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Boeing 737 Max Recertification Testing - Finally.

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Boeing 737 Max Recertification Testing - Finally.

Old 18th Nov 2020, 15:46
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However it was Boeing who moved MDD's leadership into the own company. One should ask the board of that time what that was meant to be?
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Old 18th Nov 2020, 18:40
  #462 (permalink)  
 
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Frank Shrontz resigned from all corporate roles and the Boeing board after they passed over Alan Mulally and elected Phil Condit as his successor to the Boeing chairmanship.
The destruction of the Boeing Company then followed.
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Old 18th Nov 2020, 21:14
  #463 (permalink)  
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Phil Condit was a shining example of the "Peter Principle" in action. Any rational person would know that negotiating the details of a merger between two multi-billion dollar companies over a weekend in a hotel room was a bad idea - but not Condit. The guy was in way over his head, but didn't know it.
I still remember when I heard that he'd been forced to resign - I was driving into work early in the morning when they announced his resignation. I yelled "YES!" and punched the roof of my car with enough force to hurt my hand. Then the other shoe dropped - 'and will be replaced as CEO by Harry Stonecipher'.
OH !
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Old 18th Nov 2020, 22:03
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Can anyone explain the reason for the following requirement,
'......changing the horizontal stabilizer trim wire routing installations' ?
It was to do with the insulation on the wires chafing through and possibly allowing power to run to the trim motor, resulting in an uncontrollable runaway.

It will be interesting to see the approach taken by other authorities to the return of the MAX. particularly the European and Chinese ones.
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Old 18th Nov 2020, 22:29
  #465 (permalink)  
 
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run it like a business rather than a great engineering firm

https://nlpc.org/2010/03/10/northrop...oeing-scandal/
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Old 19th Nov 2020, 10:35
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Just read the book “Boeing versus Airbus” .A fascinating read into the boardroom battles at Boeing but the key sentence in the book, for me, is the statement after the Mac D merger is that engineers were considered a cost and not an asset.

That, I suggest, is what led eventually to the. Max debacle.
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Old 19th Nov 2020, 11:19
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Originally Posted by krismiler
It was to do with the insulation on the wires chafing through and possibly allowing power to run to the trim motor, resulting in an uncontrollable runaway..
The NPRM issued in June 2020 said (note the 4th design change, my bold);
To address the unsafe condition, the FAA proposes to require four design changes: (1) Installing updated flight control software (with new control laws) for the FCC operational program software (OPS), (2) installing updated MDS display processing computer (DPC) software to generate an AOA disagree alert,[[url=https://www.federalregister.gov/documents/2020/08/06/2020-17221/airworthiness-directives-the-boeing-company-airplanes#footnote-9-p47699]9] (3) revising certain AFM flightcrew operating procedures, and (4) changing the routing of horizontal stabilizer trim wires. The first design change is intended to prevent erroneous MCAS activation. The second design change alerts the pilots that the airplane's two AOA sensors are disagreeing by a certain amount indicating a potential AOA sensor failure. The third design change is intended to ensure that the flightcrew has the means to recognize and respond to erroneous stabilizer movement and the effects of a potential AOA sensor failure. The fourth design change is intended to restore compliance with the FAA's latest wire separation safety standards.
So I suspect that a need to comply with these "latest standards" drives this design change given the opportunity to do so while the other work is in progress, although it's perfectly true to say that it will, we hope, make chafing and runaway trim less possible. (ALARP at work?). However, I wonder why they used the word "restore"? Is it a weasel word used to suggest that the design did once comply (with an older standard?), when in fact it never did?

Last edited by old,not bold; 19th Nov 2020 at 11:30.
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Old 19th Nov 2020, 21:07
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It says further down in the document (the bottom of the center column of page 4 of the PDF) that the wiring does not meet a standard issued in 2007, and that: "Since design changes must comply with FAA regulations, the FAA proposes to require changes to the wiring installation to meet the required physical separation between the horizontal stabilizer trim arm wiring and the horizontal stabilizer trim control wiring."

I think the document is saying that after the accident the FAA decided that the entire stabilizer trim system had to meet the standards current at the time the MAX was certified. But it's not entirely clear to me.
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Old 19th Nov 2020, 22:30
  #469 (permalink)  
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This is where the Changed Product Rule can get really messy. CPR basically says that parts of the aircraft that are unchanged from the previous model don't need to meet the latest regulations (assume they met the previous regulations at the time of the previous cert). But reasonable people can disagree over what constitutes a change. No first hand knowledge, but I suspect Boeing took the position that they weren't messing with the wire routing of the stab trim system - hence it was unchanged and they didn't need to meet the 2007 rule change - and since the MAX got certified the FAA must have accepted that. Now, the FAA is taking the position that MCAS makes the stab trim a changed system, and so the entire system - including wire routing - needs to meet the latest regulations.
I got caught out by this when we did the 767-2C (KC-46). My position was that the FADEC software was changing, so we had to recertify the s/w to the latest rules - but that the hardware was unchanged and hence didn't need to step up (the major difference being that the FADEC HIRF/Lightning had originally been certified via a Special Condition - now there are regulations for HIRF/Lightning - the Lightning regulations are pretty much the same as the SC, but the HIRF requirements have changed significantly). The FAA came back and said 'No, the FADEC is a changed system, the entire system needs to meet the latest regulations'. This resulted in big stink because it would have meant Pratt needed to re-test the FADEC for HIRF/Lightning (which is a seven figure expense) - even a North East FAA "National Resource Specialist" got involved - he thought the Seattle FAA wasn't interpreting CPR correctly.
Eventually we certified to the latest regulations - by taking credit for all the extra shielding we were adding to meet the military requirements for HIRF/Lightning/EMP.
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Old 20th Nov 2020, 17:23
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Thanks very much tdracer for the explanation.

Though the actual prospects for any further meaningful action in the Congress during the lame-duck session are quite "iffy" at best, I have to wonder whether some added clarity for the workings of the changed product rule either, is part of the pending House bill or Senate bill or both, or would be added in further amendment in light of the actual Return to Service action from FAA. Or if such further clarity, by legislation, would be a good idea at all?

I'm guessing that it will be a topic taken up by one or more of the "further study" efforts eventually to be mandated by the legislation, or by the ongoing DoT Inspector General work.

(Despite occupying only an SLF/atty place here, I hope I can say that sometimes it's quite surprising how much first-hand knowledge posters - I mean the real aviation pro's - take the time to post on threads.)
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Old 20th Nov 2020, 21:36
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It's really not solely a "Changed Product Rule" question - it's a basic compliance finding issue. When a change to a system causes the regulatory evaluator to have to re-examine compliance with a regulation that sets requirements that are applied at the system level, such as rules requiring a system safety analysis, a compliance finding can't be made if some other existing, unchanged part of the design makes the system non-compliant with the system level rule. You can run into these issues even when the certification basis hasn't changed.

Last edited by Dave Therhino; 20th Nov 2020 at 21:48.
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Old 22nd Nov 2020, 12:33
  #472 (permalink)  
 
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"AOA DISAGREE alert not in original MAX design"

Quite extraordinary IMO:

FAA on page 26 of the Final Rule/AD: "The AOA DISAGREE alert is a standard design feature on the 737 NG fleet (600/700/800/900/900ER) and was intended to be standard for the 737 MAX, but it was instead erroneously linked by the manufacturer to an optional AOA indicator (which some refer to as a gauge). The optional AOA indicator is a round dial that provides graphic and numeric AOA position information on both PFDs. Because of this error, only airplanes with the (optional) AOA indicator had a functioning AOA DISAGREE alert. This was incorrectly implemented by the manufacturer during the display software development, and was not identified until after the 737 MAX entered into service."
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Old 22nd Nov 2020, 14:30
  #473 (permalink)  
 
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EASA Decision not to adopt FAA AD 2020-24-02

"… EASA also found that sufficient reason exists to require certain additional actions, deemed necessary to ensure safe operation of the affected aeroplanes, including pilot training."

"… EASA will issue a Proposed AD for public consultation, the Final AD for which will replace the requirements of FAA AD 24-02 for aeroplanes operated under EU regulations.

This suggests that the technical modifications have been accepted, but not all 'actions', nor training. What is an 'action' ?

https://ad.easa.europa.eu/blob/2020-...S-2020-24-02_2
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Old 22nd Nov 2020, 14:37
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Originally Posted by D Bru
Quite extraordinary IMO:

"The AOA DISAGREE alert is a standard design feature on the 737 NG fleet (600/700/800/900/900ER) and was intended to be standard for the 737 MAX, but it was instead erroneously linked by the manufacturer to an optional AOA indicator ."
It's been a while since I read the reports however as I recall - AOA disagree was apparent when the LionAir aircraft was on the runway at relatively low speed and very early in the flight of Ethiopian. The indication of course may be inhibited say when on the ground but it seems very reasonable to think that such an indication may have affected the outcomes.

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Old 22nd Nov 2020, 14:45
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Boeing seem to want the public to trust that newly certified 737 has all been sorted out even in the light of the organisational and communications difficulties between the FAA and Boeing that have been exposed.

https://www.fierceelectronics.com/el...-before-flying

“Because the FAA has not released data on how pilots can operate MAX without MCAS and autopilot, it makes the plane safety, in our view, very problematic.”
...
Specifically, the full FAA ungrounding order of 115 pages says tests have been conducted of MCAS and that MCAS passed the tests “but the FAA doesn’t say what the test were and what the results were,” Hudson said. “There’s no way outsiders like Travis can review whether the MCAS fix is going to work safely.”
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Old 22nd Nov 2020, 15:00
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D Bru, re AoA disagree.

As an instrument alert, Disagree identifies a discrepancy between displayed information, but unlike IAS / ALT there is no StBy instrument to resolve which of the two is correct. Thus the display should be removed - potential for hazardous misleading information - not knowing which one is correct; thus no display no need for an alert.

As a system alert for other unavailabilities as a consequence of AoA error, then each of those systems should inform the crew of the state of that system, with procedures as necessary for further action. Thus where systems have separate alerting and procedures, the AoA disagree is superfluous.

AoA Disagree might resolve, or add awareness to the state of other un-annunciated systems - not warranting separate alerting or procedure; if so the AoA alert is again superficial and distracting in a complex situation.

If AoA Disagree is shown, what is the published procedure.
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Old 22nd Nov 2020, 15:20
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jimjim1

Apparent, that is, only following FDR analysis.

AFAIK neither aircraft was equipped with the optional AoA indication or Disagree warning.
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Old 22nd Nov 2020, 16:02
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@jimjim & safetypee RE: AOA DISAGREE alert NG not MAX

Many thx.

My point is that if for years and years one has been flying and in particular training for non-normal situations on the NG, the subsequent "unexpected" absence of an AOA DISAGREE alert on the MAX could leave one with an important cue less than expected if things go AWOL, as they did, in the sense that "undesired MCAS activation due to a single AOA sensor failure that could lead to a flight crew to perform a non-normal procedure".

Reason why I found the FAA observations in the Final Rule/AD of this week on the "error" by "the manufacturer" not to install an AOA DISAGREE alert on every MAX quite pedestrian.

It is therefore good to read now (and already in fact since the August 2020 FAA NPRM release) that amongst the new requirement for the MAX, the flight control laws would be changed in so far that MCAS activation requires inputs from two AOA sensors in stead of one. The updated MDS software is also to implement an AOA DISAGREE alert function on all 737 MAX airplanes (as is the case on all NG). While the lack of an AOA DISAGREE alert is not an unsafe condition itself, the FAA now mandates this software update to restore compliance with 14 CFR 25.1301 and because the flight crew procedures mandated by this AD now rely on this alert to guide flight crew action. As a result, differences between the two AOA sensors greater than a certain threshold would cause an AOA DISAGREE alert on the PFDs.

Last edited by D Bru; 22nd Nov 2020 at 16:21.
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Old 22nd Nov 2020, 17:51
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@SafetyPee: Exactly, and the Disagree "alert" is hardly conspicuous enough to even be noticed. In light of all that was going on in the accident flight decks, I'd hardly expect the pilots to make a logical connection and appropriately react.

Furthermore, the optional AoA indications have no operational procedures, normal or abnormal, related to them. At best they are advisory.
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Old 22nd Nov 2020, 22:30
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jimjim1 & linked article from fierceelectronics

The litigation referenced in that article is the FOIA (Freedom of Information Act) lawsuit which has cropped up here in a number of previous posts....the Nov. 18 court filing by FAA seeks to gain court approval for its withholding of Boeing documents that the FlyersRights group has been trying to wrestle out of FAA's confidentiality clutches.

FOIA litigation is notoriously slow-moving. Nevertheless, among the best arguments FlyersRights presented was that the public interest demanded that the FAA disclose all the relevant documents to the panel of experts FR had assembled BEFORE making a decision on ungrounding the aircraft. How this weighs into an evidently pending decision about further litigation challenges, we'll have to wait and see. (As just SLF, I only recognize that the most insistent and most strident critics of the 737 MAX, and perhaps also critics of less intensity, may be convinced the airframe has longitudinal stability problems without MCAS, despite assurances to the contrary by Boeing and others.....how can the public figure out who is correct?)

Will be worth watching to see if either the House or Senate bills which revisit FAA processes for certification (and would implement a range of other steps) will try (by amendment) to tackle exceptions for maintaining confidentiality of information submitted to FAA. There unquestionably are strong arguments against doing that but at some point, is the privilege of confidentiality being maintained lost by sufficiently egregious conduct?
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