Star Trek: Every Chief Engineer Ranked

Kelby was brought in as a replacement for Tucker on Enterprise, when the latter decided he finally felt the need to transfer to Columbia.

From the beginning, Kelby was clearly the weaker of the two. While he faced challenges that would push any engineer, his ego also created more issues. He initially refused to seek help to undo the Klingon sabotage to Enterprise, later relenting and being forced to watch Tucker return to clean up the mess.

However, once Tucker had managed to complete this, Kelby was sullen and wanted rid of him again. They continued to clash.

When the ship was host to Orion women, Kelby's emotions boiled over again, causing a fistfight with Tucker and sabotaging Enterprise in his pique. All of these actions together left Kelby with a very poor reputation among the crew.

When Tucker was taken captive by the Terra Prime extremist group, Kelby came under suspician again, this time for sabotaging a shuttle. Reed was certain that it was him, as his signature was on the docket that had signed off on the shuttlepod.

He was exonerated though once it was revealed that Tucker had reassigned him, removing him from shuttle maintenance.

Kelby was an engineer, and a decent one. However, as a chief engineer, he left a lot to be desired - allowing his emotions to govern his actions, causing friction among the crew.