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737 MAX future

Old 11th May 2019, 13:51
  #81 (permalink)  
 
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737 Driver,
Thanks for the info on TOGA, previous thread.
You overlooked my speculative ‘if’ - ‘if without MCAS could the pitch-up be excessive’.

The primary reason for two-stage TOGA was to reduce / manage the rate of pitch-up and/or excessive attitude during GA, which could reduce the stall speed margins. First press gives GA, vertical speed demand, second press is an ‘open climb’ demand with speed protection for max vertical rate in terrain limiting situations.
The NG has had problems in this area, the assumption is that the Max is similar or worse, particularly with MCAS unavailable (flaps-up ‘GA’). This in these circumstances it would be very important that the crew were aware of inoperative MCAS.

Previously you cited a recent MCAS briefing, was this on the same information as in the Boeing link https://www.boeing.com/commercial/73...e-updates.page, or some new views which might have been resubmitted to the FAA.

Re redundancy; single AoA has been the prime focus, but with additional software there are opportunities for new failure paths.
Dual systems degrade are accepted within limits, e.g. single FGC approach, but not Cat 3, the extent of any failure is bounded.
The potential effect of MCAS computational malfunction might not have similar bounding safety limits - other than pilot recognition and intervention. Which of course has been shown to be ineffective, perhaps more so if with dual AoA into MCAS, the rare ‘never saw this before’ creates even greater surprise and mental demand.

Most of the aspects above relate to the nature of the failure - input, vane, vane unit, wiring, digital conversion, or software computation, all of which are unknown (publicly).
Repeating previous comments - can any modified system be approved, risks assessed, if the initiating problem is unknown or unrepeatable.

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Old 11th May 2019, 14:07
  #82 (permalink)  
 
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Seattle Times reporting that Boeing changed the function of the stab trim switches on the MAX vs NG. (does not appear to have told anyone)

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Old 11th May 2019, 14:37
  #83 (permalink)  
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Thus, in continuation: ‘737 Max MCAS recertification and return to service’.
Yes, we can have a thread about the 737 Max return to service. We don't need multiple threads on the same theme, people won't know where to read nor post.

So this is it! Discussion on the return to revenue service of the Boeing 737 Max 8/9....
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Old 11th May 2019, 17:34
  #84 (permalink)  
 
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Interesting link here despite all MAX frenzy...

https://www.fool.com/investing/2019/...s-737-max.aspx
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Old 11th May 2019, 17:50
  #85 (permalink)  
 
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Dear Mr. 737 Driver:

It looks to me like some posters on this forum have decided that you are employed by [redacted] and are spreading bad thoughts. I don't think that, and I appreciate the information in your posts. One of your posts yesterday sounded a lot like the kind of briefing MAX line pilots are starting to get about the upcoming fix. I would sure like to hear more.

To overcome the grief you're getting from some posters, you might consider sending a private message to a long-time poster (David Reid UK or gums, for example) and inviting them to act as your WikiLeaks.

YYZjim
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Old 11th May 2019, 18:03
  #86 (permalink)  
 
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737 Driver

I appreciate You taking it upon Yourself educating us all from Your unique standpoint as an experienced 737 driver.
What You fail to see is that You and not so few 737 "drivers" are not in the game on this one, as there is a tendency to fully understand a rather ancient and outdated system.
It is up to the young and smart magenta-line N-CAA Inspectors and Regulators to be 110% happy with what FAA and Boeing have done in the Certification process and RE-Certification process.
THEN, if GO is the answer:after how many Sim maneuvers required.
And to be honest , they are doing Boeing and FAA a favor.
For, if there is a MCAS/ STS or Stall incident or accident it is all over.
It is not so much a technical/aerodynamic challenge as it is a Human factors CRM issue.
As You , I love the Old Girl, but she is ugly and she does bite.
Bit of a handfull for the young cadre, me thinks.

Just for the record:
Never in Aviation History have we had such a mess:
1 AOA failing on new aircraft.

2 AOA feeding incredible crude deadly system without redundancy ( NO Pilots are NOT part of System Redundancy, Sir!)

3 FAA total lack of involvement.

No accident has this combination, ever.

(4 A possible lack of will to understand and admit fault by Manufacturer.)

Regards
Cpt B

Last edited by BluSdUp; 11th May 2019 at 18:13. Reason: Clarety
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Old 11th May 2019, 18:06
  #87 (permalink)  
 
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Originally Posted by YYZjim View Post
One of your posts yesterday sounded a lot like the kind of briefing MAX line pilots are starting to get about the upcoming fix. I would sure like to hear more.
While there was some more detail in the brief, it was "inside baseball" type material and probably would not mean much unless you were a [redacted] operator.

To overcome the grief you're getting from some posters, you might consider sending a private message to a long-time poster (David Reid UK or gums, for example) and inviting them to act as your WikiLeaks.
Well, beside the lag time problem, I think the idea of using someone else as cover creates its own host of ethical issues. Much of what I do here is simply report how things actually work to correct the misconceptions of how some posters think they work. People can critique [redacted] all they want, but if they have a fundamental misunderstanding of the aircraft, systems or procedures, they shouldn't expect a receptive audience among those who do have a ready grasp of the material.
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Old 11th May 2019, 21:45
  #88 (permalink)  
 
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Originally Posted by 737 Driver View Post
In this operator's opinion, certainly not shared by all, the "AOA Disagree" alert that has captured so much attention is not that bid of a deal. If the AOA's are really that far apart, there will be sufficient other indications because of how the AOA information is integrated into other aircraft systems. In the case of both Lion Air flights and ET302, an active stick shaker while the aircraft is accelerating and climbing normally is the big, annoying, and very obvious indication that something is amiss with your AOA system - and that becomes active as soon as the aircraft lifts off the ground
SLF, PhD, engineer here:

Are 737 Max crews going to learn to respond to that "Special AoA stick shaker" via an iPad briefing? Because it appears simulator training for the Max pilots is excluded ...and I believe pilots are educated to know that stick shaker usually means low speed or stall, so now the stick shake signal is ambiguously getting overloaded with a second semantic.

Also don't you pilots think that having the stick shaker go off quite soon after you clean up and are accelerating (!) is a bit confusing at a moment of fairly high workload, and resolving the semantic ambiguity - AM IS STALLING OR IS THIS JUST AoA DISAGREE? - carries with it a non-negligible chance of startle factor, non-optimal pilot response, and then PIO or even as in the case of two Max airframes uncontrolled flight into terrain and grief issues for a number of families?

Is this fix really a fix without sim training?

Can one really say that with this fix the Max is sufficiently identical in behavior to the NG that neither the pilot training nor the type certificates require updates?

Edmund

On reflection, rather than making an ass of myself talking about stuff I don't know, I think from now on I'll watch this from the sidelines.

Last edited by edmundronald; 11th May 2019 at 22:04.
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Old 11th May 2019, 21:58
  #89 (permalink)  
 
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Originally Posted by edmundronald View Post
AM IS STALLING OR IS THIS JUST AoA DISAGREE? - carries with it a chance of startle factor, non-optimal response, and then PIO or even as in the case of two Max airframes uncontrolled flight into terrain?

Is this fix really a fix without sim training?

Can one really say that with this fix the Max is sufficiently identical in behavior to the NG that neither the pilot training nor the type certificates require updates?
The stick shaker behaves the same way no matter NG or MAX.
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Old 11th May 2019, 22:06
  #90 (permalink)  
 
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Originally Posted by 737 Driver View Post
Well, I do actually fly this aircraft ........ Guilty as charged!
And I do hope you are up front on my next Max flight.
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Old 11th May 2019, 22:34
  #91 (permalink)  
 
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Originally Posted by edmundronald View Post
SLF, PhD, engineer here:

Are 737 Max crews going to learn to respond to that "Special AoA stick shaker" via an iPad briefing? Because it appears simulator training for the Max pilots is excluded ...and I believe pilots are educated to know that stick shaker usually means low speed or stall, so now the stick shake signal is ambiguously getting overloaded with a second semantic.

Also don't you pilots think that having the stick shaker go off quite soon after you clean up and are accelerating (!) is a bit confusing at a moment of fairly high workload, and resolving the semantic ambiguity - AM IS STALLING OR IS THIS JUST AoA DISAGREE? - carries with it a non-negligible chance of startle factor, non-optimal pilot response, and then PIO or even as in the case of two Max airframes uncontrolled flight into terrain and grief issues for a number of families?
In terms of the thought process that the 737 pilot goes through to determine whether a stick shaker warning is either 1) correct thus requiring stall avoidance procedures, or 2) false thus requiring faulty AOA or airspeed input procedures (i.e. Airspeed Unreliable NNC), the 737NG and MAX are absolutely identical and no difference training is needed. This thought/decision process should occur very quickly, even accounting for the startle effect.

If you can figure this out in the NG, you can figure it out in the MAX. The corollary is, however, if you can't figure it out in an NG, you are not going to figure it out in the MAX either.
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Old 11th May 2019, 22:43
  #92 (permalink)  
 
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Originally Posted by overhill45 View Post
Question - how much altitude is lost when using manual trim wheel to crank back to the trim value in use when the flaps go up, Hal goes wild, to its max amount and pilot shuts of either or both primary and b/u switches immediately. Can it be done by ONE pilot or does it take two ?

Yes, I knows it is speed dependent as to required force to spin wheel ( nose up ) depending on which way failure is ..
Hopefully, the answer is zero. There will probably be some up and down on the altitude as the aircraft is stabilized, but if the pilots correctly apply the runaway stab procedure then there should be no significant loss of altitude. (From the data released to date, it appears the Lion Air 610 accident pilots did not accomplish this procedure, and the ET302 pilots did not accomplish the procedure correctly).

While the procedure itself can be accomplished by one pilot, every procedure on the 737 (normal and non-normal) is designed to be accomplished as a crew to ensure that it is done correctly. If the stab is significantly out of trim when the electric trim is cutout, it will likely require the efforts of both pilots to use the manual trim to return the aircraft to a neutral trim state.
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Old 11th May 2019, 23:13
  #93 (permalink)  
 
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Originally Posted by Smythe View Post
.
Seattle Times reporting that Boeing changed the function of the stab trim switches on the MAX vs NG. (does not appear to have told anyone)
.
.
Yes on the first part (covered extensively in previous threads). No on the second part - the change in labeling and function was disclosed in the FCOM. The changes did not include a detailed wiring diagram, but one was not needed either.

Seattle Times article can be found here: link​​​​​​

Also covered extensively in previous threads, the change in functionality made no difference procedurally. The 737NG and the MAX runaway stab procedure calls for the use of both switches. I had speculated previously that the two switches were retained on the MAX, in part, to provide commonality with the NG. The article above has this statement from a Boeing spokesperson:

.
​​​​​​Boeing said in a statement that the company had historically called for pilots to flip both switches to shut of a problematic or “runaway” stabilizer, so the change on the MAX ensured that the function of the switches matched that procedure. The company said the two switches “were retained for commonality of the crew interface.”
.
So it appears that speculation was correct.

Last edited by 737 Driver; 11th May 2019 at 23:39.
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Old 11th May 2019, 23:34
  #94 (permalink)  
 
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Latest Update

The Amsterdam seminar for Max customers on Tuesday had limited information and time lines to offer.
EASA is talking late summer.
Was covered on a closed thread.

Regards
Cpt B
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