Originally Posted by
Snyggapa
Well, in theory you should design to be safe for the worst crews on their worst days. Even if something is designed to be usable by the "average crew", nearly half of your pilots on a given day will be below the level that you designed for.
In technical certifications, we create three standard candidates for the test we're about to write:
- The Clearly Acceptable Candidate: this is a candidate who should pass the exam with minimal to no preparation;
- The Minimally Acceptable Candidate: this is a candidate who should pass the exam with some preparation. Some will pass with high marks, while some will score the cut-score or just above;
- The Not Acceptable Candidate: this is a candidate who lacks the proficiency to pass the exam and should fail;
Any system that you design should be built to the specs of the Minimally Acceptable Candidate: someone who is unfamiliar with the matter (let's say, a pax) does not necessarily need to understand the system. However, those who are trained and licensed to fly should be able to understand the system without much difficulties. If one needs to be an expert on the system itself in order to use it, it is by definition unusable.
Similar to the big internet. Everyone reading this uses the internet, but I doubt more than 1% will even remotely know what a BGP community is. And that's fine, because this system was designed for the "average" user.
When I passed my Private's checkride, I had a reasonable understanding of the 172 I was flying. Engine, electrical systems, flight controls, instruments; the lot. I even understood the workings of the shimmy dampener (it does help if you fly an aircraft with a broken shimmy for a change). Any airman should be able to understand MCAS, or any other flight system for that matter, even on a bad day. If not, then either the system is too complex and risky to introduce, or the airman should not have received their license and rating(s).