We’re still collecting data for this aircraft. Routes appear once we’ve seen it fly enough times.
A phase-to-phase arc in the left heat exchanger cooling fan relay, which ignited the surrounding wire insulation and other combustible materials within the electrical power center panel. Contributing to the left heat exchanger fan relay malfunction was the unauthorized repair that was not to the manufacturer's standards and the circuit breakers' failure to recognize an arc-fault.
Douglas DC-9-32