As far as I understand, the older 737 models also exhibit a nose-up pitching behavior in high-thrust/low-speed situations, to the point that stall recovery procedure explicitly specifies that the nose has to come down first, before thrust is increased. And maximum thrust may not be used, only max continuous thrust (or something similar) because otherwise the pitch moment from the engines may overwhelm elevator control.
Good question, apparently on the 737 Max this is more pronounced with the larger/forward LEAP engines.
This was enough of a problem that it constantly has to be checked and MCAS has to trigger if it is off by too much.
Most planes have a nose down pitch over time but the 737 is smaller/lighter so maybe the engines have always affected flying.
With the 737 Max and new LEAP engines, here it was enough for Boeing to make a system for it, they didn't make it just for extra, it was a cost cutting measure already.
> stall recovery procedure explicitly specifies that the nose has to come down first, before thrust is increased
Pulling the nose down is probably standard on any stall recovery because the nose up exacerbates conditions for a stall.
The problem wasn't really with the nose pitch up, but the nose pitch up created the need for nose up detection/monitoring and an MCAS in case of issues.
The major problem is that MCAS relies on a single sensor and a single point of failure, which can result in the MCAS constantly pitching the nose down if it is bad data or a broken/incorrect AoA sensor.
The root cause of this major problem is the cost cutting retro-fitting that Boeing did and their reliance on a single point of failure that can trigger a catastrophic nose dive.
This is one of those cases that the fix to keep the 737 flying the same as previous versions, without pilot knowledge of the MCAS initially, caused more damage than just the pitch up might do.
So what is "normal" nose-up pitching?
As far as I understand, the older 737 models also exhibit a nose-up pitching behavior in high-thrust/low-speed situations, to the point that stall recovery procedure explicitly specifies that the nose has to come down first, before thrust is increased. And maximum thrust may not be used, only max continuous thrust (or something similar) because otherwise the pitch moment from the engines may overwhelm elevator control.