Indonesian aircraft missing off Jakarta
Accident investigation protocol says that only the lead investigating authority (here the NTSC/KNKT) will release data such as FDR/CVR recordings, if deemed appropriate.
The US NTSB (not FAA), representing the state of manufacture will have the status of an accredited representative to the investigation, and can choose in turn to consult other parties (Boeing, GE, FAA, etc), but none of those parties will release data independently.
The US NTSB (not FAA), representing the state of manufacture will have the status of an accredited representative to the investigation, and can choose in turn to consult other parties (Boeing, GE, FAA, etc), but none of those parties will release data independently.
My point is that a) we don't know that they were, and b) it's possible to argue that they had no need to be so based. (Of course if the LionAir a/c had not been lost in what little we know of the circumstances, the Boeing/FAA stuff would likely not have appeared so promptly in the form it did, even if they concluded, from past events, that operators were not sufficiently aware of what MCAS can do in manual flight when the sensor data is unreliable).
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Nothing that Boeing or the FAA have said so far is explicitly linked to the FDR for this airframe. The FAA directive could be part-based on the FDR data; but it could equally - imho - be based on what is known about the flight from ATC data and communications, plus paperwork and witness statements about the prior difficulties that this particular a/c had recently encountered. So, previous flight crews could all have said that, having gone to manual flight following sensor disagree alerts, they then encountered strong and unexpected nose-down stab trim, uncommanded by them.
Well, could be that way, but my money is on the 20deg came from the FDR, and I reckon Occam's is too.
Last edited by infrequentflyer789; 15th Nov 2018 at 10:03. Reason: fingers got wrong acronym
In my humble opinion much too much is made out of the MCAS issue. All the fleet transition and training documents available from the manufacturer have included it. Anyhow, as Boeing have mentioned themselves, a malfunction with it is already covered by present procedures. It's operation is transparent to the crew, so in case of false MCAS activation due to unreliable AOA data we basically have a runaway stabilizer - and flipping the cutout switches mitigates the problem.
Recall/memory checks need simple triggers and a short list of items as these will inevitably be needed/actioned in times of high workload and distraction. An large collection of disparate clues requiring Holmes-type deduction to end up with the right response is set up to fail, IMHO.
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There are several failures that can cause a stab trim runaway - and not all are solved by turning the system 'OFF". In addition to welded switch contacts, the motor can fail in such a way that you can't turn it off. These failures are rare, but not impossible - the only way to 100% disable the system is to pull the circuit breaker(s) (and that's not something they like to tell the pilots to do).
Psychophysiological entity
As someone that was accused of wanting to know about every last widget in the kit I flew, the last paragraph of this item leaves me breathless - and belies some of the earlier post links.
https://theaircurrent.com/aviation-s...em-mcas-jt610/
https://theaircurrent.com/aviation-s...em-mcas-jt610/
As someone that was accused of wanting to know about every last widget in the kit I flew, the last paragraph of this item leaves me breathless - and belies some of the earlier post links.
https://theaircurrent.com/aviation-s...em-mcas-jt610/
https://theaircurrent.com/aviation-s...em-mcas-jt610/
“One high-ranking Boeing official said the company had decided against disclosing more details to cockpit crews due to concerns about inundating average pilots with too much information — and significantly more technical data — than they needed or could digest.”
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From the outside looking in..
Interesting "out" there by Boeing.
I fail to see why "decided against disclosing" can be seen as anything other than a contributor to this accident.
Also the TC quandrum ---when does a 737 stop being a 737?
No doubt the shrill will point out I am just an average, stupid, Joe....
I fail to see why "decided against disclosing" can be seen as anything other than a contributor to this accident.
Also the TC quandrum ---when does a 737 stop being a 737?
No doubt the shrill will point out I am just an average, stupid, Joe....
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As someone that was accused of wanting to know about every last widget in the kit I flew, the last paragraph of this item leaves me breathless - and belies some of the earlier post links.
https://theaircurrent.com/aviation-s...em-mcas-jt610/
https://theaircurrent.com/aviation-s...em-mcas-jt610/
training on moving from the old 737 NG model cockpit to the new 737 MAX consisted of little more than a one-hour session on an iPad
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I am just an electronics engineer (non-aero) _and_ I may well have missed some important information from this discussion.
But earlier, I think it was mentioned that either one or the other of two possible sources of AoA information is selected "automatically" and remains throughout the flight, then switch to the other one for the next flight. Is this more or less correct? What is the rationale behind this? To me it appears as "we did not quite know what to do with two AoA sensors here". Presumably this also went through some review by the FAA ... who were happy with the explanation?
But earlier, I think it was mentioned that either one or the other of two possible sources of AoA information is selected "automatically" and remains throughout the flight, then switch to the other one for the next flight. Is this more or less correct? What is the rationale behind this? To me it appears as "we did not quite know what to do with two AoA sensors here". Presumably this also went through some review by the FAA ... who were happy with the explanation?
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- it has not been established that MCAS operation was a causal factor in this accident and
- even if it were, it has not been established that knowledge of MCAS operation would then have prevented the accident.
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For all those questions about WHY this MCAS on B737 MAX fleet, the following link has a very nice easy to follow explanation with clear graphics written by a test pilot Bjorn Fehrm.
When you apply a lot of lipstick to an old lady like B737, something else goes wrong. Boeing had to do this change as the large engines made the aircraft stability to go wrong. Thanks Bjorn. I think it will clear up several questions about MCAS, STS, etc. in this forum.
https://leehamnews.com/2018/11/14/bo...to-the-pilots/
When you apply a lot of lipstick to an old lady like B737, something else goes wrong. Boeing had to do this change as the large engines made the aircraft stability to go wrong. Thanks Bjorn. I think it will clear up several questions about MCAS, STS, etc. in this forum.
https://leehamnews.com/2018/11/14/bo...to-the-pilots/
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1, An AOA disagree causes the ADIRUs to have problems and leads to Unreliable Airspeed indications
2. However, a lot now depends on which of the AOAs is being used by MCAS which apparently depends on the random squat switch (weight on wheels) swap from one to the other
3. If AOA disgree AND PF is on the non-failed AOA side AND MCAS is using the non-failed AOA - then the aircraft can be treated as if it has an unreliable airspeed only and recovered (as in the previous flight)
ELSE IF AOA disagree AND PF is on the Failed AO side and MCAS is using the FAILED AOA then MCAS believes the failed AOA AND IF that failure indicates a stalled aircraft THEN MCAS will start trimming nose down only stopping briefly with PF trim inputs.
So it is not a simple if AOA fails then MCAS crashes you. MCAS has to be using the failed AOA and the failure has to indicate stall. IF at any stage the crew switch off stab trim with the cutoff then the problem goes away.
There are more slices of cheese that have to line up than appreciated. However, the design decision to switch from one AOA to the other effectively at random rather than have a system that discards all AOA input on AOA disagree seems to be a little shaky.
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Piling on?
https://www.seattletimes.com/busines...ion-air-crash/
...Three former Boeing flight control experts were startled by the FAA’s description last week of the new MAX system. In an airworthiness directive, the FAA cited an analysis by Boeing that “if an erroneously high single angle of attack (AOA) sensor input is received by the flight control system, there is a potential for repeated nose-down trim commands” that will swivel the plane’s horizontal tail to pitch the nose downward.
The fact that the plane’s nose could be automatically and repeatedly pushed down due to one false signal shocked Peter Lemme, a former Boeing flight controls engineer, who said it looks like a design flaw.
“To contemplate commanding the (horizontal tail to pitch the jet) nose down clearly is a major concern. For it to have been triggered by something as small as a sensor error is staggering,” Lemme said. “It means somebody didn’t do their job. There’s going to be hell to pay for that.”
The fact that the plane’s nose could be automatically and repeatedly pushed down due to one false signal shocked Peter Lemme, a former Boeing flight controls engineer, who said it looks like a design flaw.
“To contemplate commanding the (horizontal tail to pitch the jet) nose down clearly is a major concern. For it to have been triggered by something as small as a sensor error is staggering,” Lemme said. “It means somebody didn’t do their job. There’s going to be hell to pay for that.”
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I'm somewhat amazed at the apparent broad based assumption that the MCAS is in fact the root issue in the crash. No question that it's potentially a significant "hole in the cheese" but there is a very really underlying issue. It's abundantly clear that for some reason the crew failed to follow SOP specific to power and pitch settings. Without the CVR we have no real insight into the cockpit CRM and the crews intent and/or issues. Was the apparent decision to try and maintain 5,000 a by product of another technical issue or was it undertaken for a specific reason. Did the plane suffer a structural issue do to overspeed (late flap retraction?)? Was the technician in jump seat, if so what was his interaction with the crew and did it effect the outcome adversely?
All we know for certain is that for the three previous segments the technical issues were manageable and addressed with the existing protocols. On this flight we have clear evidence that those protocols were not executed in a timely manner but no real understanding of why. If in fact this is the first clear incident of a Boeing plane succumbing to "what is it doing now" then we've reached a point where both major manufacturers have reached a point where "safety kills", however it is entirely possible....even probable that the root cause of this tragic event lies at the decision to deviate from the proscribed SOP for this malfunction (UAS) even if in fact it was a compound failure. What if any specific difference occurred in comparison to the previous flight that appears to have suffered an identical initial "upset" before recovery and successful completion of the flight???
All we know for certain is that for the three previous segments the technical issues were manageable and addressed with the existing protocols. On this flight we have clear evidence that those protocols were not executed in a timely manner but no real understanding of why. If in fact this is the first clear incident of a Boeing plane succumbing to "what is it doing now" then we've reached a point where both major manufacturers have reached a point where "safety kills", however it is entirely possible....even probable that the root cause of this tragic event lies at the decision to deviate from the proscribed SOP for this malfunction (UAS) even if in fact it was a compound failure. What if any specific difference occurred in comparison to the previous flight that appears to have suffered an identical initial "upset" before recovery and successful completion of the flight???
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Can’t imagine
Being an engineer involved in the design or testing of this feature. Do we know if there were any significant objections raised prior to implementation? I recall the clashes between contractors and engineers over Challenger O-ring.
Was there pushback internally over this?
Was there pushback internally over this?
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This is one of the reasons 737 could not be equipped with P&W GTF engine. The base design (wing-ground clearance) is from the 60's. It worked fine for turbojets, needed squashed nacelles for larger turbofan but GTF is just step too far. You can only stretch the design so much...
Wonder if it the same people who added the tail flutter to the 777.
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Mad (Flt) Scientist - likely you were addressing (1256) a couple posts I set out (1198, 1203).
Very pertinent info regarding how test pilot community determines capacities of the......here's where perhaps an issue arises. The phrasing "average pilot" most reasonably would refer to an at least minimally professionally capable one. The regs don't say "average"; they refer to non-exceptional. Which makes perfect sense of course, even more so with your explanatory comments in view.(And it's probably more akin to "minimally professionally capable plus a margin of additional skill, alertness and/or strength", isn't it?)
But when the public sees "average", the meaning includes some items that are above that level or value, some that are below. And while of course there always will be variations among any quite large population, the implication in the phrasing was too easily that some aviators have to have nominal information sets dumbed-down.
It still leaves the question, with advancing cockpit and flight control automation generally, and the complexities it tends to bring with, does the baseline of the "non-exceptional yet still positively professionally capable" pilot mask variations in ability to stay ahead of both the airplane and its automated systems? Maybe the eventual investigation findings will negate this factor as relevant, but so far it appears important.
WillowRun 6-3
Very pertinent info regarding how test pilot community determines capacities of the......here's where perhaps an issue arises. The phrasing "average pilot" most reasonably would refer to an at least minimally professionally capable one. The regs don't say "average"; they refer to non-exceptional. Which makes perfect sense of course, even more so with your explanatory comments in view.(And it's probably more akin to "minimally professionally capable plus a margin of additional skill, alertness and/or strength", isn't it?)
But when the public sees "average", the meaning includes some items that are above that level or value, some that are below. And while of course there always will be variations among any quite large population, the implication in the phrasing was too easily that some aviators have to have nominal information sets dumbed-down.
It still leaves the question, with advancing cockpit and flight control automation generally, and the complexities it tends to bring with, does the baseline of the "non-exceptional yet still positively professionally capable" pilot mask variations in ability to stay ahead of both the airplane and its automated systems? Maybe the eventual investigation findings will negate this factor as relevant, but so far it appears important.
WillowRun 6-3
Last edited by WillowRun 6-3; 16th Nov 2018 at 00:30.
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I think that a point has been missed that is to do with the apparent architecture of the system.
1, An AOA disagree causes the ADIRUs to have problems and leads to Unreliable Airspeed indications
2. However, a lot now depends on which of the AOAs is being used by MCAS which apparently depends on the random squat switch (weight on wheels) swap from one to the other
3. If AOA disgree AND PF is on the non-failed AOA side AND MCAS is using the non-failed AOA - then the aircraft can be treated as if it has an unreliable airspeed only and recovered (as in the previous flight)
ELSE IF AOA disagree AND PF is on the Failed AO side and MCAS is using the FAILED AOA then MCAS believes the failed AOA AND IF that failure indicates a stalled aircraft THEN MCAS will start trimming nose down only stopping briefly with PF trim inputs.
So it is not a simple if AOA fails then MCAS crashes you. MCAS has to be using the failed AOA and the failure has to indicate stall. IF at any stage the crew switch off stab trim with the cutoff then the problem goes away.
There are more slices of cheese that have to line up than appreciated. However, the design decision to switch from one AOA to the other effectively at random rather than have a system that discards all AOA input on AOA disagree seems to be a little shaky.
1, An AOA disagree causes the ADIRUs to have problems and leads to Unreliable Airspeed indications
2. However, a lot now depends on which of the AOAs is being used by MCAS which apparently depends on the random squat switch (weight on wheels) swap from one to the other
3. If AOA disgree AND PF is on the non-failed AOA side AND MCAS is using the non-failed AOA - then the aircraft can be treated as if it has an unreliable airspeed only and recovered (as in the previous flight)
ELSE IF AOA disagree AND PF is on the Failed AO side and MCAS is using the FAILED AOA then MCAS believes the failed AOA AND IF that failure indicates a stalled aircraft THEN MCAS will start trimming nose down only stopping briefly with PF trim inputs.
So it is not a simple if AOA fails then MCAS crashes you. MCAS has to be using the failed AOA and the failure has to indicate stall. IF at any stage the crew switch off stab trim with the cutoff then the problem goes away.
There are more slices of cheese that have to line up than appreciated. However, the design decision to switch from one AOA to the other effectively at random rather than have a system that discards all AOA input on AOA disagree seems to be a little shaky.
The way the system is architectured means if the AOA on standby side fails, it may be undetected and henced unfixed, since it is not used for function. The failure becomes latent. Now when the active control side AOA fails after, you have BOTH AOA faulty. Flight crew would have no chance to even diagnose the issue themselves.
That is why the industry standard approach is to have system detect and respond/announce to failure in real time
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Being an engineer involved in the design or testing of this feature. Do we know if there were any significant objections raised prior to implementation? I recall the clashes between contractors and engineers over Challenger O-ring.
Was there pushback internally over this?
Was there pushback internally over this?
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