Boeing 737 Max8 Crashes

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#31 Re: Boeing 737 Max8 Crashes

Post by Jun » Mon Mar 18, 2019 7:47 pm

Gaybutton wrote:
Mon Mar 18, 2019 10:14 am
Why am I not surprised?
Having worked as an engineer, I'm somewhat surprised, since self certification of all the detail within the systems is pretty common in all sorts of safety critical systems in various industries. Most engineers and their management recognize that they are working on safety critical systems and do not cut corners. Killing the customers is immoral, is bad for the business and creates an awful lot of hassle. All known.

This is why aircraft, road vehicles etc have so many complex systems which improve safety & bad failure modes are extremely rare.

I would suspect Boeing may have suffered from human error in the engineering process, since doing FMEA type work is very tedious.
However, if the information is correct, it is remarkable how they could have signed off a system like this working on just one sensor, with no back up sensors or plausibility checking of the system. I actually struggle to believe the system would work like that.

Perhaps the pressure to get the plane out and into the market to compete with Airbus may have contributed.

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#32 Re: Boeing 737 Max8 Crashes

Post by fountainhall » Mon Mar 18, 2019 10:55 pm

I understand from what I have been reading that unlike virtually all other systems on all aircraft, the new MCAS system might not have redundancy back up. Further, the information provided to the FAA regarding the angle of nose down stated it was only about one quarter of the actual angle. The repeated nose down action by MCAS even after it had been manually switched off may also have been omitted from the certification documentation.

I am obviously passing on information. But reports that the Inspector General at the Transport Department has launched a probe regarding the FAA's approval of Boeing's certification procedures and that a Grand Jury has issued a subpoena seeking from one individual at Boeing involved in the development of the 737 Max aircraft "documents, including correspondence, emails and other messages" indicates the possibility of civll - and perhaps even criminal - action against either or both Boeing and the FAA.
Jun wrote:
Mon Mar 18, 2019 7:47 pm
Perhaps the pressure to get the plane out and into the market to compete with Airbus may have contributed.
I think that is becoming very clear!

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#33 Re: Boeing 737 Max8 Crashes

Post by Jun » Wed Mar 20, 2019 6:38 am

fountainhall wrote:
Mon Mar 18, 2019 10:55 pm
I understand from what I have been reading that unlike virtually all other systems on all aircraft, the new MCAS system might not have redundancy back up.
This would be remarkable. Even in road vehicles, safety critical systems should either have a safe failure mode or redundancy. In an aircraft, it beggars belief.

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#34 Re: Boeing 737 Max8 Crashes

Post by fountainhall » Wed Mar 20, 2019 6:57 am

The system had too much power and lacked redundancy, the Seattle Times reports.

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#35 Re: Boeing 737 Max8 Crashes

Post by firecat69 » Wed Mar 20, 2019 7:30 pm

As usual with these type of things , it may take months before we have the definitive answer. Always lots of experts around to feed the news sources but we will just have to wait.

I vividly remember when Captain Sully landed his plane in the Hudson River and nobody injured. At the beginning there were many experts saying he made the wrong decision and he should have turned back or tried to land at a smaller private aviation airport.

Eventually after all the computer models were run and analyzed, they had to admit he made the only logical decision and I'm sure many of those same passengers who are on future flights , hope they have a Captain Sully in the left seat.

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#36 Re: Boeing 737 Max8 Crashes

Post by firecat69 » Wed Mar 20, 2019 7:34 pm

Here is a recent scary article. Not sure about its veracity.

https://www.yahoo.com/finance/news/excl ... 49642.html

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#37 Re: Boeing 737 Max8 Crashes

Post by Jun » Fri Mar 22, 2019 1:28 am

According to the following article, Boeing has an OPTIONAL angle of attack indicator and disagree light for two angle of attack sensors.
My view is if there is a significant disagreement between the two sensors, this MCAS system should switch off automatically and inform the pilot of this.

https://www.nytimes.com/2019/03/21/busi ... harge.html

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#38 Re: Boeing 737 Max8 Crashes

Post by fountainhall » Fri Mar 22, 2019 12:22 pm

This part of the NYT article strikes me as madness -
The angle of attack indicator will remain an option that airlines can buy. Neither feature was mandated by the Federal Aviation Administration. All 737 Max jets have been grounded.

“They’re critical, and cost almost nothing for the airlines to install,” said Bjorn Fehrm, an analyst at the aviation consultancy Leeham. “Boeing charges for them because it can. But they’re vital for safety”
.
A vital safety feature is not incorporated into the basic price of the aircraft? It must be paid for as an extra? Boeing must be wishing aircraft to crash to persuade operators to cough up the extra cash. I find this utterly sickening.

I hope the lawyers come down on Boeing with a string of huge lawsuits - and that they win. If what we are reading is correct, the company is not only directly responsible for the deaths of hundreds of passengers and crew, it is guilty of deliberately putting defective aircraft into the air.

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#39 Re: Boeing 737 Max8 Crashes

Post by fountainhall » Fri Mar 22, 2019 3:10 pm

Like all chat rooms, thr pprune.org professional pilots site has its fair share of disagreements and bashing of some posters’ comments. This one (post 2333) by a pilot about the way Boeing has developed the various versions of the 737 aircraft is worrying. Less perhaps to the traveling public because the “cobbling together” of improvements has generally not resulted in accidents, and more to Boeing itself if the details become public in the course of various lawsuits.

The post was made in response to another about Boeing pushing the Max version out too speedily using band aids rather that a redesign - all to catch up with the Airbus Neo programme. He suggests the MCAS system was a quick software fix to counter a “basically unstable platform.” He goes on -
In my humble opinion, they [Boeing] should have started again with the 73 about the time of the -300/-400 and completely redesigned it. As it stands, they seem to have cobbled together systems as they became available or desirable and bolted them where they could find space. (The “computer fuel summing unit” - can’t remember its exact name - is fixed outboard above the F/Os head - why not in the avionics bay?). The F/Os seat cannot be moved vary far back because of the C/B rack behind it. The elevator feel unit has its own pitot probes each side of the fin.

I only have experience of the -300/-400, but that aircraft is a mish-mash of mechanical and electronic devices, seemingly not properly integrated, but just about working. The ‘Classic’ autopilot does not trim ailerons or rudder, so when you take out the autopliot you often have to spend a mile or so on short finals getting the thing trimmed. The Cockpits of the -300/-400 look as if they were “designed” by firing a shotgun at a blank panel, and fitting the instruments and indicators whereever there was a handy hole. Generators have to be manually switched on to the buses. Later models without the round generator dials, still use the old panels with the cut-outs for the round dials rather than making a new panel....how cheap is that?

It seems to me that as each new requirement or problem came along, instead of doing a redesign, Boeing developed a standalone fix or widgit to solve the problem - but they don’t appear to have always thought it through in terms of the way the whole aircraft works, or how the pilots would interface with it.

As to why the 73 is so popular, I think South West have a lot to do with that, (they are also indirectly partly responsible for the arrested development of the 73). I have been told that Boeing also have some very creative fleet purchasing schemes for airlines.

As to MCAS, instead of affecting the THS trim, why not simply have it modify the elevator feel at hiigh AoA - which is, after all, the problem caused by the engine nacelles. Or insert a gentle down input to the elevators? But not the trim. Secondly, why have only one AoA probe, or even two? For such a critical device, why not have five?
Sorry I don’t know the meaning of some of the terms, but I think the gist of the post is more than obvious.

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#40 Re: Boeing 737 Max8 Crashes

Post by firecat69 » Fri Mar 22, 2019 7:38 pm

Jun wrote:
Fri Mar 22, 2019 1:28 am
According to the following article, Boeing has an OPTIONAL angle of attack indicator and disagree light for two angle of attack sensors.
My view is if there is a significant disagreement between the two sensors, this MCAS system should switch off automatically and inform the pilot of this.

https://www.nytimes.com/2019/03/21/busi ... harge.html
So many people trying to explain before the exhaustive investigation is done. However I saw a report that said that would have been the standard in the past ,this MCAS system was programmed to react even if only 1 of the 2 sensors determined there was an imminent stall.

But even worse there are reports if the pilots decided to override the system , it would immediately do the same thing over again. Not easy to override the system and then it snaps right back again.

Looks like there will a lot more to come and Boeing should be held responsible along with the FAA (under Dump)

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