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-   -   Boeing 737 MAX 8 crashes and effects on AA 737 MAX 8s (NOT reaccommodation) (https://www.flyertalk.com/forum/american-airlines-aadvantage/1939333-boeing-737-max-8-crashes-effects-aa-737-max-8s-not-reaccommodation.html)

TheDudeAbides Mar 11, 19 12:25 pm

Just one more reason to fly B6 SFO-FLL instead of AA SFO-MIA. Besides the 7M8 falling out of the sky and generally being a sardine can even up front, MInt is readily available for $599 each way - just booked solo-seat lie-flat round trip for under $1200 :cool:

enviroian Mar 11, 19 12:33 pm


Originally Posted by TheDudeAbides (Post 30873619)
Besides the 7M8 falling out of the sky and generally being a sardine can even up front,

Oh you're going to get a lot of love here with some posters.....

:D

SouthernCross Mar 11, 19 12:34 pm


Originally Posted by mnhusker (Post 30873440)
Remember that the MCAS auto-trim system depends on a single source of information of angle of attack to determine its input to the flight controls.

Are you positive that the MCAS uses a single pitot probe? Iím no aircraft designer, but at the pricetag of a 737 Iíd expect 2 or even better 3 redundant voting inputs.

dmsdfw Mar 11, 19 12:36 pm


Originally Posted by mnhusker (Post 30873440)
In third world operating conditions that pitot tube maybe more likely to become contaminated with particulate matter that would obstruct it and lead to it not performing appropriately.

Just a technical FYI - the pitot tube has nothing to do with measuring AoA. The pitot tube measures air pressure in the forward direction, which when coupled with the static pressure, indicates air speed. The AoA is measured by airfoil vanes that rotate based on the AoA. I'm not sure of the exact configuration on a 737 MAX, but this is what they look like on an A330: https://www.google.com/imgres?imgurl...act=mrc&uact=8

dmsdfw Mar 11, 19 12:48 pm


Originally Posted by SouthernCross (Post 30873653)


Are you positive that the MCAS uses a single pitot probe? Iím no aircraft designer, but at the pricetag of a 737 Iíd expect 2 or even better 3 redundant voting inputs.

My understanding is that while there are multiple AoA sensors (not pitot tubes), the MCAS system will initiate a stall avoidance maneuver (by trimming the nose down) if any of the sensors indicate an excessive AoA. I assume the logic behind this is that one of the scenarios where the plane could be flown into a stall condition is when there is an AoA sensor disagreement, in which case the plane will need to be flown manually with conflicting, and hence confusing, data. However, the logic doesn't allow for the case where the plane is flying perfectly well, at a normal AoA, but one AoA sensor has failed in a mode giving an excessive reading.

mnhusker Mar 11, 19 12:50 pm


Originally Posted by SouthernCross (Post 30873653)


Are you positive that the MCAS uses a single pitot probe? I’m no aircraft designer, but at the pricetag of a 737 I’d expect 2 or even better 3 redundant voting inputs.



I am being corrected that its not a pitot tube but rather a vein system that detects angle of attack.

mnhusker Mar 11, 19 12:54 pm

[QUOTE=SouthernCross;30873653]




I am being corrected that its not a pitot tube but rather a vein system that detects angle of attack.

SouthernCross Mar 11, 19 1:03 pm

Some AOA systems use pitot, some use vane. But regardless redundant sensors is still good design. Iím curious how many sensors the 737 MAX MCAS has.

Also, nowadays an AOA indicator should be be a standard instrument on all aircraft.

mnhusker Mar 11, 19 1:12 pm

dmsdfw:
Thank you for your insight!!

That is the correct information about how the software handles the input from the left and right angle of attack sensors.

I found this information about the Lion Air crash:

https://www.flightglobal.com/news/ar...-crash-453455/

ON the flight prior to the crash, there had been anomalies in airspeed between captain and first officers instruments as well as AOA indicators. AOA sensors were replaced prior to crash.

As dmsdfw points out, with two inputs to the software, it appears that at present the software defaults to the "bad" reading and commands a response of avoidance of stall.

I stand by the need to validate the intact status of these sensors prior to every flight, disconnect the software, or you are going to have to ground the 737 Max fleet pending some other fix.

msv777 Mar 11, 19 1:22 pm


Originally Posted by econometrics (Post 30873477)
All ex-MIA, yes. Save the LAX-DCA flight that was recently changed to a 7M8 (AA163).

And, the occasional AC swap... I ended up on 7M8's ex-SJC in the last couple of weeks (one to DFW, and another to ORD), which both were originally scheduled to be 738 config. My seat # changed both times as a result. So, you never know...

Cheers.

mnhusker Mar 11, 19 1:25 pm

And now the Ethiopian Crash looks nothing like a 737Max problem:

https://www.reuters.com/article/uk-e...-idUKKBN1QS1LH

plane on fire, trailing smoke before it crashed.......

MarkOK Mar 11, 19 1:35 pm


Originally Posted by mnhusker (Post 30873880)
And now the Ethiopian Crash looks nothing like a 737Max problem:

https://www.reuters.com/article/uk-e...-idUKKBN1QS1LH

plane on fire, trailing smoke before it crashed.......

As much as memories can warp in the mind for witnesses to a tragedy, I would say there is not much there to go by.

"Rattling" noises, trailing smoke (and clothes and paper!?), all sounds like fuzzy post-witness memory jumble to me.

SouthernCross Mar 11, 19 1:36 pm


Originally Posted by mnhusker (Post 30873880)
And now the Ethiopian Crash looks nothing like a 737Max problem:

https://www.reuters.com/article/uk-e...-idUKKBN1QS1LH

plane on fire, trailing smoke before it crashed.......

Eyewitness accounts are notoriously unreliable. Yes there is smoke and fire involved, but the timelines get all sorts of jumbled. The human brain just isnít good at this sort of thing.

IADCAflyer Mar 11, 19 1:43 pm

The CVR and FDR have both been found, so readouts will be critical. Photos of one of the recorders show a muddy and dirty case but one that does not look fire damaged or compromised. I'm going to assume the memory module inside survived.

mnhusker Mar 11, 19 3:09 pm

Out running errands with my son and that space gave me more time to think about this.

Boeing with the 737Max, and this software is thinking like Airbus: "Let's not trust the pilots, we will make the plane fly the way it needs to fly".

This is way out of line with their past corporate history.

What to do now?

1. Disable the software.

2. Train all 737Max pilots a set number of hours in simulator to deal of the characteristics of AOA issues that the software was meant to deal with.

3. Mandate quarterly simulator hours ("CME: continuing medical education, that's what I do in my job :)) of the same training to make sure pilots stay familiar with the 737Max's foibles.

4. Boeing to work on long term fix for issues (if there can be one).

It is much better to train pilots to fly the plane as it is than to train them to fly the plane when it is trying to kill them!


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