Wunwing
I was speaking from the perspective of flight test, where there are usually several 'non-pilots' (like me
) on the flight deck "observing" the testing in question. Hence the 'invisible wall' - you don't want people messing with the controls that aren't pilots (or flight engineers).
That 747-300 flight test was the only time I spent in-flight time on the flight deck of a flight engineer equipped aircraft. I fully understand the necessity to adjust individual throttles to equalize EPR/N1 on the classic 747 (some of the allowed 747/JT9D engine intermix configurations would have made aligning EPR on all four engines nearly a full time job
).
Throttle stagger became a big focus for cert related to crew workload on the 2 crew flight decks (with FADEC being a huge help), hence we've never certified rating intermix for a Boeing FADEC aircraft.