Ethiopian Airlines plane crashes on way to Nairobi

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Re: Ethiopian Airlines plane crashes on way to Nairobi

Unread post by biffvj » Tue Apr 30, 2019 6:47 am

"Southwest Airlines says Boeing did not disclose that it had deactivated a safety feature on its 737 Max jets until after one of the airliners crashed last year.
At issue is an alert that tells pilots if a sensor — called an “angle of attack” (AOA) indicator — is transmitting bad data about the pitch of a plane’s nose. The sensor’s alerts had been operational in previous versions of the 737 but were switched off in the 737 Max.
The news first appeared Sunday in The Wall Street Journal.
The Journal also reported that Federal Aviation Administration safety inspectors and supervisors did not know about the change either. The FAA declined to comment."
From Time magazine.

What could Boeing's reason be for doing this?
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Re: Ethiopian Airlines plane crashes on way to Nairobi

Unread post by heisan » Tue Apr 30, 2019 9:30 am

biffvj wrote:
Tue Apr 30, 2019 6:47 am
"Southwest Airlines says Boeing did not disclose that it had deactivated a safety feature on its 737 Max jets until after one of the airliners crashed last year.
At issue is an alert that tells pilots if a sensor — called an “angle of attack” (AOA) indicator — is transmitting bad data about the pitch of a plane’s nose. The sensor’s alerts had been operational in previous versions of the 737 but were switched off in the 737 Max.
The news first appeared Sunday in The Wall Street Journal.
The Journal also reported that Federal Aviation Administration safety inspectors and supervisors did not know about the change either. The FAA declined to comment."
From Time magazine.

What could Boeing's reason be for doing this?
Because Southwest did not order the AoA indicators, so they did not get the AoA disagree indicators. Anyway, as pointed out earlier, it would not have made any difference to either of the accidents, even if it was fitted.

It is extremely unlikely that the FAA did not know about it either - as with the previous assertions, this is probably more due to journalists speaking to the wrong people at FAA, than the FAA not knowing.
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Re: Ethiopian Airlines plane crashes on way to Nairobi

Unread post by heisan » Tue Apr 30, 2019 9:34 am

Ugly Duckling wrote:
Tue Apr 30, 2019 12:07 am
On Apr 27th 2019 it became known, that four independent whistleblowers, current and former Boeing employees, had called the FAA hotline for whistleblowers regarding aviation safety concerns on Apr 5th 2019. The concerns reported were wiring damage to the AoA related wiring as result of foreign object damage as well as concerns with the TRIM CUTOUT switches. The FAA believes these reports may open completely new investigative angles into the causes of the two crashes in Indonesia and Ethiopia.
http://avherald.com/h?article=4c534c4a/0045&opt=0
It seems like Boeing has a serious problem with disgruntled ex-employees. But from what little info is provided in that article, these issues would not have affected the Ethiopian accident (although wiring issues could possibly be involved in the Lion Air accident).

Also interesting to note that similar complaints were registered for the 787, and yet it is statistically one of the safest airliners ever manufactured...
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Re: Ethiopian Airlines plane crashes on way to Nairobi

Unread post by heisan » Tue Apr 30, 2019 5:38 pm

Some (very superficial) insight into the design process - but it confirms that the initial safety analysis assumed that pilots would be able to identify trim runaway and correctly follow the trained procedure.

https://www.seattletimes.com/business/b ... ax-design/
“We have gone back and confirmed again, as we do the safety analysis, the engineering analysis, that we followed exactly the steps in our design and certification processes that consistently produce safe airplanes,” he said. “It was designed per our standards. It was certified per our standards.”
...
He pointed to actions by the pilots on the two flights, who he said did not completely follow the standard procedure when uncommanded tail movements begin to push the jet’s nose down. He added that Boeing’s system safety analysis of MCAS, a technical document prepared by Boeing during certification of the MAX, depends in part on the pilot making the appropriate response in the case of a system failure.
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Re: Ethiopian Airlines plane crashes on way to Nairobi

Unread post by Stephan van Tonder » Tue Apr 30, 2019 7:27 pm

heisan wrote:
Tue Apr 30, 2019 9:34 am
It seems like Boeing has a serious problem with disgruntled ex-employees. But from what little info is provided in that article, these issues would not have affected the Ethiopian accident (although wiring issues could possibly be involved in the Lion Air accident).

Also interesting to note that similar complaints were registered for the 787, and yet it is statistically one of the safest airliners ever manufactured...
no MCAS on 787 so failed AOA sensor( Due to wiring) does not cause a constant nose down trim....
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Re: Ethiopian Airlines plane crashes on way to Nairobi

Unread post by heisan » Tue Apr 30, 2019 8:06 pm

Stephan van Tonder wrote:
Tue Apr 30, 2019 7:27 pm
heisan wrote:
Tue Apr 30, 2019 9:34 am
It seems like Boeing has a serious problem with disgruntled ex-employees. But from what little info is provided in that article, these issues would not have affected the Ethiopian accident (although wiring issues could possibly be involved in the Lion Air accident).

Also interesting to note that similar complaints were registered for the 787, and yet it is statistically one of the safest airliners ever manufactured...
no MCAS on 787 so failed AOA sensor( Due to wiring) does not cause a constant nose down trim....
I was referring to the fact that there were a number of anonymous 'whistleblowers' reporting serious safety issues on the 787, which has so far turned out to be one of the safest airliners ever flown. Anonymous whistleblower reports are often more malicious than productive.
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Re: Ethiopian Airlines plane crashes on way to Nairobi

Unread post by tansg » Wed May 01, 2019 9:52 am

Ladies and gentlemen, below is an article which at last addresses the root cause of this issue as explained to me by my numerous Boeing Avionics and software engineer contacts who presently work on various Boeing projects or who have recently retired from Boeing.

https://edition.cnn.com/2019/04/30/poli ... index.html
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Re: Ethiopian Airlines plane crashes on way to Nairobi

Unread post by jimdavis » Wed May 01, 2019 10:07 am

tansg wrote:
Wed May 01, 2019 9:52 am
Ladies and gentlemen, below is an article which at last addresses the root cause of this issue as explained to me by my numerous Boeing Avionics and software engineer contacts who presently work on various Boeing projects or who have recently retired from Boeing.

https://edition.cnn.com/2019/04/30/poli ... index.html
Tansg I am afraid that looks like more sensationalism from CNN. The sort of thing you might expect from 'You' magazine.

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Re: Ethiopian Airlines plane crashes on way to Nairobi

Unread post by tansg » Wed May 01, 2019 10:45 am

jimdavis wrote:
Wed May 01, 2019 10:07 am
tansg wrote:
Wed May 01, 2019 9:52 am
Ladies and gentlemen, below is an article which at last addresses the root cause of this issue as explained to me by my numerous Boeing Avionics and software engineer contacts who presently work on various Boeing projects or who have recently retired from Boeing.

https://edition.cnn.com/2019/04/30/poli ... index.html
Tansg I am afraid that looks like more sensationalism from CNN. The sort of thing you might expect from 'You' magazine.

jim
The sad bit is I wish it was, but it isn't. Don't lose the message due to the medium by which it is conveyed.
The whole issue with single source data is the very root of this issue, everything else is a bye the bye. The best practice, as explained to me by the guy who designed the avionics fit for the B747-8, is that you require at least a 3 source data input on any flight critical system to allow the system to compare and exclude any erroneous data inputs. The information I have been given is that this is not the case for MCAS. AOA sensors are notorious for their unreliability and susceptibility to operational damage and so reliance on a single AoA as data source is hard to believe and thus some very hard questions being asked about the certification process of this aircraft, including how redundant systems were simulated and checked and certain design assumptions used in determining the system architecture.
When recent revelations as to the challenges Boeing is presently facing with build quality (internal FOD) issues (see UASF refusals to accept KC-46s and Qatar refusing to accept aircraft from particular production lines) is taken into account the holes start to line up. With further questions now being raised about the reliability of the cut-out switches (lots of noise about a lower quality of switch being delivered) I get worried. I have been repeatedly told by ex-Boeing engineers that Boeing's culture has changed recently with the engineers losing dominance to the accountants and sales staff and these engineering issues are becoming more prevalent. We all hope this is not so and that these and whole lot more of the issues not yet in the public domain are quickly addressed so that incidents like this do not happen again.
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Re: Ethiopian Airlines plane crashes on way to Nairobi

Unread post by StressMerchant » Wed May 01, 2019 2:00 pm

At this stage I'm still interested in the exact purpose of the MCAS system. My first thought was that it was there to ensure compliance with controllability and maneuverability requirements (FAR 25.143). Subsequently the available information suggested that it was essentially ensuring stability in the approach to the stall, ie FAR 25.203 (and FAR 25.173). I still haven't seen the Max manuals, but I managed to get a look at some -800 manuals which suggest that the stall identification aspect is handled by the speed trim system, and was already doing that in the NG series. Which leads me back to the actual purpose of MCAS?
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Re: Ethiopian Airlines plane crashes on way to Nairobi

Unread post by jimdavis » Wed May 01, 2019 6:07 pm

StressMerchant wrote:
Wed May 01, 2019 2:00 pm
At this stage I'm still interested in the exact purpose of the MCAS system. My first thought was that it was there to ensure compliance with controllability and maneuverability requirements (FAR 25.143). Subsequently the available information suggested that it was essentially ensuring stability in the approach to the stall, ie FAR 25.203 (and FAR 25.173). I still haven't seen the Max manuals, but I managed to get a look at some -800 manuals which suggest that the stall identification aspect is handled by the speed trim system, and was already doing that in the NG series. Which leads me back to the actual purpose of MCAS?
My understanding is that it was to make the handling so similar to the previous aircraft that little or no pilot training would be needed when transitioning.

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Re: Ethiopian Airlines plane crashes on way to Nairobi

Unread post by biffvj » Wed May 01, 2019 7:35 pm

Karlene Petitt's doctoral dissertation on safety makes for interesting reading.

"The objective of this study was to understand pilots’ proclivity toward automation usage
by identifying the relationship among pilot training, aircraft and systems understanding,
safety culture, manual flight behavior, and aviation passion."

7492 pilots participated in her research.

https://drive.google.com/file/d/1_t1Bcv ... b2QXi/view
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Re: Ethiopian Airlines plane crashes on way to Nairobi

Unread post by Ugly Duckling » Thu May 02, 2019 10:10 am

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Re: Ethiopian Airlines plane crashes on way to Nairobi

Unread post by StressMerchant » Thu May 02, 2019 1:01 pm

Ugly Duckling wrote:
Thu May 02, 2019 10:10 am
Quite interesting
https://www.salon.com/2019/04/27/boeing ... m_partner/
I think they are trying to tie together a whole bunch of disparate threads into a story that matches their political outlook.
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Re: Ethiopian Airlines plane crashes on way to Nairobi

Unread post by Ugly Duckling » Thu May 02, 2019 1:50 pm

StressMerchant wrote:
Thu May 02, 2019 1:01 pm
Ugly Duckling wrote:
Thu May 02, 2019 10:10 am
Quite interesting
https://www.salon.com/2019/04/27/boeing ... m_partner/
I think they are trying to tie together a whole bunch of disparate threads into a story that matches their political outlook.
Oops. Will be interesting to see what comes out of the woodwork next.
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