Memory Alpha
Memory Alpha

The assistant chief engineer or assistant engineer was the primary assistant or backup to the chief engineer.

In situations when the chief engineer was away from the engine room, the assistant chief engineer was responsible for overseeing engineering until the chief engineer returns. (TNG: "The Naked Now")

If a chief engineer was either incapacitated or killed in action, the assistant chief engineer was made chief engineer. (VOY: "Caretaker", "Parallax")

List of assistant chief engineers

Enterprise NX-01

USS Enterprise

USS Enterprise-D

Varro generational ship

USS Voyager

Unnamed Y-500 class freighter