Ethiopian airliner down in Africa
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Shortly after takeoff, the data suggest that the Left AOA vane was damaged by some foreign object, likely a bird strike. This then likely caused a short in the heating element. This would have annunciated the Master Caution/Anti-Ice lights on the forward glareshield.
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The Anti-Ice annunciation would have directed the pilots to the relevant area of the overhead panel which would have shown a "L Alpha Vane" light illuminated on the Probe Heat control panel.
So when both pilots say "Left Alpha Vane", what is going on is the very standard procedure of verbally announcing the particular annunciator that generated the Master Caution light in the first place. Not really a great mystery.
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Shortly after takeoff, the data suggest that the Left AOA vane was damaged by some foreign object, likely a bird strike. This then likely caused a short in the heating element. This would have annunciated the Master Caution/Anti-Ice lights on the forward glareshield.
.
.
.
The Anti-Ice annunciation would have directed the pilots to the relevant area of the overhead panel which would have shown a "L Alpha Vane" light illuminated on the Probe Heat control panel.
So when both pilots say "Left Alpha Vane", what is going on is the very standard procedure of verbally announcing the particular annunciator that generated the Master Caution light in the first place. Not really a great mystery.
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Unfotunately most people these days want a quick easy solution to life’s complex problems.
You can see it in politics and in daily life. It leads to repetitive emphasising of dogma and it led to Trump.
You can see it in these discussions.
The tragedy is that some of the items of dogma could be valid, if discussed reasonably but can’t be heard in the torrent.
You can see it in politics and in daily life. It leads to repetitive emphasising of dogma and it led to Trump.
You can see it in these discussions.
The tragedy is that some of the items of dogma could be valid, if discussed reasonably but can’t be heard in the torrent.
bill,
I agree with the above as a wider ranging overview. This is also reflected in reduced levels of experience and views of ‘Expertise’ *.
A wider concern is where these aspects apply to manufacturing design teams and regulators. These people, like pilots, are Children of The New Age’, many not even born before the 737 first flew.
With respect to older designs, is there sufficient expertise, experience in the skills for revising designs and checking levels of safety to justify retention of ‘grandfather rights’ aircraft.
* https://www.foreignaffairs.com/artic...aith-expertise
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Originally Posted by alf5071h
These people, like pilots, are Children of The New Age’, many not even born before the 737 first flew.
737 Driver, #4683
‘You can't fix a problem until you recognize a problem exists. I humbly suggest that we collectively recognize the crew competency issues within our own ranks and devote our brain cells to addressing that problem rather than lobbing largely ineffectual grenades over the fence.’
You can be as humble as you like, but if the problem is within human thought, that there is a limit to human performance, then the competency issue resides with our (your) thoughts - Ethiopian airliner down in Africa
Hopefully you accept that there is a limit; then how is this defined, by whom. Can you enlighten us, where is the evidence of crew competency problems, particularly relating to these accidents.
Or do you use outcome - an accident, to judge competency after the fact.
How might we judge the competency of designers, regulators. With hindsight all appear deficient, but in reality everyone working as best they could, in the conditions they faced; how might they describe their conditions of work and change them.
What the industry requires is the wisdom to foresee how crews will react in extreme, rare, surprising, and life threading situations; without such vision, then crews require help in avoiding these extremes, avoid the situation, change the overall operating environment - change the aircraft system.
Heed the words of James Reason; “it’s very difficult to change the human condition, but you can change the conditions of work”.
‘You can't fix a problem until you recognize a problem exists. I humbly suggest that we collectively recognize the crew competency issues within our own ranks and devote our brain cells to addressing that problem rather than lobbing largely ineffectual grenades over the fence.’
You can be as humble as you like, but if the problem is within human thought, that there is a limit to human performance, then the competency issue resides with our (your) thoughts - Ethiopian airliner down in Africa
Hopefully you accept that there is a limit; then how is this defined, by whom. Can you enlighten us, where is the evidence of crew competency problems, particularly relating to these accidents.
Or do you use outcome - an accident, to judge competency after the fact.
How might we judge the competency of designers, regulators. With hindsight all appear deficient, but in reality everyone working as best they could, in the conditions they faced; how might they describe their conditions of work and change them.
What the industry requires is the wisdom to foresee how crews will react in extreme, rare, surprising, and life threading situations; without such vision, then crews require help in avoiding these extremes, avoid the situation, change the overall operating environment - change the aircraft system.
Heed the words of James Reason; “it’s very difficult to change the human condition, but you can change the conditions of work”.
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I am just going to accept at face value that you haven't read my previous posts. Both I and other participants have commented on this extensively, perhaps too extensively for some people's tastes. Perhaps you should take a moment and review those posts?
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Interesting and very carefully chosen words in Boeing's statement https://boeing.mediaroom.com/news-re...ts?item=130426, issued in response to media reports yesterday.
It goes on to state that if you did not opt for the AOA display, your disagree alert was "not operable". However, there will be an optional service bulletin to tell you how to make it operable on aircraft already delivered. So that's OK then.
It goes on to state that if you did not opt for the AOA display, your disagree alert was "not operable". However, there will be an optional service bulletin to tell you how to make it operable on aircraft already delivered. So that's OK then.
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I don't see any language in the release that insinuates that this was in any way the customer's fault or that it is to a lack of the customer's understanding.
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now. The 707 had no hydraulic controls except rudder boost and even that was not needed. We had no proper simulator so a lot of training was done on a real plane including stab runaway/ emergency descent from high level and engine failures.
So, when the Max returns to the skies and
ends up with a life of several decades, it will be a century old design with a few electronic add ons when it finally retires.
Y
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How did you arrive at that interpretation of the press release? Because I arrived at the exact opposite conclusion. Boeing has admitted that they screwed up by tying the activation of the AOA Disagree alert to the the selection of the AOA indicator customer option.
I don't see any language in the release that insinuates that this was in any way the customer's fault or that it is to a lack of the customer's understanding.
I don't see any language in the release that insinuates that this was in any way the customer's fault or that it is to a lack of the customer's understanding.
Boeing included the disagree alert as a standard feature on the MAX, although this alert has not been considered a safety feature on airplanes and is not necessary for the safe operation of the airplane. Boeing did not intentionally or otherwise deactivate the disagree alert on its MAX airplanes.
The disagree alert was intended to be a standard, stand-alone feature on MAX airplanes. However, the disagree alert was not operable on all airplanes because the feature was not activated as intended.
The disagree alert was intended to be a standard, stand-alone feature on MAX airplanes. However, the disagree alert was not operable on all airplanes because the feature was not activated as intended.
As to safety it would have helped prevent Lion air since it would have flagged AoA on penultimate flight.
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Does anyone on this topic know about Boeings system design ? and if so can they please explain to this simple pilot why mcas was designed in the waay it was, If I understand correctly MCAS is a sub-system designsd solely to counteract the lift generated by the engine nacelles at higher than normal AOT. It does this by trimming the stab nose down meaning that if the MCAS system fails due to incorrect AOA info, unless corrected by the PF its heading for disaster.
Why did they not simply alter the elevator feel circuit so that higher force was required to pull back on the stick, sorry column if the AOT was too high and the stick forces were reducing due to the nacelle lift
This could surely have been done so that forward ie nose down column movement was not affected.
This would mean that what ever happened the aircraft would not be left with a nose down trim and would not therefore be trying to fly into the ground.
Why did they not simply alter the elevator feel circuit so that higher force was required to pull back on the stick, sorry column if the AOT was too high and the stick forces were reducing due to the nacelle lift
This could surely have been done so that forward ie nose down column movement was not affected.
This would mean that what ever happened the aircraft would not be left with a nose down trim and would not therefore be trying to fly into the ground.
Does anyone on this topic know about Boeings system design ? and if so can they please explain to this simple pilot why mcas was designed in the waay it was, If I understand correctly MCAS is a sub-system designsd solely to counteract the lift generated by the engine nacelles at higher than normal AOT. It does this by trimming the stab nose down meaning that if the MCAS system fails due to incorrect AOA info, unless corrected by the PF its heading for disaster.
Why did they not simply alter the elevator feel circuit so that higher force was required to pull back on the stick, sorry column if the AOT was too high and the stick forces were reducing due to the nacelle lift
This could surely have been done so that forward ie nose down column movement was not affected.
This would mean that what ever happened the aircraft would not be left with a nose down trim and would not therefore be trying to fly into the ground.
Why did they not simply alter the elevator feel circuit so that higher force was required to pull back on the stick, sorry column if the AOT was too high and the stick forces were reducing due to the nacelle lift
This could surely have been done so that forward ie nose down column movement was not affected.
This would mean that what ever happened the aircraft would not be left with a nose down trim and would not therefore be trying to fly into the ground.
There are about four of us on this thread who think that. So you are in good company.
Boeing has a history of faffing with stab trim to compensate feel inputs and to them I guess it came naturally.
However, a fail mode in the control feel or a separate dedicated feel box would only cause a harder pull - once - and could be trimmed out.
That is what should have been installed (says I) and even if retrofitted may well be:
- cheaper than losing public trust
- easier to explain to the world and the pilots
- a much less critical system than MCAS can become.
B
How did you arrive at that interpretation of the press release? Because I arrived at the exact opposite conclusion. Boeing has admitted that they screwed up by tying the activation of the AOA Disagree alert to the the selection of the AOA indicator customer option.
I don't see any language in the release that insinuates that this was in any way the customer's fault or that it is to a lack of the customer's understanding.
I don't see any language in the release that insinuates that this was in any way the customer's fault or that it is to a lack of the customer's understanding.
Count me in on that!
Nothing that some year dot bicycle technology (much like the rest of the flight control system) couldn't have resolved with simplicity, redundancy & no additional training requirements - it's considering this that make me wonder far more broadly about MCAS.
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Regardless of the presence of a AOA disagree alert, the system had the data with which to disarm MCAS. Boeing’s recent statements that nothing was wrong with the design has already twice been disproven. And it’s wrong for at least two reasons, use of a single AOA sensor, the second, that when AOA sensors disagree, the MCAS is not disarmed.
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Dare I say it, but the differences between A & B philosophy really show here. In the early days of A, I was like many pilots - dubious and wary of automation. Over a generation of flying later we seem to have got our head around they fact that HAL(A) has matured, is now rather good at his job and, generally speaking, our side of the house only gets into trouble when we ignore HAL(A). Meanwhile, HAL(B) appears to still be at school and capable of having hissy-fits, just like my teenage daughter. 
What was clear to this engineer was the difference in philosophy between A & B Hals - HAL(A) will protect the pilot from him/herself overriding control inputs because HAL(A) knows best, while HAL(B) will warn pilots and make difficult what it considers as "incorrect" control inputs it will always allow the pilot to stuff it up if they really want because the pilot knows best.
The hissy-fit system HAL(MAX) seems to me to overturn the old B philosophy and head much more towards A, but worse, it decides it knows best (where best is mistrim AND to the stops at high speed and low alt) based on a single AOA sensor rather than the multiply redundant sensor sets of HAL(A) (or B).
That to me is the really sad thing - Boeing knows (or knew) how to do this stuff properly, but for some reason they decided not to for MAX. It's not just doing FBW properly 777-style, it's MCAS itself - it's looking like they ripped MCAS straight off the KC-46, except that there it uses 2 AOA inputs, so at some point in copying the system they reduced the number of AOA inputs to the MCAS system. Why on earth would anyone do that?
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Salute!
From Bill
The problem, Bill, et al, is that the plane required an aerodynamic fix for pitch moments approaching the stall AoA. Sure, in noirmal, non-FBW systems you would expect increasing back force to increase AoA. The new motor mount and such resulted in less back force per each increase in AoA - aero force, not the artificial feel sustem they already had. A pure cable system with no "help" would have made that very obvious for most of us here, especially those with lottsa light plane time. So Boeing figured they would just crank the stab to generate more nose down pitch moment, and the existing feel and such would take care of everything else, huh?
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- Make the sucker nose heavy and use a single AoA vane to trigger it. Don't sweat a FUBAR vane, as the stick shaker would prolly be going off and provide a clue that something wasn't right
- Let her rip for almost ten seconds and 2.x units nose down, then wait 5 seconds and do it again.
- Don't look at airspeed, just flaps and autopilot settings besides the AoA vane
- To disable the doofer, simply turn off all the electric trim to the stab. Neat, huh? Oh, you lose the yoke trim Gums! No biggie, we can crank that little wheel 50 times. Just don't get fast.
- Yeah that's it. And let's increase the authority of MCAS a bit to be on the "safe" side and don't advertise this, as it might require a sim ride or something.
================
And finally today's comment: @ driver. The first crew call I can see about AoA vane is about 4 minutes from WoW. It could be that at that point they turned the electric trim back on.. at 43:11 we see manual trim from yoke, and sure enuf, 5 seconds later we see MCAS crank the trim down to 1.0 from 2.3 units and they were doomed.
Gums sends...
From Bill
If I understand correctly MCAS is a sub-system designsd solely to counteract the lift generated by the engine nacelles at higher than normal AOT........
=======
Why did they not simply alter the elevator feel circuit so that higher force was required to pull back on the stick, sorry column if the AOT was too high and the stick forces were reducing due to the nacelle lift
=======
Why did they not simply alter the elevator feel circuit so that higher force was required to pull back on the stick, sorry column if the AOT was too high and the stick forces were reducing due to the nacelle lift
.
- Make the sucker nose heavy and use a single AoA vane to trigger it. Don't sweat a FUBAR vane, as the stick shaker would prolly be going off and provide a clue that something wasn't right
- Let her rip for almost ten seconds and 2.x units nose down, then wait 5 seconds and do it again.
- Don't look at airspeed, just flaps and autopilot settings besides the AoA vane
- To disable the doofer, simply turn off all the electric trim to the stab. Neat, huh? Oh, you lose the yoke trim Gums! No biggie, we can crank that little wheel 50 times. Just don't get fast.
- Yeah that's it. And let's increase the authority of MCAS a bit to be on the "safe" side and don't advertise this, as it might require a sim ride or something.
================
And finally today's comment: @ driver. The first crew call I can see about AoA vane is about 4 minutes from WoW. It could be that at that point they turned the electric trim back on.. at 43:11 we see manual trim from yoke, and sure enuf, 5 seconds later we see MCAS crank the trim down to 1.0 from 2.3 units and they were doomed.
Gums sends...
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Originally Posted by weemonkey 
No, just show us the evidence.
Please define what you mean by "evidence."
No, just show us the evidence.
Please define what you mean by "evidence."
What is available are a precious few facts and (sometimes strongly held) opinions and theories based on individuals backgrounds.
While some (my self included) may disagree with 737 drivers analysis on some points he has presented detailed explanations and insight that clearly provide an experienced pilots view of things.
In that context it would be equally (not) usefull to say "show me the evidence it was -not- primarily pilot error".
If you have not read his longer posts they are well worth reading, even if you do not end up agreeing with all the points.
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At 05:38:44, shortly after liftoff, the left and right recorded AOA values deviated. Left AOA decreased to 11.1° then increased to 35.7° while value of right AOA indicated 14.94°. Then after, the left AOA value reached 74.5° in 3⁄4 seconds while the right AOA reached a maximum value of 15.3°. At this time, the left stick shaker activated and remained active until near the end of the recording. Also, the airspeed, altitude and flight director pitch bar values from the left side noted deviating from the corresponding right side values. The left side values were lower than the right side values until near the end of the recording.
At 05:38:43 and about 50 ft radio altitude, the flight director roll mode changed to LNAV.
At 05:38:46 and about 200 ft radio altitude, the Master Caution parameter changed state. The First Officer called out Master Caution Anti-Ice on CVR. Four seconds later, the recorded Left AOA Heat parameter changed state.
<snip>
At 05:42:51, the First-Officer mentioned Master Caution Anti-Ice. The Master Caution is recorded on DFDR.
At 05:42:54, both pilots called out “left alpha vane”.
At 05:38:43 and about 50 ft radio altitude, the flight director roll mode changed to LNAV.
At 05:38:46 and about 200 ft radio altitude, the Master Caution parameter changed state. The First Officer called out Master Caution Anti-Ice on CVR. Four seconds later, the recorded Left AOA Heat parameter changed state.
<snip>
At 05:42:51, the First-Officer mentioned Master Caution Anti-Ice. The Master Caution is recorded on DFDR.
At 05:42:54, both pilots called out “left alpha vane”.
From the data provided, it appears that the Left Alpha Vane warning was triggered within 10 seconds after liftoff. The First Officer called out "Master Caution, Anti-Ice" as would have been procedure. Normally, that call should have been followed up with a verbalization of what particular malfunction triggered the Master Caution light. The crew did not actually get around to doing this until a little more than four minutes after the light first illuminated.
Further examination of the DFDR output indicates that the first Master Caution alert was reset. This is normal procedure to allow for additional alerts, but it also extinguished the "Anti-Ice" annunciator. It appears that the crew simply forgot to look for the actual malfunction annunciated on the overhead panel. For reasons, that are not entirely clear from the data, the Master Caution light came on again at around the 5:42:50 mark, re-illuminating the "Anti-Ice" annunciator. The Master Caution light was reset again. It is at this point, four minutes after the original alert, that the pilots looked up and confirmed the "L ALPHA VANE" annunciation.
737 Driver sends.....
Last edited by 737 Driver; 30th Apr 2019 at 21:43. Reason: added comment