Go Back  PPRuNe Forums > Flight Deck Forums > Rumours & News
Reload this Page >

Ethiopian airliner down in Africa

Rumours & News Reporting Points that may affect our jobs or lives as professional pilots. Also, items that may be of interest to professional pilots.

Ethiopian airliner down in Africa

Old 23rd Mar 2019, 01:30
  #2381 (permalink)  
 
Join Date: Jan 2008
Location: Australia
Posts: 68
Originally Posted by Loose rivets View Post
So what's being said is, the AoA vane hub is rotated in error by one screw-hole place?

For it to be able to be so misaligned seems impossible - for the main casting to not be designed D shaped, or have a flat edge would be deeply worrying.
I think that it's been established elsewhere on the thread/s that there are lugs or something that means that they can only be installed in the correct orientation - but tdracer has said that he has seen them carefully machined off so that they can in fact be incorrectly fitted...
artee is offline  
Old 23rd Mar 2019, 02:32
  #2382 (permalink)  
Psychophysiological entity
 
Join Date: Jun 2001
Location: Tweet Rob_Benham Famous author. Well, slightly famous.
Age: 80
Posts: 4,877
The only reason I can think of for doing that would be for one unit to be able to fit a new aircraft. Hmmm . . . now let me think.

'We could make those NG vanes fit the MAX if we shaved the lug a little.'
Loose rivets is online now  
Old 23rd Mar 2019, 03:23
  #2383 (permalink)  
 
Join Date: Feb 2019
Location: shiny side up
Posts: 431
Since it has not been disclosed the conditions and settings where the engine nacelles provide extra lift and nose up the ac (if/when MCAS kicks in)...an AoA sensor is meaningless.

The UT AoA sensors have an offset bolt pattern to insure correct installation.


Last edited by Smythe; 23rd Mar 2019 at 03:39.
Smythe is offline  
Old 23rd Mar 2019, 03:39
  #2384 (permalink)  
 
Join Date: Dec 2010
Location: Balikpapan, INDONESIA
Age: 68
Posts: 536
Operational useof angle of attack - boeing

Does this help

OPERATIONAL USEOF ANGLE OF ATTACK
WingNut60 is offline  
Old 23rd Mar 2019, 03:39
  #2385 (permalink)  
 
Join Date: Nov 2015
Location: Bay Area, CA
Posts: 65
A nuance that I have not seen stated here previously, one well worth considering as people go back and forth arguing over whether or not the pilots should have saved the day:

MCAS introduced a single point of failure that without pilot intervention in a highly specific way results 100 percent of the time in the aircraft flying itself into the ground. Either the pilot nails the answer to the question while all hell is breaking loose and g-loads are all over the place (about a system which they had no awareness existed), and they do it within a very very short period of time, or the airplane will 100 percent fly itself into the ground. Straight into the ground BTW.

I cannot recall any other instance of a single point of failure system or sensor (or any system for that matter) on a commercial airplane which places the airplane in a state where the only chance for survival is a single action by the pilot, without which the airplane will crash. Once the AOA failed in Indonesia the airplane was essentially trying to fly itself into the ground. The Capt. kept that from happening for a bit, then it succeeded when he handed the airplane to the FO to grab the book and look for an answer that was not in fact there.

I can recall tons of technical issues that resulted in incidents and accidents, in fact I’ve survived a few on my own, but none where the failure of a single sensor meant that a perfectly good airplane was literally trying to kill everyone on board.

We can go round and round about whether or not the flight crew should have been able to aviate their way out of the circumstance they found themselves in, but if the penalty for failure to act quickly enough and perfectly enough on any given in-flight issue on a single sensor and a system about which you knew nothing was immediate death for you and your passengers would you still choose to fly?? Are you that certain of your perfection in the air??

If you knew that there might be a system on your airplane that you knew nothing about and that had the power to command the airplane to try to kill you, would you fly in that airplane, or god forbid take command of it with a couple hundred people in your care??

That is exactly what Boeing did to every MAX crew that flew the airplane. And whether with ill-intent or not they did it knowingly and deliberately. We don’t know them now, but Boeing is filled with smart people. Someone(s) knew exactly what Boeing was doing putting MCAS into service in the clandestine way they did, and I presume it was done that way for an (as yet unknown) reason. Those people will speak up at some point, or I hope they will anyway because it was no accident that MCAS anonymously arrived in the MAX without flight crews being made aware of its presence.

We can argue that the Lion Air crews who successfully survived an otherwise fatal experience should have alerted the airline, and we can argue a ton of other things too.

What we cannot argue, for one moment, is that the regulatory system that allowed Boeing to self-certify safety of the 737 MAX functioned as intended.

What we cannot argue is that Boeing and the regulatory system produced a safe airplane.

Quite to the contrary they produced an airplane that with the right type of single sensor failure would immediately try to kill everyone on board, with only the immediate and correct intervention of the pilots, who had no idea that the system trying to kill them even existed, to prevent that outcome.

The surprising thing isn’t that it happened, it’s that it took so long to happen.

Regards-
dce
wonkazoo is offline  
Old 23rd Mar 2019, 03:40
  #2386 (permalink)  
 
Join Date: Jul 2014
Location: Harbour Master Place
Posts: 662
Originally Posted by GH5 View Post
There is a Boeing document made around year 2000 regarding how Boeing defines AOA I cannot post the link but the cover sheet label is
" operational use of angle of attack on modern commercial airplanes "

Aero 10 Flight operations
John cashman director
brian d kelley technical fellow

can be downloaded as a pdf or viewed in html
Here is your link: OPERATIONAL USE OF ANGLE OF ATTACK (pdf)
CurtainTwitcher is offline  
Old 23rd Mar 2019, 03:41
  #2387 (permalink)  
 
Join Date: Dec 2010
Location: Balikpapan, INDONESIA
Age: 68
Posts: 536
Originally Posted by Smythe View Post
Since it has not been disclosed the conditions and settings where the engine nacelles provide extra lift and nose up the ac (if/when MCAS kicks in)...an AoA sensor is meaningless.

The UT AoA sensors have an offset bolt pattern to insure correct installation.
What about positioning of the internal sensors? Are they indexed for location?
Can you take the units apart?


WingNut60 is offline  
Old 23rd Mar 2019, 03:51
  #2388 (permalink)  
 
Join Date: Feb 2019
Location: shiny side up
Posts: 431
Yes, the sensor vane is integral to the internals.


It is indexed, according to the individual aircraft angle of attack of the wing to fuselage angle. I believe that if you consider the fuselage horizontal or at 0, the wing chord line is at an angle of 2.5 degrees on the 737?

What is unclear to me is why it is necessary for the AoA sensor to be a vane outside of the ac. It is assumed that airflow is horizontal, and the fuselage/wing combination is at an angle to horizontal. Why is the AoA sensor not internal like the IRU gyro?

Last edited by Smythe; 23rd Mar 2019 at 04:12.
Smythe is offline  
Old 23rd Mar 2019, 03:53
  #2389 (permalink)  
 
Join Date: Dec 2010
Location: Balikpapan, INDONESIA
Age: 68
Posts: 536
Originally Posted by CurtainTwitcher View Post
Here is your link: OPERATIONAL USE OF ANGLE OF ATTACK (pdf)
Metadata indicates that this document was created and last edited in Sept 2009.
WingNut60 is offline  
Old 23rd Mar 2019, 04:01
  #2390 (permalink)  
 
Join Date: Jul 2014
Location: Harbour Master Place
Posts: 662
Originally Posted by WingNut60 View Post
Metadata indicates that this document was created and last edited in Sept 2009.
OK, there is an archive.org version of the document from < 2004 Version OPERATIONAL USE OF ANGLE OF ATTACK
CurtainTwitcher is offline  
Old 23rd Mar 2019, 04:02
  #2391 (permalink)  
 
Join Date: Feb 2009
Location: Seattle
Posts: 379
Originally Posted by Takwis View Post
Several times over the last few days, people have reached the conclusion that with full nose down trim on the stabilizer, there is not enough elevator authority to overcome the trim condition. This Reuters article repeats that idea. I just searched my manual, and in the section on loss of electric trim, the statement is made that:
"NOTE: Elevator Control is sufficient to safely land the aircraft regardless of stabilizer position." Is that difference in control available due to blowdown on the elevator at high speed, or some other reason, or simply not true?
I believe that manual statement refers to the design criteria that continued safe flight and landing must be possible with the horizontal stabilizer frozen in any normally encountered position. The key here is ďnormally encounteredĒ. This statement does not imply that it will be possible to safely land after running the stabilizer all the way to one end of its travel. Another key part of being able to safely return and land is not accelerating and cleaning up flaps with a frozen stabilizer.
FCeng84 is offline  
Old 23rd Mar 2019, 04:33
  #2392 (permalink)  
 
Join Date: May 2008
Location: us
Posts: 16
Originally Posted by FCeng84 View Post

Another key part of being able to safely return and land is not accelerating and cleaning up flaps with a frozen stabilizer.
A shame Boeing didn't include such warnings in the event of MCAS driving the stab nose down.

Oh wait, Boeing didn't even admit the existence of MCAS.
runner1021 is offline  
Old 23rd Mar 2019, 04:36
  #2393 (permalink)  
 
Join Date: Oct 2007
Location: Here
Posts: 771
Originally Posted by Alchad View Post
For example, the ARINC 429 representation of AoA uses two's complement fraction binary notation (BNR). It is interesting to note that bit 26 represents 22.5 degrees which would be the bit "flipping" between the Captain and F/O AoA values
https://www.satcom.guru/2019/03/ethi...lion.html#more

The full post contains quite a few comments which I think will generate a few talking points.

From preliminary report.
"PRELIMINARY
KNKT.18.10.35.04"

Copy here for now -
http://www.flightradar24.com/blog/wp...ary-Report.pdf

- At least one AoA sensor was changed immediately before penultimate flight. Presumably there was a percieved AoA sensor issue.
"replaced angle of attack sensor"

- Captain side AoA sensor showed 22 degree error for entirity of penultimate flight.

- Captain side AoA sensor showed 22 degree error for entirity of crash flight.

Perhaps the AoA sensor was not faulty and the issue lay elsewhere and was not correctly repaired?

I like** the idea of an encoding error. (**like the idea as an explanation for the observed symptoms - I don't like it that there was a crash - added in the hope of deflecting the present preposterous PPRuNe pedants)

I doubt very much it was a transmission/reception error on the BUS since that almost certainly has CRC error detection.

The sensor is an analog device and there will be an A to D converter at some stage.

A bad bit within the AD converter data path seems a distinct possibility.

Last edited by jimjim1; 23rd Mar 2019 at 09:27. Reason: fixed bad flightradar24 link
jimjim1 is offline  
Old 23rd Mar 2019, 04:39
  #2394 (permalink)  
 
Join Date: Sep 2018
Location: Laredo, TX
Posts: 121
Originally Posted by wonkazoo View Post
A nuance that I have not seen stated here previously, one well worth considering as people go back and forth arguing over whether or not the pilots should have saved the day:

MCAS introduced a single point of failure that without pilot intervention in a highly specific way results 100 percent of the time in the aircraft flying itself into the ground. Either the pilot nails the answer to the question while all hell is breaking loose and g-loads are all over the place (about a system which they had no awareness existed), and they do it within a very very short period of time, or the airplane will 100 percent fly itself into the ground. Straight into the ground BTW.

I cannot recall any other instance of a single point of failure system or sensor (or any system for that matter) on a commercial airplane which places the airplane in a state where the only chance for survival is a single action by the pilot, without which the airplane will crash. Once the AOA failed in Indonesia the airplane was essentially trying to fly itself into the ground. The Capt. kept that from happening for a bit, then it succeeded when he handed the airplane to the FO to grab the book and look for an answer that was not in fact there.

I can recall tons of technical issues that resulted in incidents and accidents, in fact Iíve survived a few on my own, but none where the failure of a single sensor meant that a perfectly good airplane was literally trying to kill everyone on board.

We can go round and round about whether or not the flight crew should have been able to aviate their way out of the circumstance they found themselves in, but if the penalty for failure to act quickly enough and perfectly enough on any given in-flight issue on a single sensor and a system about which you knew nothing was immediate death for you and your passengers would you still choose to fly?? Are you that certain of your perfection in the air??

If you knew that there might be a system on your airplane that you knew nothing about and that had the power to command the airplane to try to kill you, would you fly in that airplane, or god forbid take command of it with a couple hundred people in your care??

That is exactly what Boeing did to every MAX crew that flew the airplane. And whether with ill-intent or not they did it knowingly and deliberately. We donít know them now, but Boeing is filled with smart people. Someone(s) knew exactly what Boeing was doing putting MCAS into service in the clandestine way they did, and I presume it was done that way for an (as yet unknown) reason. Those people will speak up at some point, or I hope they will anyway because it was no accident that MCAS anonymously arrived in the MAX without flight crews being made aware of its presence.

We can argue that the Lion Air crews who successfully survived an otherwise fatal experience should have alerted the airline, and we can argue a ton of other things too.

What we cannot argue, for one moment, is that the regulatory system that allowed Boeing to self-certify safety of the 737 MAX functioned as intended.

What we cannot argue is that Boeing and the regulatory system produced a safe airplane.

Quite to the contrary they produced an airplane that with the right type of single sensor failure would immediately try to kill everyone on board, with only the immediate and correct intervention of the pilots, who had no idea that the system trying to kill them even existed, to prevent that outcome.

The surprising thing isnít that it happened, itís that it took so long to happen.

Regards-
dce
I donít think MCAS was clandestine. The Brazilian certifying authority listed it as a training difference in their OER where a Boeing chief technical pilot was listed as one of the authors or such. I still do not know how GOL addressed the required training for their Max pilots but they grounded their fleet after the second accident so they probably were not confident that whatever training they implemented was sufficient. The FAA and other certifying authorities must have know about MCAS but bought the company line about info overload.

Last edited by jimtx; 23rd Mar 2019 at 04:51.
jimtx is offline  
Old 23rd Mar 2019, 05:08
  #2395 (permalink)  
 
Join Date: Jul 2014
Location: Harbour Master Place
Posts: 662
Originally Posted by jimjim1 View Post
From preliminary report.
"PRELIMINARY
KNKT.18.10.35.04"

Copy here for now -
www.flightradar24.com/blog/wp-content/uploads/2018/10/2018-035-PK-LQP-Preliminary-Report.pdf
Your link didn't work for me (cutting and pasting the URL does, but clicking directly doesn't), this one should: PRELIMINARY KNKT.18.10.35.04 Aircraft Accident Investigation Report PT. Lion Mentari Airlines Boeing 737-8 (MAX); PK-LQP Tanjung Karawang, West Java Republic of Indonesia 29 October 2018
CurtainTwitcher is offline  
Old 23rd Mar 2019, 06:19
  #2396 (permalink)  
 
Join Date: Jul 2014
Location: Berkeley, Ca
Age: 32
Posts: 6
Originally Posted by wonkazoo View Post
A nuance that I have not seen stated here previously, one well worth considering as people go back and forth arguing over whether or not the pilots should have saved the day:

MCAS introduced a single point of failure that without pilot intervention in a highly specific way results 100 percent of the time in the aircraft flying itself into the ground. Either the pilot nails the answer to the question while all hell is breaking loose and g-loads are all over the place (about a system which they had no awareness existed), and they do it within a very very short period of time, or the airplane will 100 percent fly itself into the ground. Straight into the ground BTW.

I cannot recall any other instance of a single point of failure system or sensor (or any system for that matter) on a commercial airplane which places the airplane in a state where the only chance for survival is a single action by the pilot, without which the airplane will crash. Once the AOA failed in Indonesia the airplane was essentially trying to fly itself into the ground. The Capt. kept that from happening for a bit, then it succeeded when he handed the airplane to the FO to grab the book and look for an answer that was not in fact there.

I can recall tons of technical issues that resulted in incidents and accidents, in fact Iíve survived a few on my own, but none where the failure of a single sensor meant that a perfectly good airplane was literally trying to kill everyone on board.

We can go round and round about whether or not the flight crew should have been able to aviate their way out of the circumstance they found themselves in, but if the penalty for failure to act quickly enough and perfectly enough on any given in-flight issue on a single sensor and a system about which you knew nothing was immediate death for you and your passengers would you still choose to fly?? Are you that certain of your perfection in the air??

If you knew that there might be a system on your airplane that you knew nothing about and that had the power to command the airplane to try to kill you, would you fly in that airplane, or god forbid take command of it with a couple hundred people in your care??

That is exactly what Boeing did to every MAX crew that flew the airplane. And whether with ill-intent or not they did it knowingly and deliberately. We donít know them now, but Boeing is filled with smart people. Someone(s) knew exactly what Boeing was doing putting MCAS into service in the clandestine way they did, and I presume it was done that way for an (as yet unknown) reason. Those people will speak up at some point, or I hope they will anyway because it was no accident that MCAS anonymously arrived in the MAX without flight crews being made aware of its presence.

We can argue that the Lion Air crews who successfully survived an otherwise fatal experience should have alerted the airline, and we can argue a ton of other things too.

What we cannot argue, for one moment, is that the regulatory system that allowed Boeing to self-certify safety of the 737 MAX functioned as intended.

What we cannot argue is that Boeing and the regulatory system produced a safe airplane.

Quite to the contrary they produced an airplane that with the right type of single sensor failure would immediately try to kill everyone on board, with only the immediate and correct intervention of the pilots, who had no idea that the system trying to kill them even existed, to prevent that outcome.

The surprising thing isnít that it happened, itís that it took so long to happen.

Regards-
dce

Perfectly put.
Reliance on a single sensor driving a system that was not known to the crew and that could take over command of the aircraft is sheer madness (not to mention extreme negligence).
mosquito88 is offline  
Old 23rd Mar 2019, 06:32
  #2397 (permalink)  
 
Join Date: Jan 2018
Location: Gold coast
Posts: 31
Great video to aid understanding


wayne
Jetman346 is offline  
Old 23rd Mar 2019, 07:41
  #2398 (permalink)  
 
Join Date: Nov 2018
Location: Vancouver
Posts: 67
Originally Posted by jimjim1 View Post
From preliminary report.
"PRELIMINARY
KNKT.18.10.35.04"

Copy here for now -
www.flightradar24.com/blog/wp-content/uploads/2018/10/2018-035-PK-LQP-Preliminary-Report.pdf


- At least one AoA sensor was changed immediately before penultimate flight. Presumably there was a percieved AoA sensor issue.
"replaced angle of attack sensor"

- Captain side AoA sensor showed 22 degree error for entirity of penultimate flight.

- Captain side AoA sensor showed 22 degree error for entirity of crash flight.

Perhaps the AoA sensor was not faulty and the issue lay elsewhere and was not correctly repaired?

I like** the idea of an encoding error. (**like the idea as an explanation for the observed symptoms - I don't like it that there was a crash - added in the hope of deflecting the present preposterous PPRuNe pedants)

I doubt very much it was a transmission/reception error on the BUS since that almost certainly has CRC error detection.

The sensor is an analog device and there will be an A to D converter at some stage.

A bad bit within the AD converter data path seems a distinct possibility.
It's somewhere inside the system, perhaps, as you suggested, it's in the AD converter. The replaced AOA vane had been sent to Florida by Indonesian Investigator for analysis and diagnostic. It will be interesting if it turns out there's nothing wrong with the vane.
..
Found on pp. 7/8/9 of NTSC's Preliminary Report


Looking back to that AC and its symptoms, problems seemed to have revolved around the same area the whole time, albeit it had gotten progressively worse up until that fateful flight when ALL indicators found completely unreliable.
patplan is offline  
Old 23rd Mar 2019, 09:33
  #2399 (permalink)  
 
Join Date: Feb 2009
Location: Seattle
Posts: 379
Originally Posted by mosquito88 View Post
Perfectly put.
Reliance on a single sensor driving a system that was not known to the crew and that could take over command of the aircraft is sheer madness (not to mention extreme negligence).
Beyond that it is clearly a violation of the FARs for a system to have a failure mode arrived at by (1) any combination of failures whose probability is greater that 1x10E-9 or (2) any single failure that results in a catestrophic hazard level.

While in hindsight it may be found to be otherwise, I am certain that both Boeing and FAA determined that the hazard level associated with an AOA sensor signal failed high on a 737MAX was not catestrophic. As I have mentioned in previous posts I think this all comes down to assumptions regarding pilot actions given this failure and the sum total of its effects. I am not singling out the crew as solely responsible for the Lion Air accident. We need to focus on the assumptions. As for the Ethiopian accident that is the intended focus of this thread, we simply do not yet have the data necessary to determine if any of this MCAS and errant AOA signal discussion actually applies.
FCeng84 is offline  
Old 23rd Mar 2019, 09:42
  #2400 (permalink)  
Thread Starter
 
Join Date: Feb 2008
Location: UK
Age: 63
Posts: 126
My pal yesterday took photos at TFS (Tenerife South) showing the grounded TUI UK Max 8 (G-TUMH) and also another Max 8 belonging to Norwegian Air both of which were stranded when the flight ban was imposed leaving them unable to fly back to their respective bases.
Guess that no EU dispensations were granted for ferry flights.
rog747 is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.