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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 20th Mar 2019, 17:22
  #2161 (permalink)  
PJ2
 
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Originally Posted by OldnGrounded View Post
Unless I've missed it, this Reuters story hasn't been addressed here.
The link to this story was posted by Armchairpilot96114 earlier in the thread, here.

From the NYTimes: 2015 OIG Audit Report
FAA LACKS AN EFFECTIVE STAFFING MODEL AND RISK-BASED
OVERSIGHT PROCESS FOR ORGANIZATION DESIGNATION AUTHORIZATION
Federal Aviation Administration
https://www.oig.dot.gov/sites/defaul...5E10-15-15.pdf

Last edited by PJ2; 20th Mar 2019 at 17:44.
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Old 20th Mar 2019, 17:30
  #2162 (permalink)  
 
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Originally Posted by jimtx View Post
Is that certification requirement an airframe stabilty criteria. Because MCAS does not operate with the autopilot on and that nacelle effect would still be there. I don't know if the MCAS envelope would be normally encountered with the autopilot on but one case I envision is a long final where you stay clean and get a windshear event. If MCAS wasn't there when you performed the escape would you not still fly attitude no matter what the stick force was? I think you also can do the escape on autopilot and it wouldn't be affected but maybe you can't activate an automatic escape when clean.
The requirement is explicitly about required control forces, which is simply not applicable when the autopilot is engaged.

Bernd
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Old 20th Mar 2019, 17:31
  #2163 (permalink)  
 
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Originally Posted by PJ2 View Post
The link to this story was posted by Armchairpilot96114 earlier in the thread, here.
Thanks. Armchairpilot's link was to a version of the story published in Straits Times and the headline cited ddn't get my attention. I posted the link to the other version largely because "a source" who supposedly heard the CVR recording or read a transcript noted that the crew didn't appear to have noticed the H-stab trimming.
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Old 20th Mar 2019, 17:47
  #2164 (permalink)  
BRE
 
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Using the trim to counter a pitch up moment seems counterintuitive.

1. It is fairly slow in comparison to e.g. windshear.
2. The change remains there even after the disturbance is gone.

A brief push on the stabilizer seems more adequate to deal with a quick and transient upset. I suppose the actuator is not there because the 737 stab is not FBW?
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Old 20th Mar 2019, 17:58
  #2165 (permalink)  
 
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Automation Surprise - or 'What's it doing now?'

Originally Posted by OldnGrounded View Post
Thanks. Armchairpilot's link was to a version of the story published in Straits Times and the headline cited ddn't get my attention. I posted the link to the other version largely because "a source" who supposedly heard the CVR recording or read a transcript noted that the crew didn't appear to have noticed the H-stab trimming.
Everything points to 'automation surprise' which occurs when automation does something you do not expect.
See "Automation Surprise" in Aviation: Real-Time Solutions Here is the abstract:
Conflicts between the pilot and the automation, when pilots detect but do not understand them, cause "automation surprise" situations and jeopardize flight safety. We conducted an experiment in a 3-axis motion flight simulator with 16 pilots equipped with an eye-tracker to analyze their behavior and eye movements during the occurrence of such a situation. The results revealed that this conflict engages participant's attentional abilities resulting in excessive and inefficient visual search patterns. This experiment confirmed the crucial need to design solutions for detecting the occurrence of conflictual situations and to assist the pilots. We therefore proposed an approach to formally identify the occurrence of "automation surprise" conflicts based on the analysis of "silent mode changes" of the autopilot. A demonstrator was implemented and allowed for the automatic trigger of messages in the cockpit that explains the autopilot behavior. We implemented a real-time demonstrator that was tested as a proof-of-concept with 7 subjects facing 3 different conflicts with automation. The results shown the efficacy of this approach which could be implemented in existing cockpits.
MCAS is a 'silent mode change' of the aircraft and so too was the AoA disagree in some ways.

So had there been a warning "AoA Disagree expect unreliable airspeed, Stick Shaker and MCAS" followed by "MCAS TRIMMING DOWN"

There would have been no automation surprise as the crew wouldn't have been left trying to find out 'what's it doing now?' and two aircraft could have landed safely.

Indeed just these warnings may be all the software change needed.
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Old 20th Mar 2019, 18:22
  #2166 (permalink)  
 
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Automation surprise

RE Ian:
Full pdf doc here:
https://core.ac.uk/download/pdf/33664589.pdf
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Old 20th Mar 2019, 18:39
  #2167 (permalink)  
 
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Originally Posted by FCeng84 View Post
If it turns out the the Ethiopian accident was the result of the same issues that led to the Lion Air accident our industry has some major soul searching to do.

While the MCAS software update developed after the Lion Air accident that is almost ready to go to the fleet will likely remove reliance on the three MCAS design assumptions listed above and thus would have greatly improved the likelihood of a safe outcome for the Ethiopian event we are left with a huge elephant in the room. After making the planned update we still must address the following:
A. How many other key points in the 737MAX safety story are based on pilot response assumptions that may not be valid?
B. How about other airplane models? Are they deemed safe based on faulty assumptions regarding pilot action?
- For instance, how may current 737 crews (all models) would not respond quickly enough to a classic stabilizer runaway that was not arrested by column cutout (i.e., pulling the column far enough)? I know this is covered in simulator sessions for 737 pilots, but is that enough?
C. Moving forward with the current status and future of commercial aviation have we gotten to the point where basic flying skills and system awareness are so low that we are at risk throughout the whole industry?
D. Can current and future pilot reaction short falls be addressed through training? If so, what kind, how much, and how often?
E. How will we know that we have achieved a sufficient industry wide level of safety?

Hoping to see FDR data from the Ethiopian accident soon. I sure hope someone from the PPRuNe community will find a way to get ahold of it and share it here.
FCeng84 - Excellent comments on the ‘bigger picture’ of the problem. You refer to “the elephant in the room”, this does not only apply to MCAS. Some years ago when I was an aviation safety assessor, shortly after the loss of AF447, it became clear to me the premise that ADU TAS output is not a ‘safety critical’ parameter was a badly flawed concept. The approach of suppliers and the aviation authorities was that TAS was only ‘advisory information’ and that incorrect data would be handled by ‘good airmanship’. It is ‘obvious’ from AF447 and three other incidents I am aware of, the probability that pilots can always safely deal with bad Air Data is not high enough to mitigate the ADS to be not a safety critical system. Sadly this elephant is still hidden away, for now.

The same flawed argument now seems to being applied to AoA with MCAS. I am only aware of three cases of the MCAS not working correctly, in only one case did the crew manage to safely deal with the situation. The real hard evidence suggests that a significant proportion of pilots (somewhere between 10% and 90%) would not be able to cope. From what I understand about MCAS from the PPRuNe posts, I would expect this probability of pilots failing to cope would need to be of the order of 0.1% (or lower) in order for the MCAS to be considered as not safety critical. IHO, only a basic understanding of Human Factors is needed to show that the MCAS safety assessment is fundamentally flawed. This is the elephant in the room, Boeing might perhaps try to hide it with a software patch, but it will still be there.

The software patch looks inadequate to me for the following reasons:-
A) Quote from https://www.seattletimes.com/busines...ion-air-crash/
“According to a detailed FAA briefing to legislators, Boeing will change the MCAS software to give the system input from both angle-of-attack sensors. It will also limit how much MCAS can move the horizontal tail in response to an erroneous signal. And when activated, the system will kick in only for one cycle, rather than multiple times.”
I find this quite disturbing:-
i) They seem to have ‘defined’ the software patch before they even know the cause.
ii) How does having both inputs help if one of them is ‘erroneous, but believable’?
iii) Presumably the software would have be set to be cautious and use the higher (potentially wrong) value?
iv) MCAS was originally designed at its current limits in order to counteract a known problem. Presumably lowering the limits mean that more ‘real’ problems will not now be safely dealt with.

B) There may well be failure modes other than the AoA vane that need to be considered. From https://leehamnews.com/2018/11/07/bo...-air-accident/ the Alpha Vanes input to the ADIRUs, presumably there they are at least A to D converted. Are the (non-safety critical) ADIRUs a potential source of failures?

C) From The Seattle Times report, the MCAS was not considered to be a Level 1 safety critical system, so presumably the software was not designed, developed and tested to Level 1 standards. In which case, a software failure within the MCAS has to be considered as a feasible cause of the MCAS’s undesirable behaviour.

Considering your points A to E on the future of aviation safety: I fear the aviation industry is approaching a ‘perfect storm’ dilemma:
a) aircraft are becoming more complex, even Boeing consider that “average” pilots cannot cope with the workload of extra information about MCAS
b) air traffic is increasing and new aircraft designs are ‘down-sizing’ as smaller aircraft are more cost effective; this means many more new, inexperienced, pilots will be needed
c) it is not possible to train pilots such that they all become ‘super Sulleys’.

My conclusions are:-
a) systems must no longer use human intervention as part of their safety case; we are too unpredictable.
b) safety critical systems must get smarter; garbage in, garbage out is not an option, neither is giving up and disconnecting.

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Old 20th Mar 2019, 18:51
  #2168 (permalink)  
 
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Gordon Bethune, former Continental CEO, on FAA and Boeing

https://www.cnbc.com/video/2019/03/1...ental-ceo.html
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Old 20th Mar 2019, 18:55
  #2169 (permalink)  
 
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Salute!

Thanks, infrequent, good post about previous flight; And I would not trust all what is being bandied about concerning the extra set of eyes on that previous flight. Did that dude know about MCAS? I doubt it. Was he holding up to 40 or 50 pounds of a vibrating wheel? Ws he looking about to see if he could help? Probably. Was he more likely to notice the trim wheel moving more than the normal STS movement? Maybe. Maybe he was one of the Yeager, Doolittle or Lindbergh clones we have here or like Luke? "Something ain't right, R2, let's go manual!"
So I will like to see his actual interview and description of what happened.
As far as the other previous crewmembers go, I really feel they did a fatal disservice to the accident crew with their log entry. No mention of the stick shaker or turning off the stab trim motor and so forth. We won't know exactly what they did until they testify in one of the lawsuits. I am sure they won't say a word before then, and maybe the dead head troop won't either.

As with Mick, I am cutting the accident crew some slack.

Gums sends...
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Old 20th Mar 2019, 19:03
  #2170 (permalink)  
 
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Using the trim to counter a pitch up moment seems counterintuitive.
I understand that the the trim operates the complete horizontal stabiliser and therefore offers far greater surface area than the flight control surfaces.
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Old 20th Mar 2019, 19:17
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Originally Posted by VicMel View Post

The software patch looks inadequate to me for the following reasons:-
[...]
ii) How does having both inputs help if one of them is ‘erroneous, but believable’?
That's a key point. If you have two watches you never really know what time it is. With two inputs, how do you know which is correct?
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Old 20th Mar 2019, 19:21
  #2172 (permalink)  
 
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Originally Posted by gums View Post
Salute!

Thanks, infrequent, good post about previous flight; And I would not trust all what is being bandied about concerning the extra set of eyes on that previous flight. Did that dude know about MCAS? I doubt it. Was he holding up to 40 or 50 pounds of a vibrating wheel? Ws he looking about to see if he could help? Probably. Was he more likely to notice the trim wheel moving more than the normal STS movement? Maybe. Maybe he was one of the Yeager, Doolittle or Lindbergh clones we have here or like Luke? "Something ain't right, R2, let's go manual!"
So I will like to see his actual interview and description of what happened.
As far as the other previous crewmembers go, I really feel they did a fatal disservice to the accident crew with their log entry. No mention of the stick shaker or turning off the stab trim motor and so forth. We won't know exactly what they did until they testify in one of the lawsuits. I am sure they won't say a word before then, and maybe the dead head troop won't either.

As with Mick, I am cutting the accident crew some slack.

Gums sends...
Gums- you are legendary

Originally Posted by Ian W View Post
Everything points to 'automation surprise' which occurs when automation does something you do not expect.
See "Automation Surprise" in Aviation: Real-Time Solutions Here is the abstract:


MCAS is a 'silent mode change' of the aircraft and so too was the AoA disagree in some ways.

So had there been a warning "AoA Disagree expect unreliable airspeed, Stick Shaker and MCAS" followed by "MCAS TRIMMING DOWN"

There would have been no automation surprise as the crew wouldn't have been left trying to find out 'what's it doing now?' and two aircraft could have landed safely.

Indeed just these warnings may be all the software change needed.
This is one scenario that I had hypothesized about a week ago, and the subsequent reaction from some posters led to me becoming disillusioned with this forum, coupled with work commitments, I've missed 30 odd pages of posts. With last week being Cheltenham, I kept an eye out for any of their usernames to win the Gold Cup- on such high horses, surely they would have walked to victory!

At that time a multitude of 'experts' derided the idea that MCAS, since Lion Air, could be a factor- 'sure everyone knows what to do'. It's really not that simple! Some on this forum even insinuated that the first thing they'd do in any abnormal circumstance is flick the Stab Cut-Outs- sorry, what??? You've got a spectrum of warnings, stick shaker etc. and some forum experts believe they'd have performed perfectly every time? It's easy to make those statements in hindsight and fixating on one single issue- in this case MCAS. I was fed up with constant comments that just jumped to some conclusion that 'it's the crew's fault'.

Even those that use the Lion Air's previous flight crew as an example of what should be done- if this scenario was scientifically tested- I'd like to know the % of success/failure in the exact same scenario. At the minute- 50% for Lion Air- is that a success rate acceptable to the industry? Or do we need to revert to a 3 man flight deck? MCAS activation in the situation described is by and large silent automation- which is why it is dangerous.

I welcome all posts and find this forum to be an excellent place to discuss. In the spirit of following CRM best practice, let's be constructive, rather than posting spurious condescending comments- by users who expect every pilot to act like Sully, and deride any suggestion that the situation may be somewhat difficult for the crew in the given circumstances.

Last edited by positiverate20; 20th Mar 2019 at 20:49.
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Old 20th Mar 2019, 19:57
  #2173 (permalink)  
 
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“...when activated, the system will kick in only for one cycle, rather than multiple times.”

So....what the heck does that mean exactly? MCAS is off for the rest of the flight?

There must be some re-set feature?
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Old 20th Mar 2019, 20:57
  #2174 (permalink)  
 
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Gums says 'cutting accident crew some slack". So does everyone I think. If they made an error and we have no idea if they did, it would not be their fault but poor training. I have never met or heard of a pilot who sets out to do a bad job or kill himself. Other than the Pyrenees incident of co
course.
There seems to be a bit of a muddle about AoA sensors and Airpspeed disagree. They are not necessarily connected in any way.

AoA detects a stall by measuring the angle of attack with two sensors, one each side. Measuring the angle of airflow.
Speed is measured by sensing air pressure in a tube facing forwards (pitot)and converting that into Indicated Airpspeed. Not the same as real speed.
GPS measures real speed and is almost never wrong.
Say you have blocked pitot tubes as per aF 447, the AoA still works and stall warning still works.
Say you have frozen AoA vanes so that they are not able to detect stall, or incorrectly detect a stall (as is suggested in these Max incidents) then the Airspeed should still work.
Another scenario is that one airspeed is faulty, but the other two work - there are three airspeed indicators. That one is easy since you go for the two that agree. Backed up with GPS.
And in all these cases GPS will still work.
So the changes of losing AoA information AND Airspeed information at the same time are pretty remote.
This is just for information since there seems to be a misunderstanding about the functions of the various systems here.
There is one last way of determining speed. Pitch and power. 6 degrees of pitch and 60% N1 power will fly straight and level and at a safe speed NO MATTER WHAT ANY OF THESE OTHER SYSTEMS ARE SAYING. [True for lower levels]
The point is I suppose that this is a very complicated area but we can also overcomplicate it.
Yanrair


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Old 20th Mar 2019, 21:15
  #2175 (permalink)  
 
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Originally Posted by yanrair View Post
Another scenario is that one airspeed is faulty, but the other two work - there are three airspeed indicators. That one is easy since you go for the two that agree. Backed up with GPS.
And in all these cases GPS will still work.
So the changes of losing AoA information AND Airspeed information at the same time are pretty remote.
This is just for information since there seems to be a misunderstanding about the functions of the various systems here.
Airspeed has little to do with GPS (ground speed). It is something you can look at if you approximately know the winds of course but calling it a backup?
(And at 7000 ft you also have to take air density into account, which makes ground speed even harder to use)

As has been stated before, the airspeed and altitude are corrected for AoA.

That is because the static ports and pitot probes are affected by the airflow around the airframe.
At different angles of attack that flow is different, thus there is a relatively small correction made.

Just have a look at the differing airspeed/altitude introduced by the AoA misreading in the Lion Air report FDR graphs:
https://www.flightradar24.com/blog/w...ary-Report.pdf

Last edited by wiedehopf; 20th Mar 2019 at 21:35.
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Old 20th Mar 2019, 21:19
  #2176 (permalink)  
 
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Originally Posted by yellowtriumph View Post
Boeing's mission is the same as any other publicly listed company - to maximise profits for the shareholders and to act in their best interests. To do otherwise would probably be a dereliction of the directors legal responsibilities. It does this by designing and manufacturing equipment to the highest standards but that is not its mission, it's the means to the end. I do not mean to denigrate Boeing's equipment and staff and all their efforts which I personally admire hugely. But it's the truth.
Beg to differ

https://www.washingtonpost.com/news/...=.7882f492e5aa
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Old 20th Mar 2019, 21:20
  #2177 (permalink)  
 
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Originally Posted by derjodel View Post


Doesn’t Boeing basically admit negligence and responsibility for the crash with the original design?

The whole “it was safe but now it’s safer” spin is like mcdonalds lowering the temperature of coffee “just to make it even safer and more full bodied now”. Remember, mcdonalds had to pay 2.7M just for burns - to a single person.
Likewise, when I read their statement, "to make a safe airplane safer" I also raised the eyebrow.
Evidently FAA and Boeing both agreed these were required changes to MCAS logic from what they could learn from LionAir. Why the type was not grounded then and instead they let the fleet fly while developing the fix which is now being required to have them airworthy again is very questionable...
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Old 20th Mar 2019, 21:30
  #2178 (permalink)  
 
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Originally Posted by VicMel View Post
FCeng84 - Excellent comments on the ‘bigger picture’ of the problem. You refer to “the elephant in the room”, this does not only apply to MCAS. Some years ago when I was an aviation safety assessor, shortly after the loss of AF447, it became clear to me the premise that ADU TAS output is not a ‘safety critical’ parameter was a badly flawed concept. The approach of suppliers and the aviation authorities was that TAS was only ‘advisory information’ and that incorrect data would be handled by ‘good airmanship’. It is ‘obvious’ from AF447 and three other incidents I am aware of, the probability that pilots can always safely deal with bad Air Data is not high enough to mitigate the ADS to be not a safety critical system. Sadly this elephant is still hidden away, for now.

The same flawed argument now seems to being applied to AoA with MCAS. I am only aware of three cases of the MCAS not working correctly, in only one case did the crew manage to safely deal with the situation. The real hard evidence suggests that a significant proportion of pilots (somewhere between 10% and 90%) would not be able to cope. From what I understand about MCAS from the PPRuNe posts, I would expect this probability of pilots failing to cope would need to be of the order of 0.1% (or lower) in order for the MCAS to be considered as not safety critical. IHO, only a basic understanding of Human Factors is needed to show that the MCAS safety assessment is fundamentally flawed. This is the elephant in the room, Boeing might perhaps try to hide it with a software patch, but it will still be there.

The software patch looks inadequate to me for the following reasons:-
A) Quote from https://www.seattletimes.com/busines...ion-air-crash/
“According to a detailed FAA briefing to legislators, Boeing will change the MCAS software to give the system input from both angle-of-attack sensors. It will also limit how much MCAS can move the horizontal tail in response to an erroneous signal. And when activated, the system will kick in only for one cycle, rather than multiple times.”
I find this quite disturbing:-
i) They seem to have ‘defined’ the software patch before they even know the cause.
ii) How does having both inputs help if one of them is ‘erroneous, but believable’?
iii) Presumably the software would have be set to be cautious and use the higher (potentially wrong) value?
iv) MCAS was originally designed at its current limits in order to counteract a known problem. Presumably lowering the limits mean that more ‘real’ problems will not now be safely dealt with.

B) There may well be failure modes other than the AoA vane that need to be considered. From https://leehamnews.com/2018/11/07/bo...-air-accident/ the Alpha Vanes input to the ADIRUs, presumably there they are at least A to D converted. Are the (non-safety critical) ADIRUs a potential source of failures?

C) From The Seattle Times report, the MCAS was not considered to be a Level 1 safety critical system, so presumably the software was not designed, developed and tested to Level 1 standards. In which case, a software failure within the MCAS has to be considered as a feasible cause of the MCAS’s undesirable behaviour.

Considering your points A to E on the future of aviation safety: I fear the aviation industry is approaching a ‘perfect storm’ dilemma:
a) aircraft are becoming more complex, even Boeing consider that “average” pilots cannot cope with the workload of extra information about MCAS
b) air traffic is increasing and new aircraft designs are ‘down-sizing’ as smaller aircraft are more cost effective; this means many more new, inexperienced, pilots will be needed
c) it is not possible to train pilots such that they all become ‘super Sulleys’.

My conclusions are:-
a) systems must no longer use human intervention as part of their safety case; we are too unpredictable.
b) safety critical systems must get smarter; garbage in, garbage out is not an option, neither is giving up and disconnecting.
VicMel - I really appreciate your thoughtful response. I sense that overall you and I are on the same page. Please allow me to provide a few inputs on your points:

A i) The update in work by Boeing is in response to the Lion Air accident, not the Ethiopian accident. Hopefully we will know more about the Ethiopian accident soon and only then will it be possible to determine if this same update would have helped lead to a better outcome in Ethiopia.
A ii) It seems that the proposed update will disable MCAS if the two AOA vanes do not track each other sufficiently. The severity of the degradation in handling qualities without MCAS must be minor enough to allow for this reduction in MCAS availability. Boeing must be assuming some probability for an AOA sensor failure and then showing that it is acceptable to turn MCAS off twice as often as a failure of either AOA sensor would lead to MCAS shut down.
A iii) No MCAS when AOA vanes do not track. See A ii above.
A iv) I doubt that we will find that the MCAS update reduces the size of a single increment of MCAS stabilizer motion. I can't imagine that Boeing would have given this function any more authority than absolutely needed to meet FARs and thus there is probably no room to reduce its single increment authority.
C) MCAS is implemented within the FCC within the same software that controls other automatic stabilizer control functions such as offload when A/P is engaged and STS. This code already required to be designed to high standards.
Conclusion a) We may need to rely less on critical crew action, but there must be some base level that can be counted upon. I suggest at least:
- RTO for engine out below V1
- Pull for takeoff somewhere near Vr
- Gear and flap management and coordination with associated speeds throughout flight
- Comply with ATC guidance
- Ability to navigate to destination
- Ability to capture and follow glideslope and localizer to runway and command landing flare
- Recognize unstable approach and execute go-around
- Sorry for the length of this list. My point is that there are many pilot actions we count on to maintain safe operation
Conclusion b) I fully agree and suggest adding that if the inputs are garbage the system should be robust enough to maintain safety.
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Old 20th Mar 2019, 21:38
  #2179 (permalink)  
 
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Originally Posted by yanrair View Post
AoA detects a stall by measuring the angle of attack with two sensors, one each side. Measuring the angle of airflow.
Speed is measured by sensing air pressure in a tube facing forwards (pitot)and converting that into Indicated Airpspeed. Not the same as real speed.
GPS measures real speed and is almost never wrong.
Say you have blocked pitot tubes as per aF 447, the AoA still works and stall warning still works.
Say you have frozen AoA vanes so that they are not able to detect stall, or incorrectly detect a stall (as is suggested in these Max incidents) then the Airspeed should still work.
Another scenario is that one airspeed is faulty, but the other two work - there are three airspeed indicators. That one is easy since you go for the two that agree. Backed up with GPS.
There is a lot wrong here. I understand the point you're trying to make - we can cross-check a lot of things and make smarter decisions about what might be wrong - but let's be accurate, since a lot of non-pilots and non-aero-engineers are viewing this thread.

AOA sensors are not always duplicated. Yes, on the 737 they are, as with nearly all commercial aircraft, but that's not a universal fact.

Pitot *AND* static pressures are both required for measuring airspeed. In fact, airspeed is a function of the difference between the two.

Pitot/static speed as shown to the pilot on his airspeed indicator *IS* a real speed. Yes, it's got some assumptions wrapped in it - specifically, standard day pressure - but it's far more useful to a pilot than GPS speed. The airplane cares not a whit how fast over the ground it's moving; it flies according to the pressure field around it, which is a function of altitude and temperature and humidity.

GPS speed is not "almost never wrong". Its accuracy is strongly dependent on the relative position of the satellites. Yes, it's fairly reliable. But onboard air data sensors are far more predictable and reliable.

GPS speed by itself is fairly useless unless you know (with some certainty) the speed and direction of the wind and the airplane altitude and the ambient temperature and humidity. To get back to a useful airspeed, you need quite a bit of additional data. In fact, calibrating airplane Pitot/static systems using GPS data is astoundingly difficult. I should know - I developed several test methods for doing exactly that.

Some airplanes do use Pitot/static data for stall warning. In fact, most commercial airliners (like the 737) show a "zipper" of minimum speed which is also used to activate stall prevention systems; this is computed directly from Pitot/static data.

AOA data is used to correct Pitot/static errors. An incorrect AOA can definitely screw up the indications of altitude and airspeed, and cause changes in automation that depends on those values.
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Old 20th Mar 2019, 21:39
  #2180 (permalink)  
 
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No links from me yet, but a snip from a Seattle Times story posted this afternoon (partial url: :...http://www.seattletimes.com/business...oeing-737-max/)


By Steve Miletich, Seattle Times staff reporter
The FBI has joined the criminal investigation into the certification of the Boeing 737 MAX, lending its considerable resources to an inquiry already being conducted by U.S. Department of Transportation agents, according to people familiar with the matter.

The federal grand jury investigation, based in Washington, D.C., is looking into the certification process that approved the safety of the new Boeing plane, two of which have crashed since October.

The FBI’s Seattle field office lies in proximity to Boeing’s 737 manufacturing plant in Renton, as well as nearby offices of Boeing and Federal Aviation Administration (FAA) officials involved in the certification of the plane.

The investigation, which is being overseen by the U.S. Justice Department’s criminal division and carried out by the Transportation Department’s Inspector General, began in response to information obtained after a Lion Air 737 MAX 8 crashed shortly after takeoff from Jakarta on Oct. 29, killing 189 people, Bloomberg reported... citing an unnamed source.
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