations over various oil fields, the pilot was conducting an instrument approach to the airport. During the approach, the aircraft drifted off the extended centerline of the runway. Shortly after this deviation, the pilot communicated that a fire had ignited inside the cabin. Following this report, the aircraft experienced a rapid loss of altitude, and radar tracking was subsequently lost.
Investigation of the wreckage revealed that the aircraft hit the ground at a high velocity and a low impact angle. Evidence from the debris field showed that both nose baggage compartment doors were located approximately two miles south of the primary crash site. The separation of these doors appeared to occur nearly simultaneously and likely preceded the pilot's distress call.
Findings
Analysis of the wreckage indicated that the smoke source was located upstream of the cockpit windshield, as soot was found on the exterior of a shattered Plexiglas fragment but not on the fracture surface. While the baggage compartment doors showed no signs of a high-energy explosion, investigators considered that an overpressure event caused by the ignition of a fuel-air mixture in the nose could have forced the doors open. Such an event involving a lean mixture might not leave visible soot deposits.
Regarding the aircraft's equipment, the air sampling system located behind the co-pilot's seat showed no involvement in the fire. Although the combustion heater in the nose baggage compartment showed no signs of fuel leakage, a loose fuel fitting was identified during the post-accident examination.