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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 11th Dec 2019, 18:58
  #4401 (permalink)  
 
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Seems like the Boeing event went down well with this reporter – see the “conclusion” below.

Translation from French by Google is unmodified here....

“Conclusion of these two days

If we consider that all the information provided to us is reliable (I dare not imagine that Boeing can try to lie hide anything), then I think we were convinced. The aircraft is ultimately not unstable and the presence of the MCAS desirable. The initial error is repaired and the pilots present, first concerned,confirmed their confidence in the plane and their willingness to take back orders at the earliest (I made an interview with the president of a Chinese pilots association , I am waiting for the validation of my images in the simulator to share them at the same time).”
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Old 11th Dec 2019, 20:29
  #4402 (permalink)  
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Originally Posted by Grebe View Post
Fit to hit shan on FAA view of MAX - this extract from WSJ this am says it all - the article is longer

Oh. yes. World CAAs will be even less comfortable with piggy-backing on FAA certs. For those who get stopped by the WSJ paywall:

US Regulators Allowed Boeing 737 Max to Keep Flying After First Crash Despite FAA Analysis Predicting More

Last edited by OldnGrounded; 11th Dec 2019 at 22:21.
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Old 11th Dec 2019, 20:40
  #4403 (permalink)  
 
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Originally Posted by Takwis View Post
For comparison, on November 11th, they were saying "1700+ (link removed)"
Reading those announcements (1700 or 1850 hours) carefully shows it doesn't mean anything:

So in November Boeing stated 900+ test and production flights with new software totaling 1700+ hours".

Now we're hearing "Boeing told attendees the company has flown 1,850 flight hours with the software updates".

Note that in the Nov announcement (1700+ hours) it was test and PRODUCTION flights. Also, it was "with new software" or "the software updates", but no specifics mentioned as to what softwares were updated in those flights.
Does it count if the coffee machine was updated? Inflight entertainment system updated with new movie releases? Sounds like a software update...

I'm guessing that out of the 900+ flights, 800 or so account for ferrying grounded planes to storage.
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Old 11th Dec 2019, 21:07
  #4404 (permalink)  
 
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This whole saga just keeps getting worse and worse. 18 months ago you’d think it incredible.

I sincerely hope Boeing comes out of this better, with a renewed focus on engineering a safety. Airbus need the competition.
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Old 12th Dec 2019, 01:14
  #4405 (permalink)  
 
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Originally Posted by Water pilot View Post
Interesting to note the PR judo going on here, world class in that department at least. Boeing announces that the regulators will approve the fix by December, a timeline that could not legally have been based on anything other than hope. (The implication to the stockholders was that they had an inside line to the FAA.) The FAA denied that there was any such timeline. Now Boeing is blaming the potential revenue hit on "delays by regulators." Nicely done, Boeing PR.
Not only that, this statement was made to the Securities & Exchange Commission. Now the SEC are no fools, and if they determine that Boeing has been peddling nonsense about service re-entry and resumption of sales revenue, both to investors and now to them, that will not go down well.

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Old 12th Dec 2019, 04:36
  #4406 (permalink)  
 
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As of the 11 December 2019 Boeing are still to provide requested information.
Part of Kiefer's testimony.

During these meetings, which included multiple online conferences and two face-to-face meetings at Boeing, our team had the full cooperation of the Boeing engineering and flight test staff as well as good participation from the avionics sub-contractor. After these meetings, briefings and demonstrations the team gathered to assemble our findings and recommendations. Some of these we have determined are necessary before returning the aircraft to service. These recommendations/action items are being actively tracked internally to the TAB and with Boeing and the FAA. All recommendations that the team made for return to service have either been addressed and closed or are presently in work. The TAB is still working with Boeing to accept products to close the remaining action items. Once all of this work is complete the TAB will present a final report to the FAA.

The TAB still has work to do to complete our assessment of the changes to the B737 MAX systems as we are awaiting more information on the development assurance, testing of the software, final safety assessments and final training for aircrew.

https://transportation.house.gov/imo...0Testimony.pdf
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Old 12th Dec 2019, 05:13
  #4407 (permalink)  
 
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Originally Posted by Outofthefray View Post
Seems like the Boeing event went down well with this reporter – see the “conclusion” below.

Translation from French by Google is unmodified here....

“Conclusion of these two days

If we consider that all the information provided to us is reliable (I dare not imagine that Boeing can try to lie hide anything), then I think we were convinced. The aircraft is ultimately not unstable and the presence of the MCAS desirable. The initial error is repaired and the pilots present, first concerned,confirmed their confidence in the plane and their willingness to take back orders at the earliest (I made an interview with the president of a Chinese pilots association , I am waiting for the validation of my images in the simulator to share them at the same time).”
So the bird is not unstable. I would suppose that and have always thought that. Why is MCAS “desirable”? If the bird became light in pitch in a steep turn that wouldn’t bother me. What envelope would make me decide a trim down to increase my pitch force up input would be desirable? And once I put the bird in trim in that envelope, offsetting MCAS, what am I in danger from? And what will any abnormal procedure that kills electric trim advise the crew what to do/not do because that now have the the “desirable” MCAS” is dissabled. Can somebody give me a rational explanation why they can’t just turn MCAS off? The FAS doesn’t require a new type rating between the 757 and 767 and various 737 pre 800 birds. But pilots will tell you they don’t handle the same especially in landing. It is a minor issue. To tell the truth, we now might need separate type ratings to fly a lightweight version of the bird we are current on vs the heavy version of it, whichever airplane that might be
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Old 12th Dec 2019, 05:33
  #4408 (permalink)  
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Originally Posted by jimtx View Post
Can somebody give me a rational explanation why they can’t just turn MCAS off?
Sure. They can't just turn MCAS off because, without it, the MAX wouldn't meet the FAA requirement for stick force gradient and couldn't be certified.*


* Or so we're told. Some of the skeptical among us** are still stubbornly wondering about that stability thing.

** To include the Joint Authorities Technical Review

Last edited by OldnGrounded; 12th Dec 2019 at 14:39. Reason: Typo
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Old 12th Dec 2019, 05:36
  #4409 (permalink)  
 
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Re: flight hours: Boeing had stated they were flight testing updated software prior to the second crash, had they not? So maybe they are counting some of that time?

Not saying they should; on the contrary, they don't get to start counting final fix flight test hours until they have a final fix, with no further revisions, approved by all global authorities. That final rev? Yeah, count those hours.

More relevant would be the number of times they pushed into the corners in question, with minimum acceptance trained pilots at the controls, and got MCAS to activate, plus actual failure modes activated in flight, with the same experience level pilots. Do that x# of times, simulating 20 years worth of the global fleet experiencing those corners/failures, and I'll even accept more experienced pilots for the later tests, approximating the maturation of the global experience levels.

So what we talking about, fleet wise? Several hundred envelope corner excursions, and thousands of single AoA vane failures? Plus a couple dozen 2x vane failures, plus all the added related equipment/computer failures? More? Less? By orders of magnitude?

Whatever it is, add it up. Fly them all, with at least nominal surprise (OK, test pilots will know something will happen in testing, just not what and when). You're asking us to fly it all over time; OK, you first, Boeing.

Last edited by DieselOx; 12th Dec 2019 at 05:47.
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Old 12th Dec 2019, 07:08
  #4410 (permalink)  
 
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Originally Posted by Outofthefray View Post
Seems like the Boeing event went down well with this reporter – see the “conclusion” below.

Translation from French by Google is unmodified here....

“Conclusion of these two days

If we consider that all the information provided to us is reliable (I dare not imagine that Boeing can try to lie hide anything), then I think we were convinced. The aircraft is ultimately not unstable and the presence of the MCAS desirable. The initial error is repaired and the pilots present, first concerned,confirmed their confidence in the plane and their willingness to take back orders at the earliest (I made an interview with the president of a Chinese pilots association , I am waiting for the validation of my images in the simulator to share them at the same time).”

I do not know how/why this ex-military pilot was invited, probably only because he is the manager of the Centre de Traitement de la Peur de l'Avion (Airplane Fear Treatment Centre); it reinforces that this event was only a PR one.
In any case, this gentleman did not follow too much the B737Max/MCAS matter before his visit; in the comments below his paper (automatic translation and my emphasizing):

"- the origin of the MCAS, which seemed new to me, has in fact been recurrent for months, it has simply never been covered in the media (and it is therefore not a communication invention imagined for our trip)"
"- the question of the aircraft's nose-up tendency is also raised by Boeing. It is not clear whether this is an ANU tendency of the aircraft in these particular flight conditions, or a lightness of the control column that could cause pilots to pull too much."

So, probably better to wait for the conclusions of a non-PR event, written by someone knowing....

.
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Old 12th Dec 2019, 07:23
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Federal Aviation Administration chief Stephen Dickson said that the plane, which has been grounded worldwide since March, will not be certified to fly this year, dashing Boeing’s hopes of getting the popular family of planes back in the air in 2019.

“If you do the math, it’s going to extend into 2020,” Dickson told CNBC Wednesday
How very helpful that the 'math' behind that has been so carefully explained.
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Old 12th Dec 2019, 08:27
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Originally Posted by pilotmike View Post
How very helpful that the 'math' behind that has been so carefully explained.

Simples - 30 days minimum after final submission of fix for re-certification.

Given Boeing as of 11 December have not supplied the required information requested, including pilot training requirements.

Maths suggests any time in 2019 is not possible ( there is not 30 days left in 2019!)

See my post just above what is outstanding for Boeing to supply before a recommendation can be given to the regulator, then the 30 day (minimum) count can start.
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Old 12th Dec 2019, 08:44
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Is there any draft document available about the actual changes finally intended to be submitted by Boeing? If we are as close as claimed why is there no detailed info available?
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Old 12th Dec 2019, 10:15
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Originally Posted by Less Hair View Post
Is there any draft document available about the actual changes finally intended to be submitted by Boeing? If we are as close as claimed why is there no detailed info available?
It is clear some changes have been made and accepted (in principle) and it is clear it is a secret.

There are four main changes to the B737 MAX flight control system software that have been developed to prevent future accidents like the ones that happened with the Lion Air and Ethiopian Air flights. They include the following:

1. Angle of Attack (AoA) comparison – an addition to MCAS that will now compare readings from both angle of attack sensors on the aircraft. If there is a difference of more than 5.5 degrees the speed trim system will be disabled. Also included in this change is something known as a “midvalue select” which uses data from both sensors together to create a third input that will help to filter out any AOA signal oscillatory failures or spurious sensor failures. This modification will prevent MCAS from commanding nose down trim when a single AoA sensor reports a false AoA as it happened in the two accident flights.

2. MCAS resynchronization – this change will account for manual electric trim inputs made by the pilot while MCAS is activating. It will track whatever input the pilot makes and return the pitch trim to that setting when MCAS retrims back to normal.

3. Stab trim command limit – is an addition that will limit the maximum nose down trim that the automatic flight control system can command to prevent the pitch trim from reaching an uncontrollable situation.

4. FCC monitors – software monitors have been added to the flight control computers that will cross check pitch trim commands against each other. If a difference is detected by these monitors the automatic trim functions are disabled. This protection helps prevent erroneous trim commands from a myriad of causes that could occur in the automatic flight control system.
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Old 12th Dec 2019, 12:44
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Any of you older folks typed on the 737, when did they remove the "roller coaster" technique from the FCOM?

I never saw it, but was that ever trained in the sim?
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Old 12th Dec 2019, 12:46
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turbidus,

No idea, but it was taught on the 707
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Old 12th Dec 2019, 12:52
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Originally Posted by turbidus View Post
Any of you older folks typed on the 737, when did they remove the "roller coaster" technique from the FCOM?

I never saw it, but was that ever trained in the sim?
In the day before it was removed from FCOM it seems the sim was a useful tool.

Now it is a box that is ticked - and admitted as not correct in some simulations in areas for many years.

But the box still gets ticked.
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Old 12th Dec 2019, 13:00
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Originally Posted by WHBM View Post
Not only that, this statement was made to the Securities & Exchange Commission. Now the SEC are no fools, and if they determine that Boeing has been peddling nonsense about service re-entry and resumption of sales revenue, both to investors and now to them, that will not go down well.
I would assume that the SEC is as zealous as the FAA😂

Edmund
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Old 12th Dec 2019, 13:40
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Assumptions all over, but... imho re-entry into service could be achieved by the following:
  1. ensure MCAS can only activate if both sensors agree;
  2. ensure the original cutout which pilots relied on for many years (column cutout) is instated for MCAS cutout
The above can be fixed by software for condition 1. and some change in circuits around the column cutout for condition 2

How these changes are made is likely to remain confidential until approved to ensure the impartiality and integrity of design changes.
Time will tell, think it won't be much longer as the earliest time it takes for these stages to complete is coming towards fruition soon.
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Old 12th Dec 2019, 14:08
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Originally Posted by Skyjob View Post
Assumptions all over, but... imho re-entry into service could be achieved by the following:
  1. ensure MCAS can only activate if both sensors agree;
  2. ensure the original cutout which pilots relied on for many years (column cutout) is instated for MCAS cutout
The above can be fixed by software for condition 1. and some change in circuits around the column cutout for condition 2

How these changes are made is likely to remain confidential until approved to ensure the impartiality and integrity of design changes.
Time will tell, think it won't be much longer as the earliest time it takes for these stages to complete is coming towards fruition soon.
With respect, fulfilling your condition 2 would obviate the stated purpose of MCAS which is to increase apparent stick force required to 'pull up' in certain parts of the flight envelope. If PF can pull back on the stick and cause MCAS to cease operation then the purpose will not be achieved.

If 2 is required then another solution to the flight instability (which is not instability) will be needed
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