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sgrow787
Posts: 222
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 6:33 am

xmp125a wrote:
1) I seriously doubt the tasks you described regarding MCAS are outlier among all other tasks FCC has to do. It has to monitor the flight anyway, so MCAS 2.0 could be only the last straw that broke the camel's back, and not the dominant CPU hogger, IF the problem appeared first with MCAS 2.0.


I seriously doubt there were other significant changes to the NG FCC code. Boeing had a business case sold to the airlines of taking a 737 NG, adding fuel efficient engines to it, and letting it fly with no additional training. They would not have touched the FCC beyond what was absolutely necessary. In any case, yes the MCAS was the straw that broke everything.
Just one sensor,
Oh just one se-en-sor,
Just one sensor,
Ooh ooh oo-ooh
Oo-oo-ooh.
 
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SANFan
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 6:33 am

My first post on the MAX grounding threads but I have a question.

I see that as of today (June30/July 1, depending on your time zone) AS still shows their inaugural MAX9 flights scheduled for August 27 (2019)! The plane is shown to fly SEA-SAN-SEA-LAX-SEA on that day. Here's a link to the AS source: https://www.alaskaair.com/schedule/submit

Will that be happening? That's now less than 2 months away and AS seems to be sticking with it... Appreciate your input.

bb
 
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seahawk
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 7:19 am

Revelation wrote:
Seems hypocritical to me to push back on my reaction, yet ignore jabs like "737MAX, designed by third world engineers".

Also seems hypocritical to me for people here who railed against criticism of "third world pilots" (that was not actually made!) to now be silent while the ability of "third world engineers" to code to Boeing's specifications is being openly criticized.

I guess their dog ears can only hear whistles tuned to certain frequencies.


There is a huge difference between the role of the end user and the role of a subcontractor. But in the end it does not matter where the subcontractor is based, as the integration of his product is the job of Boeing and they have to verify and certify the quality of the product delivered.

But in the end it comes down to the fact that the end user can not be required to fix faults of the product, while Boeing is required to fix faults in the work of a subcontractor.

All in all the whole story is way overblown. The 737 is and was a perfectly save plane and with a little training, an up-date flight manual, extra warning lights in the cockpit and an extra switch to turn off MCAS, it would be perfectly fine even with MCAS 1.0.

The problem is that Boeing wants to avoid any difference or need for extra training compared to the NG.
 
FluidFlow
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 8:15 am

xmp125a wrote:
FluidFlow wrote:
Money is not everything for top-talent. I do not know how generous Boeing is in terms of social benefits. I know of Top Employers that give up to 6 months of parental payed leave and 8-10 weeks payed holiday aswell as massive pension funds. Thats what the best talent looks for and I hope Boeing can offer this. Otherwise the best ones will rather go to other companies.


Does not change my argument. Boeing was a hugely profitable company with reputation to boot. Whether compensation or perks, they could offer anything to the top talent. And on top of that, they have insane economies of scale - how many MAX orders they had? 1700? Software that runs all of these has to be done only once, but done right.

All indications point towards them willingly letting the expertise to rot and be lost. Inexcusable.



I am not arguing against you, you are right about Boeings failure to secure talent. They could if they want but the decision was not to.

That has nothing to do tho with the fact that a really bad education system paired with stupid immigration laws leads to loss of talent in the US as well as in the EU. One of them factors has to be good but if both are against corporations because of populistic policies the jobs will go to the talent instead of the talents to the job.
 
B777LRF
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 8:23 am

FluidFlow wrote:
Money is not everything for top-talent. I do not know how generous Boeing is in terms of social benefits. I know of Top Employers that give up to 6 months of parental payed leave and 8-10 weeks payed holiday aswell as massive pension funds. Thats what the best talent looks for and I hope Boeing can offer this. Otherwise the best ones will rather go to other companies.


If that was true, all the worlds top-talent in the world of programming would all be living in Scandinavia - where 6/12 months of paid parental leave and 6 weeks of paid vacation is something every single wage earner has a right to.

Here's a hint: They're not.
Signature. You just read one.
 
FluidFlow
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 8:45 am

B777LRF wrote:
FluidFlow wrote:
Money is not everything for top-talent. I do not know how generous Boeing is in terms of social benefits. I know of Top Employers that give up to 6 months of parental payed leave and 8-10 weeks payed holiday aswell as massive pension funds. Thats what the best talent looks for and I hope Boeing can offer this. Otherwise the best ones will rather go to other companies.


If that was true, all the worlds top-talent in the world of programming would all be living in Scandinavia - where 6/12 months of paid parental leave and 6 weeks of paid vacation is something every single wage earner has a right to.

Here's a hint: They're not.


They would be if the jobs be there too. Dont forget, it needs jobs and benefits. The point is, it needs business friendly and employee friendly laws and opportunities to create an environment to recruit and hold talent. And it is actually interesting how much new tech comes from scandinavia despite their relative small population (eg. EA DICE and spotify)
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 9:06 am

LDRA wrote:
There is nothing wrong with using single sensor, STS also relies on single air speed signal. The key is to limit control authority so that elevator still can overpower stab in fault condition

Then explain why Boeing now compare two AoA sensors.
 
XRAYretired
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 10:00 am

sgrow787 wrote:
So if adding MCAS fix caused the overload of FCC computer(s), and MCAS is part of STS, can we say that STS is not a separate LRU but has been merged into FCC? But I think it was Captain Carey who, in the recent congressional hearing, stated that MCAS was a federated system. Also, do we know if the FCCs are talking to each other and if one goes bad the other one takes over (with or without pilot input)?

I scribbled on the back of a paper bill I got last week when the recent "data flow" flaw was leaked, that the "Max is dead". I wrote that because I was thinking surely a processor error must have redundancy (ie another identical processor running in parallel in real time) for a safety critical system like MCAS. And if the STS system didn't have that redundancy, then it would be a hardware/systems fix in addition to the software development to create that redundancy. But if it's all-inclusive in the FCC(s) all along, then surely they already have the redundancy designed in, so no additional hardware/systems development needed. I quoted "data flow" because to me it seems a resource allocation issue.. the processor (and it's associated circuitry) being the resource that isn't fast enough.

Regardless though, SHTFF for Boeing to reallocate time slices, and/or move the MCAS code to some other subsystem that isn't as resource intensive.

On the outsourcing, coming from a contractor software engineer who has not once, in her 15 yrs in aerospace, worked on a project that didn't include a team of foreign engineers, it is a problem if there is no local expertise to oversee the foreign work. There is a lack of investment. Typically the work I see is good for a one time use - ie, it does the job at the time the job is needed, but reuse down the road is next to impossible due to poor or zero documentation. And sadly, aerospace companies are sending the FAA these large volumes of test data for certification that is poorly documented that they can't possibly perform the certification if they had a 100 years to do it. So the FAA allocates the work to the ODAs and the entire aerospace industry suffers. Safety is on the back burner.


Thanks for trying to pull this thread back on topic.

Firstly, as far as can see, STS functionality has always been hosted by the FCCs and MCAS functionality certainly has since its inception.

From the data available, I summarise. There are two FCCs on the A/C. each FCC has two processors. It may be that the two processors are dis-similar hardware, the two software loads are stated to be dis-similar software implemented by separate teams to meet the same requirements. Each FCC acts independently. The system functionality each distributed between the two processors with probably some functionality duplicated. Some critical inputs and functions are cross checked between the two processors especially for auto control functions like AP and similarly cross checked with the other FCC doing the same job. Either FCC can trip out the auto functions if a non conformance is detected (within bounds of course). As far as I can tell, the FCC in control is selected at A/C power up and cannot then be swapped for the other during the flight leg, The only thing you swap is the Pilot In Control if necessary.

STS, MACH Trim and MCAS all appear to fall into what I will call the non-critical functions bracket. They are hosted within one of the two processors only (in each FCC). There is no cross check of inputs or outputs with the other processor in the channel or the other FCC (at MCAS V1.0, V2.0 will have an input cross check of two sensors). So, no redundancy at all on a current flight leg.
https://www.satcom.guru/2018/11/737-fcc ... mmand.html

As regards software out-sourcing. Since we don't actually know the task split between Boeing, Collins and Honeywell or even if Boeing actually do any of the FCC software implementation, or if Collins or Honeywell outsourced any software implementation or, if they did, where, and since the problem lies in the Boeing System Design and Safety Analyses anyway, the whole question is, at this time, totally irrelevant to the subject. It was a successful deflection though, judging by the last few pages of this thread.

Ray
 
XRAYretired
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 11:26 am

sgrow787 wrote:
xmp125a wrote:
1) I seriously doubt the tasks you described regarding MCAS are outlier among all other tasks FCC has to do. It has to monitor the flight anyway, so MCAS 2.0 could be only the last straw that broke the camel's back, and not the dominant CPU hogger, IF the problem appeared first with MCAS 2.0.


I seriously doubt there were other significant changes to the NG FCC code. Boeing had a business case sold to the airlines of taking a 737 NG, adding fuel efficient engines to it, and letting it fly with no additional training. They would not have touched the FCC beyond what was absolutely necessary. In any case, yes the MCAS was the straw that broke everything.


There is large amount of functionality added for MAX, start with auto/FBW Spoilers and much more, including MCAS tiny in comparison no matter what Boeing would have had everyone believe. In the link this is referred to as P10.0 software.
www.b737.org.uk/glareshield.htm#fcc

If we assume the original NG software hit EIS with a modicum of spare capacity (and there has been no significant hardware upgrade since), as would have been the aim, by the time we get to P9.0, this would have been eroded by new functionality and mods quite significantly, then we add MAX 8 with further significant erosion, then it would appear we add specifics for MAX 9 (P11.0), then a major mod to P11.1, then addition of specific for MAX 7 and -8200 (P12.0), and now we have proposed P12.1 (to include MACS V2.0) It would not surprise me at all if the load is running up against the buffers (no pun intended) and a lot of optimisation already done.

I think they are going to have to go for hardware mod pretty soon even if they get P12.1 in order and certified.

If I were to guess, I would say that the worst case testing may well have been performed previously may be at P10.0, P11.0 and/or P11.1 and got through.

I would suspect JT610 was probably around P10.0 or P11.0 software and ET302 P10.0, P11.0 or possibly P11.1.

Ray
 
FluidFlow
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 11:42 am

XRAYretired wrote:
sgrow787 wrote:
xmp125a wrote:
1) I seriously doubt the tasks you described regarding MCAS are outlier among all other tasks FCC has to do. It has to monitor the flight anyway, so MCAS 2.0 could be only the last straw that broke the camel's back, and not the dominant CPU hogger, IF the problem appeared first with MCAS 2.0.


I seriously doubt there were other significant changes to the NG FCC code. Boeing had a business case sold to the airlines of taking a 737 NG, adding fuel efficient engines to it, and letting it fly with no additional training. They would not have touched the FCC beyond what was absolutely necessary. In any case, yes the MCAS was the straw that broke everything.


There is large amount of functionality added for MAX, start with auto/FBW Spoilers and much more, including MCAS tiny in comparison no matter what Boeing would have had everyone believe. In the link this is referred to as P10.0 software.
http://www.b737.org.uk/glareshield.htm#fcc

If we assume the original NG software hit EIS with a modicum of spare capacity (and there has been no significant hardware upgrade since), as would have been the aim, by the time we get to P9.0, this would have been eroded by new functionality and mods quite significantly, then we add MAX 8 with further significant erosion, then it would appear we add specifics for MAX 9 (P11.0), then a major mod to P11.1, then addition of specific for MAX 7 and -8200 (P12.0), and now we have proposed P12.1 (to include MACS V2.0) It would not surprise me at all if the load is running up against the buffers (no pun intended) and a lot of optimisation already done.

I think they are going to have to go for hardware mod pretty soon even if they get P12.1 in order and certified.

If I were to guess, I would say that the worst case testing may well have been performed previously may be at P10.0, P11.0 and/or P11.1 and got through.

I would suspect JT610 was probably around P10.0 or P11.0 software and ET302 P10.0, P11.0 or possibly P11.1.

Ray


If the amount of tasks generated under MCAS activation is too high to be handled by the FCC within reasonable amount of time then it should also be tested if this also occurs at other flight situations when a lot of tasks are generated.

This also leads to the further question if it is better for Boeing to upgrade the hardware now to be safe for the future, because if more software changes are mandated in the future that could lead to more tasks generated and the FCC cannot handle that load, then there will be a possible future grounding of the fleet. This is of course speculation but at this moment, a worst-case analysis should be made. Another grounding 3-5 years down the road would definitely be a killer for the MAX program. So it might be way better to actually upgrade the hardware now and be safe in the future.
 
MartijnNL
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 1:46 pm

LDRA wrote:
There is nothing wrong with using single sensor, STS also relies on single air speed signal. The key is to limit control authority so that elevator still can overpower stab in fault condition

From the Bloomberg article:"During the crashes of Lion Air and Ethiopian Airlines planes that killed 346 people, investigators suspect, the MCAS system pushed the planes into uncontrollable dives because of bad data from a single sensor.

That design violated basic principles of redundancy for generations of Boeing engineers, and the company apparently never tested to see how the software would respond, Lemme said. "It was a stunning fail. A lot of people should have thought of this problem - not one person - and asked about it", he said."


There is nothing wrong with a single sensor?! I believe I don't understand you. A single sensor is what cost 346 people their lives.
 
LDRA
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 1:53 pm

MartijnNL wrote:
LDRA wrote:
There is nothing wrong with using single sensor, STS also relies on single air speed signal. The key is to limit control authority so that elevator still can overpower stab in fault condition

From the Bloomberg article:"During the crashes of Lion Air and Ethiopian Airlines planes that killed 346 people, investigators suspect, the MCAS system pushed the planes into uncontrollable dives because of bad data from a single sensor.

That design violated basic principles of redundancy for generations of Boeing engineers, and the company apparently never tested to see how the software would respond, Lemme said. "It was a stunning fail. A lot of people should have thought of this problem - not one person - and asked about it", he said."


There is nothing wrong with a single sensor?! I believe I don't understand you. A single sensor is what cost 346 people their lives.


Yes nothing wrong with single sensor. What is wrong with MCAS V1 is lack of limit on control authority. Limiting total MCAS trim adjustment to 2.5degrees will ensure there is still enough elevator authority for pitch control
 
planecane
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 1:56 pm

MartijnNL wrote:
LDRA wrote:
There is nothing wrong with using single sensor, STS also relies on single air speed signal. The key is to limit control authority so that elevator still can overpower stab in fault condition

From the Bloomberg article:"During the crashes of Lion Air and Ethiopian Airlines planes that killed 346 people, investigators suspect, the MCAS system pushed the planes into uncontrollable dives because of bad data from a single sensor.

That design violated basic principles of redundancy for generations of Boeing engineers, and the company apparently never tested to see how the software would respond, Lemme said. "It was a stunning fail. A lot of people should have thought of this problem - not one person - and asked about it", he said."


There is nothing wrong with a single sensor?! I believe I don't understand you. A single sensor is what cost 346 people their lives.


Some of you are so quick to jump down somebody's throat as soon as you read something that can be remotely construed as "defending Boeing." Did you read the last part of LDRA's post where it says, "The key is to limit control authority so that elevator still can overpower stab in fault condition."
 
XRAYretired
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 1:58 pm

hivue wrote:
sgrow787 wrote:
(3). Per an anonymous Boeing employee interview (see 60 Minutes Australia), MCAS 1.0 was intentionally designed to use exactly one AOA sensor.


I believe this is not correct. MCAS 0.0 was designed with two sensor inputs: one AoA and G. When it was discovered during flight test that the "stick lightening" problem extended beyond just wind up turns, the requirement for the G input became redundant and that input was dropped. Boeing believed the resulting one-input configuration represented a potential "hazardous" category threat with an extraordinary low probability of ever occurring, and thus qualified for single sensor input. They did not "intentionally design" a one sensor input MCAS 1.0.

Sorry, you cant say the deign isn't the design. Except you just did!

Anyway, the article you are referring to indicates that single sensor (no G Sensor component) at low speed was assessed as 'Major' so they could get away with ~10E-5 I.e. the published sensor failure rate, and assumed the 'Hazardous' failure condition still only applied in high speed wind up turn and therefore a rate of ~E10-5*~10E-5 (assuming ~10E-5 is roughly the frequency of entering wind-up turn) = ~E-10 (i.e. better than E-09).

This was reported as the reason why the safety assessment was not formally revised and submitted to FAA and why the change from maximum 0.6 units in 9.26 seconds to maximum 2.5 units in 9.26 seconds was not advised either.

It would seem to me that they did not consider a hard AOA Sensor Fail high or at least not adequately (since it is probably not listed as an AOA Sensor failure mode) that can be accepted as a valid trigger in any flight condition with Flaps Up. Not forgetting that the other consequences e.g. Airspeed Disagree, Altitude Disagree etc. may kick out the autopilot if engaged, or prevent it being engaged. Such as during climb out (funnily enough), cruise, descent and approach until flaps are lowered.

Ray
 
Interested
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 2:05 pm

planecane wrote:
MartijnNL wrote:
LDRA wrote:
There is nothing wrong with using single sensor, STS also relies on single air speed signal. The key is to limit control authority so that elevator still can overpower stab in fault condition

From the Bloomberg article:"During the crashes of Lion Air and Ethiopian Airlines planes that killed 346 people, investigators suspect, the MCAS system pushed the planes into uncontrollable dives because of bad data from a single sensor.

That design violated basic principles of redundancy for generations of Boeing engineers, and the company apparently never tested to see how the software would respond, Lemme said. "It was a stunning fail. A lot of people should have thought of this problem - not one person - and asked about it", he said."


There is nothing wrong with a single sensor?! I believe I don't understand you. A single sensor is what cost 346 people their lives.


Some of you are so quick to jump down somebody's throat as soon as you read something that can be remotely construed as "defending Boeing." Did you read the last part of LDRA's post where it says, "The key is to limit control authority so that elevator still can overpower stab in fault condition."


Seriously - there is an opportunity to make the plane safer with two sensors AND limiting authority

But people are proposing just limit the authority next time and just accept more fault conditions in the future rather than less?

Why?

Really - that's the approach to safety now is it?

On a plane this important?
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 2:20 pm

planecane wrote:
MartijnNL wrote:
LDRA wrote:
There is nothing wrong with using single sensor, STS also relies on single air speed signal. The key is to limit control authority so that elevator still can overpower stab in fault condition

From the Bloomberg article:"During the crashes of Lion Air and Ethiopian Airlines planes that killed 346 people, investigators suspect, the MCAS system pushed the planes into uncontrollable dives because of bad data from a single sensor.

That design violated basic principles of redundancy for generations of Boeing engineers, and the company apparently never tested to see how the software would respond, Lemme said. "It was a stunning fail. A lot of people should have thought of this problem - not one person - and asked about it", he said."


There is nothing wrong with a single sensor?! I believe I don't understand you. A single sensor is what cost 346 people their lives.


Some of you are so quick to jump down somebody's throat as soon as you read something that can be remotely construed as "defending Boeing." Did you read the last part of LDRA's post where it says, "The key is to limit control authority so that elevator still can overpower stab in fault condition."

It's far from "defending Boeing." when someone say something that even Boeing disagree with: MCAS v2 have more fixes than just dual AoA sensors redundancy and elevator authority protection. Take the real raw facts instead of speculate like before the Boeing MCAS v2 fix was known to the public.
 
LDRA
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 2:25 pm

Interested wrote:
planecane wrote:
MartijnNL wrote:
From the Bloomberg article:"During the crashes of Lion Air and Ethiopian Airlines planes that killed 346 people, investigators suspect, the MCAS system pushed the planes into uncontrollable dives because of bad data from a single sensor.

That design violated basic principles of redundancy for generations of Boeing engineers, and the company apparently never tested to see how the software would respond, Lemme said. "It was a stunning fail. A lot of people should have thought of this problem - not one person - and asked about it", he said."


There is nothing wrong with a single sensor?! I believe I don't understand you. A single sensor is what cost 346 people their lives.


Some of you are so quick to jump down somebody's throat as soon as you read something that can be remotely construed as "defending Boeing." Did you read the last part of LDRA's post where it says, "The key is to limit control authority so that elevator still can overpower stab in fault condition."


Seriously - there is an opportunity to make the plane safer with two sensors AND limiting authority

But people are proposing just limit the authority next time and just accept more fault conditions in the future rather than less?

Why?

Really - that's the approach to safety now is it?

On a plane this important?


Two sensors also means twice the failure rate. So availability of MCAS actually goes down with two sensors solution

Why Boeing is going with two sensors now? Probably pressure from public opinion
 
FluidFlow
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 2:45 pm

LDRA wrote:
Interested wrote:
planecane wrote:

Some of you are so quick to jump down somebody's throat as soon as you read something that can be remotely construed as "defending Boeing." Did you read the last part of LDRA's post where it says, "The key is to limit control authority so that elevator still can overpower stab in fault condition."


Seriously - there is an opportunity to make the plane safer with two sensors AND limiting authority

But people are proposing just limit the authority next time and just accept more fault conditions in the future rather than less?

Why?

Really - that's the approach to safety now is it?

On a plane this important?


Two sensors also means twice the failure rate. So availability of MCAS actually goes down with two sensors solution

Why Boeing is going with two sensors now? Probably pressure from public opinion


Thats wrong. The two sensor solution should guarantee detection if one of them fails while a one sensor solution delivers a signal that might be wrong.
 
kalvado
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 2:46 pm

LDRA wrote:
Interested wrote:
planecane wrote:

Some of you are so quick to jump down somebody's throat as soon as you read something that can be remotely construed as "defending Boeing." Did you read the last part of LDRA's post where it says, "The key is to limit control authority so that elevator still can overpower stab in fault condition."


Seriously - there is an opportunity to make the plane safer with two sensors AND limiting authority

But people are proposing just limit the authority next time and just accept more fault conditions in the future rather than less?

Why?

Really - that's the approach to safety now is it?

On a plane this important?


Two sensors also means twice the failure rate. So availability of MCAS actually goes down with two sensors solution

Why Boeing is going with two sensors now? Probably pressure from public opinion

Because false positive - aka uninvited actuation of controls - is seen as a bigger problem than non-availability of an emergency system.
Also, if you want to talk about dispatch reliability - we're talking about 2-3 cancelled flights over the lifetime of a plane, reducing plane dispatch reliability approximately by 1 in 10k flights, or by 0.01%. Hardly a deal breaker.
 
Interested
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 2:54 pm

Or don't have MCAS on a 737 and take away the risk of any sensors failing or having to reduce any authority or add any new training

All reasons why Max 737 can't ever be as safe as 737 NG

We've added problems
 
XRAYretired
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 2:55 pm

kalvado wrote:
LDRA wrote:
Interested wrote:

Seriously - there is an opportunity to make the plane safer with two sensors AND limiting authority

But people are proposing just limit the authority next time and just accept more fault conditions in the future rather than less?

Why?

Really - that's the approach to safety now is it?

On a plane this important?


Two sensors also means twice the failure rate. So availability of MCAS actually goes down with two sensors solution

Why Boeing is going with two sensors now? Probably pressure from public opinion

Because false positive - aka uninvited actuation of controls - is seen as a bigger problem than non-availability of an emergency system.
Also, if you want to talk about dispatch reliability - we're talking about 2-3 cancelled flights over the lifetime of a plane, reducing plane dispatch reliability approximately by 1 in 10k flights, or by 0.01%. Hardly a deal breaker.

Zero despatch reliability hit because AOA Sensor is not on the MMEL!

Ray
 
LDRA
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 3:29 pm

kalvado wrote:
LDRA wrote:
Interested wrote:

Seriously - there is an opportunity to make the plane safer with two sensors AND limiting authority

But people are proposing just limit the authority next time and just accept more fault conditions in the future rather than less?

Why?

Really - that's the approach to safety now is it?

On a plane this important?


Two sensors also means twice the failure rate. So availability of MCAS actually goes down with two sensors solution

Why Boeing is going with two sensors now? Probably pressure from public opinion

Because false positive - aka uninvited actuation of controls - is seen as a bigger problem than non-availability of an emergency system.
Also, if you want to talk about dispatch reliability - we're talking about 2-3 cancelled flights over the lifetime of a plane, reducing plane dispatch reliability approximately by 1 in 10k flights, or by 0.01%. Hardly a deal breaker.


2.5degree total MCAS output command limit just mitigated unintended activation failure, so false positive is no longer a high hazardous failure
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 3:42 pm

LDRA wrote:
Two sensors also means twice the failure rate. So availability of MCAS actually goes down with two sensors solution
That probably why Airbus now mount 4 AoA sensors on the A350: to quadruple the failure rate and to slash as down as possible the availability... Thanks for the joke :rotfl:

LDRA wrote:
Why Boeing is going with two sensors now? Probably pressure from public opinion
Sure enough, no expert ever asked for two sensors... :crazy:
 
olle
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 3:58 pm

FluidFlow wrote:
xmp125a wrote:
FluidFlow wrote:
Money is not everything for top-talent. I do not know how generous Boeing is in terms of social benefits. I know of Top Employers that give up to 6 months of parental payed leave and 8-10 weeks payed holiday aswell as massive pension funds. Thats what the best talent looks for and I hope Boeing can offer this. Otherwise the best ones will rather go to other companies.


Does not change my argument. Boeing was a hugely profitable company with reputation to boot. Whether compensation or perks, they could offer anything to the top talent. And on top of that, they have insane economies of scale - how many MAX orders they had? 1700? Software that runs all of these has to be done only once, but done right.

All indications point towards them willingly letting the expertise to rot and be lost. Inexcusable.



I am not arguing against you, you are right about Boeings failure to secure talent. They could if they want but the decision was not to.

That has nothing to do tho with the fact that a really bad education system paired with stupid immigration laws leads to loss of talent in the US as well as in the EU. One of them factors has to be good but if both are against corporations because of populistic policies the jobs will go to the talent instead of the talents to the job.



I work at one big heavy truck producer in Sweden. I see so many immigrants first or second generation working with developing products no one thought was possible 15 years back. If they was not talented they would not do what they are doing.

The white man world on the other hand took the decision that a MBA was more important then a engineer degree.

I consider your comment both racist and uneducated.
 
LDRA
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 4:01 pm

PixelFlight wrote:
LDRA wrote:
Two sensors also means twice the failure rate. So availability of MCAS actually goes down with two sensors solution
That probably why Airbus now mount 4 AoA sensors on the A350: to quadruple the failure rate and to slash as down as possible the availability... Thanks for the joke :rotfl:

LDRA wrote:
Why Boeing is going with two sensors now? Probably pressure from public opinion
Sure enough, no expert ever asked for two sensors... :crazy:


Nope 4 sensors increases availability of function, since it takes three sensor failures to cause loss of function
Last edited by LDRA on Mon Jul 01, 2019 4:04 pm, edited 1 time in total.
 
planecane
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 4:02 pm

PixelFlight wrote:
LDRA wrote:
Two sensors also means twice the failure rate. So availability of MCAS actually goes down with two sensors solution
That probably why Airbus now mount 4 AoA sensors on the A350: to quadruple the failure rate and to slash as down as possible the availability... Thanks for the joke :rotfl:

LDRA wrote:
Why Boeing is going with two sensors now? Probably pressure from public opinion
Sure enough, no expert ever asked for two sensors... :crazy:

Every added sensor increases the likelihood that you will have a sensor failure on any given flight. The more sensors that are installed the lower the chance of a sensor failure leading to a serious problem. It isn't a joke, it's the way statistics work. If you aren't allowed to dispatch with an AoA sensor failure, the more that are installed, the lower the dispatch reliability will be.
 
FluidFlow
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 4:03 pm

olle wrote:
FluidFlow wrote:
xmp125a wrote:

Does not change my argument. Boeing was a hugely profitable company with reputation to boot. Whether compensation or perks, they could offer anything to the top talent. And on top of that, they have insane economies of scale - how many MAX orders they had? 1700? Software that runs all of these has to be done only once, but done right.

All indications point towards them willingly letting the expertise to rot and be lost. Inexcusable.



I am not arguing against you, you are right about Boeings failure to secure talent. They could if they want but the decision was not to.

That has nothing to do tho with the fact that a really bad education system paired with stupid immigration laws leads to loss of talent in the US as well as in the EU. One of them factors has to be good but if both are against corporations because of populistic policies the jobs will go to the talent instead of the talents to the job.



I work at one big heavy truck producer in Sweden. I see so many immigrants first or second generation working with developing products no one thought was possible 15 years back. If they was not talented they would not do what they are doing.

The white man world on the other hand took the decision that a MBA was more important then a engineer degree.

I consider your comment both racist and uneducated.


I think you missunderstood me, what I am saying is, that there is way more talent out there that we should bring to europe to fill the vacancies instead of transfering the jobs away fron europe.

I see it here too, alot of great talent here is of the generation that had to flee the war in yugoslavia and the next big talents are the ones now fleeing the ME. But we do not help them people enough to come here and bring their talent. Its a shame we could be so much more productive and innovative if we would use their skill here. Instead we transfer jobs away.
 
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sassiciai
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 4:17 pm

The white man world on the other hand took the decision that a MBA was more important then a engineer degree.

I consider your comment both racist and uneducated.[/quote]

I will disagree with you about the MBA decisions! Maybe in the US of A an MBA is seen as a great thing, but here in the old continent, there is no headlong charge to have an MBA, and I think that graduation figures for engineers outway MBAs by an order of magnitude (or more). Just going on the feedback from my own 4 children, 3 of whom have passed through the system!

I think that undue respect of an MBA is very much an America thing - in my entire career in the IT industry, I only encountered one MBA (or at least any others hide this from their colleagues)

He was partially responsible for a major project cock-up (he inherited the case from his predecessor without digging deep enough during any due diligence). I benefited from the mess, and spent 15 months in Singapore working at the airport to get this project back on the rails!

I'm sure that there is a humorous alternative meaning for MBA! I invite suggestions!
 
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seahawk
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 4:23 pm

planecane wrote:
PixelFlight wrote:
LDRA wrote:
Two sensors also means twice the failure rate. So availability of MCAS actually goes down with two sensors solution
That probably why Airbus now mount 4 AoA sensors on the A350: to quadruple the failure rate and to slash as down as possible the availability... Thanks for the joke :rotfl:

LDRA wrote:
Why Boeing is going with two sensors now? Probably pressure from public opinion
Sure enough, no expert ever asked for two sensors... :crazy:

Every added sensor increases the likelihood that you will have a sensor failure on any given flight. The more sensors that are installed the lower the chance of a sensor failure leading to a serious problem. It isn't a joke, it's the way statistics work. If you aren't allowed to dispatch with an AoA sensor failure, the more that are installed, the lower the dispatch reliability will be.


1. you do not dispatch with a faulty AoA sensor anyway
2. the current iteration of the software switches between the 2 sensors after each flight and it does not actual tell the crew which it is using.
 
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Revelation
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 4:31 pm

aaexecplat wrote:
There is TONS of great quality software engineering talent available in the world...but not at $9/hr unless you just want the Tickle Me Elmo doll to tell you what it wants for lunch...

For the record, in the now locked thread on the software outsourcing topic there was plenty of people local to India saying $9/hr is a good wage in the market for software developers, and a lot of people saying many people were confusing what US/EU firms paid per hour for the services versus what the India locals were being paid, yet drawing conclusions based on presuming that the US/EU firms were paying $9/hr thus getting bottom of the barrel talent.

The article itself says:

Increasingly, the iconic American planemaker and its subcontractors have relied on temporary workers making as little as $9 an hour to develop and test software, often from countries lacking a deep background in aerospace -- notably India.

People should note that the lowest amount the worker is being paid is $9, and Boeing has confirmed this has nothing to do with MCAS, and at this point it's only talking about parts of two subsystems that were outsourced and there are no specific issues being reported with regard to these two subsystems.
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hivue
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 5:49 pm

XRAYretired wrote:
Sorry, you cant say the deign isn't the design. Except you just did!


Relax. The poster I quoted was trying to provide the summary of "known facts" that a previous poster had requested for part 1 this new thread. I was just trying to clean up the "known facts" part in the interest of accuracy.
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
h1fl1er
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 5:56 pm

the MCAS implementation went into infinite loop until full nose down...this was obviously stupid and where the problem lies. it will be fixed.
nobody is taking any chances and the rest of the plane is getting a fine toothed comb

people above need to can the offensive posts
 
XRAYretired
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 6:08 pm

hivue wrote:
XRAYretired wrote:
Sorry, you cant say the deign isn't the design. Except you just did!


Relax. The poster I quoted was trying to provide the summary of "known facts" that a previous poster had requested for part 1 this new thread. I was just trying to clean up the "known facts" part in the interest of accuracy.

All cool here man!

Ray
 
MrBretz
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 6:19 pm

h1fl1er wrote:
the MCAS implementation went into infinite loop until full nose down...this was obviously stupid and where the problem lies. it will be fixed.
nobody is taking any chances and the rest of the plane is getting a fine toothed comb

people above need to can the offensive posts


We really don’t know what happened. And I doubt your statement but admit it might have happened.

Having programmed real time light computers in the past, they run with a very specialized runtime real time OS. The ones I’ve seen have programs that run something like every 32, 16, 8, etc. times a second. Navigation programs in particular have to run at this rate so extrapolations are accurate. I suspect the MCAS detection calculation runs probably at 32/sec and they just found out that under a previously undiscovered set of conditions, the calculation did not finish. So the the calculation is probably unrecoverable. Of course, I am just taking a guess, but it is based on how we did it.

I do know exactly what happened is known by just a few sets of software and system engineers. But all your speculation is entertaining.
 
TTailedTiger
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 6:24 pm

Is there any article that explains just what the FAA did to fry the MCAS CPU? We need some context. If it happened out of the blue then that's an issue that needs to be fixed, but if they intentionally did something to exceed design limitations then that is just the FAA misleading the public. The FAA is trying to save face and pulling a "oh look what else we discovered is wrong" could be their way of doing it. Most likely that is not some brand new processor. New aircraft are known for using previous generation technology since it has known reliability.
 
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JetBuddy
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 7:01 pm

TTailedTiger wrote:
Is there any article that explains just what the FAA did to fry the MCAS CPU? We need some context. If it happened out of the blue then that's an issue that needs to be fixed, but if they intentionally did something to exceed design limitations then that is just the FAA misleading the public. The FAA is trying to save face and pulling a "oh look what else we discovered is wrong" could be their way of doing it. Most likely that is not some brand new processor. New aircraft are known for using previous generation technology since it has known reliability.


I strongly doubt the FAA is trying to mislead the public. It could backfire massively. I think anyone even suggesting such a thing would get thrown out the door immediately. Especially in the light of the recent MCAS situation.
 
kalvado
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 7:12 pm

h1fl1er wrote:
the MCAS implementation went into infinite loop until full nose down...this was obviously stupid and where the problem lies. it will be fixed.
nobody is taking any chances and the rest of the plane is getting a fine toothed comb

people above need to can the offensive posts

People above think that such tests should have been done before first delivery; and assume that Boeing would save itself from embarrassment of being hit with another delay at the time everyone expected final fix and return to flight.
Love it or hate it - but I had a much better opinion about Boeing in terms of being able to do things right, at least on a second attempt. Well, maybe third time is a charm?
 
TTailedTiger
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 7:19 pm

JetBuddy wrote:
TTailedTiger wrote:
Is there any article that explains just what the FAA did to fry the MCAS CPU? We need some context. If it happened out of the blue then that's an issue that needs to be fixed, but if they intentionally did something to exceed design limitations then that is just the FAA misleading the public. The FAA is trying to save face and pulling a "oh look what else we discovered is wrong" could be their way of doing it. Most likely that is not some brand new processor. New aircraft are known for using previous generation technology since it has known reliability.


I strongly doubt the FAA is trying to mislead the public. It could backfire massively. I think anyone even suggesting such a thing would get thrown out the door immediately. Especially in the light of the recent MCAS situation.


I hope you are correct but the FAA needs to be transparent with this issue. Tell us exactly what happened that lead to the fault.
 
kalvado
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 7:23 pm

TTailedTiger wrote:
Is there any article that explains just what the FAA did to fry the MCAS CPU? We need some context. If it happened out of the blue then that's an issue that needs to be fixed, but if they intentionally did something to exceed design limitations then that is just the FAA misleading the public. The FAA is trying to save face and pulling a "oh look what else we discovered is wrong" could be their way of doing it. Most likely that is not some brand new processor. New aircraft are known for using previous generation technology since it has known reliability.

I bet FAA basically went through Boeing failure analysis in marked some interesting things in red. Then those red-colored scenarios were sent to simulator and tested in terms of sim matching BOeing's assessment.
With this particular scenario, BOeing's rating was "major" - e.g. most people walk away from landed plane, some needing clean underwear. Sim showed that test pilot - more qualified than most line pilots - could barely handle the situation.
I suspect re-assessment of risks for many failures is now on the table.
 
LDRA
Posts: 273
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 7:28 pm

Reading online it appears the actual failure mode tested is one FCC inop. That configuration requires the second FCC to handle more computation than normal case.

It does appear that worst case computation resource analysis is botched so that FCC task overrun and hence electric trim not responding is not showing up as aircraft level effect. That is why it takes an actual flight sim test to find the real effect and associated hazard classification
 
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Revelation
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 7:42 pm

TTailedTiger wrote:
Is there any article that explains just what the FAA did to fry the MCAS CPU? We need some context.

We all need some context if you think the "MCAS CPU" was "fried", because such a statement is not consistent with what we've read so far.

kalvado wrote:
People above think that such tests should have been done before first delivery; and assume that Boeing would save itself from embarrassment of being hit with another delay at the time everyone expected final fix and return to flight.
Love it or hate it - but I had a much better opinion about Boeing in terms of being able to do things right, at least on a second attempt. Well, maybe third time is a charm?

There's no doubt the delay in response should not have happened.

What's not clear to me if this was some sort of "special" test FAA was doing to "bless" some or all of the MCAS fix, or if this was a "routine" test activity that FAA participates in as a part of its job as regulator to make sure the base line functionality is solid before doing MCAS testing. Given the media says it wasn't a MCAS specific test and MCAS was not involved in the issue that was found it would seem it's more of the later than the former.

LDRA wrote:
Reading online it appears the actual failure mode tested is one FCC inop. That configuration requires the second FCC to handle more computation than normal case.

It does appear that worst case computation resource analysis is botched so that FCC task overrun and hence electric trim not responding is not showing up as aircraft level effect. That is why it takes an actual flight sim test to find the real effect and associated hazard classification

Which source are you reading to reach this kind of understanding?

All of this is murky because all we have are various leaks in the media written by non-technical writers.
Wake up to find out that you are the eyes of the world
The heart has its beaches, its homeland and thoughts of its own
Wake now, discover that you are the song that the morning brings
The heart has its seasons, its evenings and songs of its own
 
kalvado
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 7:46 pm

Revelation wrote:

What's not clear to me if this was some sort of "special" test FAA was doing to "bless" some or all of the MCAS fix, or if this was a "routine" test activity that FAA participates in as a part of its job as regulator to make sure the base line functionality is solid before doing MCAS testing. Given the media says it wasn't a MCAS specific test and MCAS was not involved in the issue that was found it would seem it's more of the later than the former.

I suspect this is part of test package for new software release. It is not that Boeing just updates MCAS.dll, it is a single piece firmware being updated.
 
tropical
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 7:52 pm

Question to those with the technical know-how: putting aside the financial side of things for a moment, if instead of creating and installing MCAS Boeing had simply designed the MAX without it and opted to tackle the different handling characteristics of the model by requiring additional training for the pilots, would the plane be considered as unsafe? A bit more challenging to handle than the model it replaces I’m sure, but surely still perfectly reasonable and I suspect still more forgiving and easier to fly than many aircraft models from the 60s and 70s that nobody would describe as unsafe if flown by a properly trained pilot.

In other words, if Boeing had bitten the bullet of the additional training costs associated with the pilot training that would have been required by the different handling characteristics of an NG and a MAX without MCAS, the MAX would still have been a highly fuel efficient plane and attractive to many airlines, and with the right training no less safe than other models. And the tragic crashes would have been avoided. Hindsight is a wonderful thing, of course.
 
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flyingphil
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 8:02 pm

So where do we go from here?
What are the next steps to get the 737MAX ungrounded?

Best case – flying again in 3-4 months?
• The FAA plus all the worldwide aviation authorities give the 737MAX the green light, dependant on MCAS 2.1 being approved and other simple software / hardware fixes.
• The pilot unions agree that the 737MAX is good to go.
• Pilots to have additional upset training in 737MAX Simulators and the checklists are updated.
• The 737MAX’s in storage are reactivated and positioned to appropriate hubs.
• The Route planners put the 737MAX back in the schedules.
• PR campaign by airlines and Boeing to persuade the public that the 737MAX (insert new name) is safe for you and your loved ones.

Worst case – 2-3 years?? If ever
• The FAA dig their heels in… mandate new software, new flight control hardware, aerodynamic changes, new type rating, more test flying.
• More issues discovered, more whistleblowing by disgruntled ex-Boeing employees.
• The Chinese, the Europeans no longer trust the FAA and make their own demands.
• Airlines want their money back and cancel orders.
• Pilot Unions not happy, make their own demands for better pay and conditions to fly the 737MAX.
• Shortage of 737MAX Simulators and doubts they accurately reproduce the flying characteristics.
• Consumer advocates like Ralph Nader mount campaigns to get the 737MAX permanently grounded.
• The leasing companies see the value of the 737MAX plummet.
• Boeing compensation payments to airlines and leasing companies’ balloon, Boeing embroiled in lawsuits and class actions.

What are your best guesses? Should Boeing give up on the 737MAX?

Meanwhile the onslaught of bad publicity continues, didn’t know they outsourced to Russia too .. https://www.chicagobusiness.com/manufac ... -engineers
 
DenverTed
Posts: 247
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 8:25 pm

tropical wrote:
Question to those with the technical know-how: putting aside the financial side of things for a moment, if instead of creating and installing MCAS Boeing had simply designed the MAX without it and opted to tackle the different handling characteristics of the model by requiring additional training for the pilots, would the plane be considered as unsafe? A bit more challenging to handle than the model it replaces I’m sure, but surely still perfectly reasonable and I suspect still more forgiving and easier to fly than many aircraft models from the 60s and 70s that nobody would describe as unsafe if flown by a properly trained pilot.

In other words, if Boeing had bitten the bullet of the additional training costs associated with the pilot training that would have been required by the different handling characteristics of an NG and a MAX without MCAS, the MAX would still have been a highly fuel efficient plane and attractive to many airlines, and with the right training no less safe than other models. And the tragic crashes would have been avoided. Hindsight is a wonderful thing, of course.

As I understand it from asking the question on this thread, MCAS was required to meet the pitch stability for righting moment as the aircraft entered a high speed and low speed stall. But I have never seen this question answered by Boeing or the FAA. Seems like an easy enough question for either of them to answer.
 
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glideslope
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 8:36 pm

Personally, I would like to see the test run again with line Max pilots not FAA Pilots. It's not beyond the scope for this to have been an attempt to "see we are being tough" by the FAA. I would not put this past them given their current quandary. There is simply too much of a disconnect in information being released and interpretations.
To know your Enemy, you must become your Enemy.” Sun Tzu
 
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Revelation
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 8:43 pm

flyingphil wrote:
Worst case – 2-3 years?? If ever
• The FAA dig their heels in… mandate new software, new flight control hardware, aerodynamic changes, new type rating, more test flying.
• More issues discovered, more whistleblowing by disgruntled ex-Boeing employees.
• The Chinese, the Europeans no longer trust the FAA and make their own demands.
• Airlines want their money back and cancel orders.
• Pilot Unions not happy, make their own demands for better pay and conditions to fly the 737MAX.
• Shortage of 737MAX Simulators and doubts they accurately reproduce the flying characteristics.
• Consumer advocates like Ralph Nader mount campaigns to get the 737MAX permanently grounded.
• The leasing companies see the value of the 737MAX plummet.
• Boeing compensation payments to airlines and leasing companies’ balloon, Boeing embroiled in lawsuits and class actions.

Worse case in my book is if DoJ/FBI probe finds deliberate lying (fraud) along the lines of Dieselgate.

Such a deliberate act would open the door to far more bad things than the current "sorry, we put too much work load on the pilots" scenario.

Short of that, it flies again.

flyingphil wrote:
Should Boeing give up on the 737MAX?

No one should hope for that.

It'd take ~half the narrow body airliner production out of the market for ~five years and lay waste to lots of airline's plans.
Wake up to find out that you are the eyes of the world
The heart has its beaches, its homeland and thoughts of its own
Wake now, discover that you are the song that the morning brings
The heart has its seasons, its evenings and songs of its own
 
sgrow787
Posts: 222
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 9:18 pm

glideslope wrote:
Personally, I would like to see the test run again with line Max pilots not FAA Pilots. It's not beyond the scope for this to have been an attempt to "see we are being tough" by the FAA. I would not put this past them given their current quandary. There is simply too much of a disconnect in information being released and interpretations.


FAA is the last stop. Any coziness with Boeing is on hold I would think, as investigators are breathing down their necks. No one can afford another crash.

On a side note, if Boeing could do it over, would they have preferred MCAS1.0+2AOA and eaten the simulator training? After all, there was only one Max sim. They could have slowed the pilot queue down and convinced the then-cozy FAA to temporarily accept ipad training.
Just one sensor,
Oh just one se-en-sor,
Just one sensor,
Ooh ooh oo-ooh
Oo-oo-ooh.
 
sgrow787
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 9:46 pm

Revelation wrote:
TTailedTiger wrote:
Is there any article that explains just what the FAA did to fry the MCAS CPU? We need some context.

We all need some context if you think the "MCAS CPU" was "fried", because such a statement is not consistent with what we've read so far.

kalvado wrote:
People above think that such tests should have been done before first delivery; and assume that Boeing would save itself from embarrassment of being hit with another delay at the time everyone expected final fix and return to flight.
Love it or hate it - but I had a much better opinion about Boeing in terms of being able to do things right, at least on a second attempt. Well, maybe third time is a charm?

There's no doubt the delay in response should not have happened.

What's not clear to me if this was some sort of "special" test FAA was doing to "bless" some or all of the MCAS fix, or if this was a "routine" test activity that FAA participates in as a part of its job as regulator to make sure the base line functionality is solid before doing MCAS testing. Given the media says it wasn't a MCAS specific test and MCAS was not involved in the issue that was found it would seem it's more of the later than the former.

LDRA wrote:
Reading online it appears the actual failure mode tested is one FCC inop. That configuration requires the second FCC to handle more computation than normal case.

It does appear that worst case computation resource analysis is botched so that FCC task overrun and hence electric trim not responding is not showing up as aircraft level effect. That is why it takes an actual flight sim test to find the real effect and associated hazard classification

Which source are you reading to reach this kind of understanding?

All of this is murky because all we have are various leaks in the media written by non-technical writers.


According to Satcomguru, each FCC is identical - copilot v pilot. But there are two processors on each FCC, and each one is running a DFCS app that was developed independently:

FCCp - FCC pilot
FCCc - FCC copilot
results in..
DFCSp_honey
DFCSp_collins
DFCSc_honey
DFCSc_collins

Because of independent development, its safe to assume that a resource allocation issue on one architecture (eg DFCSc_collins) wouldnt exist (or wouldnt exist at the same time) for the other architecture running in parallel.

And if, during a DFCSp_collins lockup, the design is supposed to transfer control - along with onside data - to the other sides FCC, well because that DFCSc_collins is also likely experiencing the same lockup (its the same architecture) then you have the failure affecting the usable flight control system.

In summary, this architecture is a failsafe against a fried processor and or entire FCC. So it cant possibly be what was tested for. Instead, the FAA guy likely did a performance stress test of sorts to cause the above scenario.

Note: I assumed here that a locked DFCSc_collins would cause a disagree flag and the design would transfer control to the other side FCC.
Last edited by sgrow787 on Mon Jul 01, 2019 10:04 pm, edited 1 time in total.
Just one sensor,
Oh just one se-en-sor,
Just one sensor,
Ooh ooh oo-ooh
Oo-oo-ooh.
 
RickNRoll
Posts: 1755
Joined: Fri Jan 06, 2012 9:30 am

Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 01, 2019 9:54 pm

LDRA wrote:
Reading online it appears the actual failure mode tested is one FCC inop. That configuration requires the second FCC to handle more computation than normal case.

It does appear that worst case computation resource analysis is botched so that FCC task overrun and hence electric trim not responding is not showing up as aircraft level effect. That is why it takes an actual flight sim test to find the real effect and associated hazard classification
That makes sense. Similar to disabling an engine during take off. The plane should still make it off the ground safely.
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Military Aircraft Every type from fighters to helicopters from air forces around the globe

Classic Airliners Props and jets from the good old days

Flight Decks Views from inside the cockpit

Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior

Cargo Aircraft Pictures of great freighter aircraft

Government Aircraft Aircraft flying government officials

Helicopters Our large helicopter section. Both military and civil versions

Blimps / Airships Everything from the Goodyear blimp to the Zeppelin

Night Photos Beautiful shots taken while the sun is below the horizon

Accidents Accident, incident and crash related photos

Air to Air Photos taken by airborne photographers of airborne aircraft

Special Paint Schemes Aircraft painted in beautiful and original liveries

Airport Overviews Airport overviews from the air or ground

Tails and Winglets Tail and Winglet closeups with beautiful airline logos