How is quality built in to a safety-critical project ?

Question

There needs to be a "rachet" mechanism to stop quality going backwards.

Question prompted by :

<<Q/On a safety critical project, might each quality factor decline after reaching perfection ?

A/Very remote chance! Quality factors are, or should be, like non-return valves in a fluid duct system: there should be no question of decline, or a return, after the point of perfection! Absolutely one-way traffic!>>

(insight by swanjarv..)

Answer 1

You build a feedback circuit passing through a moderator to monitor the efficiency of the QC. The moderator applies sufficient pressure to  hold QC to goal levlels.