Ethiopian 737 MAX 8 crash
03-19-2019, 06:29 AM
#321
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Originally Posted by nfnsquared
1. Yes, something like that. I assume all sensors feed to a data bus of some sort? As I understand it, each of the 2 FCCs gets data from a single AOA sensor, not both. Wondering if the fix is for the active FCC to read from both AOAs or for the active FCC interact with the non-active FCC to compare AOA inputs?
2. Already done, but I know what you mean...
3. I would assume it could be done fairly quickly, assuming a central data bus or an easy interconnect between data busses which would make the fix purely a programming fix? That may be the fix that Boeing was about to push?
I assume a disable switch would just be a logic input to tell the active FCC to quit the MCAS routine?
Also probably some sort of cockpit indication that MCAS is functioning. Probably also a limit on repetitive MCAS operations, so it doesn't keep repeating the process indefinitely in response to bad data. It doesn't move the trim that far or that fast, the problem is when it keeps doing it over and over again intermittently.
03-19-2019, 06:38 AM
#322
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Posts: 281
Originally Posted by Fdxlag2
Thus the fix. The problem wasn’t the system is bad. The problem was a singled failed AOA indicator could activate it. The fix is it will take two to activate it. If both AOA indicators say you are stalled, you are probably stalled.
03-19-2019, 06:39 AM
#323
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Originally Posted by BoilerUP
Boeing may have destroyed the tooling, but I’d bet they still have all the engineering documents for them...
Boeing and Airbus are good at what they do, but their ecosystems are not designed or evolved to restart long-dead production lines. Much harder than you might think.
It would be an economically ludicrous proposition anyway. They are not even sure they can make a business case for a NEW design NMA...
03-19-2019, 07:21 AM
#324
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Originally Posted by F4E Mx
I probably did not make myself clear and apologize. What kind of failure would it take for the system not to be blocked out when the flaps are deployed? Would the failure of a (single?) flap position sensor allow for the system to engage with the flaps deployed when both AOA sensors sensed a high AOA at lift-off or landing? Does the MAX have or does it need two flap position sensors in addition to the other fix?
They are not stupid, but they did take shortcuts to get the max approved. It will cost them plenty.
03-19-2019, 09:44 AM
#325
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Posts: 222
Originally Posted by Fdxlag2
Beats me. One single actuation of the MCAS is not going to make an aircraft uncontrollable. The problem was there were multiple cumlative activations of nose down trim.
03-19-2019, 09:46 AM
#326
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Originally Posted by BoilerUP
Boeing may have destroyed the tooling, but I’d bet they still have all the engineering documents for them...
Not sure on this. but didn't Boeing re start the 767 line so they could build the USAF some tankers?
I would much rather be flying around in an updated, and quite capable, quite tested, and very proven B 757 then trying to put the round peg in the square hole from a design perspective with these new Maxxed out 737's.
Boeing should simply say this: The Mission of the B737 is X. The mission of the B 757 is Y. Which jet do you want? We can and will build what you need.
I guess we are being forced to wait for the 797 to get the replacement for the 757?
03-19-2019, 09:48 AM
#327
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Originally Posted by baseball
Not sure on this. but didn't Boeing re start the 767 line so they could build the USAF some tankers?
I would much rather be flying around in an updated, and quite capable, quite tested, and very proven B 757 then trying to put the round peg in the square hole from a design perspective with these new Maxxed out 737's.
Boeing should simply say this: The Mission of the B737 is X. The mission of the B 757 is Y. Which jet do you want? We can and will build what you need.
I guess we are being forced to wait for the 797 to get the replacement for the 757?
I would much rather be flying around in an updated, and quite capable, quite tested, and very proven B 757 then trying to put the round peg in the square hole from a design perspective with these new Maxxed out 737's.
Boeing should simply say this: The Mission of the B737 is X. The mission of the B 757 is Y. Which jet do you want? We can and will build what you need.
I guess we are being forced to wait for the 797 to get the replacement for the 757?
03-19-2019, 09:54 AM
#328
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Originally Posted by sgrd0q
The problem is, the system was designed to kick in multiple times. In not, then in an actual stall, with a nose up trim, the system will activate, you will click the thumb switch to relieve the perceived pressure which will kill the MCAS. In that configuration with substantial nose up trim and in a stall you may not recover unless you apply nose down trim.
03-19-2019, 04:47 PM
#329
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Originally Posted by Peacock
MCAS doesn’t work with the autopilot on. The whole point is to avoid pitching nose up at high AoA when hand flying. Also, if this is the same thing as the Lion Air incident autopilot was probably not an option.
The flight the night before the Lion Ait crash had stick shaker start at rotation, with associated stall warnings which leads one to believe the airspeed is unreliable. Once they climbed away and raised the flaps, MCAS started trimming nose down. The crew the night before used the stab trim cutout switches and landed.
The flight the night before the Lion Ait crash had stick shaker start at rotation, with associated stall warnings which leads one to believe the airspeed is unreliable. Once they climbed away and raised the flaps, MCAS started trimming nose down. The crew the night before used the stab trim cutout switches and landed.
Climb out normal. Autopilot on. AOA sensor fail. Airspeed disagree. Autopilot will disconnect. That situation could be handled perfectly by keeping everything the same. Same pitch same power. You are now hand flying. Now enter MCAS. This complicates things and can lead - even at first application - to pitch oscillations.
And the accident sequence. It’s not one thing that will get you.
03-19-2019, 04:55 PM
#330
In a land of unicorns
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Originally Posted by rickair7777
Maybe. It's frankly also realistic to assume that US pilots can handle this sort of thing better. Maybe not all regional crews, but anyone flying a MAX in the US should have the experience and skill.
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