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 4th Apr 2019, 08:38
  #3041 (permalink)  
 
Join Date: May 2011
Location: Hampshire
Age: 72
Posts: 796
So the prelim report, issued by the Ethiopian government says the crew "repeatedly followed procedures recommended by Boeing.."
https://www.bbc.co.uk/news/business-47812225
KelvinD is offline  
Old 4th Apr 2019, 08:46
  #3042 (permalink)  
 
Join Date: Aug 2009
Location: Seat 0A
Posts: 516
Repeatedly?! How is that possible?
STBYRUD is offline  
Old 4th Apr 2019, 08:48
  #3043 (permalink)  
 
Join Date: Feb 2000
Location: 500 miles from Chaikhosi, Yogistan
Posts: 3,693
Interesting. When it appears in print and is verified, I await all those that said that "sub standard training was the cause", and that "it would never have happened in the US" to say they were wrong.
compressor stall is online now  
Old 4th Apr 2019, 08:49
  #3044 (permalink)  
 
Join Date: Jan 2008
Location: Berkshire
Age: 57
Posts: 5
From the Ethiopian Airlines press release,
"The preliminary report clearly showed that the Ethiopian Airlines Pilots who were commanding FlightET 302/10 March have followed the Boeing recommended and FAA approved emergency procedures to handle the most difficult emergency situation created on the airplane. Despite their hard work and full compliance with the emergency procedures, it was very unfortunate that they could not recover the airplane from the persistence of nose diving"
commsbloke is offline  
Old 4th Apr 2019, 09:01
  #3045 (permalink)  
 
Join Date: Mar 2012
Location: Arizona
Posts: 10
Wall Street Journal article

The Wall Street Journal, relying on sources who have seen the flight data recorder readout, reported that the pilots, upon experiencing uncommanded nose-down trim, used the 737’s stabilizer trim cutout switches. And while the 737 MAX 8 retains the manual trim wheels it has had from day one, it’s not known if they used these to re-trim the aircraft. The sources told the Journal that the pilots appeared to have reengaged the stabilizer trim cutout switches, which would have re-enabled the MCAS stall protection system.

The underline is mine. Why would a pilot reengage a failed system? If they wanted to control the stab trim after turning of the electric stab trim switches, why did they not use the manual trim wheel?
warbirdfinder is offline  
Old 4th Apr 2019, 09:02
  #3046 (permalink)  
 
Join Date: Aug 2005
Location: London, UK
Posts: 194
No “foreign object damage” or “structural design problem” identified

That’s likely to be a significant finding
oversteer is offline  
Old 4th Apr 2019, 09:08
  #3047 (permalink)  
 
Join Date: Dec 2004
Location: Southern England
Posts: 109
Originally Posted by compressor stall View Post
Interesting. When it appears in print and is verified, I await all those that said that "sub standard training was the cause", and that "it would never have happened in the US" to say they were wrong.
I think it would be wise to wait for the report. If the aircraft wasn't put in trim using the switches as per Boeing recommendation before placing them to cutout and it turns out that the switches were then turned back on, again contrary to guidance, the press release from Ethiopian is misleading to say the least.

​​​​​​
Albino is offline  
Old 4th Apr 2019, 09:09
  #3048 (permalink)  
 
Join Date: Dec 2003
Location: Tring, UK
Posts: 1,461
Why would a pilot reengage a failed system? If they wanted to control the stab trim after turning of the electric stab trim switches, why did they not use the manual trim wheel?
Maybe because the control loadings at the speed they were doing made it difficult/impossible to manually trim, so they tried the electric trim again? If you’ve got both (or even four) hands on the control column trying to stop the aircraft pitching down, there’s not many hands left for the manual trim...
FullWings is offline  
Old 4th Apr 2019, 09:12
  #3049 (permalink)  
 
Join Date: Aug 2018
Location: Madrid
Posts: 21
Originally Posted by warbirdfinder View Post
Why would a pilot reengage a failed system? If they wanted to control the stab trim after turning of the electric stab trim switches, why did they not use the manual trim wheel?
Speculatively with both pilots hauling back on the control column and no electric trim, the moment any of them lets go to give the wheel a try the nose would dip down again. Additionally, at nose low and high speed with stab overloaded the wheel might have been much too stiff to both move and do so enough times to make an impact.
I hate to speculate on this but it points to proper action by crew finding themselves unable to bring nose up with manual means and reactivating the cutouts to regain electric trim capability. (Which should come back and if used should stop MCAS either way, unless...)
jagema is offline  
Old 4th Apr 2019, 09:24
  #3050 (permalink)  
 
Join Date: Aug 2000
Posts: 1,384
Originally Posted by Albino View Post
I think it would be wise to wait for the report. If the aircraft wasn't put in trim using the switches as per Boeing recommendation before placing them to cutout and it turns out that the switches were then turned back on, again contrary to guidance, the press release from Ethiopian is misleading to say the least.

​​​​​​
The Boeing NNC regarding runaway trim, or MCAS, has never told us to trim to neutral before placing the switches to cut off. It tells us to stop the trim with the switches if the trim doesn’t stop after disconnecting the autopilot. Then use manual trim. Period.

The armchair experts have now moved from «They should just have placed the cut off switches to off and contained the problem» to «They should just have trimmed neutral and then used cut out switches and contained the problem».
Congratulations! It took only a few weeks to come to this conclusion.
The Lion Air and Ethiopian pilots only had a few minutes.
ManaAdaSystem is offline  
Old 4th Apr 2019, 09:33
  #3051 (permalink)  
kwh
 
Join Date: Oct 2007
Location: Carmarthen
Posts: 63
Originally Posted by jagema View Post
Speculatively with both pilots hauling back on the control column and no electric trim, the moment any of them lets go to give the wheel a try the nose would dip down again. Additionally, at nose low and high speed with stab overloaded the wheel might have been much too stiff to both move and do so enough times to make an impact.
I hate to speculate on this but it points to proper action by crew finding themselves unable to bring nose up with manual means and reactivating the cutouts to regain electric trim capability. (Which should come back and if used should stop MCAS either way, unless...)
If this turns out to be correct, could it be because the Boeing recommended response to the unwelcome MCAS activation was developed in a simulator incapable of generating the forces that the real world can generate, so the pilots developing & “testing” the protocol could pull back the sim yoke with one hand, while rotating the easy to spin manual trim wheel with the other? “Don’t worry, this is easy to get out of if we just add a page to the manual to tell people what to do, watch...”. Also “Flight test the fix on a real aircraft? Sounds like a lot of work, dude... let’s not, OK?”

No, well spotted, I’m not a pilot, but I assume that not every control in a simulator for an aircraft where the force felt through the controls relates to the forces the control surfaces they connect to are experiencing [i.e. a non-fully-FBW plane] will be 100% accurate?
kwh is offline  
Old 4th Apr 2019, 09:41
  #3052 (permalink)  
 
Join Date: Feb 2015
Location: The woods
Posts: 1
Originally Posted by ManaAdaSystem View Post


The Boeing NNC regarding runaway trim, or MCAS, has never told us to trim to neutral before placing the switches to cut off. It tells us to stop the trim with the switches if the trim doesn’t stop after disconnecting the autopilot. Then use manual trim. Period.

The armchair experts have now moved from «They should just have placed the cut off switches to off and contained the problem» to «They should just have trimmed neutral and then used cut out switches and contained the problem».
Congratulations! It took only a few weeks to come to this conclusion.
The Lion Air and Ethiopian pilots only had a few minutes.
And that highlights a big difference between runaway stab. and MCAS unwanted operation:

With runaway stab you can’t catch it by trimming - it is running away...

With MCAS unwanted (for want of a better description) operation you can theoretically catch (reverse) it by trimming.

Another difference is that in an AoA fault caused unwanted MCAS operation other factors also come into play - even before MCAS operation on flap retraction:

Autothrottle, Instrument anomaly, Stall warning etc. which can cause:

Unwanted rise in speed, initial pilot input nose down response, cockpit confusion.

Therefore the standard drill for stab runaway does not necessarily apply. Trimming to neutral and ATS disconnect might well have priority over stab trim cutoff operation.

Of course we didn’t know this, the poor crews didn’t know it and it is a scenario which Boeing will be looking at hard before submitting a suitable procedure for recertification, I am sure.

bill fly is offline  
Old 4th Apr 2019, 09:49
  #3053 (permalink)  
 
Join Date: Nov 2018
Location: madrid
Posts: 47
[QUOTE=bill fly;10438384]
Originally Posted by ManaAdaSystem View Post


The Boeing NNC regarding runaway trim, or MCAS, has never told us to trim to neutral before placing the switches to cut off. It tells us to stop the trim with the switches if the trim doesn’t stop after disconnecting the autopilot. Then use manual trim. Period.

The armchair experts have now moved from «They should just have placed the cut off switches to off and contained the problem» to «They should just have trimmed neutral and then used cut out switches and contained the problem».
Congratulations! It took only a few weeks to come to this conclusion.
The Lion Air and Ethiopian pilots only had a few minutes.
[/QOTE]
And that highlights a big difference between runaway stab. and MCAS unwanted operation:

With runaway stab you can’t catch it by trimming - it is running away...

With MCAS unwanted (for want of a better description) operation you can theoretically catch (reverse) it by trimming.

Another difference is that in an AoA fault caused unwanted MCAS operation other factors also come into play - even before MCAS operation on flap retraction:

Autothrottle, Instrument anomaly, Stall warning etc. which can cause:

Unwanted rise in speed, initial pilot input nose down response, cockpit confusion.

Therefore the standard drill for stab runaway does not necessarily apply. Trimming to neutral and ATS disconnect might well have priority over stab trim cutoff operation.

Of course we didn’t know this, the poor crews didn’t know it and it is a scenario which Boeing will be looking at hard before submitting a suitable procedure for recertification, I am sure.
You are both right. But Boing introduced a very "clever" sentence in the AD:

"Electric estabilizer trim can be used to neutralize control column pitch forces before moving the stab trim cutout switches to cutout"

Can: means that if you do it and you crash, they would say they didn't tell you to do it, but if you don't do it and you crash they will say that they mentioned it for something.

Not that any amount of words is going to change the fact that they are responsible. If only they were as clever in the design as they are with legal-related documents.
ecto1 is offline  
Old 4th Apr 2019, 09:49
  #3054 (permalink)  
 
Join Date: Feb 2000
Location: 500 miles from Chaikhosi, Yogistan
Posts: 3,693
They should've kept airframe and hydraulics (99% of them, just a touch here and there)
DO you have any idea of how much of the 737 does not meet the modern day safety standards and is grandfathered? That's probably worthy of a thread of its own.

Nearly 25 years ago Airbus complained to JAA about Boeing's grandfather rights that were letting the 737 get away with nearly half a dozen more seats than a comparable newly certified airliner could, all being equal.
compressor stall is online now  
Old 4th Apr 2019, 09:52
  #3055 (permalink)  
 
Join Date: Dec 2004
Location: Southern England
Posts: 109
Originally Posted by ManaAdaSystem View Post


The Boeing NNC regarding runaway trim, or MCAS, has never told us to trim to neutral before placing the switches to cut off. It tells us to stop the trim with the switches if the trim doesn’t stop after disconnecting the autopilot. Then use manual trim. Period.

The armchair experts have now moved from «They should just have placed the cut off switches to off and contained the problem» to «They should just have trimmed neutral and then used cut out switches and contained the problem».
Congratulations! It took only a few weeks to come to this conclusion.
The Lion Air and Ethiopian pilots only had a few minutes.
Have you read the Boeing bulletin?

​​​​​​Under operating instructions
'Electric stabilizer trim can be used to neutralise control column pitch forces before moving the stab trim switches to cutout'

Why wouldn't you?
Albino is offline  
Old 4th Apr 2019, 09:59
  #3056 (permalink)  
 
Join Date: Feb 2013
Location: Buckinghamshire
Posts: 34
Originally Posted by FullWings View Post
Maybe because the control loadings at the speed they were doing made it difficult/impossible to manually trim, so they tried the electric trim again? If you’ve got both (or even four) hands on the control column trying to stop the aircraft pitching down, there’s not many hands left for the manual trim...
Agreed.. I think the FAA's AD acknowledges the challenge that pilot's might face. At the bottom of (h) it reads:
"Initially, higher control forces may be needed to overcome any stabilizer nose down trim already applied. Electric stabilizer trim can be used to neutralize control column pitch forces before moving the STAB TRIM CUTOUT switches to CUTOUT. Manual stabilizer trim can be used before and after the STAB TRIM CUTOUT switches are moved to CUTOUT."

The pilots runaway stabilizer checklist.... is clear... operate the CUTOUT. It doesn't say... try and trim first. For me the AD has never been clear. Are the pilots supposed to follow their trained checklists... and the very same AD, a few paragraphs above, that simply says operate the CUTOUT... Or are they required to make the judgment that they'll never have the strength to turn the trim manually, so they need to rely on the failing electrical trim first.... and then CUTOUT?
quentinc is offline  
Old 4th Apr 2019, 10:07
  #3057 (permalink)  
 
Join Date: Jul 2013
Location: Australia
Posts: 193
Originally Posted by GarageYears View Post
Ok, I have to confess I’m confused.

All this talk of manual trim forces, etc.

MCAS applies trim in increments of 2.5 degrees over 10 seconds. Any pilot pickle switch trim ceases MCAS action for 5 seconds.

If MCAS runs again, again any pilot trim action defeats MCAS.

There is is no need to manually trim against any large nose down MCAS trim surely? Electrically trim the aircraft neutral AND THEN DISABLE ELECTRIC TRIM. From then on you are tweaking trim manually and no heroic fight against aero forces is required.

Am I wrong?

- GY
They were already trying to deal with a stickshaker event. Then they followed Boeings list and disabled electrical trim. They then found that they could not use manual trim to recover. As can be seen in videos, manual trim can be a lot harder for some people than others.
RickNRoll is offline  
Old 4th Apr 2019, 10:11
  #3058 (permalink)  
 
Join Date: May 2000
Location: London, UK
Posts: 339
Anyone got a link to the report (or a scanned copy of it)?

All I can find are press reports as to what it says.....



SLF3 is offline  
Old 4th Apr 2019, 10:12
  #3059 (permalink)  
 
Join Date: Dec 2015
Location: Aus
Posts: 61
Originally Posted by quentinc View Post
Agreed.. I think the FAA's AD acknowledges the challenge that pilot's might face. At the bottom of (h) it reads:
"Initially, higher control forces may be needed to overcome any stabilizer nose down trim already applied. Electric stabilizer trim can be used to neutralize control column pitch forces before moving the STAB TRIM CUTOUT switches to CUTOUT. Manual stabilizer trim can be used before and after the STAB TRIM CUTOUT switches are moved to CUTOUT."

The pilots runaway stabilizer checklist.... is clear... operate the CUTOUT. It doesn't say... try and trim first. For me the AD has never been clear. Are the pilots supposed to follow their trained checklists... and the very same AD, a few paragraphs above, that simply says operate the CUTOUT... Or are they required to make the judgment that they'll never have the strength to turn the trim manually, so they need to rely on the failing electrical trim first.... and then CUTOUT?

actually it does.......


“Control airplane pitch attitude manually with control column and main electric trim as needed”

its the point in the memory items right after disengagjng the autopilot......
Switchbait is offline  
Old 4th Apr 2019, 10:14
  #3060 (permalink)  
 
Join Date: Feb 2015
Location: The woods
Posts: 1
Originally Posted by quentinc View Post
Agreed.. I think the FAA's AD acknowledges the challenge that pilot's might face. At the bottom of (h) it reads:
"Initially, higher control forces may be needed to overcome any stabilizer nose down trim already applied. Electric stabilizer trim can be used to neutralize control column pitch forces before moving the STAB TRIM CUTOUT switches to CUTOUT. Manual stabilizer trim can be used before and after the STAB TRIM CUTOUT switches are moved to CUTOUT."

The pilots runaway stabilizer checklist.... is clear... operate the CUTOUT. It doesn't say... try and trim first. For me the AD has never been clear. Are the pilots supposed to follow their trained checklists... and the very same AD, a few paragraphs above, that simply says operate the CUTOUT... Or are they required to make the judgment that they'll never have the strength to turn the trim manually, so they need to rely on the failing electrical trim first.... and then CUTOUT?
Yes that’s the Point, There should be a runaway stab checklist and a different one for unwanted MCAS operation.

This should specify the possible symptoms.
It should then cover the AD items and go further to disconnecting ATS and flying pitch and thrust. It could well suggest reselecting flap and landing as soon as possible.
bill fly 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.