Cirrus Design Corporation SR22T N229TX accident near Addison, Texas

Probable cause

Maintenance personnel’s improper maintenance, which resulted in the incorrect wiring of the No. 1 alternator and a subsequent electrical system fire during taxi. Contributing to the accident was the airplane manufacturer's inadequate maintenance documentation that did not depict updated electrical system wiring options.

NTSB analysis

The airplane experienced an electrical fire while taxiing to the departure runway. A postaccident examination revealed that a grounded shield wire was improperly attached to the alternator's auxiliary power terminal instead of the alternator's case-ground connection during recent maintenance. The mechanic who had recently removed the alternator stated that he did not identify the location of the wire harness leads during removal and that the manufacturer's documentation did not depict where the power shield wire should be attached on the alternator, so he decided to attach the shield wire to the auxiliary power terminal, which was not correct.

The manufacturer's wiring manual did not depict the optional electrical system wiring configuration, which included the incorporation of the No. 1 alternator power shield wire. As a result of the accident, the airplane manufacturer updated the wiring manual to explicitly account for the shield wires and the unused auxiliary power terminal. Caution messages were added to the maintenance manuals warning mechanics that the airplane might be equipped with cable shielding and, if so, where to connect the shielding on the alternator.

Text from the NTSB. Open the NTSB docket for CEN12LA220 for the full record.