Bad actor loop
A loop that consistently performs poorly and consumes disproportionate attention.
What it means
A bad actor is the loop everybody knows about — the one that gets put in manual during upsets, the one with a note on the console, the one that has been re-tuned four times without improving.
The repeated re-tuning is the tell. A loop that does not respond to tuning is telling you the tuning was never the constraint. Bad actors are usually mechanical: a sticking valve, an oversized trim, a measurement problem, or a control structure that was wrong from the start.
Also called
On a plant you will hear this called problem loop, poor performer. They mean the same thing.
Related
Glossary
Where this comes up
Last reviewed 2026-08-01.