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scbriml
Posts: 19111
Joined: Wed Jul 02, 2003 10:37 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Wed Apr 03, 2019 11:30 pm

Super80Fan wrote:
I know we can trust the media when it comes to aviation as far as we can throw them but now they're saying a damaged sensor caused by a bird/foreign object hitting the plane caused the crash? That seems very odd and implausible unless it took out the pitot tubes or something....

https://abcnews.go.com/Politics/damaged ... dlines_hed


The article says it damaged the AOA sensor which caused bad AOA data (like the Lion flight), which eventually activated MCAS.

morrisond wrote:
The story also says they didn't try to use Electric Trim to counteract MCAS before hitting the cut-off switches.


https://leehamnews.com/2019/04/03/et302 ... more-29790
Time flies like an arrow. Fruit flies like a banana!
There are 10 types of people in the World - those that understand binary and those that don't.
 
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PixelFlight
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 1:07 am

flybucky wrote:
XRAYretired wrote:
Now it all makes sense.

Well, according to PixelFlight, schematics show otherwise.

PixelFlight wrote:
According to the identified publicly available schematic, your speculation is unfortunately wrong.
Both STAB TRIM CUTOFF switches have to be ON to have a powered actuator. If any of the switches is OFF, the actuator can't move.

Darn, too bad. Does what you say apply to both 737 NG and MAX?

Must be formally verified but this is my understanding from what I have read so far. And the schematic have a "MCAS ENGAGE" function into the FCC A/B box (center bottom). MCAS only exists on the 737 MAX.

flybucky wrote:
Do you have links to those schematics? I did some searching and found these links. Are any of these it?
viewtopic.php?f=3&t=1407217&p=21198009#p21198009
https://www.satcom.guru/2018/11/stabilizer-trim.html

In fact the schematic was posted by "fadecfault" (and not in the Satcom Guru blog, sorry for the confusion)
viewtopic.php?f=3&t=1407217&start=1650#p20886627
The same discussion is here:
viewtopic.php?f=3&t=1417545&start=4300#p21247403

flybucky wrote:
What about this quote from the satcom.guru article?

Stabilizer trim requires power to the trim motor. A cutout switch provides a means for the pilot to remove power from the trim motor.
Autopilot trim commands are routed through a second cutout switch, which isolates the autopilot command from the trim motor.

The schematic say something a bit different: as the STAB TRIM CONTROL signal (From P6 CB PANEL) pass trough both switches, both provides a means for the pilot to remove power from the trim motor.
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
mzlin
Posts: 128
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 3:42 am

Per WSJ (https://www.wsj.com/articles/pilots-tak ... 1554347116)
"Preliminary findings from the second crash, which occurred last month in Ethiopia, are expected to stoke criticism from pilots that Boeing and U.S. regulators fell short in highlighting steps crews are supposed to take BEFORE turning off a stall-control feature implicated in both crashes... Other pilots said executing such manual controls to first get the plane into a stable position was instinctive piloting, and there is no need to revise the current checklist. “That’s flying the airplane,” one U.S. pilot said."

At least there is now awareness that one should retrim (using electrical trim tabs) before cutting off the power to the stabilizer. Sadly it's a bit late; maybe it wouldn't have hurt to have emphasized this in the FDA directive.

IMO the WSJ and Seattle Times have provided the best coverage of this crisis so far, with detail and with accuracy. It's refreshing to read these news articles after reading inaccuracies, finger-pointing, statements of indignation, and pronouncements of doom bounce back and forth on various forums.
 
SuperEighty
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 4:09 am

Super80Fan wrote:
I know we can trust the media when it comes to aviation as far as we can throw them but now they're saying a damaged sensor caused by a bird/foreign object hitting the plane caused the crash? That seems very odd and implausible unless it took out the pitot tubes or something....

https://abcnews.go.com/Politics/damaged ... dlines_hed


Several outlets are reporting that the AOA sensor was indeed damaged by a bird or other foreign object on takeoff.

Big news if true.
 
Backseater
Posts: 478
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 5:37 am

Super80Fan wrote:
I know we can trust the media when it comes to aviation as far as we can throw them but now they're saying a damaged sensor caused by a bird/foreign object hitting the plane caused the crash? That seems very odd and implausible unless it took out the pitot tubes or something....

https://abcnews.go.com/Politics/damaged ... dlines_hed

Bole Int airport was/is(?) known for bird strikes by pigeons, doves, black kites, ... A study in 1995 found 33 bird strikes in a year, many early in the morning. And in 1998 at an airport in Northern Ethiopia, a 737 crashed after ingesting 15 pigeons!
If they are looking for an act of God to explain why they are not responsible, that is indeed a good possibility.
Let us see whether the FDR recorded a sudden spike during the latter part of the take-off roll when there may be enough combined kinetic energy to do the deed (unless they have low flying, Mach 0.3 birds out there!)
If they cannot find the sensor's swept vane that is supposed to have been hit, maybe they can provide the autopsy report of the incriminated bird because it was probably sliced in half by the sharp profile of the vane.
 
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N14AZ
Posts: 4140
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 5:45 am

SuperEighty wrote:
Big news if true.

Hmm, but a bird strike should not lead to a modern aircraft crashing.
 
majano
Posts: 272
Joined: Sun Oct 14, 2018 10:45 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 5:49 am

mzlin wrote:
Per WSJ (https://www.wsj.com/articles/pilots-tak ... 1554347116)
"Preliminary findings from the second crash, which occurred last month in Ethiopia, are expected to stoke criticism from pilots that Boeing and U.S. regulators fell short in highlighting steps crews are supposed to take BEFORE turning off a stall-control feature implicated in both crashes... Other pilots said executing such manual controls to first get the plane into a stable position was instinctive piloting, and there is no need to revise the current checklist. “That’s flying the airplane,” one U.S. pilot said."

At least there is now awareness that one should retrim (using electrical trim tabs) before cutting off the power to the stabilizer. Sadly it's a bit late; maybe it wouldn't have hurt to have emphasized this in the FDA directive.

IMO the WSJ and Seattle Times have provided the best coverage of this crisis so far, with detail and with accuracy. It's refreshing to read these news articles after reading inaccuracies, finger-pointing, statements of indignation, and pronouncements of doom bounce back and forth on various forums.

Despite all that is being reported, the so-called "US Pilot" blames the cockpit crew again. I feel that the WSJ is being used by Boeing as a mouthpiece, to manage the message.
 
Interested
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 5:56 am

majano wrote:
mzlin wrote:
Per WSJ (https://www.wsj.com/articles/pilots-tak ... 1554347116)
"Preliminary findings from the second crash, which occurred last month in Ethiopia, are expected to stoke criticism from pilots that Boeing and U.S. regulators fell short in highlighting steps crews are supposed to take BEFORE turning off a stall-control feature implicated in both crashes... Other pilots said executing such manual controls to first get the plane into a stable position was instinctive piloting, and there is no need to revise the current checklist. “That’s flying the airplane,” one U.S. pilot said."

At least there is now awareness that one should retrim (using electrical trim tabs) before cutting off the power to the stabilizer. Sadly it's a bit late; maybe it wouldn't have hurt to have emphasized this in the FDA directive.

IMO the WSJ and Seattle Times have provided the best coverage of this crisis so far, with detail and with accuracy. It's refreshing to read these news articles after reading inaccuracies, finger-pointing, statements of indignation, and pronouncements of doom bounce back and forth on various forums.

Despite all that is being reported, the so-called "US Pilot" blames the cockpit crew again. I feel that the WSJ is being used by Boeing as a mouthpiece, to manage the message.


If you Google Max 737 and just read the news headlines alone there's very little (if any) positive messages in any way for Boeing

If they are trying to use any media as mouthpieces it's not working for them at this stage. They've bee overwhelmed with scrutiny and criticism from so many sides. As have the FAA
 
Backseater
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 5:58 am

And I hope that somebody at the news conference will ask:
"Sir, have you recovered the two angle of attack sensors that were installed on the aircraft? Any pictures?"
"Can you please provide their serial numbers?"
 
sgrow787
Posts: 450
Joined: Fri May 16, 2014 8:12 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:01 am

jollo wrote:
Statement 2: Pressure to implement no-additional-training solution
"Rick Ludtke, a former Boeing engineer who worked on designing the interfaces on the MAX’s flight deck, said managers mandated that any differences from the previous 737 had to be small enough that they wouldn’t trigger the need for pilots to undergo new simulator training."

"He said that if the group had built the MCAS in a way that would depend on two sensors, and would shut the system off if one fails, he thinks the company would have needed to install an alert in the cockpit to make the pilots aware that the safety system was off. And if that happens, Ludtke said, the pilots would potentially need training on the new alert and the underlying system. That could mean simulator time, which was off the table."


This is what I've been saying all along: All the missing MCAS info was because of type certification and reduced training. Basically Boeing found incompetent engineers to sign off on bad process, in order to hide the existence of MCAS (as well as downplaying it to the FAA for certification purposes?). Things start making sense when you look at previous Boeing issues with the 787 batteries, and the lack of quality process at the 787 plant in Charleston, SC:

https://www.youtube.com/watch?v=UqIzcuNpXP0&t=3s
Just one sensor,
Oh just one se-en-sor,
Just one sensor,
Ooh ooh oo-ooh
Oo-oo-ooh.
 
rideforever
Posts: 23
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:07 am

What's the story with Boeing management, has something changed in the last decade or so ?
Is a "management class" in charge now, with little engineering understanding ?
 
kalvado
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:23 am

Backseater wrote:
And I hope that somebody at the news conference will ask:
"Sir, have you recovered the two angle of attack sensors that were installed on the aircraft? Any pictures?"
"Can you please provide their serial numbers?"

recovering AOA sensors for high speed nose down crash?
If this is a joke - it's a pretty stupid one!
 
Backseater
Posts: 478
Joined: Fri Aug 19, 2005 3:20 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:41 am

kalvado wrote:
Backseater wrote:
And I hope that somebody at the news conference will ask:
"Sir, have you recovered the two angle of attack sensors that were installed on the aircraft? Any pictures?"
"Can you please provide their serial numbers?"

recovering AOA sensors for high speed nose down crash?
If this is a joke - it's a pretty stupid one!

I beg your pardon, this is not a joke!
Of course they will be badly damaged. All I am interested in are the metal plates that show P/N and S/N! Those should still be legible.
 
pugman211
Posts: 527
Joined: Thu Dec 20, 2012 1:55 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:43 am

Surely the bird strike (if if happened) would be heard on the CVR and possibly discussed between the crew?
 
WIederling
Posts: 9307
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 6:52 am

MildBlueYonder wrote:
Also, it just seems a bit circular and stupid that MCAS, which is a safety measure intended to catch pilots with poor training who decide to firewall the throttles rather than push the nose forward on the approach to stall, should itself be designed to rely entirely on stellar training to prevent catastrophe in the event of malfunction.


M(aneuvering)CAS is there to avoid too much nose up in coordinated turning ( when depending on roll angle you need more lift for the same sinkrate ). It is not about pilots overamplifying input. Never been made clear how narrow that then hugs a stall.
MCAS is about more than NG feelgood behavior.
Murphy is an optimist
 
ELBOB
Posts: 322
Joined: Sun Jun 21, 2015 6:56 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 7:03 am

rideforever wrote:
What's the story with Boeing management, has something changed in the last decade or so ?
Is a "management class" in charge now, with little engineering understanding ?


Boeing culture and management changed with the merger in 1997, this is well known.

But the company itself has a long history of gotchas and indifference. For over a decade after entering service the 737-200 had a reputation for unpredictable, vicious pitch-up and roll-off on take-off when icing formed symmetrically on the leading edges. Boeing's advice was to go easy on the rotation... Thankfully eventually the NTSB issued a series of recommendations and ADs to address the issue.
 
Interested
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 7:16 am

ELBOB wrote:
rideforever wrote:
What's the story with Boeing management, has something changed in the last decade or so ?
Is a "management class" in charge now, with little engineering understanding ?


Boeing culture and management changed with the merger in 1997, this is well known.

But the company itself has a long history of gotchas and indifference. For over a decade after entering service the 737-200 had a reputation for unpredictable, vicious pitch-up and roll-off on take-off when icing formed symmetrically on the leading edges. Boeing's advice was to go easy on the rotation... Thankfully eventually the NTSB issued a series of recommendations and ADs to address the issue.


The failings of FAA are also clear to see. But it's half understandable. You would just assume that with all the skills and money and talent at Boeing - they surely aren't going to design a plane that's not at least as safe as the one it replaces.

So you wouldn't feel like you need to oversee every decision they make.

As most have said Boeing staff wouldn't deliberately make a plane to kill people

You wouldn't feel you need to watch every step they take when designing this plane
 
gia777
Posts: 145
Joined: Thu Dec 03, 2015 4:12 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 7:40 am

it's still Boeing fault regardless bird strike or foreign object strike...a single broken component should have not caused the plane into disaster.... autopilot should not fight against human pilot. just like in thecar, as soon as I pressed my brake, the cruise control went inactive.
Cheers,

GIA777 :coffee:
 
seb76
Posts: 76
Joined: Tue May 20, 2008 5:02 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 7:50 am

Interested wrote:
ELBOB wrote:
rideforever wrote:
What's the story with Boeing management, has something changed in the last decade or so ?
Is a "management class" in charge now, with little engineering understanding ?


Boeing culture and management changed with the merger in 1997, this is well known.

But the company itself has a long history of gotchas and indifference. For over a decade after entering service the 737-200 had a reputation for unpredictable, vicious pitch-up and roll-off on take-off when icing formed symmetrically on the leading edges. Boeing's advice was to go easy on the rotation... Thankfully eventually the NTSB issued a series of recommendations and ADs to address the issue.


The failings of FAA are also clear to see. But it's half understandable. You would just assume that with all the skills and money and talent at Boeing - they surely aren't going to design a plane that's not at least as safe as the one it replaces.

So you wouldn't feel like you need to oversee every decision they make.

As most have said Boeing staff wouldn't deliberately make a plane to kill people

You wouldn't feel you need to watch every step they take when designing this plane


In the software design world for example. You will not use your programmers for hunting the bugs. They are the worse people for doing that since the person who designs something will generally always use it in the way it was intended (test success guaranteed) and reproducing the scenarios it had in mind when he designed it. On the other hand, once you use it in the real world (user acceptance tests), unexpected things may happen because the users are sometimes creative, uninformed or take alternative paths to bypass the design limitations. It's only at this point that you will detect most mistakes in an efficient way.

Why certify at all if you are not going to study the design using a different approach and point of view? This is complacency at best and a conflict of interests. If my department gets audited, the auditors will want to see things by themselves, they will not blindly trust all I say because they assume that I work in the best interest of the company... That would just defeat the purpose of having an audit process in place.
 
lutfi
Posts: 888
Joined: Wed Sep 27, 2000 6:33 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 8:24 am

Backseater wrote:
kalvado wrote:
Backseater wrote:
And I hope that somebody at the news conference will ask:
"Sir, have you recovered the two angle of attack sensors that were installed on the aircraft? Any pictures?"
"Can you please provide their serial numbers?"

recovering AOA sensors for high speed nose down crash?
If this is a joke - it's a pretty stupid one!

I beg your pardon, this is not a joke!
Of course they will be badly damaged. All I am interested in are the metal plates that show P/N and S/N! Those should still be legible.


The aircraft paperwork will give the P/N and S/N, unless you don't think ET follow basic regulations on maintenance
 
mjoelnir
Posts: 9386
Joined: Sun Feb 03, 2013 11:06 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 8:34 am

lutfi wrote:
Backseater wrote:
kalvado wrote:
recovering AOA sensors for high speed nose down crash?
If this is a joke - it's a pretty stupid one!

I beg your pardon, this is not a joke!
Of course they will be badly damaged. All I am interested in are the metal plates that show P/N and S/N! Those should still be legible.


The aircraft paperwork will give the P/N and S/N, unless you don't think ET follow basic regulations on maintenance


In such a new airplane I would rather look at Boeing if the numbers do not match.
 
vaughanparry
Posts: 73
Joined: Fri Nov 16, 2007 7:46 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 8:35 am

This from today's Daily Telegraph: "Ethiopian air pilots followed Boeing emergency procedures but could not stop plane going down, report says":

https://www.telegraph.co.uk/news/2019/0 ... res-could/
Last edited by vaughanparry on Thu Apr 04, 2019 9:01 am, edited 1 time in total.
 
StTim
Posts: 3714
Joined: Thu Aug 08, 2013 7:39 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 8:42 am

So the preliminary report says the pilots followed the published MCAS failure procedures and yet could still not recover control of the plane.

https://www.bbc.co.uk/news/business-47812225

I am not sure this gets much worse at this point for Boeing and the FAA.
 
pdp
Posts: 245
Joined: Thu Dec 14, 2017 7:14 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 8:51 am

StTim wrote:
So the preliminary report says the pilots followed the published MCAS failure procedures and yet could still not recover control of the plane.

https://www.bbc.co.uk/news/business-47812225

I am not sure this gets much worse at this point for Boeing and the FAA.


Why would it keep nosediving though? Did they disable the electric trim then try and recover, or was there a more fatal flaw?
 
sgrow787
Posts: 450
Joined: Fri May 16, 2014 8:12 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 8:55 am

Interested wrote:
As most have said Boeing staff wouldn't deliberately make a plane to kill people


It's not that simple. You don't have to want to kill people to put people's lives at risk. With a large company like Boeing, together with the complex processes involved with certification, a lot of responsibility gets spread around everywhere, so much so that no one person can be held to blame for a potential catastrophe. Was it the bad sensor? Maybe the bad maintenance on the sensor? Or was it the badly design system that incorrectly used the data from the bad sensor? Or was it the FAA who improperly certified the final product? Maybe it was the pilots for not being trained or having enough flying time on type?

But somewhere in all this was a business decision to put forward a product by a certain date to be competitive with the A320neo. And that is a reactionary business model, based on a lack of confidence in one's own creativity and engineering skill to see the value in long term strategy. Are American engineers not confident in what they can create? Or perhaps there's a management layer that is too business based, and less engineering based?
Just one sensor,
Oh just one se-en-sor,
Just one sensor,
Ooh ooh oo-ooh
Oo-oo-ooh.
 
uta999
Posts: 917
Joined: Mon Jun 14, 2010 11:10 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 8:56 am

So are Boeing now saying both crashes were 'probably' caused by something hitting the single nose AoA vane, causing the MCAS to kick-in repeatedly, owing to a software bug?

Implausible - MUCH!

And impossible to verify / prove either way.

https://www.google.com/search?q=aoa+van ... 20&bih=937
Your computer just got better
 
mjoelnir
Posts: 9386
Joined: Sun Feb 03, 2013 11:06 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:05 am

uta999 wrote:
So are Boeing now saying both crashes were 'probably' caused by something hitting the single nose AoA vane, causing the MCAS to kick-in repeatedly, owing to a software bug?

Implausible - MUCH!

And impossible to verify / prove either way.

https://www.google.com/search?q=aoa+van ... 20&bih=937


Investigators have not identified any damage to aircraft sensors in relation to crash
https://edition.cnn.com/africa/live-new ... index.html

quote: “We can confirm that we haven’t found any foreign object damage,” Colonel Amdeye Fenta, chief of Ethiopian Accident Information Bureau, told reporters at a news conference on Thursday, speaking through a translator.

I think we can lay the "bird strike" hypothesis to rest.
 
mjoelnir
Posts: 9386
Joined: Sun Feb 03, 2013 11:06 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:08 am

https://edition.cnn.com/africa/live-new ... index.html

Preliminary report says crew 'performed all procedures repeatedly'
quote: The preliminary report finds that the Ethiopian Airlines crew "performed all procedures repeatedly provided by the manufacturer but were unable to control the aircraft," according to Ethiopian safety investigators in the capital Addis Ababa.

I would say over to you Boeing
 
mjoelnir
Posts: 9386
Joined: Sun Feb 03, 2013 11:06 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:31 am

Interested wrote:
ELBOB wrote:
rideforever wrote:
What's the story with Boeing management, has something changed in the last decade or so ?
Is a "management class" in charge now, with little engineering understanding ?


Boeing culture and management changed with the merger in 1997, this is well known.

But the company itself has a long history of gotchas and indifference. For over a decade after entering service the 737-200 had a reputation for unpredictable, vicious pitch-up and roll-off on take-off when icing formed symmetrically on the leading edges. Boeing's advice was to go easy on the rotation... Thankfully eventually the NTSB issued a series of recommendations and ADs to address the issue.


The failings of FAA are also clear to see. But it's half understandable. You would just assume that with all the skills and money and talent at Boeing - they surely aren't going to design a plane that's not at least as safe as the one it replaces.

So you wouldn't feel like you need to oversee every decision they make.

As most have said Boeing staff wouldn't deliberately make a plane to kill people

You wouldn't feel you need to watch every step they take when designing this plane


The battery problem in the 787 should have been a wake up call for the FAA. It seems they went to sleeping straight away again.
 
sadiqutp
Posts: 290
Joined: Thu Sep 08, 2016 5:05 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:36 am

mjoelnir wrote:
https://edition.cnn.com/africa/live-news/ethiopian-airlines-black-box-report/index.html

Preliminary report says crew 'performed all procedures repeatedly'
quote: The preliminary report finds that the Ethiopian Airlines crew "performed all procedures repeatedly provided by the manufacturer but were unable to control the aircraft," according to Ethiopian safety investigators in the capital Addis Ababa.

I would say over to you Boeing

Beside the conference, The report is not published, right? I can't find it
 
RawSushi
Posts: 89
Joined: Sun Aug 19, 2018 9:02 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:36 am

WIederling wrote:
M(aneuvering)CAS is there to avoid too much nose up in coordinated turning ( when depending on roll angle you need more lift for the same sinkrate ). It is not about pilots overamplifying input. Never been made clear how narrow that then hugs a stall.
MCAS is about more than NG feelgood behavior.


I was wondering about this. MCAS has been characterized as an anti-stall system in the media and most posters here. Some have even said it's really a variation of "stick pusher". The way Boeing implemented it makes it behaves like an anti-stall system too.

This runs against the original purpose of MCAS, which is explained here very well at http://www.b737.org.uk/mcas.htm
MCAS is a longitudinal stability enhancement. It is not for stall prevention (although indirectly it helps) or to make the MAX handle like the NG (although it does); it was introduced to counteract the non-linear lift generated by the LEAP-1B engine nacelles at high AoA and give a steady increase in stick force as the stall is approached as required by regulation.


If that's the purpose, then the way it is currently implemented is appallingly unfit for purpose. Counteracting a non-linear lift force generated by the engine nacelles at high AoA should just be about trimming the stabilizer to the appropriate level so that the nose-down force exactly counter-balances the nose-up force from the engine nacelles. Shouldn't this ideally be done by a computer that knows how much stab trim adjustment is needed at specific AoAs, roll angles and airspeed and then make the necessary adjustment to ensure that the nose-up/down forces balances out and handling remains neutral? How engineers at Boeing believe that this should be done by repeating arbitrarily large movements of the stabilizer on a cumulative basis per-activation is totally mind-boggling to me. Did some people completely misunderstand the brief?
 
RossW
Posts: 31
Joined: Sat May 08, 2010 3:39 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:38 am

sadiqutp wrote:
mjoelnir wrote:
https://edition.cnn.com/africa/live-news/ethiopian-airlines-black-box-report/index.html

Preliminary report says crew 'performed all procedures repeatedly'
quote: The preliminary report finds that the Ethiopian Airlines crew "performed all procedures repeatedly provided by the manufacturer but were unable to control the aircraft," according to Ethiopian safety investigators in the capital Addis Ababa.

I would say over to you Boeing

Beside the conference, The report is not published, right? I can't find it


"While Ethiopian investigators announced in a press conference the findings of the preliminary report, they haven't actually published the report.

CNN anchor and aviation expert Richard Quest said this was "unusual."

"We are slightly taking their word for what they are saying is in the report," he said."
 
XRAYretired
Posts: 870
Joined: Fri Mar 15, 2019 11:21 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:39 am

mjoelnir wrote:
uta999 wrote:
So are Boeing now saying both crashes were 'probably' caused by something hitting the single nose AoA vane, causing the MCAS to kick-in repeatedly, owing to a software bug?

Implausible - MUCH!

And impossible to verify / prove either way.

https://www.google.com/search?q=aoa+van ... 20&bih=937


Investigators have not identified any damage to aircraft sensors in relation to crash
https://edition.cnn.com/africa/live-new ... index.html

quote: “We can confirm that we haven’t found any foreign object damage,” Colonel Amdeye Fenta, chief of Ethiopian Accident Information Bureau, told reporters at a news conference on Thursday, speaking through a translator.

I think we can lay the "bird strike" hypothesis to rest.


Recommend hold the horses before coming to that conclusion. We have potentailly conflicting reports here. It may be that the sensors have not yet been recovered or they could not confirm damage to them beyond the crash damage and may have other evidence for a bird strike.

Suggest 'open mind' should be the order of the day.

Ray
 
Interested
Posts: 887
Joined: Thu May 19, 2016 12:19 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:43 am

sgrow787 wrote:
Interested wrote:
As most have said Boeing staff wouldn't deliberately make a plane to kill people


It's not that simple. You don't have to want to kill people to put people's lives at risk. With a large company like Boeing, together with the complex processes involved with certification, a lot of responsibility gets spread around everywhere, so much so that no one person can be held to blame for a potential catastrophe. Was it the bad sensor? Maybe the bad maintenance on the sensor? Or was it the badly design system that incorrectly used the data from the bad sensor? Or was it the FAA who improperly certified the final product? Maybe it was the pilots for not being trained or having enough flying time on type?

But somewhere in all this was a business decision to put forward a product by a certain date to be competitive with the A320neo. And that is a reactionary business model, based on a lack of confidence in one's own creativity and engineering skill to see the value in long term strategy. Are American engineers not confident in what they can create? Or perhaps there's a management layer that is too business based, and less engineering based?


I read that new design would take Boeing 10 years and adding to 737 would take 6 years. And that American Airlines talking to airbus about a big order prompted Boeing to promise a new plane in the 6 year timescale

So it's not just about confidence in the engineers but timescales to deliver

And it's a rush job that's led to this situation
 
WIederling
Posts: 9307
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:43 am

seb76 wrote:
In the software design world for example. You will not use your programmers for hunting the bugs. They are the worse people for doing that since the person who designs something will generally always use it in the way it was intended (test success guaranteed) and reproducing the scenarios it had in mind when he designed it.


Minimum Man by Robert Sheckley:
http://booksonline.com.ua/view.php?book=133793
Murphy is an optimist
 
WIederling
Posts: 9307
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:56 am

RawSushi wrote:
WIederling wrote:
M(aneuvering)CAS is there to avoid too much nose up in coordinated turning ( when depending on roll angle you need more lift for the same sinkrate ). It is not about pilots overamplifying input. Never been made clear how narrow that then hugs a stall.
MCAS is about more than NG feelgood behavior.


I was wondering about this. MCAS has been characterized as an anti-stall system in the media and most posters here. Some have even said it's really a variation of "stick pusher". The way Boeing implemented it makes it behaves like an anti-stall system too.

This runs against the original purpose of MCAS, which is explained here very well at http://www.b737.org.uk/mcas.htm
MCAS is a longitudinal stability enhancement. It is not for stall prevention (although indirectly it helps) or to make the MAX handle like the NG (although it does); it was introduced to counteract the non-linear lift generated by the LEAP-1B engine nacelles at high AoA and give a steady increase in stick force as the stall is approached as required by regulation.


If that's the purpose, then the way it is currently implemented is appallingly unfit for purpose. Counteracting a non-linear lift force generated by the engine nacelles at high AoA should just be about trimming the stabilizer to the appropriate level so that the nose-down force exactly counter-balances the nose-up force from the engine nacelles. Shouldn't this ideally be done by a computer that knows how much stab trim adjustment is needed at specific AoAs, roll angles and airspeed and then make the necessary adjustment to ensure that the nose-up/down forces balances out and handling remains neutral? How engineers at Boeing believe that this should be done by repeating arbitrarily large movements of the stabilizer on a cumulative basis per-activation is totally mind-boggling to me. Did some people completely misunderstand the brief?


your two quotes show facets of the same problem domain.
relaxed counter stick forces make it easy to increase AoA unintentionally.
The algorithm that does the trim adjust needs the physical action of the plane as a reaction to trim down ( AoA reduced) to "close the loop". Initially no checking, the configuration is a I Controller with limits determined by the hardware ( trim spindle). perfect for runaway behavior.
Murphy is an optimist
 
mjoelnir
Posts: 9386
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 10:06 am

XRAYretired wrote:
mjoelnir wrote:
uta999 wrote:
So are Boeing now saying both crashes were 'probably' caused by something hitting the single nose AoA vane, causing the MCAS to kick-in repeatedly, owing to a software bug?

Implausible - MUCH!

And impossible to verify / prove either way.

https://www.google.com/search?q=aoa+van ... 20&bih=937


Investigators have not identified any damage to aircraft sensors in relation to crash
https://edition.cnn.com/africa/live-new ... index.html

quote: “We can confirm that we haven’t found any foreign object damage,” Colonel Amdeye Fenta, chief of Ethiopian Accident Information Bureau, told reporters at a news conference on Thursday, speaking through a translator.

I think we can lay the "bird strike" hypothesis to rest.


Recommend hold the horses before coming to that conclusion. We have potentailly conflicting reports here. It may be that the sensors have not yet been recovered or they could not confirm damage to them beyond the crash damage and may have other evidence for a bird strike.

Suggest 'open mind' should be the order of the day.

Ray


Who did a conflicting report, the NTSB, or some Boeing friends? Some fake news flat earhthers conspiracy theorists?

As far as I know there is one preliminary report about the crash and that is the status one should discuss.
 
User avatar
PW100
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 10:08 am

MildBlueYonder wrote:
dtw2hyd wrote:
If KC-46 already has a better implementation of MCAS, why can't Boeing just port it to MAX. This is not the right to keep counting beans.


Yeah, I’ve been wondering the same. Seems like the engineering and failure mode analyses for the KC-46 version of MCAS yielded all of the protections now being retrofitted into the MAX implementation. Kinda argues circumstantially in favor of external influence being applied to the latter.

Also, it just seems a bit circular and stupid that MCAS, which is a safety measure intended to catch pilots with poor training who decide to firewall the throttles rather than push the nose forward on the approach to stall, should itself be designed to rely entirely on stellar training to prevent catastrophe in the event of malfunction.


Well, the KC-46 probably did not have any implementation constraints with respect to training.

Apparently, one of the design constraints in the 737 MAX was that (pilot) conversion from NG to MAX should be very limited and no sim training.
I don't expect that USAF put such constraints on the KC-46.
Immigration officer: "What's the purpose of your visit to the USA?" Spotter: "Shooting airliners with my Canon!"
 
Interested
Posts: 887
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 10:14 am

https://www.theverge.com/2019/4/4/18294 ... ash-report

This report says pilots not to blame as they followed procedure, no foreign objects involved and focus of the crash investigation is on the plane automation
 
mxaxai
Posts: 1885
Joined: Sat Jun 18, 2016 7:29 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 10:17 am

XRAYretired wrote:
Recommend hold the horses before coming to that conclusion. We have potentailly conflicting reports here. It may be that the sensors have not yet been recovered or they could not confirm damage to them beyond the crash damage and may have other evidence for a bird strike.

Suggest 'open mind' should be the order of the day.

Ray

Even if there was a bird strike, it should not have catastrophic consequences. The Concorde crash was ultimately caused by a piece of scrap metal / FOD, but Concorde was still grounded until the fuel tanks and tyres had been reinforced.
After all, why should engines be tested to withstand a turkey when a tit impact on the nose can do just the same?
 
planecane
Posts: 1572
Joined: Thu Feb 09, 2017 4:58 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 10:21 am

sgrow787 wrote:
Interested wrote:
As most have said Boeing staff wouldn't deliberately make a plane to kill people


But somewhere in all this was a business decision to put forward a product by a certain date to be competitive with the A320neo. And that is a reactionary business model, based on a lack of confidence in one's own creativity and engineering skill to see the value in long term strategy. Are American engineers not confident in what they can create? Or perhaps there's a management layer that is too business based, and less engineering based?


Boeing wanted to do a clean sheet replacement but said that the engine technology needed for the efficiency gain to make it worth it (I believe they said 15% or 20% better than the A320 NEO) wouldn't be available until at least 2025. They wanted to just keep selling the 737NG as their narrowbody offering until then. Airbus decided to do the NEO and Airlines, specifically AA, told Boeing that they would not wait until after 2025 and that if they didn't offer something with similar efficiency to the NEO in a similar time frame they would order the A320NEO series.

In a nutshell, a clean sheet with the same engines as the A320NEO would not have been that much more efficient than the A320NEO and would not have commanded enough of a price premium over the A320NEO.

I could ask the question (sarcastically) are European engineers not confident in what they can create? After all, they just slapped new engines on the A320 series and didn't have do do nearly the design work that Boeing engineers had to do to put the same generation engines on the 737. Is Airbus management too business based to do the NEO instead of a clean sheet replacement?
 
XRAYretired
Posts: 870
Joined: Fri Mar 15, 2019 11:21 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 10:22 am

mjoelnir wrote:
XRAYretired wrote:
mjoelnir wrote:

Investigators have not identified any damage to aircraft sensors in relation to crash
https://edition.cnn.com/africa/live-new ... index.html

quote: “We can confirm that we haven’t found any foreign object damage,” Colonel Amdeye Fenta, chief of Ethiopian Accident Information Bureau, told reporters at a news conference on Thursday, speaking through a translator.

I think we can lay the "bird strike" hypothesis to rest.


Recommend hold the horses before coming to that conclusion. We have potentailly conflicting reports here. It may be that the sensors have not yet been recovered or they could not confirm damage to them beyond the crash damage and may have other evidence for a bird strike.

Suggest 'open mind' should be the order of the day.

Ray


Who did a conflicting report, the NTSB, or some Boeing friends? Some fake news flat earhthers conspiracy theorists?

As far as I know there is one preliminary report about the crash and that is the status one should discuss.


No formal preliminary report has been issued.
I refer to statements reported in this thread that you must have read or you would not be mentioning foreign object damage. Suggest you refrain from posting if you cant take constructive remarks.
 
morrisond
Posts: 2720
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 10:42 am

Interested wrote:
https://www.theverge.com/2019/4/4/18294317/boeing-737-max-ethiopian-airlines-crash-report

This report says pilots not to blame as they followed procedure, no foreign objects involved and focus of the crash investigation is on the plane automation


Yes but that is offset by this report

https://abcnews.go.com/International/da ... dlines_hed

Which says that they did not follow all procedures and they did not trim up before turning off MCAS and that they were the ones (the pilots) to turn MCAS back on. It sounds like they knew how to turn Electric trim and MCAS off but weren't using the electric trim to counteract MCAS.

I'm also pretty sure that the procedure for avoiding a stall is to not let your speed to go beyond the safe airspeed limit of 230 knots either.

They should have been able to cross check there airspeed with the Standby instrument (unless it's feed was damaged as well) which I would have to guess would have been a published procedure as well.

It's just as important on a Jet (any jet) to keep your speed below the upper limit as above the lower limit.

All that being said all this is speculation without seeing the full FDR traces.

The fact that it is an Ethiopian Crash Investigation of an Ethiopian Airline and an Ethiopian Crew does not give me a lot of confidence - I'm sure they will do whatever they can to hold themselves blameless.

Would anyone on here accept MCAS was fixed if Boeing were allowed to self certify again and not show the work they have done or any evidence?

The most interesting thing I learned this morning was that they were airborne for 6 minutes - I thought it was 40 seconds.
Last edited by morrisond on Thu Apr 04, 2019 10:50 am, edited 1 time in total.
 
RossW
Posts: 31
Joined: Sat May 08, 2010 3:39 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 10:46 am

Can we wait until the preliminary report is released please?

So much speculation regarding the procedures of the pilots.
 
sadiqutp
Posts: 290
Joined: Thu Sep 08, 2016 5:05 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 10:47 am

morrisond wrote:

The fact that it is an Ethiopian Crash Investigation of an Ethiopian Airline and an Ethiopian Crew does not give me a lot of confidence - I'm sure they will do whatever they can to hold themselves blameless.
.


I thought NTSB is taking part of the investigation :wave:
 
XRAYretired
Posts: 870
Joined: Fri Mar 15, 2019 11:21 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 10:48 am

mxaxai wrote:
XRAYretired wrote:
Recommend hold the horses before coming to that conclusion. We have potentailly conflicting reports here. It may be that the sensors have not yet been recovered or they could not confirm damage to them beyond the crash damage and may have other evidence for a bird strike.

Suggest 'open mind' should be the order of the day.

Ray

Even if there was a bird strike, it should not have catastrophic consequences. The Concorde crash was ultimately caused by a piece of scrap metal / FOD, but Concorde was still grounded until the fuel tanks and tyres had been reinforced.
After all, why should engines be tested to withstand a turkey when a tit impact on the nose can do just the same?

Of course not. The question was related to why the AoA sensor may have been providing incorrect data (assuming it did). Read the thread for credible hypothesis for single AoA sensor failed high can lead to catestrophic consequences, as it seems it probably did.
Ray
 
dtw2hyd
Posts: 8344
Joined: Wed Jan 09, 2013 12:11 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 10:53 am

morrisond wrote:
does not give me a lot of confidence .


I don't think anyone looking for your stamp of approval. Most are looking for an amicable resolution. Everyone pretends to care about facts, but we all know facts will be known to only a few people.
All posts are just opinions.
 
morrisond
Posts: 2720
Joined: Thu Jan 07, 2010 12:22 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 10:57 am

RossW wrote:
Can we wait until the preliminary report is released please?

So much speculation regarding the procedures of the pilots.


It would be nice if they actually released it along with the FDR traces to back it up.

Right now most of the news stories are quoting Ethiopian Airlines press release on the preliminary report.

Apparently the full report won't be out for a year.
 
mjoelnir
Posts: 9386
Joined: Sun Feb 03, 2013 11:06 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 11:01 am

morrisond wrote:
Interested wrote:
https://www.theverge.com/2019/4/4/18294317/boeing-737-max-ethiopian-airlines-crash-report

This report says pilots not to blame as they followed procedure, no foreign objects involved and focus of the crash investigation is on the plane automation


Yes but that is offset by this report

https://abcnews.go.com/International/da ... dlines_hed

Which says that they did not follow all procedures and they did not trim up before turning off MCAS and that they were the ones (the pilots) to turn MCAS back on. It sounds like they knew how to turn Electric trim and MCAS off but weren't using the electric trim to counteract MCAS.

I'm also pretty sure that the procedure for avoiding a stall is to not let your speed to go beyond the safe airspeed limit of 230 knots either.

They should have been able to cross check there airspeed with the Standby instrument (unless it's feed was damaged as well) which I would have to guess would have been a published procedure as well.

It's just as important on a Jet (any jet) to keep your speed below the upper limit as above the lower limit.

All that being said all this is speculation without seeing the full FDR traces.

The fact that it is an Ethiopian Crash Investigation of an Ethiopian Airline and an Ethiopian Crew does not give me a lot of confidence - I'm sure they will do whatever they can to hold themselves blameless.

Would anyone on here accept MCAS was fixed if Boeing were allowed to self certify again and not show the work they have done or any evidence?

The most interesting thing I learned this morning was that they were airborne for 6 minutes - I thought it was 40 seconds.


That is not a report, that is a news story.

The point to the speed is, the pilots had stall warning and unreliable airspeed, so according to that checklist you hardly reduce speed to be sure to not hit the lower limit. Higher speed makes trimming more difficult because of higher forces on tailplane and elevator.
The checklist you need to use for MCAS according to Boeing does not mention trimming to neutral first before hitting the cutout, it is perhaps logical, but not on the list. Trying to get electrical trim again by throwing the switches to on again seems not to have helped them either.
 
mjoelnir
Posts: 9386
Joined: Sun Feb 03, 2013 11:06 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 11:08 am

morrisond wrote:
RossW wrote:
Can we wait until the preliminary report is released please?

So much speculation regarding the procedures of the pilots.


It would be nice if they actually released it along with the FDR traces to back it up.

Right now most of the news stories are quoting Ethiopian Airlines press release on the preliminary report.

Apparently the full report won't be out for a year.


Not Ethiopian Airlines press release. It is the press release of the investigators preliminary report.

Are you really astonished about how long it will take to come to the full report? How long did it take the NTSB for the relatively simple battery fire on the 787? Where is the full report of the NTSB on Atlas Air 3591? The full reports take always a long time. Preliminary reports are for preliminary information, so some action can be taken.

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