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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 9th Oct 2019, 12:52
  #2981 (permalink)  
 
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David, #2980,
Being positive, the aircraft will be fixed.

Training is not a fix, and that which will be required will be consequential to the technical solution.

The level or mix of software / hardware revision depends what has to be fixed and the regulatory requirements for the changes.
There are indications (rumours) that some authorities are reticent to agree changes until the exact nature of the accident are know. This is significant if no particular component or software configuration has been identified as ‘failing’. No bent or stuck AoA vane (NB possible accident damage); no specific computational failure.

There was considerable speculative debate on the software issue in previous Tech Log discussions, concluding with convincing arguments (for me) as to the possibility of a ‘glitch’ which could cause a failure, but not subsequently identifiable. Software fixes for such glitches are well known, but might involve major change to computational system architecture and even require triplex integrity.
Any lesser solution could be seen as a ‘wet blanket’, i.e. the exact nature of the problem is unknown, but it cannot happen again because of … ‘fix’ xyz. This approach is a debatable certification technique, although previously used, but perhaps not for such a catastrophic outcome.

Hardware changes beyond the AoA vanes, probably involve the trim system and ability to manually trim in all conditions. Regulatory views on this and wider ranging human behaviour vary, and as with a ‘wet blanket’ solution depend on judgement vice a hard, quantifiable requirement. e.g. the pilots’ contribution to identifying and control of system failures.
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Old 9th Oct 2019, 13:29
  #2982 (permalink)  
 
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Originally Posted by The AvgasDinosaur
Learned Contributors,
I have read thousands of posts on dozens of threads. I am seeking clarification, please.
Does the team think that the apparently open ended delays in re-certifying the MAX is due to
A) The aircraft can't be fixed by software and I-Pad YET ?
B) The aircraft can't be fixed by software and simulator ?
C) The aircraft can't be fixed by software, hardware and I-Pad ?
D) The aircraft can be fixed by software, hardware and simulator ?
E) The aircraft can't be fixed !
Thank you for your time and patience.
Your comments and observations will be much appreciated.
Be lucky
David
The aircraft would be just fine if it did not need to comply a "feel" requirement that would almost never be experienced by all crews ever.

Just needed to tell all, and train them about it.

But that was not a Grandfather right even for a exclusion or exemption.
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Old 9th Oct 2019, 13:43
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The aircraft would be just fine if it did not [b=left]need[/b] to comply a "feel" requirement that would almost never be experienced by all crews ever.=left
To follow your argument to its natural conclusion, you appear to be advocating removal of the FAR 25/ CS 25 requirements for stick force gradient. The aircraft was clearly not fine before installation of MCAS or the FAA test pilots would simply have accepted it as presented. If inadequate stick force gradient in any part of the envelope - however likely the encounter - is OK for the MAX, does that make it OK for every aircraft?
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Old 9th Oct 2019, 14:14
  #2984 (permalink)  
 
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Originally Posted by safetypee
David, #2980,
Being positive, the aircraft will be fixed.

Training is not a fix, and that which will be required will be consequential to the technical solution.

The level or mix of software / hardware revision depends what has to be fixed and the regulatory requirements for the changes.
There are indications (rumours) that some authorities are reticent to agree changes until the exact nature of the accident are know. This is significant if no particular component or software configuration has been identified as ‘failing’. No bent or stuck AoA vane (NB possible accident damage); no specific computational failure.

There was considerable speculative debate on the software issue in previous Tech Log discussions, concluding with convincing arguments (for me) as to the possibility of a ‘glitch’ which could cause a failure, but not subsequently identifiable. Software fixes for such glitches are well known, but might involve major change to computational system architecture and even require triplex integrity.
Any lesser solution could be seen as a ‘wet blanket’, i.e. the exact nature of the problem is unknown, but it cannot happen again because of … ‘fix’ xyz. This approach is a debatable certification technique, although previously used, but perhaps not for such a catastrophic outcome.

Hardware changes beyond the AoA vanes, probably involve the trim system and ability to manually trim in all conditions. Regulatory views on this and wider ranging human behaviour vary, and as with a ‘wet blanket’ solution depend on judgement vice a hard, quantifiable requirement. e.g. the pilots’ contribution to identifying and control of system failures.

For avgas dinosaur -- and everyone else asking similar questions about Max's return to service -- safetypee's answer (2982) is as good and accurate an update as you will find in any public discourse.

Grizz
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Old 9th Oct 2019, 15:25
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Originally Posted by safetypee
David, #2980,
Being positive, the aircraft will be fixed.

Training is not a fix, and that which will be required will be consequential to the technical solution.

The level or mix of software / hardware revision depends what has to be fixed and the regulatory requirements for the changes.
There are indications (rumours) that some authorities are reticent to agree changes until the exact nature of the accident are know. This is significant if no particular component or software configuration has been identified as ‘failing’. No bent or stuck AoA vane (NB possible accident damage); no specific computational failure.

There was considerable speculative debate on the software issue in previous Tech Log discussions, concluding with convincing arguments (for me) as to the possibility of a ‘glitch’ which could cause a failure, but not subsequently identifiable. Software fixes for such glitches are well known, but might involve major change to computational system architecture and even require triplex integrity.
Any lesser solution could be seen as a ‘wet blanket’, i.e. the exact nature of the problem is unknown, but it cannot happen again because of … ‘fix’ xyz. This approach is a debatable certification technique, although previously used, but perhaps not for such a catastrophic outcome.

Hardware changes beyond the AoA vanes, probably involve the trim system and ability to manually trim in all conditions. Regulatory views on this and wider ranging human behaviour vary, and as with a ‘wet blanket’ solution depend on judgement vice a hard, quantifiable requirement. e.g. the pilots’ contribution to identifying and control of system failures.
As a worst case backup, Boeing is presumably working hard on a permanent fix for the issues identified above, even though that may require extensive aircraft rework.
In the nearer term though, to get the aircraft back into service, there will be need for an interim solution, including perhaps more extensive pre flight monitoring or other operational constraints. Such constrained operations are a normal response to aircraft deficiencies.
What is unclear is whether the regulators have any such plan or willingness to even consider something less than a fully definitive fix.
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Old 9th Oct 2019, 16:10
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Article Alleges Many Abuses Behind the Scenes at ET

Some people here believe that the problem is just the airplane, and some believe that the problem is poor airmanship/maintenance. But many of us (?most) believe that it is a combination of the factors that led to these hull losses. This is an eye opening article which alleges many abuses that go on inside ET, a carrier that many have suggested is a paradigm of a third world modern carrier:


https://hosted.ap.org/article/5ff095...ds-after-crash
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Old 9th Oct 2019, 16:11
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etudiant;
I just don't see how there can be an 'interim' solution and permanent solution. Either the problem is resolved or it isn't. Getting the aircraft back into service to my mind is not the priority (though no doubt it is for Boeing execs!).
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Old 9th Oct 2019, 16:13
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Originally Posted by etudiant
What is unclear is whether the regulators have any such plan or willingness to even consider something less than a fully definitive fix.
Given that this will to be the most picked over fix in aviation history, where the regulator will be under as much scrutiny as the manufacturer, both Boeing and the FAA would be very foolish to try anything on.

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Old 9th Oct 2019, 16:38
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Originally Posted by Speed of Sound
Given that this will to be the most picked over fix in aviation history, where the regulator will be under as much scrutiny as the manufacturer, both Boeing and the FAA would be very foolish to try anything on.
There will soon be a thousand stranded MAXes and Boeing's financial ability to act decisively is eroding with every additional MAX produced. I think there must be a near term return with restrictions, just to get the system working again.
That will buy time to do it right while the restrictions ensure continued pressure to deliver a fully serviceable aircraft.
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Old 9th Oct 2019, 17:00
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Originally Posted by Longtimer
IAre they viable on other aircraft?
No. That particular version of the Leap is 737 Max only and has many differences to the Leap powering the A320N, not least a much smaller fan and a different pylon.
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Old 9th Oct 2019, 18:48
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Originally Posted by etudiant
There will soon be a thousand stranded MAXes and Boeing's financial ability to act decisively is eroding with every additional MAX produced. I think there must be a near term return with restrictions, just to get the system working again.
That will buy time to do it right while the restrictions ensure continued pressure to deliver a fully serviceable aircraft.
Given the circumstances, I can't imagine world CAAs -- or pax -- accepting an interim or partial resolution. The airlines' liability insurance carriers probably wouldn't be enthusiastic, either.

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Old 10th Oct 2019, 00:56
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As on an Airbus?
Hmm . . . fair comment, but at the same time it doesn't go all floppy on the relevant axis.

gums' description of a solid stick I found very hard to imagine, but let's look at that extreme.

You pull on the rigid control and feel the resultant g force. After an hour or so on type even the slightest pressures would give anticipated responses. But imagine if the control surfaces became progressively easier to move compared to that known feel on your gloved hand. That gets really ugly.
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Old 10th Oct 2019, 05:13
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Another week went by. Nothing happend! What are they doing all day?
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Old 10th Oct 2019, 08:54
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Originally Posted by babemagnet
Another week went by. Nothing happend! What are they doing all day?
Makes you wonder doesn’t it? What was it last count, 700 test flights and still questions? No updated estimate on submitting changes to the FAA, more questions from agencies outside the US. Last Boeing official statement was flying by 4th quarter if I recall correctly. Not a chance.

The bean counting pin heads and their MBA enablers are getting a long overdue and well deserved lesson in the importance of professional engineering, skilled end user (flight crews) critical input and quality control. The constant push of enhancing every possible smidgeon of “share holder value” might very well cripple the very same shareholders they supposedly held so near and dear. At the end of the day (or months/years) this dumpster fire will be extinguished with a dollar value of damages virtually impossible to fathom. Billions upon billions are being vaporized. The industry duopoly exists for many reasons but that duopoly metric is probably going to shift heavily in one direction now. Not good for the industry, innovation and competitiveness but Boeing is holding a big bag of $%#@ and the stench will follow this circus for years. Overall this could end up, and might already be, the biggest disaster in aircraft manufacturing we’ll have ever seen in our lifetimes.

This is a five alarm fire and they’re still dispatching units. The blaze rages on.
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Old 10th Oct 2019, 13:07
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Update on return to service by Jon Ostrower: link
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Old 10th Oct 2019, 13:16
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Boeing is not out of the woods yet.
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Old 10th Oct 2019, 13:42
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When are the reports for the crashes (Lion and Ethiopian) due out?

What if the regulators allow the Max back into service with all of its modified software for MCAS but the reports reveal, at a later date, another slice of cheese that contributed to the accidents, alongside MCAS going belly down?
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Old 10th Oct 2019, 14:52
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Salute!

As several have opined very early, even a partilal FBW implementation would have solved the Max "control force versus AoA" problem. It would have been expensive to go full authority as in the 'bus and the fighter types we have had for 40 years. But considering the existing STS feature, I do not understand why they could not have done something sinilar abd not have the "bang - bang" stab movement at an obscene rate and length of application. Sheesh. How come they couldn't get a waiver of some sort.

@ Rivets.......As far as the feel and force goes, thousands of :bus drivers seem to have no problems with their lack of force feedback. Feedback on that stick and on the one I flew yeards ago was just a spring or piezo element that related force to commanded gee or roll rate. Besides gees, the visual feedback of the aircraft's performance/attitude was a biggie.

As with any spring, the force required to move the thing increases per unit of displacement. That's the 'bus. Our Viper was a fairly linear force until 34 or 35 pounds ( the 9 gee command) and the stick moved about an eigth of an inch, so it was a very stiff spring compared to the bus, but also very precise, As with the Luscombe and Champ I flew as a yute, precision required one to use forces more than large physical displacement unless performing acrobatics. Agreed? And as Rivets points out, getting used to a rigid stick took almost no time - I soloed dozens and it took them about 10 or 20 seconds, heh heh. Just watch the Thunderbirds to appreciate how only a few ounces of pressure provides exremely precise formation flying. Yet that same stick can command 9 gees and a few hudred degrees per second of roll rate.

Lastly, for Rivets, et al...... The FBW systems, as a rule, move the control surfaces to achieve the body rates and gees and they may only move a degree or they may move to full deflection depending on dynamic pressure ( the "gains")

Gums sends...
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Old 10th Oct 2019, 16:39
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Gums, I'm not a fan of FBW, but I concede that it has some advantages. If I learned to fly one, I might even like it. The problem here is that you can't do FBW in a half-assed fashion. One air data computer, or two...using one every other flight, isn't going to cut it. One AOA input at a time, not going to work, either. Boeing tried to sneak some FBW bits into a manual reversion airplane, with deadly results. We haven't even heard the beginnings of a discussion of FBW spoilers to assist with a delicate landing attitude, due to the lengthened nose strut...with one AOA input. No doubt, one COULD go whole hog on a FBW 737, but then it wouldn't be a 737. But I am seeing piecemeal fixes to a piecemealed FBW application...and I am not happy with it.

Salute!
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Old 10th Oct 2019, 17:48
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Interesting aspects emerging from the link (8 Oct) @#3004
Checklist discussions involve those listed below; the last three could (or should) involve new annunciations / alerting.
Unreliable airspeed
Unreliable altitude
Angle of Attack (AoA) disagree
Speed trim failure
Stabilizer out of trim
Runaway stabilizer trim

Unreliable airspeed and altitude are linked to the ADC, as is unreliable AoA which invokes all three together; thence current discussions on multiple alerting, distraction, surprise, workload.
Might these now be separated somehow. Also how might unreliable AoA be integrated with stick shake; with only two sensors a difference can be identified but not which is correct, implying that stickshake cannot be differentiated true or false (as today).

Speed trim failure - new ? How engineered.
Stab out of trim; very interesting, how determined.
Runaway stab trim; similarly challenging, with significant issues involving crew alerting, crew reaction (drill and switching - modified switches?), and an unambiguous memory items.

No MCAS ‘FAIL’ (inhibited) annunciation ?

There is also the need for both flight control computers to be available for dispatch (MMEL). This suggest use of dual computing paths involving the critical trim functions.
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