Umm, a little confused here, if the center of gravity shifted forward, why will the pitch up tendency increase?

Because the center of thrust is also moved forward, and its effect is much greater than that offset by the center of mass. The 737 airframe was never designed to handle such powerful engines.

Sure it would. Here's a better explanation than I care to make: https://www.quora.com/Where-should-the-center-of-mass-lift-a...

"If the Center of Thrust does not act through the Center of Gravity there will be a moment causing the aircraft to pitch, yaw or roll about the axes of the aircraft and the moment(s) must be counter balanced by design (including provision for trimming when the thrust is varied)."

Boeing chose to counteract that newly induced pitch moment with software, so that they could sell the MAX 8 to airlines as not requiring any new training or type ratings. And now nearly 400 people are dead because of a marketing decision.

Source: Physics 101

I'm not implying you're wrong, just very surprised to see this low a number. I would have guessed much closer to something like 45deg, maybe even more.

Let me know if that makes sense.

Please explain.

It also could be with the engines moved forward from the wings a bit, their thrust tends to rotate the air frame "up".

Source: I am a pilot.

The Center of thrust is offset down and somewhat in front of the CG, this means high thrust imparts a pitch up moment. Small, but present.

The bigger problem is the nacelles shape though, they create body lift at high AoA; imagine a vacuum bubble trying to suck the wing/nacelle backwards forming in the airstream, "pulling" them back.

Combine both of these characteristics, and you have an airframe demonstrating near stall positive pitch instability. I.e. you get a moment that if left uncountered will reinforce itself until the plane ends up stalling; behavior completely unprecedented in the airframe.

So in order to "counter" this behavior an automated system was introduced which supposedly restored the pilot relative flight characteristics in line with the old airframe's specs.

I'm probably oversimplifying, but it's the closest I can get to a visualization that makes some sense.

reminds a typical enterprise software project - deep serious issues stemming from screwed up basic architecture are hastily patched up by software patches. Sounds like it was a money saving architectural decision as development of more deep modifications to the airframe to allow for those engines to be positioned safely would definitely cost more than a software patch. And after the Lion crash the Boeing is doing patches for the patch ...

The bigger engines provide a lot of thrust and with the new position of the engines, it’s a lot easier for the plane to stall. So the plane was outfitted with a sensor and software that reads the angle of attack and it corrects it in case the plane reaches the factor of safety angle.

If the sensor malfunctions, the software would get wrong readings and try to correct something that doesn’t need correction. It moves the plane nose down. Pilots correct. Process repeats. Hence the elevation fluctuations seen in Lion Air and Ethiopian Airlines.

Just the one sensor?

https://www.cbsnews.com/news/boeing-737-max-8-boeing-737-800...