Indonesian aircraft missing off Jakarta
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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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https://spaceflight.nasa.gov/outreac...ion_report.pdf
https://www.gpo.gov/fdsys/pkg/GPO-CR...99hrpt1016.pdf
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If the nose of the airplane starts to move towards the ground wouldn't you automatically pull the control column AND move the stabilizer trim switches to the nose up position which would stop this MCAS trimming nose down?
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You might, and you might think you had everything resolved once you had restored roughly level flight. But if the fault is still there, then as soon as you think you are safely trimmed in level flight and move on to addressing something else, it comes back into operation and does it to you again.
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If you are a company man-woman who engages the autopilot at 1,000 ft on every departure, you are not going to be familiar with that reaction. So if the autopilot hands back control at 1,500 ft, you might be left in unfamiliar territory.
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The stick shake was going all the while, wasn't it?
irrespective of the mantra to adopt a sensible pitch/power setting, it is quite a leap of faith to pull hard on the yoke while the stick shake is going. Horrible scenario.
The flight international report also mentioned that the trim brake is inhibited when the MCAS is running due to high AOA.
irrespective of the mantra to adopt a sensible pitch/power setting, it is quite a leap of faith to pull hard on the yoke while the stick shake is going. Horrible scenario.
The flight international report also mentioned that the trim brake is inhibited when the MCAS is running due to high AOA.
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The stab trim switch would stop it and it would start again after 5 seconds.
They had been flying more or less stable at around 5000 ft for quite a while (7 minutes) before they plummeted so the sudden pitch down is a puzzle.
It's hard to speculate any further without additional info but anyway:
Maybe the fault was intermittent?
Maybe they believed the stick shaker that they were stalled when they started the last pitch down?
Then when trying to pull up they could not because of the trim?
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From the Leehamnews article:
It can be stopped by the Pilot counter-trimming on the Yoke or by him hitting the CUTOUT switches on the center pedestal. It’s not stopped by the Pilot pulling the Yoke, which for normal trim from the autopilot or runaway manual trim triggers trim hold sensors.
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The aggressive trim down due to AoA failure occurs only after the flaps are retracted. (MCAS)
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First of many Law suits
Lion Air crash: Boeing sued by victim's family over aircraft design
Image copyright Reuters Image caption Investigators examine one of the engines from the doomed Lion Air flight JT 610
The family of a passenger killed when a Lion Air flight crashed into the sea near Indonesia are suing Boeing over an alleged fault with the jet's design.
The lawsuit accuses the US aircraft manufacturer of failing to inform pilots and airlines of a feature with its new 737 Max plane system that could "push the nose down unexpectedly".
Investigators have been looking into reported technical issues.
Boeing maintains that it is "confident in the safety of the 737 Max".
Lion Air flight JT 610 was carrying 189 people when it crashed on 29 October.
It plummeted into the Java Sea following a request from the pilot for permission to turn back to the airport just moments after taking off from Jakarta.
It was later established that the aircraft had had an airspeed indicator problem on its final four flights.
On Thursday, a complaint was filed by a Florida-based law firm on behalf of the parents of Rio Nanda Pratama, who was on board the ill-fated flight JT 610.
The lawsuit focuses on the 737 Max's new automated flight control system, which it says was designed to help prevent pilots from raising the aircraft's nose "dangerously high".
However, the lawsuit adds: "Under certain conditions [the system] can push the nose down unexpectedly and so strongly that the pilot cannot pull it back up in time to avoid a crash.
"This automated feature can be triggered even if pilots are manually flying the aircraft and don't expect flight-control computers to kick in.
"It is particularly surprising to hear from safety experts and the heads of pilots' unions that Boeing failed to warn its customers and the pilots of its new 737 Max aircraft about this significant change in the flight-control systems."
Boeing, meanwhile, has said that it is not able to "discuss specifics of an ongoing investigation".
Image copyright Reuters Image caption Investigators examine one of the engines from the doomed Lion Air flight JT 610
The family of a passenger killed when a Lion Air flight crashed into the sea near Indonesia are suing Boeing over an alleged fault with the jet's design.
The lawsuit accuses the US aircraft manufacturer of failing to inform pilots and airlines of a feature with its new 737 Max plane system that could "push the nose down unexpectedly".
Investigators have been looking into reported technical issues.
Boeing maintains that it is "confident in the safety of the 737 Max".
Lion Air flight JT 610 was carrying 189 people when it crashed on 29 October.
It plummeted into the Java Sea following a request from the pilot for permission to turn back to the airport just moments after taking off from Jakarta.
It was later established that the aircraft had had an airspeed indicator problem on its final four flights.
- Victim's fiancée takes wedding photos alone
- Lion Air crash: Images of the unfolding tragedy
- Social media identifies crash couple
On Thursday, a complaint was filed by a Florida-based law firm on behalf of the parents of Rio Nanda Pratama, who was on board the ill-fated flight JT 610.
The lawsuit focuses on the 737 Max's new automated flight control system, which it says was designed to help prevent pilots from raising the aircraft's nose "dangerously high".
However, the lawsuit adds: "Under certain conditions [the system] can push the nose down unexpectedly and so strongly that the pilot cannot pull it back up in time to avoid a crash.
"This automated feature can be triggered even if pilots are manually flying the aircraft and don't expect flight-control computers to kick in.
"It is particularly surprising to hear from safety experts and the heads of pilots' unions that Boeing failed to warn its customers and the pilots of its new 737 Max aircraft about this significant change in the flight-control systems."
Boeing, meanwhile, has said that it is not able to "discuss specifics of an ongoing investigation".
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"Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots"
https://leehamnews.com/2018/11/14/bo...to-the-pilots/
https://leehamnews.com/2018/11/14/bo...to-the-pilots/
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So when you are at high AoA, your MAX may become pitch divergent (without MCAS). At the same time you are likely to be slow but with high thrust beneath the wings, pitching you upward into the stall.
One thing that keeps coming up considering how much importance the AoA signal now has in the MAX, is whether there is redundancy in the two vanes. I think the answer is not really, as many conditions (rolling, yawing!) will lead to expected AoA disagree between the two sides of the nose. A warning (i.e. stick shaker) based on a single high alpha vane is reasonable, but any kind of consensus signal from two vanes only with severe consequence for faulty data is quite problematic.
So the current two vanes are really only one sensor for the purposes of redundancy. I wonder whether to have such a high degree of reliance on a AoA signal you should incorporate three vanes on each side.
Last edited by LEOCh; 16th Nov 2018 at 04:53. Reason: spelling
The Leeham News article is quite informative of why the MCAS is required on the MAX, and fills in some blanks. I originally thought heavier engines further forward should if anything bring COG forward (unless balanced by other modifications), creating a more longitudinally stable MAX. However the idea that at high AoA the nacelles become aerodynamic surfaces sufficient to longitudinally destabilise the aircraft is interesting. It's a big aside, but a similar problem was noted on the WWII Supermarine Spitfire. As development to more powerfull engines dictated more and more propeller blade area, the non obvious effect of this as an aerodynamic surface way forward of the aerodynamic center caused degraded longitudinal stability margin.
So when you are at high AoA, your MAX may become pitch divergent (without MCAS). At the same time you are likely to be slow but with high thrust beneath the wings, pitching you upward into the stall.
One thing that keeps coming up considering how much importance the AoA signal now has in the MAX, is whether there is redundency in the two vanes. I think the answer is not really, as many conditions (rolling, yawing!) will lead to expected AoA disagree between the two sides of the nose. A warning (i.e. stick shaker) based on a single high alpha vane is reasonable, but any kind of consensus signal from two vanes only with severe consequence for faulty data is quite problematic.
So the current two vanes are really only one sensor for the purposes of redundancy. I wonder whether to have such a high degree of reliance on a AoA signal you should incorporate three vanes on each side.
So when you are at high AoA, your MAX may become pitch divergent (without MCAS). At the same time you are likely to be slow but with high thrust beneath the wings, pitching you upward into the stall.
One thing that keeps coming up considering how much importance the AoA signal now has in the MAX, is whether there is redundency in the two vanes. I think the answer is not really, as many conditions (rolling, yawing!) will lead to expected AoA disagree between the two sides of the nose. A warning (i.e. stick shaker) based on a single high alpha vane is reasonable, but any kind of consensus signal from two vanes only with severe consequence for faulty data is quite problematic.
So the current two vanes are really only one sensor for the purposes of redundancy. I wonder whether to have such a high degree of reliance on a AoA signal you should incorporate three vanes on each side.
Slow rolling the aircraft’s Test program with pax? Testing potential failures that demonstrably don’t meet statistical proofs with manufacturers prior “approval”?
What else is new and exciting? What other issues are too complex in failure to overwhelm the “average pilot” such that they need not to know and train for them?
Iceberg. Tip of....?
Last edited by Concours77; 16th Nov 2018 at 05:16.
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That’s changes to Pitch done and dusted. If the manual did not include something as tricky as sole source AoA data FAIL, what else is missing? Are there new issues as regards OEI? Roll problems? ETOPS? Will I fly to Hawaii on MAX? Yaw damping? What manner of control issues are different? MCAS is not so much about erroneous data recovery as it is about the whole picture.
What else is new and exciting? What other issues are too complex in failure to overwhelm the average pilot such that they need not to know and train for them?
Iceberg. Tip of....?
Thus it is in the interest of the manufacturer, the airlines and the regulator to keep the changes to a minimum.
So it may be the case that this was 'forgotten' or considered sufficiently similar not to warrant inclusion or simply part of the permitted differences.
What ought be readily apparent now, is that this system is substantially different and it would appear increasingly the case that it changes handling characteristics. That the pilot ought never see it in normal operation, it is of concern that when 'it does make itself known' that the pilots may have not even been aware what 'it did'
It is approaching the time where the FAA may be forced to require operators to train the pilots.
Clearly to date the intent of the manufacturer, airline customers and the regulator has to not impact the commercial return.
Are we approaching a point whereby pilots refuse to operate the aircraft until a differences course inclusive of this (be it simulator or ground modules) is completed.
Will it be the pilots and their organised labour representatives that do what the regulator ought conceivably do?
This ought concern all aviation professionals.
Willow #1287, and previous MFS, and td, #1255 1257.
A very good assessment of the certification issues.
The certification considers the aircraft and the situation together, the context; it does not judge or rate pilots.
This is a very difficult process, particularly nowadays with rapidly advancing and varied technologies.
Additionally there is range of design philosophies, even within one manufacturer; and challenges of grandfather rights spanning 40+ years. Although not required to meet all of the latest regulations, ask if this system would be approved on a new aircraft, a useful thought for guidance. (Special conditons sheet)
Is the situation beyond reasonable human capability; can any training ensure correct recall and actions in these situations.
Also in this period, levels of experience have changed, operations more varied, and surprising events more surprising due to higher levels of safety
Certification assessment is even more difficult when considering what appears to be an undeclared system, a failure, complex consequential implications, and without any published drill.
SLF, #1284. See # 1282. Why. Random, depending on a ‘by chance’ change of squat switch.
A very good assessment of the certification issues.
The certification considers the aircraft and the situation together, the context; it does not judge or rate pilots.
This is a very difficult process, particularly nowadays with rapidly advancing and varied technologies.
Additionally there is range of design philosophies, even within one manufacturer; and challenges of grandfather rights spanning 40+ years. Although not required to meet all of the latest regulations, ask if this system would be approved on a new aircraft, a useful thought for guidance. (Special conditons sheet)
Is the situation beyond reasonable human capability; can any training ensure correct recall and actions in these situations.
Also in this period, levels of experience have changed, operations more varied, and surprising events more surprising due to higher levels of safety
Certification assessment is even more difficult when considering what appears to be an undeclared system, a failure, complex consequential implications, and without any published drill.
SLF, #1284. See # 1282. Why. Random, depending on a ‘by chance’ change of squat switch.
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Does MCAS explain fr24 data
If MCAS is a key contributor to this crash, how does it fit with the fr24 data for the flight ?
For MCAS to be implicated, the pilots have disengaged AP or it has disengaged itself, right ?
The pilots would also have read the previous crew's report about STS running reverse, and hence stab trim would have been at the forefront of their mind in the event of flight control difficulties.
Two questions emerge :
1. Knowing the stabiliser was pitching the nose down, why didn't they activate the CUTOUT switch ?
2. Knowing the stabiliser was pitching the nose down, and having counteracted it successfully for six minutes, how did they eventually lose control of the aircraft ?
For MCAS to be implicated, the pilots have disengaged AP or it has disengaged itself, right ?
When did that happen? At the two minute mark ?
There is then an ascent to 5000 feet which is untidily maintained for six minutes before the final dive. If MCAS is aggressively STAB trimming the nose down during those six minutes, the pilots must have been aware of that fact and compensating / counteracting it. Otherwise, the plane would have crashed much earlier, correct ?The pilots would also have read the previous crew's report about STS running reverse, and hence stab trim would have been at the forefront of their mind in the event of flight control difficulties.
Two questions emerge :
1. Knowing the stabiliser was pitching the nose down, why didn't they activate the CUTOUT switch ?
2. Knowing the stabiliser was pitching the nose down, and having counteracted it successfully for six minutes, how did they eventually lose control of the aircraft ?
Mad (Flt) Scientist - likely you were addressing (1256) a couple posts I set out (1198, 1203).
SNIP
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.
SNIP
WillowRun 6-3
SNIP
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.
SNIP
WillowRun 6-3
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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.
link removed
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.
link removed
One wonders why Boeing insists on keeping the basic wing unchanged. It would save them lots of headache if it could be moved up a bit (=enable GTF, make it less "flippable" etc.) (I suppose there are certification bills that prevented this, so more lipstick was applied
)
