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DWG

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A follow-on problem must be that even if the faulty IRS is shut down, accumulated positional and attitude/directional errors will then need to be corrected.
That's a fairly normal part of having a multiply redundant system. Normally you'd use a rolling* average of all the values, so as soon as you switch one system out the average should start to converge on the value from the still operating system(s).

*i.e averaged over a set period so a single spurious value doesn't cause a sharp deviation.
 

steelpillow

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A follow-on problem must be that even if the faulty IRS is shut down, accumulated positional and attitude/directional errors will then need to be corrected.
That's a fairly normal part of having a multiply redundant system. Normally you'd use a rolling* average of all the values, so as soon as you switch one system out the average should start to converge on the value from the still operating system(s).

*i.e averaged over a set period so a single spurious value doesn't cause a sharp deviation.
Except, a ring laser gyro gives you the current delta from its baseline. Positional error depends on the accumulated sum of past deltas in direction, weighted according to ground speed and wind direction at the time. For example if you discover and fix a dodgy compass then you can now set an accurate heading, but you still have no idea of where you had got to up to that point or where that puts you in relation to your destination. Same goes for altitude error. To correct for those, either all past data points from the good IRS must have been stored, or current data from conventional GPS, compass, altimeter, turn-and-bank, etc. must be substituted. If both are available, pilots should be given the choice which to use - and the QR guide should pick up on that. This one presumably didn't.
 
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DWG

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Except, a ring laser gyro gives you the current delta from its baseline.
Good point, the rolling average doesn't work in that case. OTOH in a contemporary aircraft, at least in cruise, GPS should be the default instrument WRT location and altitude, as the one with lowest error, with radalt and baro altitude as further back-up options for altitude.
 

steelpillow

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But Mr Barnett is not the only Boeing employee to have raised concerns about Boeing's manufacturing processes. Earlier this year, for example, it emerged that following the Ethiopian Airlines 737 Max crash in March, four current or former employees contacted an FAA hotline to report potential issues.
Mr Barnett believes that the concerns he has highlighted reflect a corporate culture that is "all about speed, cost-cutting and bean count (jobs sold)". He claims managers are "not concerned about safety, just meeting schedule".
That's a view which has support from another former engineer, Adam Dickson, who was involved with the development of the 737 Max at Boeing's Renton factory in Washington state.
...
Boeing recently commissioned an independent review of its safety processes, which it says "found rigorous enforcement of, and compliance with, both the FAA's aircraft certification standards and Boeing's aircraft design and engineering requirements." It said that the review had "established that the design and development of the [737] Max was done in line with the procedures and processes that have consistently produced safe airplanes."
Nevertheless, as a result of that review, in late September the company announced a number of changes to its safety structures. They include the creation of a new "product and services safety organization".
Air safety is not like politics or management, you need more than whitewash to get rid of a bad smell.
 

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Arjen

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Please, please start your own topic about Airbus. You are mistaking my exasperation for irony.
 
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DWG

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O'Leary: “We have now reduced our expectation of 30 Max aircraft being delivered to us in advance of peak summer 2020 down to 20 aircraft and there is a real risk of none.”

 

Arjen

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[snip] pointed the irresponsibles at 100y old Boeing for dairing to create such an evil system.
I think that putting things back into perspective to depassionate a debate around the death of several hundred of trusty passengers was not a commodity.
So what is your perspective? An honest mistake by 100 year old Boeing? Gross exaggeration by the knowledgable world? Remember that all 737 MAX aircraft are grounded, with the FAA reconsidering its certification process - precisely because of two deadly crashes. Insiders have already come forward with tales of Boeing management fixated on profit to the detriment of safety.
 
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Foo Fighter

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A long time ago when running a forum myself, I came to the conclusion that a simple policy should be entertained and it is a very simple policy. "Do not feed Trolls or folk who create argument from nothing, they are probably looking for reaction and attention". Relevant?
 

steelpillow

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A long time ago when running a forum myself, I came to the conclusion that a simple policy should be entertained and it is a very simple policy. "Do not feed Trolls or folk who create argument from nothing, they are probably looking for reaction and attention". Relevant?
I was just about to say the same.
However I am not bothered by this particular one any more. I went to their user page and clicked the [ignore] button, so none of it ever gets displayed to me any more. I only know it's still happening because you guys have little red boxes in your posts where you quoted him. I can recommend it.
 

overscan (PaulMM)

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  • No Trolling.
    This means no posts aimed at stirring controversy with other users, inciting racial or religious arguments or pointless speculations.
    [*]Don't Feed Trolls. If you see a troll post (as above) report it to the moderators. Don't start posting replies, it only encourages them.
It's in the rules already.

I deleted some posts.

I'm also fed up with the constant sniping about Airbus from TomcatVIP in Boeing topics, not sure if he invested his pension fund in Boeing shares or something but it's just trolling 'whataboutery". If there's an interesting story to tell, create a new topic about Airbus problems. Further action may occur if this goes on.

I'll delete these last few posts in a few days and we can go back to discussing the Boeing 737 Max.
 
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TomcatViP

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Making compareason with Airbus products is relevant:
- industry wise, it's the only other peer in term of size, product range and market competition
- in term of FCS, Airbus did priviligise a more drastic approach than Boeing starting with its A320 product.

It should be then perfectly valid to pick the difference, even in media approach regarding the MCAS, placcarded like it was. This is not Apple and Bannana.

I do regret that being impolite and harassing other members (like pairing my comments with a troll insult each time I mention Airbus or Dassault) would seemingly be legitimated by such action, Overscan. But your in charge and this forum is private. At the end the freedom of opinion remains a right only to be exercised. So please don't take it personally.
 

overscan (PaulMM)

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Take this to private messages if you want to discuss further. I hope you can understand that posting "what about the other guys" every time someone posts about Boeing MCAS issues is deeply annoying. I get it, Airbus has had problems with FCS at times as well. Please accept that everyone know this now.

In fact, the entire MCAS issue probably deserves its own topic separate from the 737 Max topic.
 

Arjen

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Interview with EASA's director Patrick Ky
When you testified at the European Parliament, you said there are parts of the return-to-service exercise where a lot of work remains to be done. Has that part become a lot smaller?
Yes, there is light at the end of the tunnel. We are on a good path that enables us to really start contemplating the end of this very sad story. There are still quite a few open items, but it has now come to a manageable number. There are items around workload during the takeoff phase.
One specific item is angle-of-attack integrity if there is a single sensor failure. How can we make sure it does not have any major impact on safety, and what are the best ways to deal with it? We now have quite a good idea about what the solutions can be.
On the flight control systems, Boeing did a very good job in reviewing their designs and has come back with a much more rational design. You now have independent processes between executing a function and monitoring it, particularly on trim runaway. We wanted to have two independent processes that are looking at dealing with it and monitoring what is happening. The software changes that were made were a good way to deal with the problem.
[...]
After all we have seen over the last year, are you concerned about Boeing’s culture?
No, honestly not. I meet a lot of Boeing people these days. EASA was created 15 years ago, so we have had 15 years of relationships with Boeing. This is a great company, and Boeing aircraft are great aircraft. In this particular instance, a number of mistakes were made, but the overall culture in Boeing is a great culture. It is a company for which safety is the highest priority. They always say that, and I think it is actually the truth. I have no real issue with the intrinsic Boeing culture. There needs to be some action for a better safety governance, though.
What then went wrong?
If only I knew.
More at the link. Login required.
 

Foo Fighter

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Not sure where he is talking from but from the statements of whistle blowers et al, I do not believe a single word and I doubt I am alone in this. Too many projects with big shoes out there in Boeing land. How much do they need to lose before applying for chapter 11 protection?
 

steelpillow

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Yes, the bad smell is still there. "What then went wrong?" "If only I knew" hardly supports the kind of confidence and certainty being expressed in the previous replies. Why the two faces, Mr. Ky?
 

Foo Fighter

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The one thing common in history is that when big companies are in trouble, the louder and bigger the denial, the closer they are to shutting the doors.
 

steelpillow

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A good summary by the BBC of the Ethiopian Airlines pilots' dilemma. Basically, if they had reduced speed early enough they could have saved the situation. But they had a stick-shaker warning of impending stall, the knowledge that pitch/power coupling would push the nose even more sharply down, and the fact that the advisory procedure issued following the LionAir Crash had just failed them. They were "caught between a rock and a hard place".
Chief among the experienced pilots who still throw blame is a Republican politician. Huh!
I might add that the deactivation of MCAS when the flaps are down could not possibly have been in the flight manual, because MCAS was not mentioned at all. Does anybody know what, if anything, the LionAir advisory said about it?
 
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Fluff

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'We now have quite a good idea about what the solutions can be. '

I'm pretty sure the aviation world had a pretty good idea before you fitted the lowest cost option, which failed with fatal consequences.

Would love to see what options were proposed at the design stage, and how/why they picked this option.
The one thing common in history is that when big companies are in trouble, the louder and bigger the denial, the closer they are to shutting the doors.
Its not going to kill them, but a heart transplant and a frontal lobotomy may be called for.
 

Fluff

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This is only a UK reference, but remember when BSE was in the cows - mad cow disease, and the health minister fed his kids a burger, on TV.

Maybe the boeing board will put their kids on a plane, and fly them round.....
 

DWG

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This is only a UK reference, but remember when BSE was in the cows - mad cow disease, and the health minister fed his kids a burger, on TV.

Maybe the boeing board will put their kids on a plane, and fly them round.....
The article on Ryanair I linked the other day says United, American and Southwest place to have hundreds of demo flights before return to service and to put senior managers aboard.
 

DWG

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A good summary by the BBC of the Ethiopian Airlines pilots' dilemma. Basically, if they had reduced speed early enough they could have saved the situation. But they had a stick-shaker warning of impending stall
It's an interesting article, basically they were in an artificially-induced 'coffin-corner' - the part of any aircraft's flight envelope where the difference between flying too slow to be safe, and too fast to be safe, is only a handful of knots.

ETA: Potentially relevant to this, I just had a very quick glance at the Indonesian accident report and it mentions that in the previous incident aboard the Lion Air aircraft (i.e. the non-fatal one that preceded the crash), the max speed and min speed indications on the captain's airspeed indicator, the barber-pole, merged, meaning he had no indication of a safe airspeed. It appears he was able to use the co-pilot's ASI, but that's going to decrease any pilot's confidence in his instruments. It'll be interesting to hear whether that was also true on the Ethiopian aircraft.
 
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Foo Fighter

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I would not bet against it.
 

Fluff

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This is only a UK reference, but remember when BSE was in the cows - mad cow disease, and the health minister fed his kids a burger, on TV.

Maybe the boeing board will put their kids on a plane, and fly them round.....
The article on Ryanair I linked the other day says United, American and Southwest place to have hundreds of demo flights before return to service and to put senior managers aboard.
Er wow - there's one email I would forget to open.
 

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This pitch/power coupling (velocity in fact) does exist for any aircraft that has... wings. I don't see why it has to be a key point in this long otherwise remarkable BBC report.

I would rather be more afraid hearing someone qualifying as an expert telling that pilots are terrified to move the throttle.
 
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DWG

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This pitch/power coupling (velocity in fact) does exist for any aircraft that has... wings. I don't see why it has to be a key point in this long otherwise remarkable BBC report.
MCAS was giving continuous nose-down inputs, pitch/power coupling (which is considerably different from velocity alone) can give a nose-up input. It's difficult to understand your attempt to deny it any significance. Lift is also a characteristic of any aircraft with wings, are we now to deny that lift is significant to flight?
 

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What does denial have to do with physics? I don't understand what's your meaning. If so (I think), understand that MCAS has nothing to do with speed but With swept wing behavior regarding AoA.

Classic on straight wing and Airfoil theory here:


Wiki has it also on a more compact read:

 

DWG

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What does denial have to do with physics?
What indeed. All your links do is confirm the point the BBC article made.

The aircraft was subject to a continuous (or at least rapidly repeating) uncommanded nose-down input from MCAS. To counter that the aircraft needed a nose-up input. The pilots could generate one by increasing thrust. QED.
 

DWG

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Interesting comment from the site below (highlight mine):

"The preliminary report into the Ethiopian accident, appears to show that after the crew had switched off the Stab trim cut-out switches they were unable to operate the trim wheel manually and subsequently switched them back on again to get electric trim which unfortunately also allowed MCAS to reactivate. The reason for why the trim wheel could not be operated manually is still unknown (hopefully only until the final report is issued) but it is probable that the control forces on the stab, and therefore the wheel, were too high due to the very high IAS at the time. It is now known that the FAA has doubts about the ability of some pilots (eg women) to have the level of strength required to operate the manual trim wheel at high IAS. This is applicable for all series of 737, not just the MAX. "

This point is repeated further down in the quoted EASA findings:
"- Too high forces needed to move the manual trim wheel in case of a stabiliser runaway "

We have to remember this situation kicked off at very low altitude, with the stick-shaker sounding, and the aircraft at take-off thrust. That's a lot of drivers for maintaining or increasing thrust, not reducing it. Unfortunately the effect was to increase control forces beyond what the pilots could apply, while reducing thrust would add a further nose down force to the one they were trying to prevent. They were stuck between the proverbial rock and a hard place.

(The page also gives the background for the DoJ criminal investigation - interesting, I hadn't considered fraud as a possible interpretation of the certification process. It's disturbing Boeing's former Chief Technical Pilot Mark Forkner - he of the text messages saying they've inadvertently misled the certification authorities - has pled the fifth)


I've also seen one article (below) that suggests the MCAS nose-down input is back-driven into the pilot's control-columns. I haven't managed to confirm that from anywhere else, but this is entirely possible, it's something a lot of manufacturers do to create synthetic feel, but one of the effects here would be to increase the force needed by the pilots to override the MCAS input, creating a further driver for them to use automatic rather than manual trim. (I do think this article has some problems, but mostly around the author's lack of awareness of how aerospace software work is done. However it's possible this should refer to the trim wheel, not the control column).

"When the flight computer trims the airplane to descend, because the MCAS system thinks it’s about to stall, a set of motors and jacks push the pilot’s control columns forward. It turns out that the Elevator Feel Computer can put a lot of force into that column—indeed, so much force that a human pilot can quickly become exhausted trying to pull the column back "


 

Arjen

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Back in the day when Hoskins was in automotive he had this bright idea.
- "You know how the competition is into this thing called power-assisted steering? And that you totally lose touch with the road?¨
- "Out with it, Hoskins. What have you thought of NOW?¨
- "Power-resisted steering, man! Instantly enhanced experience of the road AND a workout at the wheel if you dial up the power! Win-win!¨
- "That won't fly, Hoskins. We dreamed up powered steering to enable the lesser-muscled specimens of our species to drive cars without breaking a sweat."
"Won't fly, won't fly" Hoskins thought morosely as his eyes wandered over the industrial estate. Then his eyes lit up. Maybe those nice people in the flying business next door would listen to him?
 
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Foo Fighter

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The problem I have with whole situation comes in a two part question:-

1. Can we do this?
2. Does this mean we SHOULD do this?

I know hindsight is 20:20 but when the bean counters/management have precedence over engineers the hand basket becomes over employed.
 

DWG

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The problem I have with whole situation comes in a two part question:-
1. Can we do this?
2. Does this mean we SHOULD do this?
I don't actually have a particular problem with the concept of MCAS, it's no different to a lot of things that other FBW systems do. It's the implementation I have a problem with. And that there wasn't harder pushback from Boeing's own technical people, engineers and pilots both.
 

Foo Fighter

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My point is about the whole decision making process rather than the software systems alone. The failings with manuals etc merely exacerbated the problem. As has been mentioned before, the whole thing equaled a major change of the aircraft rather than a minor change that they tried to get away with and this led to many death's and much grief. There was NO need for it to happen. I only hope something good comes from this situation.
 

DWG

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A major change that didn't bother the thousand of aircrew daily flying this monster :rolleyes:
Did you seriously think this was an appropriate comment? I think we can count the Lion Air and Ethiopian crews as pretty terminally bothered.
 

Arjen

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Depressing reading.

Information overload of the crew, First Officer with documented (in 2016)
difficulties to control aircraft during manual flight
[...]
[First Officer's] application exercise for stall recovery is difficult due to wrong concept of the basic principle for stall recovery in high or low level” during a 2017 observation
Recurring maintenance issues/errors, exacerbating
absence of an illuminated AOA DISAGREE alert, due to a misconfiguration in the MAX’s software that Boeing discovered in 2017 but did not plan to fix until 2020
[...]
“The AOA DISAGREE alert was not correctly enabled during Boeing 737-8 (MAX) development,” the NTSC says. “As a result, it did not appear during flight with the miscalibrated AOA sensor, could not be documented by the flight crew and was therefore not available to help maintenance.”
[...]
The runaway stabilizer checklist calls for using the cutout switches if other actions, including electric trim inputs, do not stop the runaway condition. On both JT610 and the March 10, 2019, crash of Ethiopian Airlines Flight 302, another 737-8, pilots used electric trim to counter the MCAS. This interrupted the nose-down stabilizer movements, but faulty AOA data triggered the MCAS repeatedly.
“[Erroneous] MCAS activation does not look like a typical stabilizer runaway, which is continuous uncommanded (runaway) movement of the stabilizer,” the NTSC report says. “During the accident flight, the stabilizer movement was not continuous; the MCAS commands were bounded by the MCAS authority (up to 2.5 deg); the pilots were able to counter the nose-down movement using opposing manual electric trim inputs. . . . After the pilots released the manual electric input and MCAS was reset, there was not another MCAS command for 5 sec.”
There is no evidence of the JT610 crew referring to the runaway-stabilizer checklist or toggling center pedestal-mounted cut-out switches that would have stopped the automatic stabilizer movements. The 737 MAX flight crew operations manual did not contain any information on the MCAS. Boeing determined during the MAX’s development that the information was superfluous based on U.S. Federal Aviation Regulation Part 25.1585 (b), which says, “Information or procedures not directly related to airworthiness or not under the control of the crew must not be included, nor must any procedure that is accepted as basic airmanship.”
The FAA accepted Boeing’s logic, the NTSC report says, adding that the rationale behind the decision “was not formally documented in meeting minutes.”
Problems with an earlier flight of the crashed aircraft, contrasted with what happened on its final flight
“The absence of [JT610’s] flight crew discussion of the previous problem suggests the flight crew might not be aware of aircraft problems that might reappear during their flight,” the report says. “This was different compared to the flight crew of the [previous day’s] flight, who had awareness of the aircraft condition after discussion with the engineer about the aircraft problem and the rectification prior to the flight, which may have helped the flight crew to immediately identify the problem correctly. Being unaware of multiple problems that occurred on the previous flight, including the stickshaker activation and uncommanded [nose-down] trim led to the inability of the flight crew to predict and be prepared to mitigate the events that might occur.”
In reaction:
Lion Air has implemented a series of changes based on the NTSC recommendations. It updated a training syllabus to “enhance [the] flight crew decision-making concept during [an] emergency or abnormal situation,” issued instructions to improve its pilot control-handover procedure and recently introduced a “new training standard and pilot performance review program.”
More at the link.

 
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