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 17th Mar 2019, 14:26
  #1741 (permalink)  
 
Join Date: Mar 2002
Location: Florida
Posts: 4,569
Likes: 0
Received 1 Like on 1 Post
these are called lessons learned and belong to all the aircraft manufacturers.

I'm quite sure that if they were obvious, that the likes of Airbus etal. would have pointed them out to the regulators

This is the stuff that calls for "Special Condition" in the certification basis and unfortunately like all other parts of our risks in life is sometimes learned the hard way




Current and former engineers directly involved with the evaluations or familiar with the document shared details of Boeing’s “System Safety Analysis” of MCAS, which The Seattle Times confirmed.

The safety analysis:
  • Understated the power of the new flight control system, which was designed to swivel the horizontal tail to push the nose of the plane down to avert a stall. When the planes later entered service, MCAS was capable of moving the tail more than four times farther than was stated in the initial safety analysis document.
  • Failed to account for how the system could reset itself each time a pilot responded, thereby missing the potential impact of the system repeatedly pushing the airplane’s nose downward.
  • Assessed a failure of the system as one level below “catastrophic.” But even that “hazardous” danger level should have precluded activation of the system based on input from a single sensor — and yet that’s how it was designed.
The people who spoke to The Seattle Times and shared details of the safety analysis all spoke on condition of anonymity to protect their jobs at the FAA and other aviation organizations.
lomapaseo is offline  
Old 17th Mar 2019, 14:34
  #1742 (permalink)  
 
Join Date: May 2006
Location: FL510
Posts: 910
Received 0 Likes on 0 Posts
„In this atmosphere, the System Safety Analysis on MCAS, just one piece of the mountain of documents needed for certification, was delegated to Boeing.
[...]
„The higher limit meant that each time MCAS was triggered, it caused a much greater movement of the tail than was specified in that original safety analysis document.“
[...]
“None of the engineers were aware of a higher limit,” said a second current FAA engineer.
[...]
Peter Lemme, a former Boeing flight controls engineer who is now an avionics and satellite-communications consultant, said that because MCAS reset each time it was used, “it effectively has unlimited authority.”

If I was responsible for this, I'd be on my way leaving the country for good at this time.
Epic failure of certification and oversight.
safelife is offline  
Old 17th Mar 2019, 14:36
  #1743 (permalink)  
 
Join Date: Jul 2013
Location: Norway
Age: 57
Posts: 140
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by lomapaseo
these are called lessons learned and belong to all the aircraft manufacturers.

I'm quite sure that if they were obvious, that the likes of Airbus etal. would have pointed them out to the regulators

This is the stuff that calls for "Special Condition" in the certification basis and unfortunately like all other parts of our risks in life is sometimes learned the hard way
Interesting read from The Seattle Times article.

Quote
The original Boeing document provided to the FAA included a description specifying a limit to how much the system could move the horizontal tail — a limit of 0.6 degrees, out of a physical maximum of just less than 5 degrees of nose-down movement. That limit was later increased after flight tests showed that a more powerful movement of the tail was required to avert a high-speed stall, when the plane is in danger of losing lift and spiraling down.The behavior of a plane in a high angle-of-attack stall is difficult to model in advance purely by analysis and so, as test pilots work through stall-recovery routines during flight tests on a new airplane, it’s not uncommon to tweak the control software to refine the jet’s performance.

SteinarN is offline  
Old 17th Mar 2019, 14:49
  #1744 (permalink)  
 
Join Date: Jul 2013
Location: Norway
Age: 57
Posts: 140
Likes: 0
Received 0 Likes on 0 Posts
After reading the Seattle Times article I am left with a feeling that the Max has very undesirable stall characteristics, seen by the need to increase the MCAS limits from the intended and modest 0.6 degrees to the large 2.5 degrees.
SteinarN is offline  
Old 17th Mar 2019, 14:49
  #1745 (permalink)  
 
Join Date: Oct 2017
Location: Vienna
Posts: 143
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by SteinarN
Interesting read from The Seattle Times article.

The original Boeing document provided to the FAA included a description specifying a limit to how much the system could move the horizontal tail — a limit of 0.6 degrees, out of a physical maximum of just less than 5 degrees of nose-down movement. That limit was later increased after flight tests showed that a more powerful movement of the tail was required to avert a high-speed stall, when the plane is in danger of losing lift and spiraling down.The behavior of a plane in a high angle-of-attack stall is difficult to model in advance purely by analysis and so, as test pilots work through stall-recovery routines during flight tests on a new airplane, it’s not uncommon to tweak the control software to refine the jet’s performance.

Quote
Lion air's FDR show that the trim was moved to full of the available 7 notches (it's not clear how those translate to degrees). They would certainly still be alive if there as a limit. They kept it in air at ~ 3 notches. If max needs more to get out of stall, perhaps it does need a larger hstab/eleveator instead of a hacked together software?

Or perhaps the key really is the reset. Does mcas reset with each trim input and takes the current position as the new neutral? If AoA vane is sending wrong data it's easy to see how this would result in a runaway trim.

This image shows the difference between a 737-800 (yellow) and MAX (magenta). Notice the bigger nacelles and same hstab size.


Originally Posted by SteinarN
After reading the Seattle Times article I am left with a feeling that the Max has very undesirable stall characteristics, seen by the need to increase the MCAS limits from the intended and modest 0.6 degrees to the large 2.5 degrees.
I thought 0.6 was a hard limit... e.g, we move this much and then it's up to the pilot. If it was 0.6 every 5 seconds it's still bad, but at least easier to manage.
derjodel is offline  
Old 17th Mar 2019, 14:50
  #1746 (permalink)  
 
Join Date: Mar 2007
Location: In my head
Posts: 694
Likes: 0
Received 0 Likes on 0 Posts
Browsing Google Patents, I stumbled across some interesting Boeing patent applications e.g. this one 6 years ago: PRIMARY FLIGHT DISPLAY PITCH AND POWER-BASED UNRELIABLE AIRSPEED SYMBOLOGY. (Download full PDF here in order to view Figs a little better ...).

In this one I was struck by their "Background" para [0013] which reads:
QUOTE
The displayed symbology is not static and updates as the airplane weight, altitude, flap setting and thrust change. As a result, critical information is communicated in a format that is intuitive and in a form that the pilot needs, and is expediently usable by the pilot to maintain safe, stable flight conditions as a result of air data failures throughout the duration of the flight. This symbology is independent of the angle of attack (AOA) or the air data system.
UNQUOTE{my bold}

Is any of what's described yet designed into any production PFD?
slip and turn is offline  
Old 17th Mar 2019, 14:54
  #1747 (permalink)  
 
Join Date: Jun 2001
Location: Rockytop, Tennessee, USA
Posts: 5,898
Likes: 0
Received 1 Like on 1 Post
The BEA has now downloaded the FDR as well:


Airbubba is offline  
Old 17th Mar 2019, 15:02
  #1748 (permalink)  
 
Join Date: Oct 2002
Location: London UK
Posts: 7,731
Likes: 0
Received 71 Likes on 35 Posts
On many of the accidents discussed here on PPRuNe, commentators are regularly criticised for "not waiting until the accident report is released".

I wonder why, in contrast, it seems accepted that Boeing can have a software fix done in weeks, way before any reports are produced, to get the aircraft back in the air.
WHBM is online now  
Old 17th Mar 2019, 15:03
  #1749 (permalink)  
 
Join Date: Mar 2014
Location: WA STATE
Age: 78
Posts: 0
Likes: 0
Received 0 Likes on 0 Posts
Is any of what's described yet designed into any production PFD?
probably not- reason- although assigned to Boeing- the incorporation of such would require bucu approvals in house- extreme flight testing- and worst of all, payment to the inventor. Years ago, an employee ( not myself ) came up with a simple ' quick change ' drill chuck' sort of like an air hose connector. required fitting a matchin piece on each drill. Worked great- put into production and no doubt still in use. So inventor got small royalties- but after a year or two with thousands in use, the royalties added up to a tidy sum. Company said - hey we need to change our deal- employees should not make that much money off a patent. Major battle ensued- Boeing lost.

There is more than one story like that . ..

Last edited by CONSO; 17th Mar 2019 at 15:18.
CONSO is offline  
Old 17th Mar 2019, 15:06
  #1750 (permalink)  
 
Join Date: Jul 2013
Location: Norway
Age: 57
Posts: 140
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by derjodel
Lion air's FDR show that the trim was moved to full of the available 7 notches (it's not clear how those translate to degrees). They would certainly still be alive if there as a limit. They kept it in air at ~ 3 notches. If max needs more to get out of stall, perhaps it does need a larger hstab/eleveator instead of a hacked together software?

Or perhaps the key really is the reset. Does mcas reset with each trim input and takes the current position as the new neutral? If AoA vane is sending wrong data it's easy to see how this would result in a runaway trim.

This image shows the difference between a 737-800 (yellow) and MAX (magenta). Notice the bigger nacelles and same hstab size.

I thought 0.6 was a hard limit... e.g, we move this much and then it's up to the pilot. If it was 0.6 every 5 seconds it's still bad, but at least easier to manage.
What strikes me in the image is the tiny elevator? It would have been very interesting to see the same picture of the A320 tail/elevator.
SteinarN is offline  
Old 17th Mar 2019, 15:17
  #1751 (permalink)  
 
Join Date: Feb 2019
Location: shiny side up
Posts: 431
Likes: 0
Received 0 Likes on 0 Posts
A software patch to fix and inherently unstable aircraft. brilliant. Cant wait for it!
Smythe is offline  
Old 17th Mar 2019, 16:18
  #1752 (permalink)  
 
Join Date: Jul 2013
Location: Norway
Age: 57
Posts: 140
Likes: 0
Received 0 Likes on 0 Posts
I found a picture of the A320. It seems like the elevator, as a percentage of the stabilizer, is quite a bit larger.




Compared the the B737


SteinarN is offline  
Old 17th Mar 2019, 16:38
  #1753 (permalink)  
PJ2
 
Join Date: Mar 2003
Location: BC
Age: 76
Posts: 2,486
Received 2 Likes on 2 Posts
March 17, 2019 12:15 p.m. ET https://www.wsj.com/articles/ethiopian-airlines-black-boxes-showed-clear-similarities-with-lion-air-crash-11552839318?mod=hp_lead_pos4 *

Analysis of Black Boxes of Crashed Ethiopian Airlines Flight Showed ‘Clear Similarities’ With Crashed Lion Air Flight —Ethiopian Transport Minister

*Data from ET302 Black Boxes Has Been Validated by Ethiopian, U.S. Investigators—Minister
*Investigators Were Able to Recover All Relevant Data from ET302 Black Boxes—Minister
*Preliminary Report on Crash to Be Released Within 30 Days—Minister
PJ2 is offline  
Old 17th Mar 2019, 16:40
  #1754 (permalink)  
 
Join Date: Sep 2008
Location: Been around the block
Posts: 629
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by Lake1952
Light aircraft pilot since the mid 70s... under what circumstances would a 737 variant require full UP trim or full DOWN trim? On the aircraft that I have flown, the trim spends all its time somewhere in the middle of the range. So again I ask, what purpose is there to having such extreme ranges of trim that it requires huge control forces to counter?
the speed envelope and cg envelope on a swept wing, transport category aircraft is much greater than a GA aircraft.
4runner is offline  
Old 17th Mar 2019, 16:41
  #1755 (permalink)  
 
Join Date: Apr 2015
Location: Under the radar, over the rainbow
Posts: 854
Received 27 Likes on 16 Posts
Originally Posted by ferry pilot
The Electra was shedding wings but was not grounded, even after the second one, and the entire industry pitched in to find the cause, fix the problem and get it out of the headlines. There are many reasons why that will not happen now . . .
Just a reminder: Ultimately, a third of the Electras ever built were either lost in crashes or written off as too damaged to repair. Perhaps it will be a good thing if "that" does not happen now.

OldnGrounded is offline  
Old 17th Mar 2019, 16:46
  #1756 (permalink)  
 
Join Date: Dec 2013
Location: US
Age: 66
Posts: 639
Likes: 0
Received 16 Likes on 11 Posts
Originally Posted by LandIT
Read all that. Stab screw found pointed down. Are you suggesting pilots pushed it that way? Right. So furthermore they couldn't pull it back in time. Not a good system then right?
If MCAS ran the stab full down it occurred through a number of cycles and over a significant period of time. Where were the pilots?
Sailvi767 is offline  
Old 17th Mar 2019, 16:51
  #1757 (permalink)  
 
Join Date: Feb 2017
Location: Isla Grande
Posts: 997
Received 0 Likes on 0 Posts
Originally Posted by Sailvi767


If MCAS ran the stab full down it occurred through a number of cycles and over a significant period of time. Where were the pilots?
Two crews went into that trap. Doesn't this make you think more critical about the design of MCAS?
gearlever is offline  
Old 17th Mar 2019, 16:57
  #1758 (permalink)  
 
Join Date: Feb 2017
Location: Isla Grande
Posts: 997
Received 0 Likes on 0 Posts
However, pilots and aviation experts say that what happened on the Lion Air flight doesn’t look like a standard stabilizer runaway, because that is defined as continuous uncommanded movement of the tail.On the accident flight, the tail movement wasn’t continuous; the pilots were able to counter the nose-down movement multiple times.In addition, the MCAS altered the control column response to the stabilizer movement. Pulling back on the column normally interrupts any stabilizer nose-down movement, but with MCAS operating that control column function was disabled. These differences certainly could have confused the Lion Air pilots as to what was going on.Since MCAS was supposed to activate only in extreme circumstances far outside the normal flight envelope, Boeing decided that 737 pilots needed no extra training on the system — and indeed that they didn’t even need to know about it. It was not mentioned in their flight manuals.
gearlever is offline  
Old 17th Mar 2019, 17:21
  #1759 (permalink)  
 
Join Date: Dec 2001
Location: Leeds, UK
Posts: 281
Likes: 0
Received 0 Likes on 0 Posts
Ethiopian safety board

I give full respect to the Ethiopian safety board investigating this crash.

but given that the two 737max crashes raise such massive questions about aircraft manufacturing,government and trans national oversight and trillion dollar industries as well national interests for the US aircraft msnufacturing industry vis a vis China snd Europe ,are tje Ethiopians a tiny bit out of their depth?
groundbum is offline  
Old 17th Mar 2019, 17:21
  #1760 (permalink)  
 
Join Date: Mar 2019
Location: Washington
Posts: 2
Likes: 0
Received 0 Likes on 0 Posts
Wonder no more

Originally Posted by WHBM
On many of the accidents discussed here on PPRuNe, commentators are regularly criticised for "not waiting until the accident report is released".

I wonder why, in contrast, it seems accepted that Boeing can have a software fix done in weeks, way before any reports are produced, to get the aircraft back in the air.
Wonder no more --> $
DCDave is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.