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MAX’s Return Delayed by FAA Reevaluation of 737 Safety Procedures

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MAX’s Return Delayed by FAA Reevaluation of 737 Safety Procedures

Old 23rd Nov 2019, 12:14
  #4081 (permalink)  
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Originally Posted by spornrad
They seem to have recognized that MCAS column cutout override robs the pilot of his natural countermeasure. Now they leave that override, and stick a SW band-aid on top. Arghhh...
Yes, that's exactly what it looks like (from the limited information we have). You just can't sugar-coat this; it's terrible engineering.

Originally Posted by Peter H
What a pity that a little of the MAX down-time wasn't spent testing/demonstrating the truth of that position. (Acceptable bare airframe aerodynamics.)
Do we know that hasn't happened? We do know that JATR (and EASA?) have said that testing should be done.
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Old 23rd Nov 2019, 12:38
  #4082 (permalink)  
 
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"i am feeling the final decisions on acceptance will not be technically based."

This is the first leak from the regulatory community. I don't think it is a coincidence. I think it is a warning shot the bang from which could reverberate widely.

So now we have 'straight from Steve' from the FAA, and 'straight to Steve' from TCCA: 'it's out there, and we aren't going to let you fudge it'.

The more you read this email the cleverer it is: -
- It is couched as prisoners friend (we all want it back in the air)
- It pretty much says approval by Christmas is a pipe dream
- It says the fix is still not stable, and not really a fix
- It is a clear warning to the FAA
- TCCA have not disowned him, but they have not backed him either: so now they have to get off the pot in public
- He is effectively challenging Beoing to prove assertions the aerodynamic characteristics are benign
- He is making it harder for foreign regulators to go weak at the knees

I note he is a 30 year veteran. Likely reached the point where he does not need to fear for his future: or maybe he just works somehere a bit less toxic than the FAA.

Last edited by SLF3; 23rd Nov 2019 at 12:57.
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Old 23rd Nov 2019, 13:02
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From the Canadian engineer's email:
...Not knowing the exact reasons for telling us that 12.1 as a fix is not effective (ref. F2.3 recent change to CAT), the fact is that it is
another point that was just discovered...


I read this as, the main mitigation measures supposed to defuse MCAS missfire (12.1) seem to be invalidated by a recent finding, that 12.1.B) leaves a misfire still as catastrophic event:
12.1
A) Activation by AOA
B) Limit MCAS authority
C) Inline Validity monitor, i.e. follow AOA values and accept only reasonable changes
D) Delta disagree, i.e. compare both AOA values and detect a defective sensor

Invoking Santa for help:
Now (! meaning none?) of this helps get us to a level of confidence that having MCAS onboard was ever a good thing. The only way I see
moving forward at this point ( and I say at this point because it's almost Christmas and we can always believe in
miracles), is that MCAS has to go....
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Old 23rd Nov 2019, 13:32
  #4084 (permalink)  
 
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PeterH: What a pity that a little of the MAX down-time wasn't spent testing/demonstrating the truth of that position. (Acceptable bare airframe aerodynamics.)
OldnGrounded: Do we know that hasn't happened? We do know that JATR (and EASA?) have said that testing should be done.

I was meaning that if B believed that the MAX had acceptable (or near acceptable) bare airframe aerodynamics they would have be wise to put
convincing evidence into the public domain soon after the grounding. (I expect that the certifying authorities are forcing B to make some tests,
and that B is keeping both the existence and results of these tests as confidential as they can.)

However I'm certain that SLF3 has it right:
The more you read this [TCCA] email the cleverer it is:
[Among other things] He is effectively challenging Boeing to prove assertions the aerodynamic characteristics are benign
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Old 23rd Nov 2019, 13:56
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Sounds EXACTLY like the Morton Thiokol engineer who stood up and said it is too cold to launch the Challenger!
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Old 23rd Nov 2019, 15:48
  #4086 (permalink)  
 
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The basic Max did not meet the certification requirements; Max + MCAS similarly deficient.
Various MCAS modifications still not compliant.

The recent TC text appears to suggest that the ‘lesser’ non-compliant option could be certificated, allowing an aircraft which does not meet requirements to operate.
Not the best example of how to improve the public view of safety.
Nor a good safety message for the industry, or for future certification.
Other manufacturers have had to meet the certification requirements or agreed a dispensation before initial certification.
Any dispensation for the Max after two accidents, after initial certification, just because a satisfactory solution is currently not available, would not bode well for future certification or international cooperation.
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Old 23rd Nov 2019, 16:04
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Originally Posted by SLF3
"i am feeling the final decisions on acceptance will not be technically based."

This is the first leak from the regulatory community. I don't think it is a coincidence. I think it is a warning shot the bang from which could reverberate widely.

So now we have 'straight from Steve' from the FAA, and 'straight to Steve' from TCCA: 'it's out there, and we aren't going to let you fudge it'.

The more you read this email the cleverer it is: -
- It is couched as prisoners friend (we all want it back in the air)
- It pretty much says approval by Christmas is a pipe dream
- It says the fix is still not stable, and not really a fix
- It is a clear warning to the FAA
- TCCA have not disowned him, but they have not backed him either: so now they have to get off the pot in public
- He is effectively challenging Beoing to prove assertions the aerodynamic characteristics are benign
- He is making it harder for foreign regulators to go weak at the knees

I note he is a 30 year veteran. Likely reached the point where he does not need to fear for his future: or maybe he just works somehere a bit less toxic than the FAA.
I read the e-mail and quickly reached the conclusion that this was written to be leaked. He even indicates it is OK for his recipients to share it with others in their organisations making a leak of the email even more likely.
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Old 23rd Nov 2019, 16:07
  #4088 (permalink)  

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Surely you cannot have an aircraft that is non compliant with regulatory requirements getting approval. That would leave the regulators in the dock as well as Boeing at every incident involving the MAX.
The job of Boeing is to produce a compliant aircraft; when it does so the regulators could and should approve it. Until that time the place for the Max is on the ground without passengers.
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Old 23rd Nov 2019, 17:16
  #4089 (permalink)  
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Originally Posted by dufc
I read the e-mail and quickly reached the conclusion that this was written to be leaked. He even indicates it is OK for his recipients to share it with others in their organisations making a leak of the email even more likely.
I doubt that there was ever any chance this would not be shared publicly, regardless of the author's intention (although I agree that he probably wanted it widely distributed).

Imagine being one of the original recipients and wondering what life would be like if you didn't circulate this (including to press/public) and your agency signed on to MAX RTS, followed by . . . another crash.
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Old 23rd Nov 2019, 18:35
  #4090 (permalink)  
 
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From what I've been reading (on here and elsewhere) it seems like there are patches on patches but nobody wants to take responsibility to say "to hell with it, lets start again"
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Old 23rd Nov 2019, 19:33
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We've seen that MCAS misfire was classified as 'Major', if not hazardous etc...
With the new version, if AOAs disagree then MCAS is inhibited. How is MCAS inhibition classified ? Minor, Major ? Hazardous ?
If Major or Hazardous, difficult to see how reading a tablet might suffice.
If Minor only, why not dump the MCAS altogether, as proposed ?
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Old 23rd Nov 2019, 20:46
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Originally Posted by sky9
Surely you cannot have an aircraft that is non compliant with regulatory requirements getting approval. That would leave the regulators in the dock as well as Boeing at every incident involving the MAX.
The job of Boeing is to produce a compliant aircraft; when it does so the regulators could and should approve it. Until that time the place for the Max is on the ground without passengers.
The converse of this is that if regulatory compliance, and approval/disapproval of regulatory filings, is going to be conducted via leaked e-mail and innuendo then the entire cross-national regulatory regime will grind to a halt. Suppliers must have some assurance that when they file a document that is compliant with regulations and procedures that that document will be processed and approved or disapproved based on consistent criteria.
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Old 23rd Nov 2019, 22:31
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Passengers lives vs. document handling. Yeah, that’s a dilemma, all right.
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Old 23rd Nov 2019, 23:06
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The many extensions made to the 737 culminated in unacceptable stick force at high alpha. The MCAS cure proved itself worse than the disease.

So yes, begin with removing MCAS and finish with restoring aerodynamics at least as good as on the NG.

Most likely that will require a cowl location and sizing similar to the NG with an engine that fits.

The MD marketing experts at B can figure out what discount would incentivise A to take the current MAX engines off B's hands.

Perhaps a few original MAXes in drone configuration could be kept for the MBA crowd.

There was a point when B could have taken over the now A220 program for a very good price. Instead their tariff lobbying put it into A's hands.
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Old 23rd Nov 2019, 23:22
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Originally Posted by RatherBeFlying
The many extensions made to the 737 culminated in unacceptable stick force at high alpha. The MCAS cure proved itself worse than the disease.

So yes, begin with removing MCAS and finish with restoring aerodynamics at least as good as on the NG.

Most likely that will require a cowl location and sizing similar to the NG with an engine that fits.

The MD marketing experts at B can figure out what discount would incentivise A to take the current MAX engines off B's hands.

Perhaps a few original MAXes in drone configuration could be kept for the MBA crowd.

There was a point when B could have taken over the now A220 program for a very good price. Instead their tariff lobbying put it into A's hands.
There is a lot I don't know about the aero of the MAX but I don't think the original MCAS was put there for "unacceptable" stick force. It was put there for non linear stick force which would be unacceptable by the certification requirements. If you showed me how it responded in that flight regime I might say it was acceptable and of no consequence. Kinda like the T-38 I used to fly. Be careful around .9 Mach, it's more sensitive. I envision two cases where the MAX's stick force non linearity might come into play. It might make a steep turn easier if you fly the attitude you want to put the performance where you want. It also might be a problem in a clean off autopilot windshear escape. Would have to see that in the airplane or simulator.
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Old 23rd Nov 2019, 23:30
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Can you elaborate on the difference between “unacceptable stick force” and “non linear stick force which would be unacceptable for certification requirements”? I’m having a bit of trouble wrapping my head around that one.
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Old 23rd Nov 2019, 23:39
  #4097 (permalink)  
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Originally Posted by sphealey
Suppliers must have some assurance that when they file a document that is compliant with regulations and procedures that that document will be processed and approved or disapproved based on consistent criteria.
Until we can be confident that the "consistent criteria" are grounded in the application of sound engineering to advance the goal of safe aviation . . . I'm with the leaker.

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Old 23rd Nov 2019, 23:55
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Originally Posted by Takwis
Can you elaborate on the difference between “unacceptable stick force” and “non linear stick force which would be unacceptable for certification requirements”? I’m having a bit of trouble wrapping my head around that one.
If certification requirements were unnecessarily strict you could have a system that failed to meet certification requirements but were not actually a problem. That’s my reading of it anyway.
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Old 24th Nov 2019, 00:18
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Originally Posted by Takwis
Can you elaborate on the difference between “unacceptable stick force” and “non linear stick force which would be unacceptable for certification requirements”? I’m having a bit of trouble wrapping my head around that one.
I think the point is that the rate-of-change of stick force has to be acceptable, as well as its absolute value.
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Old 24th Nov 2019, 00:40
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unacceptable stick force gradient at high alpha.
My mistake. Is that better?
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