Ethiopian airliner down in Africa
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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.
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.
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.
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.
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.
It is supremely unwise to state definitively as to what the FCC can or cannot do beyond stating that this software routine has full authority of the most powerful flight control installed on the aircraft.
It is also of note that the FCC commanded the stab aircraft nose down 3 times with the flaps still set.
The STS functionality is also a software routine programmed into the FCC, it is a virtual system only.
The aviation community (outside of the test community) has become all-too-comfortable in accepting and using simplistic discrete 'system' descriptions for different functions that are actually hosted by a common system running a common code.
I readily accept and acknowledge that a number, or even the majority, of professional pilots will have their 'pedant' caption flashing when they read my words, but these distinctions matter. If and when Boeing produces an acceptable software-only fix for the current issues the only thing that will change will be the software version running in the FCCs.
The aviation community (outside of the test community) has become all-too-comfortable in accepting and using simplistic discrete 'system' descriptions for different functions that are actually hosted by a common system running a common code.
I readily accept and acknowledge that a number, or even the majority, of professional pilots will have their 'pedant' caption flashing when they read my words, but these distinctions matter. If and when Boeing produces an acceptable software-only fix for the current issues the only thing that will change will be the software version running in the FCCs.
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That's autopilot trim.
It is the autopilot keeping the aircraft in trim while it accelerates to the selected bug speed of 238 knots while engaged in LVL CHG mode. What would you have it do... fly out of trim?
(It isn't speed trim - if the pilot was flying manually, then speed trim would have activated, but it would have been nose up instead of nose down.)
If and when Boeing produces an acceptable software-only fix for the current issues the only thing that will change will be the software version running in the FCCs.
The current problem appears to be a poorly designed piece of software known as "MCAS".
The proposed solution is a better designed piece of software to replace it.
If it works, what are you getting agitated about?
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The AD does in fact say to trim the forces out before using the cutout. https://theaircurrent.com/wp-content...AX-AD-1107.pdf
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As far as I understand english, it does not. It says electric trim CAN be used to neutralise column forces before cutout (nobody would think it cannot, anyway). It says also Manual trim can be used before and after cutout. It never say electric trim MUST be used to neutralise column forces before cutout
The software under scrutiny is for the Collins FCC / DFCS P11.1 and above.
If 'better' software is the accepted solution then the FCC / DFCS software will be the only thing revised.
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For the non-pilots:
Boeing Quick Reference Handbook:
Boeing Quick Reference Handbook:
While every attempt is made to supply needed non-normal checklists, it is not possible to develop checklists for all conceivable situations.
In some multiple failure situations, the flight crew may need to combine the elements of more than one checklist. In all situations, the captain must assess the situation and use good judgement to determine the safest course of action.
The Flight Crew must be aware that checklists cannot be created for all conceivable situations and are not intended to replace good judgement. In some situations, at the Captain's discretion, deviation from a checklist can be needed.
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And the portion of the software under scrutiny is referred to as MCAS. Yes, I get it, it all gets compiled into a software version and loaded into an FCC. So what? The offending bit is MCAS. The rest is fine.
Psychophysiological entity
Derfred #3586
Well, for my money, because it's still a quasi-sentient being that can still access the aircraft's controls.
The very least I would want is full annunciation of every input* . . . and the certain ability to stop it.
*Periodic movement of the Stab Trim wheel could be there anyway, so I would want a specific annunciation.
There's been little talk of MCAS putting settings back to where it found them before an input. I'm sure I read it, but is it true? If so, it seemingly failed to do so.
The proposed solution is a better designed piece of software to replace it.
If it works, what are you getting agitated about?
If it works, what are you getting agitated about?
The very least I would want is full annunciation of every input* . . . and the certain ability to stop it.
*Periodic movement of the Stab Trim wheel could be there anyway, so I would want a specific annunciation.
There's been little talk of MCAS putting settings back to where it found them before an input. I'm sure I read it, but is it true? If so, it seemingly failed to do so.
As far as I understand english, it does not. It says electric trim CAN be used to neutralise column forces before cutout (nobody would think it cannot, anyway). It says also Manual trim can be used before and after cutout. It never say electric trim MUST be used to neutralise column forces before cutout
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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.
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.
Edmund
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FullWings Thanks for your insightful comments.
Your statement reinforces a point I made earlier. We have vividly seen how faulty AOA data on the B737 affects so many systems simultaneously, that it creates a hazard in itself.
IMO AOA disagree should never have been an optional display extra, but instead trigger a high priority checklist on its own. BTW, a false low AOA value would not trigger a stick shaker, but does comprise a degraded flight condition.
The proposed software fix will remove the possibility of catastrophic MCAS activation. However the potential for a cascade of AOA derived warnings remains on the B737, including the wider NG series, and should be a concern.
Prompt identification of the underlying AOA trigger would avoid going down multiple redundant fault trees. I understand that changing existing checklists should not be treated lightly, but IMO the current review should be an opportunity to enhance this process.
Edit: Derfred Thanks for the note about discretion to bypass checklist rules.
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
IMO AOA disagree should never have been an optional display extra, but instead trigger a high priority checklist on its own. BTW, a false low AOA value would not trigger a stick shaker, but does comprise a degraded flight condition.
The proposed software fix will remove the possibility of catastrophic MCAS activation. However the potential for a cascade of AOA derived warnings remains on the B737, including the wider NG series, and should be a concern.
Prompt identification of the underlying AOA trigger would avoid going down multiple redundant fault trees. I understand that changing existing checklists should not be treated lightly, but IMO the current review should be an opportunity to enhance this process.
Edit: Derfred Thanks for the note about discretion to bypass checklist rules.
Last edited by GordonR_Cape; 7th Apr 2019 at 12:42.
As far as I understand english, it does not. It says electric trim CAN be used to neutralise column forces before cutout (nobody would think it cannot, anyway). It says also Manual trim can be used before and after cutout. It never say electric trim MUST be used to neutralise column forces before cutout
BTW, it does say at the very start of the trim runaway (in the AD not the abbreviated memory item procedure) to disconnect the autopilot and control pitch with column and electric trim. That’s not a “may” or “can”.
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...
If they fail to do this, they must accept some liability for the failure. Whether they failed to do this is not yet ascertained...
As for training, how are you supposed to train, or direct training, for a system on which you have little or no information? If an airline ensures that its pilots complete the training recommended by the manufacturer and approved by the regulator, it would be very hard to prove at a later date it should have guessed that more needed to be done.
QUOTE] 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. [/QUOTE]
A laudable view but hard to achieve in practice. Regardless of the operation (fixed wing, rotary, commercial, non-commercial etc) there will be those who achieve and maintain a higher standard than that required simply because they are gifted as pilots, whereas others will have to work much harder. That said, I agree with the point about money/investment - it is next to impossible for pilots to voluntarily improve skills when the tools do the job are unavailable because of policies on hand-flying v automation and the absence of resources for non-jeopardy sims.
It is going to take multiple lines of specialist investigation to bottom all this out. In 3500+ posts on the thread, we still have arguments raging about what this crew should have done (with hindsight...), how MCAS works and why it was implemented, what the implications are for managing the trim system, where the design may have failed, the roles of Boeing and the FAA in the certification process, what should happen with training, and of course the inevitable PPrune sport of playing the man rather than the ball. We have had some very thoughtful and helpful interventions and some frankly unhelpful diversions
For the purposes of further meaningful discussion, I think it would be very useful if someone could collate the most valid information on MCAS and the MAX trim system and have it posted on a separate locked thread that the rest of us can use for reference. That way, some of the excellent grains of truth in this very lengthy thread would not be lost/forgotten, and we would not have to keep going round the same buoys time after time.
