Electrical systems involving a Beech Aircraft Corp C90, VH-FDW, 220km NE Mount Isa, Aerodrome, QLD on 8 September 1995

The warning light for the primary electrical inverter illuminated and then re-activated after the stand-by inverter was selected. The pilot decided to return to Mt Isa. A short time later all flight instrument "fail flags" indicated and sparks were observed near the top of the pilots instrument panel. The avionics master switch was selected off and the aircraft later landed safely. Later examination found that a section of electrical wiring under the instument panel had "shorted" and burnt. Both inverters were unserviceable and the 115 volt main fuse was blown. It was determined that the electrical fault was probably initiated by the electrical wiring chaffing and then shorting out.