Mechanic’s Improper Installation Of The Alternator Wiring Connections, Which Resulted In Electrical Arcing And Thermal Damage

Location: Tulsa, Oklahoma Incident Number: CEN24LA308
Date & Time: August 3, 2024, 13:00 Local Registration: N825JC
Aircraft: Cirrus Design Corp SR22T Aircraft Damage: Substantial
Defining Event: Fire/smoke (non-impact) Injuries: 1 None
Flight Conducted Under: Part 91: General aviation - Ferry

Analysis: An airframe and powerplant mechanic removed and replaced the airplane’s engine, which included rewiring the two alternators, and performed an engine run-up without incident. A pilot then performed a short ferry flight, also without incident. After parking the airplane at the destination airport and shutting down the engine, the pilot saw smoke coming from the engine compartment. The pilot exited the airplane, looked into the louvered vents under the engine compartment, and saw electrical arcing and smoke, but did not see any fire. The airplane battery and associated wiring sustained thermal damage. The airplane’s composite firewall sustained substantial damage due to thermal damage.

The mechanic who performed the engine replacement took a photograph of the alternator wire connections before removing the original engine, which he used as a reference when rewiring the alternator following the engine replacement. The photograph showed the correct wire connections, but those connections were different than those at the time of the accident. Postincident examination of the airplane revealed that the alternator wire connections were not done in accordance with the airplane manufacturer’s maintenance manual, which resulted in electrical arcing and substantial thermal damage to the airplane.

Probable Cause and Findings: The National Transportation Safety Board determines the probable cause(s) of this incident to be -- The mechanic’s improper installation of the alternator wiring connections, which resulted in electrical arcing and thermal damage to the airplane.

FMI: www.ntsb.gov