>> What he's probably saying is there is nothing wrong with the plane's design without the MCAS.

That is a common IMHO misconception. Since the new version with "fixed" MCAS requires additional training, it does not follow that MCAS exists simply to avoid retraining and non certifying it the same. In that case, Boeing should have simply dropped MCAS and did the certification and training. Instead they opted for the near financial disaster and disruption to their supply chain AND failure to avoid additional training.

I suspect MCAS is covering for a very bad corner case in the flight dynamics.

Your suspicion is correct.

FAA rules require on all planes that the control stick takes more and more pressure to pull back as the plane approaches stall.

The 737 MAX doesn't meet this requirement, apparently it gets easier to pull the stick back as it approaches stall due to engine nacelles. This is what MCAS fixes, as the plane approaches stall, it adjusts trim to provide that extra back-pressure on the stick.

No amount of additional pilot training will allow the plane to fly without MCAS, because this is a hard rule and it's not certifiable without it.

The idea this deficiency can be masked by software is perverse. These parts of the regulations need to be true without electrical power. They're supposed to be a function of aerodynamics.

This is only superseded in absurdity by the fact there are two switches to disable the stabilizer trim motors, thereby making the airplane no longer airworthy while in flight.

> These parts of the regulations need to be true without electrical power.

How would you make that happen in a fly-by-wire airplane? In fact, how would you implement it at all in a digital fly-by-wire system without software?

If you feel that using software to control an airplane is perverse, you might want to avoid flying.

The 737 is not fly by wire.

Airbus fly-by-wire have an alternate law mode where yoke input has matching control surface deflection, just like cable or hydraulic planes. I did not say no software anywhere ever. I said using it to mask aerodynamic deficiency is wrong.

These are transport category aircraft. Not fighter jets. Positive static and dynamic stability is required. All of this is reviewable. Is the software?

Thanks! That's the first I've heard what the actual problem was. Reducing pressure instead of increasing would make the controls inherently unstable.

It's only right at the edge a stall condition, under most normal situations the controls are stable.

> I suspect MCAS is covering for a very bad corner case in the flight dynamics.

yeah, much larger, stronger, and more forward positioned engines so the thrust leads to pitch up stalls in worst case scenarios.

> I suspect MCAS is covering for a very bad corner case in the flight dynamics.

I cannot judge the severity, but it covers for rule 14CFR §25.203(a) "Stall characteristics", see http://www.b737.org.uk/mcas.htm#background

It is important to note that the MCAS was implemented on the MAX because the larger engines, and larger possible thrust vector further away from the planes center of mass, make it much easier to flip the plane over.

The MAX is a bad aeronautical design that Boeing made more "controllable" through additional control system engineering. Problem is, the additional control system engineering was pretty bad.

> The MAX is a bad aeronautical design that Boeing made more "controllable" through additional control system engineering. Problem is, the additional control system engineering was pretty bad.

Yeah, it's really frustrating that the solution was already a band-aid, and they didn't even bother to do that properly so they covered up what was questionably fraud (the lazy way of not getting a new certification) with what was unquestionably fraud (lying about the MCAS system).

What's really sad though is it exposes just how defanged the FAA has become over the years, so now who the hell do we rely on to tell us what's safe for aviation?

Yeah the 737MAX should have been an entirely new airframe and not been a 737 at all.

757

The 757 is long dead. They stopped manufacturing it in 2004. The real answer was the 797, which Boeing scrapped in favor of the 737 MAX.

My point is that the 757 was the replacement for the 737, to accommodate high bypass engines. So we are a very long way down this road.

When it came out, the 757 was a significantly larger and more powerful plane than the 737. It was not a direct replacement, it was a new model in a class above what the 737 at that time was. Then, after the Boeing 757 was already in the skies, Boeing kept making the 737 bigger and started impinging on 757 territory, which had previously been separate.

Without the MCAS the plane would stall. Which would lead to much more accidents than without MCAS or with the broken MCAS as we have now.

I understand MCAS is only necessary when performing the most extreme, emergency maneuvers. Even then a good pilot would cope without it.

Not as I understand it. It was installed because of the Airbus accident in the South Atlantic. An extreme case, yes. But with the engines moved back, the plane has the natural tendency to stall. Which is very common.