Replies to post #3017 on Boeing Company (BA)

[Jetmek_03052]

Of course they weren’t stalling. I never said either aircraft was stalling.

I’m not a systems engineer and I don’t know exactly how MCAS interpreted the information from the AOA system.

However, the reason both aircraft crashed is that the MCAS system was not receiving information from the failed AOA sensor. It kept rolling in forward trim as a result of not getting this information. Of course this would have oversped the aircraft!

The pilots no doubt knew that somehow, the aircraft was being given incorrect inputs because it THOUGHT the aircraft was in a stall condition (stick shaker and trim driving the nose over). The pilots knew this because they could see the airspeed and angle of attack and they knew the aircraft WASN’T IN a stall configuration.

No matter thrust vectors and fancy terms. We’re both saying the same things. The cause of the crash was because the MCAS system caused an incorrect trim input (due to a failed sensor) to the elevator system. This input kept driving the nose of the aircraft down, even though the aircraft WAS NOT stalling.

The pilots couldn’t figure it out. In actuality, in ONE of the crashes, reports are that the pilot correctly disabled the MCAS system to regain control. But then he re-engaged the system a few minutes later and it eventually flew the aircraft into the ground.

Installation of separate and dual AOA sensors, and pilot training on the way the MCAS system operates (plus other changes which in probably not even aware of!) will cure this problem for the MAX aircraft.

[Jetmek_03052]

And of course, mechanics know more about systems than pilots do.

The majority of pilots know systems exist, how they affect the aircraft and how they need to interact with them in order to keep the aircraft flying.

They know little else about them.

I’m sure you are aware that once an aircraft starts exhibiting problems, you have to start troubleshooting and quickly learn how EXACTLY the system actually works, how it interacts with other systems, ect.

So you know as well as I....yes, mechanics know systems better than pilots.

[Jetmek_03052]

Just researched and found out many things about MCAS that I wasn’t aware of.

You were quite right. It wasn’t really designed as an anti-stall device.

It was designed as a “pilot-feel” device, to make it feel like the other “Next Generation” classic variants, with the CFM56 engines.

It was designed to make the MAX flying characteristics “feel” like previous models to the pilot.

The incorporation of MCAS would have the extra benefit of avoiding a need for different type rating in the aircraft and therefore more training for the pilot group.

But, the need for the system was driven by the fact that the higher and more forward position of the new LEAP engines made the aircraft more vulnerable to stall conditions in high angle of attack/lower airspeed conditions.

This is why the CEO originally called it an “anti-stall” system subsequent to the crashes.


https://en.m.wikipedia.org/wiki/Maneuvering_Characteristics_Augmentation_System