What happened
The incident began during a flight the day prior to the fire, when the flight crew disconnected the number one engine constant speed drive (CSD) after an oil pressure light illuminated. Due to unrelated maintenance requirements, the aircraft's subsequent revenue flight was canceled.
During the second shift, mechanics were assigned to perform maintenance on the aircraft and attempted to troubleshoot the CSD unit. The mechanics mechanically recoupled the CSD and started the engine; however, the start valve light failed to extinguish, prompting an engine shutdown. To assist with the troubleshooting process, a mechanic removed the main CSD wiring harness cannon plug.
Following this, the start valve was replaced and the engine underwent a runup. At the conclusion of this runup, the CSD cannon plug was not reconnected. Although the mechanic who recoupled the CSD informed the lead mechanic of his actions before leaving for the day, third-shift mechanics did not have sufficient time to replace the CSD unit itself. The number one engine was closed up and the aircraft was dispatched for flight. During taxiing following a landing, the CSD caught fire.