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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 13th Mar 2019, 00:47
  #881 (permalink)  
 
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Kiwis become the latest to suspend the Max - affecting a small number of Fiji Airways flights.
Interesting to observe the rest of the world effectively ignoring the FAA - perception versus known facts.
What a monumental debacle for Boeing.
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Old 13th Mar 2019, 00:50
  #882 (permalink)  
 
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Originally Posted by Luc Lion View Post
Airbubba, the "control column actuated trim cutout switches" are switches located in the control column that stop an electric trim movement when the control column requests an elevator deflection contradicting the trim movement. This is the immediate response to a stuck electric trim button before using the STAB TRIM MAIN ELECT cutout switch on the control stand.
Thanks, seems like there was something like that on the 727.

Originally Posted by FCeng84 View Post
There seems to be some confusion with regard to 737 switches associated with pitch trim. That is very understandable as there are quite a few and it is easy to get them mixed up. Let me take a run at an overview:

I hope this helps.
It does, thanks!
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Old 13th Mar 2019, 00:56
  #883 (permalink)  
 
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Originally Posted by hans brinker View Post
There is no control column cutout switches, ....
There are such switches, although they are hidden in the column.
See FCOM 9.20 "Controls - System Description" - "Stabilizer Trim".
Read also the function of the "Stabilizer Trim Override Switch"
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Old 13th Mar 2019, 01:01
  #884 (permalink)  
 
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Originally Posted by Icarus2001 View Post
Oh gawd here we go again, get rid of the pilots.

Q. Which form of transport is easiest to automate, rate in order?

Aircraft, trains, ships.

Now when you have thought about that ask why are there still train drivers.

FFS
Train Drivers aren't required. To run the London Underground Central Line at max capacity, drivers don't touch the controls. They run automatically. Drivers are there because the unions require them not because it's safer.
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Old 13th Mar 2019, 01:02
  #885 (permalink)  
 
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Originally Posted by A0283 View Post
Just thinking ... not judging, just wondering... so nice to be naive sometimes...

Historically Boeing has always been quite clear and open about serious issues.
And thereby one, certainly not the only, of the companies and organizations that has made aerospace as safe as it is.
That reputation certainly got dented recently during the 787 program. Some are happy with it now, others still have professional reservations.
The Lion Air case caused other dents. The suggestion is that Boeing has been withholding information. They certainly have not been open.
Boeing did not open up about the design philosophy of MCAS, the design itself, the way in which it was tested, and certified, and documented and trained, etcetera.
This Ethiopian case magnifies this unusual lack of openness.
Simply said modern certification (not only in aerospace) puts a lot of proof and testing on the desk of the manufacturer rather than on the desk of the certification authority.
You wonder what was written and agreed about what kind of 'publication obligation of the certification process and results' this shift has caused.
To this day informed people know little of MCAS. Certainly not enough for peace of mind.

So what could Boeing do to start limiting the damage that is being done and still increasing rapidly. So rapid that it may dent the industry.
What would personally appeal to me is the chief engineer of the program giving an explanation about MCAS in general. So a very competent technical person with 'signature responsibility', don't think anyone else would do anymore.
This does not disrupt the Ethiopian investigation because we don't know if MCAS is even involved. So there would be no excuse not doing it citing this one, or for that matter even the Lion investigation. It is just basic historic knowledge and intent you might say.

You get the feeling that if they don't volunteer this now that at some stage they will be ordered to do this and add a number of other people and disciplines.

Chicago has a problem.

Thanks A0283
You've about summed up my feeelings, but better and more succinctly than ever I could have.
I'd just add that the certification authorities (In other industries as well) have a historical habit or even mandated practice of not getting into a dialogue of 'The how' of implementation for meeting design or behaviour requirements
In this case, once it was obvious to both parties that a 'workaround' was going to be necessary to handle native behaviour that flouted a requirement - for make no mistake, this is a 'workaround' just as the old shaker/stick pusher pair were for T-tailed aircraft - then I'd want a dialogue to begin if I worked in AW at Boeing or the Certificating Authority... but not about 'just meeting the requirement', but looking at every aspect of its necessity in the first place, from stretch design right through to the exact relevance of stick force per G or stick force per alpha - in each particular flight domain.
With CFD I imagine Boeing saw the pitching moment - alpha curves rearing their head very early on, at the project stage.. at least I hope so!
I can picture flies on the wall in certain offices back then raising their eyebrows in a knowing way as to me, it sounds awfully like they might have been handed to the S&C boys/girls for a solution far too early
I hope that makes sense...

Last edited by HarryMann; 13th Mar 2019 at 01:15.
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Old 13th Mar 2019, 01:03
  #886 (permalink)  
 
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How many people are looking over the shoulder of the FDR/CVR analyst right now?
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Old 13th Mar 2019, 01:17
  #887 (permalink)  
 
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@FCeng84 - I really appreciate your effort to help clarify a number of issues. Hope Boeing will elaborate on this in the end ;-)

For me there is a difference between an "AoA increase" and a "positive AoA rate". Hope you can clarify that during your further explanations.

I was wondering if you were talking about "positional feedback" with MCAS or "force feedback" or both. In another explanation you exclude the "positional".

If you use the cutout and remove the power you disable MCAS ... which would put you outside the 'normal' certified envelope... do I read that correctly? ... With MCAS aimed at the NNC part of things, using the cutout appears to push you in yet again an other area, and outside certification?... Or is that a wrong interpretation?
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Old 13th Mar 2019, 01:24
  #888 (permalink)  
 
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Pretty sure the relevant curve here, would be Stick Force ~ Alpha not a derivative (e.g.Alpha rate)
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Old 13th Mar 2019, 01:26
  #889 (permalink)  
 
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Originally Posted by FCeng84 View Post
I'm glad to be able to provide some clarity. MCAS operates as a function of AOA with no regard to column position. As you state, "MCAS is to essentially negate lift (more specifically pitching moment) of the engine cowling". By cancelling out the nose up pitching moment from the cowling with increased AOA, MCAS smooths out the overall Cm-alpha (pitching moment vs. AOA) characteristic of the airplane so that column required to command a maneuver to high AOA does not decrease along the way.
But if you can achieve the high AOA state on autopilot, it doesn't need MCAS and will just put the elevator and trim where it needs to be to get the attitude it wants, just like humans should be able to do. Shut off MCAS and tell pilots to be aware of stick lightening in the, as Boeing says, envelope that you won't likely encounter.
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Old 13th Mar 2019, 01:30
  #890 (permalink)  
 
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@Harrymann
I'd want a dialogue to begin if I worked in AW at Boeing or the Certificating Authority, but not about 'just meeting the requirement', but looking at every aspect of its necessity in the first place, from stretch design right through to the exact relevance of stick force per G or stick force per alpha - in each particular flight domain ... at least I hope so! .... I hope that makes sense...
Ooooh yes ... we hope together ... it makes sense to me yes ...

And on your
Pretty sure the relevant curve here, would be Stick Force ~ Alpha not a derivative (e.g.Alpha rate)
I would join your question ... perhaps FCeng84 can answer that.

Thanks gents.
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Old 13th Mar 2019, 01:37
  #891 (permalink)  
 
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Originally Posted by A0283 View Post
@FCeng84 - I really appreciate your effort to help clarify a number of issues. Hope Boeing will elaborate on this in the end ;-)

For me there is a difference between an "AoA increase" and a "positive AoA rate". Hope you can clarify that during your further explanations.

I was wondering if you were talking about "positional feedback" with MCAS or "force feedback" or both. In another explanation you exclude the "positional".

If you use the cutout and remove the power you disable MCAS ... which would put you outside the 'normal' certified envelope... do I read that correctly? ... With MCAS aimed at the NNC part of things, using the cutout appears to push you in yet again an other area, and outside certification?... Or is that a wrong interpretation?
I think you would be correct but the NNC given by Boeing/FAA does not caution you to avoid whatever regime MCAS was designed to protect against. Takeaway being why have MCAS in the first place? Yes, I know, certification pencil whip.
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Old 13th Mar 2019, 01:38
  #892 (permalink)  
 
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Originally Posted by FCeng84 View Post
Pitching moment caused by engine thrust is a function of how much thrust and where the engine is mounted vertically with respect to the center of gravity. Thrust pitching moment is not a function of how far forward or aft the engine is located. With this in mind, the nose up thrust induced pitching moment generated by the 737MAX engine is not greater than that for a 737NG. In fact, it is probably less as the center line of the larger MAX engine is higher than the center line of the smaller NG engine given their respective attachment geometries.

Hopefully it is now clear that the pitching moment of concern with the 737MAX engines that gives rise to the need for MCAS is related to the aerodynamic impact of the engine cowling location and geometry, not the magnitude nor location of the thrust vector generated by those engines.
To add a bit to this good explanation, Bjorn at Leeham news (who wrote a very good explanation of MCAS after Lionair) has a good followup that is available by googling "Bjorn's corner: Pitch stability, Part 10. Wrap up". (The previous parts are worth reading also). He is suggesting the augmented versus augmented MAX Cm (moment coefficient) versus alpha (AoA) curve would likely look similar to the one below. These curves are easy to interpret, a stable aircraft has a negative sloped curve where the pitching moment coefficient decreases as AoA increases. The interesting thing is that the unaugmented aircraft transitions between stable and less stable during prestall (and is never neutral or unstable), but the discontinuity is the problem. Although the aircraft still requires an increase in pull force to further increase AoA (It won't start increasing AoA by itself with no further pull at constant thrust), it will feel easier for the pilot than in the NG to get from pre-stall to stall.

Figure 1. A thought pitch moment curve for Boeing’s 737 MAX. Source: Leeham Co.
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Old 13th Mar 2019, 01:51
  #893 (permalink)  
 
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Different but similar failures in US

First time poster here, and not a pilot, but... I just noticed this in an article on the Guardian. Doesn't sound like MCAS, but perhaps another example of "un-wanted" automation trying to bring a plane down. Apologies if this has been posted before, but I haven't seen it yet on this (fascinating) thread...

"Two US airline pilots filed voluntary safety reports last year to a database compiled by Nasa, saying an automated system seemed to cause their 737 Max planes to tilt down suddenly.

The pilots said that soon after engaging the autopilot on Max 8 planes, the nose tilted down sharply. In both cases, they recovered quickly after disconnecting the autopilot.

The problem did not appear related to the automated anti-stall system that is suspected of contributing to a deadly October crash in Indonesia."
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Old 13th Mar 2019, 02:19
  #894 (permalink)  
 
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Originally Posted by 42... View Post
Disagree, the 737 sim felt like a as fully stalled F15C at extreme AOA as I've felt, violent shaking would be a good description. Yet, controllable. So yes, the 737 is certified to full stall, with devices in place to avoid that condition. The MCAS is only designed to modify characteristics to make it more like the NG, not stop a stall, which apparently has gone horribly wrong.
It’s nothing more than a guess on how the aircraft might react since they don’t do enough testing flight in that regime if any to provide data to build a profile for the sim.
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Old 13th Mar 2019, 02:22
  #895 (permalink)  
 
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Not unexpected, and these movements can reverse as quickly as they occur, but ;

Boeing fell 6 percent to $375.92 at 2:09 p.m. in New York.
The company has lost about $27 billion in market value this week.
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Old 13th Mar 2019, 02:27
  #896 (permalink)  
 
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CRM vs ERM

When CRM fails, we harshly and rightly so admonish pilots.

AFAIK Amsterdam and LionAir accidents are both single channel/sensor accidents.

Is it possile to say that Boeing failed in ERM ?

(Equipment Resources Managment, failing to put good use of equipment already onboard.)

Last edited by wetbehindear; 13th Mar 2019 at 02:45.
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Old 13th Mar 2019, 02:27
  #897 (permalink)  
 
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I was sick the day they taught aerodynamics at flight
school but.....with FCENG84s help this MCAS is becoming a
lot clearer.It seems they wont be allowing the pilot to
inhibit MCAS using the stick when they make their software changes.
They obviously cant.
So the only thing that makes sense now is they wire up both AoA
indicators to MCAS and if they both agree and show high AoA
then MCAS can let rip.
This will for sure decrease the odds of an unwanted MCAS event.

FCENG84 has helped steady the ship here and calmed the
hysteria but ......what about Jodels scenario of a flapless
landing on a MAX with a birdstrike at 200
feet on finals followed by an MCAS runaway?What then?
The NG was as far as they should have taken that 1960's airframe/geometry....quit while you're ahead I say

Last edited by Rananim; 13th Mar 2019 at 03:01.
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Old 13th Mar 2019, 03:17
  #898 (permalink)  
 
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Currently the Max -9 has (9) in flight. The Max-8 has (97) in flight.
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Old 13th Mar 2019, 03:48
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The really shocking takeaway from AF447 was that first world pilots, selected and trained by the country that built the plane were completely inadequate at hand-flying the plane. The training system was shown to be in need of improvement.

With the 737-Max the takeaway seems to be that the US FAA certification system is badly broken, has become beholden to the industry and is in need of improvement.

Edmund.
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Old 13th Mar 2019, 03:48
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Originally Posted by FanControl View Post
Currently the Max -9 has (9) in flight. The Max-8 has (97) in flight.
Now down to 10 (8 in NA) Max-9 and 56 (48 in NA) Max 8
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