First I have heard this, but if so then bad for Boeing. It seems to be a perfectly valid rule to have (inputs required to maintain a position should remain stable, not go up or down) if the Boeing does not do with w/o adjustment to trim by a computer it suggests the plane is not aerodynamically stable, which is not good...

That's the 50 billion dollar question. Possibly only a lot of flight time with MCAS being disabled will judge the stability of MAX.

Having flown the 737-200 for many years with those long tubular engines proportionately balanced under the wings I was surprised in the mid 1980s to see those large engines on the 737-300. And when US Air 427 flipped out of the sky in September, 1994, it .heightened my concern that those big engines caused some unstable characteristics. Just a gut feeling. With all the intense focus on MAX, after thousands of hours of actual future flights we should have a good understanding of MAX"s stability characteristics.

One thing I haven't seen posted in this thread yet, is that the MCAS was apparently active in the ET crash. A number of people were saying it couldn't be because of flap settings but it appears it was.

https://arstechnica.com/information-...ian-737-crash/

That's not what I said. I said that the unofficial data from Flightstats suggested that the problems started below an altitude at which the flaps would normally be retracted. The articles that I've seen today also indicate that the problems started lower than when the flaps would normally be retracted.

What we don't know is if the flaps were retracted at an unusually low altitude, if the MCAS flap inhibit also failed, if they took off with flaps retracted (unlikely due to the takeoff warning horn), or some other possibility.

The good news from today's information is that if ET302 was also an unscheduled MCAS activation then the software fix that Boeing is close to releasing should fix the problem from both flights.

I have a stupid question - why is it so hard to determine from the FDR data if the MCAS did anything? Shouldn't it be logging to it?

Yes. And those who blindly supported Boeing and FAA's inexcusable inaction were clearly wrong. The single point of failure is a design defect, compounded by Boeing's lack of transparency, leading to a lack of training.

I am not a conspiracy kind of guy - I tend to trust the system. HOWEVER, what I really don't understand is how can Boeing engineers develop an undocumented system that is so critical to the handling of the plane with a single point of failure. It absolutely makes no sense to me.

Then the fact that it is taking so long to even figure out what MCAS did/did not do from the FDR data...was the whole design philosophy "let's hide it totally - not on the manual, not on the FDR, etc."?

How can this be if it is not some higher level business decision to conceal?

My suspicion is that will turn out to just be a tragic mistake. The certification shenanigans is where the conspiracy stuff comes in.

I am sure BA is in on all the data, hopefully they see the wisdom of coming clean versus doing like they did with the plane, just enough upon just enough. The company is at a crisis and inflection point, funny how that is, product lead times and billions upon billions of orders yet all could go poof with any small or wrong indecision.

Better to be open, honest, and have humility and start rebuilding the image and company's image.

The 737 MAX is aerodynamically stable on all axes in all configurations. You're confusing comments about control feel with aerodynamic stability. As soon as you release the controls, the aerodynamic stability would return the aircraft to neutral.

No single input caused the failure in these crashes; as usual, it took a whole series of inputs to bring the aircraft down.

If you really think this single input is a single point of failure, and any single point of failure is a design defect, you shouldn't be getting on any airliner ever. They're everywhere.

Can you explain this? Yes, most of these things (airplane crashes, car crashes, etc.) are "one thing lead to another" type of scenario. However, as far as MCAS is concerned, doesn't the system take only 1 AoA sensor input and repeats/increases its corrective actions based on that?

Yes, MCAS takes input from 1 AoA sensor at a time, as does the entire rest of the FCC (Flight Control Computer). MCAS has limits on what it's supposed to do, which can be countered with control column input. MCAS can be stopped by use of the electric trim control on the yoke. Electric trim can be disabled with the stab cut out switches. Trim can be done manually with your hand on the trim wheel. All of these had to fail or not be used for the crash to happen.

You posted at 427pm. That the same no. as US Air flight 427 that fell out of the sky in September .1994.

I am sure that plaintiffs counsel will be obtaining all that information in discovery.

Just to throw my unnecessary two cents in... Here's what I don't understand, and it reflects poorly on Boeing's response to the first incident, and would seem to indicate that a simple software fix might not cut it.

I thought I understood the Lion Air crash: minimally-retrained NG pilots had not been really informed about MCAS; the cockpit didn't know what was going on; and Boeing said the pilots should have realized what was happening and disabled MCAS. I figured that at that point, every MAX pilot would now be laser-focused on the possibility of a runaway MCAS and what to do about it. Then ET, with a very experienced captain, seems to have suffered the same fate, with everyone in the cockpit having full knowledge of what had reportedly happened to Lion Air, yet unable to do anything about it. I find that far scarier than the first incident.