Ethiopian airliner down in Africa
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Getting a bit fed up with this canard. Not saying it shouldn't have been done, but what exactly would this have done to the throttle position in the accident scenario?
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Ummm...it would have allowed them to manually control the thrust levers...which is exactly what basic airmanship would dictate.
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Fight the normalization of the abnormal
I see more and more posts selecting solutions which are strictly inside the coordinates of what we "know" it is possible. (EG: more training, software patch...) and not seriously mentioning much better / obvious ones.
I say: listen to people from other industries. What we sometimes believe impossible in terms of complexity / cost / time may not be so.
It's time to roll up our sleeves and produce good computer systems for planes. Systems in which sensor signals jumping straight up to off - the - scale - high are automatically rejected and have zero impact. For a start. Updating whichever rules as we go to keep a cheap but much safer solution.
We totally know how to do it right, it's just we forbid ourselves to do it by all sorts of rules and bureaucracy. Let's not accept another band aid.
Somebody wrote many pages ago he spent 30 years in the industry and failed to change substandard quality. Sorry I forgot who. But to him and everyone else, we have to keep fighting, as futile as it may be. It's simply what we have to do.
I say: listen to people from other industries. What we sometimes believe impossible in terms of complexity / cost / time may not be so.
It's time to roll up our sleeves and produce good computer systems for planes. Systems in which sensor signals jumping straight up to off - the - scale - high are automatically rejected and have zero impact. For a start. Updating whichever rules as we go to keep a cheap but much safer solution.
We totally know how to do it right, it's just we forbid ourselves to do it by all sorts of rules and bureaucracy. Let's not accept another band aid.
Somebody wrote many pages ago he spent 30 years in the industry and failed to change substandard quality. Sorry I forgot who. But to him and everyone else, we have to keep fighting, as futile as it may be. It's simply what we have to do.
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It's time to roll up our sleeves and produce good computer systems for planes. Systems in which sensor signals jumping straight up to off - the - scale - high are automatically rejected and have zero impact. For a start. Updating whichever rules as we go to keep a cheap but much safer solution.
The problem here lies much earlier, in specifying the requirements for MCAS. More specifically, the failure modes and the severity and likelihood of each were not properly analysed.
We totally know how to do it right, it's just we forbid ourselves to do it by all sorts of rules and bureaucracy. Let's not accept another band aid.
Add-on systems that bring airliners back into compliance, which are not by themselves aerodynamically completely compliant to regulations, are literally as old as jet airliners themselves. Many types have stick-nudgers or stick-pushers, and they work fine, and are perfectly sensible to use. But that does not mean one can skip due diligence in developing them, which includes a thorough risk and hazard assessment.
Bernd
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Of course that’ll be the job of Boeing lawyers to mitigate and try to reduce liability but ultimately the main culprit will come down to MCAS, it’s design, certification, discreet implementation, lack of redundancy and ultimately its power to overcome pilot actions without crews being made fully aware of its capabilities.
Perhaps as the lawyers are debating and dissecting second by second details, they should do it with the continuous Stick Shaker loop in the background. It really is an asymmetric situation for the crews, if they don't do something (following the NNM for the stick shake and shove the nose down) and save the day at that point they get no credit, yet they don't do something else everyone wants to point to them and say see, pilot error. For the manufacturer it is a business decision to hang the crew if possible as it reduces their liability. They get to cherry pick the inevitable forced pilot errors in such difficult circumstances and gloss over the manufacturers errors and omissions.
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Before rotation there is speed where AoA sensors should work in the intended way, why not check the values then and throw out the bad one. That does not help for events after rotation but would atleast check for ground damage.
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Hello all,
My understanding from these situations is one contributing factor may be that a pilot may ultimately get into a situation where he or she has little to no ability to correct a badly out of trim Max manually or electrically due to aerodynamic loads in certain flight situations. What I have not seen is anyone noting is if this inability, irregardless of how it came about, is the same in other aircraft from Boeing or Airbus. From a 320 to a 380 or a 737 NG or 747 to a 787 would a pilot have the ability to re-trim from the same situation these two flights faced?
TME
My understanding from these situations is one contributing factor may be that a pilot may ultimately get into a situation where he or she has little to no ability to correct a badly out of trim Max manually or electrically due to aerodynamic loads in certain flight situations. What I have not seen is anyone noting is if this inability, irregardless of how it came about, is the same in other aircraft from Boeing or Airbus. From a 320 to a 380 or a 737 NG or 747 to a 787 would a pilot have the ability to re-trim from the same situation these two flights faced?
TME
My understanding from these situations is one contributing factor may be that a pilot may ultimately get into a situation where he or she has little to no ability to correct a badly out of trim Max manually or electrically due to aerodynamic loads in certain flight situations.
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I see more and more posts selecting solutions which are strictly inside the coordinates of what we "know" it is possible. (EG: more training, software patch...) and not seriously mentioning much better / obvious ones.
I say: listen to people from other industries. What we sometimes believe impossible in terms of complexity / cost / time may not be so.
It's time to roll up our sleeves and produce good computer systems for planes. Systems in which sensor signals jumping straight up to off - the - scale - high are automatically rejected and have zero impact. For a start. Updating whichever rules as we go to keep a cheap but much safer solution.
We totally know how to do it right, it's just we forbid ourselves to do it by all sorts of rules and bureaucracy. Let's not accept another band aid.
Somebody wrote many pages ago he spent 30 years in the industry and failed to change substandard quality. Sorry I forgot who. But to him and everyone else, we have to keep fighting, as futile as it may be. It's simply what we have to do.
I say: listen to people from other industries. What we sometimes believe impossible in terms of complexity / cost / time may not be so.
It's time to roll up our sleeves and produce good computer systems for planes. Systems in which sensor signals jumping straight up to off - the - scale - high are automatically rejected and have zero impact. For a start. Updating whichever rules as we go to keep a cheap but much safer solution.
We totally know how to do it right, it's just we forbid ourselves to do it by all sorts of rules and bureaucracy. Let's not accept another band aid.
Somebody wrote many pages ago he spent 30 years in the industry and failed to change substandard quality. Sorry I forgot who. But to him and everyone else, we have to keep fighting, as futile as it may be. It's simply what we have to do.
Would a similar AOA failure on an NG cause a crash? Almost certainly not.
In my opinion, Boeing & FAA have stretched the definition of a derivative aircraft beyond what is reasonable. What will be interesting will be impact on 777X, I am guessing FAA will be reviewing all assumptions on that now, and we might even see the end of "NG" derivative programmes (as opposed to stretches) with authorities insisting that if you build a new plane, it meets current standards. This is how it works in contruction. Sure, you don't have to rebuild a 40 year old building to new standards, but you can't say "this design met earthquake standards in 1990, so I can just build a derivative of it"
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but there's no evidence that it's the case for electric trim.
Hello all,
My understanding from these situations is one contributing factor may be that a pilot may ultimately get into a situation where he or she has little to no ability to correct a badly out of trim Max manually or electrically due to aerodynamic loads in certain flight situations. What I have not seen is anyone noting is if this inability, irregardless of how it came about, is the same in other aircraft from Boeing or Airbus. From a 320 to a 380 or a 737 NG or 747 to a 787 would a pilot have the ability to re-trim from the same situation these two flights faced?
TME
My understanding from these situations is one contributing factor may be that a pilot may ultimately get into a situation where he or she has little to no ability to correct a badly out of trim Max manually or electrically due to aerodynamic loads in certain flight situations. What I have not seen is anyone noting is if this inability, irregardless of how it came about, is the same in other aircraft from Boeing or Airbus. From a 320 to a 380 or a 737 NG or 747 to a 787 would a pilot have the ability to re-trim from the same situation these two flights faced?
TME
The previous application of trim, 9-10 seconds' worth at around 05:30:40 resulted in a tad under 2 units (degrees) of ANU stab movement. The final two bursts of trim command were no more than 1 second each, so any stab movement would have been a fraction of a degree (which is actually just discernable on the trace).
DaveReidUK, #3647, Icarus2001, quentinc
“… no evidence that it's the case for electric trim.”
Indications in the EASA reference ‘Equivalent Safety Case’ suggest otherwise.
“Simulation has demonstrated that the thumb switch trim does not have enough authority to completely trim the aircraft longitudinally in certain corners of the flight envelope, e.g. gear up/flaps up, aft center of gravity, near Vmo/Mmo corner, and gear down/flaps up, at speeds above 230 kts.”
Also see the ‘forceful‘ arguments in https://www.satcom.guru/2019/04/stab...and-range.html
Where the Equivalent Safety Case relates to normal flight with an aircraft reasonably in trim - low tail forces - Peter L, initial diagrams with level tail +/- elevator.
However with serious trim malfunctions, the tail displacement together with adverse elevator load attempting to recover, might limit electric trim (latter diagrams). Add effects of elevator feel offset due to false stall warning, higher stick loads add to trim offset loads.
Discussions range between trim motor stall, and/or trim inhibit at large angles for trim runaway safety case.
Also remember that MCAS vs elect trim is 10 to 5 time ratio in favour of nose down.
“… no evidence that it's the case for electric trim.”
Indications in the EASA reference ‘Equivalent Safety Case’ suggest otherwise.
“Simulation has demonstrated that the thumb switch trim does not have enough authority to completely trim the aircraft longitudinally in certain corners of the flight envelope, e.g. gear up/flaps up, aft center of gravity, near Vmo/Mmo corner, and gear down/flaps up, at speeds above 230 kts.”
Also see the ‘forceful‘ arguments in https://www.satcom.guru/2019/04/stab...and-range.html
Where the Equivalent Safety Case relates to normal flight with an aircraft reasonably in trim - low tail forces - Peter L, initial diagrams with level tail +/- elevator.
However with serious trim malfunctions, the tail displacement together with adverse elevator load attempting to recover, might limit electric trim (latter diagrams). Add effects of elevator feel offset due to false stall warning, higher stick loads add to trim offset loads.
Discussions range between trim motor stall, and/or trim inhibit at large angles for trim runaway safety case.
Also remember that MCAS vs elect trim is 10 to 5 time ratio in favour of nose down.
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DaveReidUK, #3647, Icarus2001, quentinc
...
Indications in the EASA reference ‘Equivalent Safety Case’ suggest otherwise.
“Simulation has demonstrated that the thumb switch trim does not have enough authority to completely trim the aircraft longitudinally in certain corners of the flight envelope, e.g. gear up/flaps up, aft center of gravity, near Vmo/Mmo corner, and gear down/flaps up, at speeds above 230 kts.”
...
However with serious trim malfunctions, the tail displacement together with adverse elevator load attempting to recover, might limit electric trim (latter diagrams). Add effects of elevator feel offset due to false stall warning, higher stick loads add to trim offset loads.
...
Also remember that MCAS vs elect trim is 10 to 5 time ratio in favour of nose down.
...
Indications in the EASA reference ‘Equivalent Safety Case’ suggest otherwise.
“Simulation has demonstrated that the thumb switch trim does not have enough authority to completely trim the aircraft longitudinally in certain corners of the flight envelope, e.g. gear up/flaps up, aft center of gravity, near Vmo/Mmo corner, and gear down/flaps up, at speeds above 230 kts.”
...
However with serious trim malfunctions, the tail displacement together with adverse elevator load attempting to recover, might limit electric trim (latter diagrams). Add effects of elevator feel offset due to false stall warning, higher stick loads add to trim offset loads.
...
Also remember that MCAS vs elect trim is 10 to 5 time ratio in favour of nose down.
While MCAS *can* operate for up to 10 seconds, it is inhibited by the activation of the wheel trim switches. When they are activated, MCAS stops until they are released, and waits 5 seconds. There isn't a ratio of time between one and the other. You can hold the trim switch for any length of time and MCAS will stay off until 5 seconds after it is released.
Nothing stops a pilot from trimming to neutral in one long press, then using the cutout switches, beyond the counterintuitive nature of that reaction.
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Au contraire. Aviation is the industry which mandates appropriate techniques. They are well-known, and used.
Add-on systems that bring airliners back into compliance, which are not by themselves aerodynamically completely compliant to regulations, are literally as old as jet airliners themselves. Many types have stick-nudgers or stick-pushers, and they work fine, and are perfectly sensible to use. But that does not mean one can skip due diligence in developing them, which includes a thorough risk and hazard assessment.
Add-on systems that bring airliners back into compliance, which are not by themselves aerodynamically completely compliant to regulations, are literally as old as jet airliners themselves. Many types have stick-nudgers or stick-pushers, and they work fine, and are perfectly sensible to use. But that does not mean one can skip due diligence in developing them, which includes a thorough risk and hazard assessment.
IMO the MCAS software has to be redeveloped from scratch as Level A, not just patched. The risk of a bug in the software that could cause an AND runaway has to be reduced to ALARP (As Low As Reasonably Practical).
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DaveReidUK, #3647, Icarus2001, quentinc
“… no evidence that it's the case for electric trim.”
Indications in the EASA reference ‘Equivalent Safety Case’ suggest otherwise.
“Simulation has demonstrated that the thumb switch trim does not have enough authority to completely trim the aircraft longitudinally in certain corners of the flight envelope, e.g. gear up/flaps up, aft center of gravity, near Vmo/Mmo corner, and gear down/flaps up, at speeds above 230 kts.”
“… no evidence that it's the case for electric trim.”
Indications in the EASA reference ‘Equivalent Safety Case’ suggest otherwise.
“Simulation has demonstrated that the thumb switch trim does not have enough authority to completely trim the aircraft longitudinally in certain corners of the flight envelope, e.g. gear up/flaps up, aft center of gravity, near Vmo/Mmo corner, and gear down/flaps up, at speeds above 230 kts.”
Originally Posted by VicMel
The Ethiopian flight FDR showing an AoA of 75 – where is the limit check?? Even for software that was (incorrectly) not considered as DO-178C Level A, I still find it impossible to comprehend how someone somewhere in the development process did not suggest to put in a “if AoA > x deg, no trim”, perhaps only as a “just in case – belt and braces couple of lines of code”.
It could be possible to have an AOA of 75° and appreciate some assistance from the machine (MCAS) to keep the nose from getting there in the first place. The F up was making it reliant on only one sensor.
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? 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