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 7th Apr 2019, 07:50
  #3521 (permalink)  
 
Join Date: Jun 2006
Location: Brisbane
Posts: 5
Originally Posted by spornrad View Post
Before the MCAS input the PF trims up twice with the thumb switch for appr. 3 s each. This results in appr 1 U uptrim stab movement, twice.
At 5:40:15 after the first MCAS ND he trims again up for appr. 3 s. The stab movement is barely visible now on the chart. Then, unusual:
At 05:40:27, the Captain advised the First-Officer to trim up with him.
Why? Is his switch not working correctly?
The trim up (together or) by the FO is the only long one in the entire FDR recording. It shows again a stab movement at appr 1 U / 3 s. It is followed by STAB TRIM CUTOUT.
Is it possible that the PF had a broken trimswitch?

The earlier trim durations you refer to happened with flaps extended. The trim wheel moves faster with flaps extended. That explains the difference.
Derfred is offline  
Old 7th Apr 2019, 07:53
  #3522 (permalink)  
 
Join Date: May 2003
Location: Nearby
Posts: 26
Originally Posted by Lake1952 View Post
Because MCAS is not a powered device! It is software!
Well then, how about TAC (Thrust Asymmetry Compensation) on the 777? There’s a switch to isolate it...
locblue is offline  
Old 7th Apr 2019, 07:58
  #3523 (permalink)  
 
Join Date: Jul 2012
Location: Sweden
Age: 45
Posts: 1
Originally Posted by UnderDuress View Post
Nope don't work for Boeing but flew the 38M.
Prove me wrong.
If a stall warning triggers at a low altitude, the flight crew should consider that there is an immediate flight path threat, and a potential risk of ground contact. In other words, there is no time to differentiate between a real or spurious stall warning, and there is no altitude to convert to speed. However, when a stall warning triggers (i.e. stick shaker activation), aircraft still have positive climb performance capability. Note:An “approach to stall” is a controlled flight maneuver. An aircraft that is stalled is out of control, but is recoverable. Do not confuse an “approach to stall” with “a full stall”. When ground clearance is not an issue, the recommended technique is to recover from the near-stall condition in the minimum amount of time, by applying power and nose down input. When ground clearance is an issue, the recommended technique is to lose as little altitude as possible, by applying fullpower and by flying an optimum pitch attitude.
Are you saying the crew ought to have prioritized identifying the stick shaker as spurious, in your opinion?

SherwoodA is offline  
Old 7th Apr 2019, 07:59
  #3524 (permalink)  
 
Join Date: Jul 2000
Location: London
Posts: 558
Originally Posted by UnderDuress View Post
Nope don't work for Boeing but flew the 38M.
Prove me wrong.
I’m guessing you’re a troll!

I don’t have the expertise to comment on the 737 let alone MCAS, but I found your comments arrogant and insensitive in the extreme!

To you a “stick shaker” after take off is no problem and you comment about the crew’s actions amounting to a fail in the sim! WTH!!! This was real life with no doubt the crew doing their best under extreme duress. They didn’t turn up to work that fateful day to do anything other than return home that night - like we all do!
Crosswind Limits is offline  
Old 7th Apr 2019, 08:03
  #3525 (permalink)  
 
Join Date: Jan 2010
Location: South Australia
Age: 70
Posts: 19
Originally Posted by UnderDuress View Post
Gear Up.
Stick Shaker, no problem as the aircraft is in trim, flaps, etc. are all just fine. A-Thl is still in HOLD.
Aviate and navigate.
Call out "AIRPSEED UNRELIABLE MEMORY ITEMS".
Do the MI's which takes 10-15 sec if you are fast or 159 sec if slow and forget them which is usual here.
10 Deg Pitch 80% N1 and simply fly runway heading climbing slowly with slow increasing IAS.
CP calls for the NNC 10.1 and skip Step 7 for now if you wish as that will take too long to open the page. Just keep the pitch and power set above. No terrain, CB's, windshear, TCAS risk, etc.
PM makes the PAN call, reaches and opens the NNC QRH.
Step 9 leads to 10.
Step 10, leads to Step 11 & the FO has Control.
Step 12 would have not worked or maybe just for a while. When the AP drops, manual flying on a beautiful sunny morning. Easy as VMC, two AC power sources, lots of fuel, flaps and slats and gear that will extend normally and crew well rested.
Step 13 switch from Alt 1 to 2.
Step 14 would have taken painfully long as CP's and FO's usually fumble their way thru there. Eventually open NNC page PI-QRH.10.1 & 10.2 and you are finished in maybe 150 to 300 secs.
All the while with F5 and you want to burn fuel anyways.
After Take Off Checklist.
Now all under control, adivse ATC, swing north or south, prepare for an over weight landing, PA to the Seatbelted Cabin Crew and Pax. Even a visual return is no issue as they all grew up flying locally around Addis but FMC still available for the RNAV 07R.
F40, AB3, Max Reverse and expect maybe a brake cooling issue. That is also hard for many to figure out here the Brake Cooling and since over Max Landing Weight you'd need the QRH again for the landing distance,
NNC finished and you will be on the ground in 10 - 20 mins safe after pressing TOGA.
Just like the sim, but the sim sessions at ET are dramatically different and produce this outcome, plus the commercial pressure GET TO NBO ITIS reared its head for sure.
Notes:
They would have kept F5, MCAS remains dormant and you live for another day.
So it comes down to following the standard published Boeing procedures.
That will be exactly how Boeing's massive legal team will argue it for the next many years of litigation.
BUT NO IT WAS A COMPLETE DIVERSION FROM THE SOP, FOM, FCTM, AND QRH and JEP EMERGENCY PROCEDURES.

So in doing what they did, you enter the realm of being a Test Pilot.
In the sim, would have been a Fail for the actual actions taken on March 5th.

Learn from it my Pilot Friends.
Yes - it's clear that if you get a shaker that you determine to be spurious, by retracting the flaps you allow MCAS to start and thus seriously compound your problems.

However, one thing's not making sense to me - after the electric trim was defeated and they were then unable to retrim manually, they re-enabled the trim motors but after that there were only a couple of short blips of electric trim. You'd have thought that in a plane which is only being prevented from nose diving by a lot of back pressure on the controls, the crew would run nose-up trim continuously until the load came off the controls, not blip it. Is it possible that the electric trim was also unable to retrim the stab with a lot of control load?


Richard C is offline  
Old 7th Apr 2019, 08:17
  #3526 (permalink)  
 
Join Date: Jun 2006
Location: Brisbane
Posts: 5
Originally Posted by Airbubba View Post
Here's an explanation of the EASA position on the observation that the yoke trim switches on the MAX don't work throughout the entire speed envelope (with some highlighted text):



From: https://www.easa.europa.eu/sites/def...20ISS%2010.pdf
The EASA document is being mis-interpreted by many.

It notes that once you get to a certain point of AND trim (somewhere between 3 and 4 units from memory, varying by model), you cannot trim further AND with the yoke switches (flaps up). If you ever needed to, for an unusual reason (eg jammed flight controls), you would need to use manual trim. In normal ops, you would never need to.

This point is irrelevant to this discussion because it doesn’t prevent the yoke switches from trimming ANU, even if the aircraft has been trimmed full AND. It is a one directional limit switch only. It doesn’t prevent trim in the other direction.

Note: I’m referring to the limit switch in the forward trim range above. There is another limit switch aft which works similarly in reverse.

EASA have made it confusing by referring to it as trim “authority”, which could be interpreted as “the motor is not powerful enough”.

Ironically, the limit switch was implemented to help prevent either runaway trim or pilot yoke switch trim into the “danger zone” which might result in an unrecoverable dive. EASA, in recognition of this “safety improvement”, approved the implementation on the basis that it improved safety rather than reducing it.

But Boeing’s MCAS implementation has actually allowed MCAS to trim past this limit switch, which was very unwise and has turned out to have had tragic consequences.

I hope this clears it up.
Derfred is offline  
Old 7th Apr 2019, 08:17
  #3527 (permalink)  
 
Join Date: Feb 2015
Location: The woods
Posts: 1
Originally Posted by Majorbyte View Post
so you're blaming both sets of pilots? do you work for Boeing by any chance?
That post from Under Duress is unfortunately typical of what can get postulated after an accident / incident and reminds me of the criticism directed at Sullenberger and crew because it was demonstrated that a pre briefed crew, after some practice attempts could react within seconds and land the aircraft on a runway (see the documentary “Sully”). This without any time for recognition, analysis or decision. They were trained dogs performing in the sim and just about hacking it.
We should remember that lots of folk look in here - you can be sure that Boeing does too - engineers and legal team.
Any sensible suggestions will at least be taken on board - any condemnation of crew actions seen as vindication of their insistence on the suitability of the stab runaway drill for a different and complex failure.
bill fly is offline  
Old 7th Apr 2019, 08:27
  #3528 (permalink)  
 
Join Date: Jul 2005
Location: btw SAMAR and TOSPA
Posts: 565
Originally Posted by Derfred View Post


The EASA document is being mis-interpreted by many.

It notes that once you get to a certain point of AND trim (somewhere between 3 and 4 units from memory, varying by model), you cannot trim further AND with the yoke switches (flaps up). If you ever needed to, for an unusual reason (eg jammed flight controls), you would need to use manual trim. In normal ops, you would never need to.

This point is irrelevant to this discussion because it doesn’t prevent the yoke switches from trimming ANU, even if the aircraft has been trimmed full AND. It is a one directional limit switch only. It doesn’t prevent trim in the other direction.

Note: I’m referring to the limit switch in the forward trim range above. There is another limit switch aft which works similarly in reverse.



I hope this clears it up.
No. I take an aviation document as literal and binding. What you say may be from some private working papers, which is not an official numbered published document. So can be anything, including fake.
threemiles is offline  
Old 7th Apr 2019, 08:27
  #3529 (permalink)  
 
Join Date: Dec 2015
Location: Cape Town, ZA
Age: 58
Posts: 424
Originally Posted by Flt.Lt Zed View Post
Why does Boeing not delete MCAS from their new B73 8/9s?. They have thousands flying around successfully without it.
Your comment (and my response) probably deserve to be deleted, but here goes:
- Thousands of fighter jets fly every week without the election seats being used. Why not delete them, and save all that weight and complexity?
- The inflight entertainment system poses a hazard due to the risk of fire in the cabin. Why not delete it, and save all that weight and complexity?

My points are intentional hyperbole, but highlight the fact that nothing is ever added to an aircraft unless there is a purpose for it, and nothing is ever deleted from an aircraft if there is a safety aspect involved.

Passenger aircraft still carry liferafts for over water flights, its a requirement, no matter how archaic. End of rant.
GordonR_Cape is offline  
Old 7th Apr 2019, 08:40
  #3530 (permalink)  
 
Join Date: Dec 2015
Location: Cape Town, ZA
Age: 58
Posts: 424
Originally Posted by bill fly View Post


That post from Under Duress is unfortunately typical of what can get postulated after an accident / incident and reminds me of the criticism directed at Sullenberger and crew because it was demonstrated that a pre briefed crew, after some practice attempts could react within seconds and land the aircraft on a runway (see the documentary “Sully”). This without any time for recognition, analysis or decision. They were trained dogs performing in the sim and just about hacking it.
We should remember that lots of folk look in here - you can be sure that Boeing does too - engineers and legal team.
Any sensible suggestions will at least be taken on board - any condemnation of crew actions seen as vindication of their insistence on the suitability of the stab runaway drill for a different and complex failure.
Valid points, but I just read an equally convincing argument stating exactly the opposite. It was posted in a thread which is somehow in the Tech Log forum, but IMO worth cross posting (with due acknowledgement).
Originally Posted by Water pilot
I doubt there is going to be much in the way of legal arguments on this one, Boeing does not want to be anywhere near a jury. You can talk about the pilot's actions all that you want to, but ultimately you have two aircraft that were pointed to the ground at low altitude by a flight control system that was not disclosed to the pilots and that was (according to media reports) significantly different than the certification documentation described. Add in the cosy relationship with the FAA along with the whistleblower report and this is not something that goes to trial if Boeing has any competent lawyers left.

I am not a lawyer, but I don't think you ever want to be in a civil trial where the jury is wondering why the executives are not in jail yet.
GordonR_Cape is offline  
Old 7th Apr 2019, 08:48
  #3531 (permalink)  
 
Join Date: Jul 2009
Location: France
Age: 58
Posts: 44
Originally Posted by Derfred View Post


The earlier trim durations you refer to happened with flaps extended. The trim wheel moves faster with flaps extended. That explains the difference.

Nope. Look at the FO trim up input (long one) that stops MCAS. First 3 s of that input moves the stab appr. 1 U up. Even at the lousy resolution of the plot you can see the difference. I copy/pasted all 4 events together:


Or, for more precision: The FO input lasts 10 s and brings the stab up appr. 2.3 U 1.9 U. That is appr. 0.7 0.6 U / 3 s. The third blue arrow from the left does not show that much movement. Flaps up applies to both rightmost events.
And, again, as you raised: Why does PF ask FO to help with the trim (switch)? [Edited because Derfred gave more correct numbers in a later post]

Last edited by spornrad; 7th Apr 2019 at 10:00.
spornrad is offline  
Old 7th Apr 2019, 09:06
  #3532 (permalink)  
 
Join Date: Jun 2006
Location: Brisbane
Posts: 5
Originally Posted by FrequentSLF View Post
A simple question from an engineer, why a designer should put a pilot in such situation, why the designer cannot prevent and design a solid system?
They can design a solid system, although never perfect. In this case, sadly, they failed to design a solid system. That is not in question. Even Boeing have effectively admitted this.

The question now is, “how and why did this happen?”, especially in such a tightly regulated, conservative and safety-conscious industry, with one of the world’s most respected organisations. The answer to that is now under extensive inquiry.

We may or may not ever discover the truth, but typically when this many people die unnecessarily, the difficult questions finally get asked, and those with the answers are forced to actually answer.

Of course, it will fundamentally point to one thing: MONEY.

But we aren’t going to get rid of money, so it’s the movement of money, to whom and how much, and how much those in charge of money get to influence those in charge of solid design, that will come into question.


[And why if he is not able to do so the blame is on the operator? A wrong design is a wrong design, no matter how much you train the operators
Well, if by operator, you mean the airline, well they are in charge of employing sufficiently skilled pilots and providing them sufficient training to get their passengers from A to B safely. The airline is also in charge of purchasing sufficiently safe equipment to do so, and maintain it to a sufficient standard.

If they fail to do this, they must accept some liability for the failure. Whether they failed to do this is not yet ascertained - some think the pilots should have saved the passengers from the design fault, some think that’s an unreasonable ask, and some think it was impossible.


If, on the other hand, by “operator” you mean the particular pilots involved, well, in my opinion, pilots have a personal obligation to maintain a standard on top of that required by their employer and their regulator. They can also be held personally liable for the failure, and depending on the global jurisdiction may be supported and/or indemnified by their employer, or, not.

Aviation safety is a rich tapestry, that normally results in a high level of safety, but many argue that it is gradually being eroded in standards of design, training, and skills, generally by one thing: MONEY.

Think about that next time you buy the cheapest ticket available, because that MONEY only comes from one place: you. The less you pay, the less MONEY available to pay someone to design a solid system, or to pay or train the pilot to save you from the less-than-solid system.
Derfred is offline  
Old 7th Apr 2019, 09:09
  #3533 (permalink)  
 
Join Date: Jan 2004
Location: Here and there
Posts: 2,803
Has anyone tried trimming with the stick shaker going? Honest question. Is it difficult or no problem?
AerocatS2A is offline  
Old 7th Apr 2019, 09:28
  #3534 (permalink)  
 
Join Date: Jun 2006
Location: Brisbane
Posts: 5
Originally Posted by AerocatS2A View Post
Has anyone tried trimming with the stick shaker going? Honest question. Is it difficult or no problem?
In the Sim, yes.

We have done exercises pulling the aircraft into deep stall from initial stick shaker, while trimming back continuously (otherwise it’s hard to get deep stall due to increased elevator feel force - B737NG not MAX). Then having to be trimming forward again during recovery. I’ve never noticed a difficulty with this.

But not saying for one moment that the Captain in this event was not having a problem (I was the one who raised the possibility!). My stick shaker was happening at stall speed (150-ish kt), not 325 kt, and it was a Sim.
Derfred is offline  
Old 7th Apr 2019, 09:44
  #3535 (permalink)  
 
Join Date: Jul 2009
Location: France
Age: 58
Posts: 44
Originally Posted by Derfred View Post
But not saying for one moment that the Captain in this event was not having a problem (I was the one who raised the possibility!).
Thanks for your explanations. Since it would be another lottery win the thumb switch going south at that exact instance (besides why less, not no stab movement): Is there any remote possibility that software reduces the thumb switch authority on the left, not right, in those conditions (AOA disagree/MCAS activation) ?
spornrad is offline  
Old 7th Apr 2019, 09:47
  #3536 (permalink)  
 
Join Date: Jan 2014
Location: Melbourne
Age: 64
Posts: 185
Bill Fly,
Under Duress gave a pretty accurate description of what SHOULD have happened. Airline Pilots ARE “trained dogs” in certain circumstances. Few emergencies require immediate and appropriate action but stick-shaker on rotation and/or Unreliable Airspeed are definitely two of them. The metaphorical Swiss cheese started lining up from rotation and errors compounded from that point. It was badly mis-handled. Was MCAS the ultimate contributing factor? Absolutely. Was it the sole cause? Absolutely not. Most professional Pilots reading this thread with experience on the B737 would expect to do much better. By following published procedures. And exercising good Airmanship. Maybe that sounds like arrogance but that’s the nature of the beast.
Boeing and the families of victims are in a world of pain right now and comments should be worded accordingly.
But there is much more to this than MCAS.
George Glass is offline  
Old 7th Apr 2019, 09:48
  #3537 (permalink)  
 
Join Date: Jun 2006
Location: Brisbane
Posts: 5
Originally Posted by threemiles View Post
No. I take an aviation document as literal and binding. What you say may be from some private working papers, which is not an official numbered published document. So can be anything, including fake.
???

I’m explaining how the 737 stab trim works, from the manuals. Not some ‘private working papers”. I know it works that way because I’ve been flying the thing most of my life.

I even know it works that way because I’ve used it that way on the ground. Actual aircraft, not Sim. You can use yoke trim to just forward of 4 units, then it stops. You can wind it forward to 0 units manually, then you can use yoke trim to electrically wind it back. That’s how it was designed, and that’s how it performs.

EASA brought it up because it was at odds with some certification criteria, and then allowed it because it made sense from a safety perspective.

Now whether it works at 365 knots with sufficient aft control column for level flight is an entirely different question. That question is currently under congecture. My point is that the EASA document is irrelevant to that congecture because that was not the subject of the EASA document, and the word “authority” is being mis-interpreted by some here. I doubt it was mis-interpreted by the actual audience it was intended for.

We know it works at 325-330 knots, because it did. It’s on the FDR trace. Yoke trim from 0.4-2.3 units.

I hope that helps.
Derfred is offline  
Old 7th Apr 2019, 10:12
  #3538 (permalink)  
 
Join Date: Dec 2004
Location: Southern England
Posts: 109
Originally Posted by George Glass View Post
Bill Fly,
Under Duress gave a pretty accurate description of what SHOULD have happened. Airline Pilots ARE “trained dogs” in certain circumstances. Few emergencies require immediate and appropriate action but stick-shaker on rotation and/or Unreliable Airspeed are definitely two of them. The metaphorical Swiss cheese started lining up from rotation and errors compounded from that point. It was badly mis-handled. Was MCAS the ultimate contributing factor? Absolutely. Was it the sole cause? Absolutely not. Most professional Pilots reading this thread with experience on the B737 would expect to do much better. By following published procedures. And exercising good Airmanship. Maybe that sounds like arrogance but that’s the nature of the beast.
Boeing and the families of victims are in a world of pain right now and comments should be worded accordingly.
But there is much more to this than MCAS.
Spot on, it's is also the view of every colleague I have spoken to.


Albino is offline  
Old 7th Apr 2019, 10:15
  #3539 (permalink)  
 
Join Date: Dec 2003
Location: Tring, UK
Posts: 1,416
That post from Under Duress is unfortunately typical of what can get postulated after an accident / incident and reminds me of the criticism directed at Sullenberger and crew because it was demonstrated that a pre briefed crew, after some practice attempts could react within seconds and land the aircraft on a runway (see the documentary “Sully”). This without any time for recognition, analysis or decision.
Very much in agreement.

The Human Factors are, IMO, the most important/interesting part of these accidents.

To recap: There are many situations which require some sort of action from pilots, be it promptly or after consideration. The more time-critical an event is, the less time/capacity there is to figure out what to do, so responses to predictable events are based more on rules than extended cognition, hence “memory” or “recall” items are used. They need to have a simple, unambiguous trigger, e.g. an engine fails below V1, perform an RTO or GPWS says “PULL UP!”, perform the GPWS pull up manoeuvre.

When the situation is more complex and there is normally time for diagnosis, we have reference checklists which may contain decision trees, often leading to different actions and outcomes, dependent on further data. If no checklist really fits the bill completely, maybe due to multiple failures or unusual circumstances, then you need to use your general aviation understanding, backed up by specific type knowledge and all the resources you have access to in order to formulate and execute a plan of action. This is something you would generally do *after* you had determined there were no published normal or non-normal produces that were applicable, or you had applied the procedures and they had not helped or made the situation worse. Boeing specifically caution against “troubleshooting” unless all other possibilities have been exhausted but they also provide a useful “Situations Beyond the Scope of Non-Normal Checklists” guide in their training manuals.

Now, it is good aviation practice to have some kind of action associated with a single, predictable failure which affects the safe operation of the airframe, be it recall items or a reference checklist, or even just a note for crew awareness. In the case we are discussing, an AoA probe failure (which is singular, predictable and measurable) has caused a cascade of issues and warnings that are difficult to assimilate and don’t immediately point to any particular checklist, except maybe the Airspeed Unreliable one, which doesn’t include deactivating the trim. Remember we are looking at these accidents with hindsight and the warnings that occurred can be triggered by many different events that require different responses - we only know which was the correct path to take because we have most of the data in front of us to peruse at leisure.

There have been quite a few posts highlighting the startle effect plus the saturation of input channels by excess information of questionable usefulness, e.g. stick shaker, GPWS, fault messages, high control loadings, etc. It is quite easy to see how some things were missed, in fact most of the above is taught in basic HF modules but this seems have passed some manufacturers by.

It’s easy to say that you’d have disconnected the trim as soon as you got a stick shake in the climb out because the flaps are correct and power is set. Well done. But supposing that was a *real* stall warning because you put the wrong weights in the FMC so have rotated 20kts early? Not so well done now, eh? This has happened before and will happen again and is just one example of why it is so important NOT to rush to conclusions if you can absolutely help it.
FullWings is offline  
Old 7th Apr 2019, 10:44
  #3540 (permalink)  
fdr
 
Join Date: Jun 2001
Location: 3rd Rock, #29B
Posts: 784
Originally Posted by threemiles View Post
I read it that this must be shown only for speeds between minimum for steady, unstalled flight and VLO/VFE. MCAS operates when flaps are retracted. The rubber word "appropriate" may be the secret.
But... 25.173 is for static longitudinal stability, the item of note is mis trim case which comes under 25.255 and that has a further set of criteria which if anything are inadequate for this case, or the underlying potential to get out of trim that exists on the B737 in general. The MCAS is covered in 25.672 and either will be determined to meet the requirement or be inadequate to show compliance with that. The out of trim case that resulted from the characteristics of MCAS is the major concern IMHO, which raises the matters of unloading the stab etc, which has it's own set of questions. That nexus is going to take lawyers to sort out, and that is not good for the operational outcome. That an aircraft can get out of trim excessively is not purely a Boeing matter, the Max just happens to be the current headline. A few years back it was A320's like the Perpignan event, a departure or two out of Reagan, and before that, it was A310s galore in-dispersed with A300-600's. Some of those ended up in smoking holes, some missed the ground on a number of occasions in the same event. If the conditions can occur that the pilot is at odds with the plane, it deserves more than a passing comment in the FCTM or a note in the FCOM.
fdr 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.