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mjoelnir
Posts: 9396
Joined: Sun Feb 03, 2013 11:06 pm

Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 9:44 am

Interested wrote:
mjoelnir wrote:
I think Boeing needs to have a hard look at the whole trim system. Perhaps the combination of old grandfathered design and modern additions went a step to far.

The problem for Boeing will be, that that will lead to more differences between the NG and MAX, resulting in more training needed. Something that seems to be a absolut no way at Boeing Management.


You have to assume that there's no choice but for Boeing to cover the cost and inconvenience of whatever training may be needed. It's obviously better than not being able to produce and deliver these planes any more. It may of course make them less desirable to order in the future and less profitable but there's going to have to be some pain here for Boeing both short and long term. They've messed up it will cost them for sure.

But I still can't help thinking it's like putting an elastoplast on a cancer

The only reason we need MCAS and now extra training is because the initial plane design is unsafe without both or either

I've no doubt if this plane wasn't already certified and so huge an investment and project but was just at the design stage knowing what we know now it wouldn't continue

There surely has to be some doubts about it continuing even as we are?

But if it doesn't then what a huge gap needs filling in the airline industry


That is why I hope that regulators do not let Boeing get away with a quick fix software fix, but rather insist on a redesign of the complete trim system on the MAX. If it is near impossible to manually, after using the cutout switches, trim the frame fast enough to survive, than cutting electrical trim seems to be recipe for disaster rather than a safe move.

I expect Boeing to fight the need for a redesign all the way.
 
flybucky
Posts: 376
Joined: Tue Apr 17, 2018 7:44 pm

Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 9:49 am

seahawk wrote:

BoeingVista wrote:
WSJ has been briefed on the preliminary ET302 report, not great for Boeing as pilots did initially follow the new Boeing MCAS drill but they still couldn't get the plane to clmb so they flipped the electric trim motor back on and the rest is history

Would proof the blowback effect.

Not exactly. The blowback effect that Bjorn wrote about was in regards to full elevator input (yoke pulled full back) not being able to counter stabilizer full nose down at higher speeds.

This WSJ article is about the pilots hitting the Stabilizer Trim Cutouts and attempting to use the manual trim wheel, which controls the stabilizers, not elevators. This may be more related to stabilizer trim load preventing manual trim wheel usage. https://www.satcom.guru/2019/04/stabili ... range.html
 
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PixelFlight
Posts: 1026
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Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 10:17 am

flybucky wrote:
morrisond wrote:
The uncommanded pitch-down was caused by two angle of attack sensors that were jammed in their positions, causing the fly by wire protection to believe the aircraft entered a stall while it climbed through FL310. The Alpha Protection activated, forcing the aircraft to pitch down, which could not be corrected even by full stick input.

"could not be corrected even by full stick input" is wrong. The incident occurred on Nov 5, 2014, and the first part of the AV Herald article was published on Nov 14, 2014. That may have been the best information known at the time. However, the second part of the article was published on Mar 24, 2015, which gives much more detail, including from the German BFU report:

A short time later the first officer disengaged the autopilot and gave a brief nose down input. The aircraft however continued to pitch down, inputs to counter the pitch down remained without effect... Within 15 seconds the first officer made increasing nose up input until reaching 75% of the maximum travel of the side stick... About 45 seconds after the nose down began the first officer alerted the captain who took control of the aircraft, that at this time had reached a rate of descent of 4000 feet per minute and a pitch of -3.5 degrees. The captain provided a maximum nose up input which caused the aircraft to pitch up again and the rate of descent decreased and the aircraft entered level flight. The captain was able to maintain altitude by providing a continuous nose up input deflecting the side stick about 50% of its travel. The autopilot could not be engaged again, and a manual nose up trim was not possible.

The FO gave partial stick back input, but it did not have any effect (because stick behavior changes in Alpha Protection). The FO may have been afraid to pull back further since he was afraid of stalling. However, the Captain was able to level out the flight with full stick back input.

morrisond wrote:
The crew disconnected the related Air Data Units and were able to recover the aircraft.

At first read, it makes it sound like the crew simply realized they needed to disconnect the ADU, and everything was fine after that. But if you read into the details, it was anything but simple to arrive at that conclusion. Here's a timeline of events (times are Z/UTC):

  • 07:03 Plane climbing through FL310, starts to pitch down and continues despite FO stick 75% back input.
  • Within 45s, reaches -4000 ft/min and -3.5º pitch.
  • Captain takes over and gives 100% stick back input, which was able to level out the flight at FL270.
  • Captain needs to give continuous 50% stick back input to maintain level flight. Trim does not work.
  • Pilots look in Quick Reference Handbook, don't find anything relevant.
  • Pilots reset Flight Augmentation Computers 1 and 2. No effect.
  • 07:24 Pilots send telex message to Maintenance.
  • 07:31 Maintenance suggests to turn off Air Data Reference 3.
  • 07:36 Pilots turn off ADR3, but no effect (actually, ADR3 was already disengaged by the system since AOA 3 was outvoted). Pilots turn ADR3 back on.
  • 07:52 Maintenance tells Pilots that they reviewed the data (sent by ACARS) and found that AOA 1 and 2 sensors were frozen. Suggested to turn off ADR2.
  • 07:59 Pilots turn off ADR2. Plane goes into Alternate Law, and it was no longer necessary to pull the stick back to maintain level flight. Autotrim and Autopilot function again.

Summary:
  • The pilots were troubleshooting on their own for 20 mins without finding the solution.
  • It took Maintenance 28 mins to find the correct solution.
  • It look 56 min for the pilots to take the correct action after the incident. Nearly an hour of fighting the computer, holding the stick back at 50%.

It's a good thing they were at FL310 when it happened. If they were less than 5000 ft AGL like JT610, ET302, or GXL888T, they probably would have been goners. Also shows that the pilots were not able to figure out the solution on their own. It took a non-flying pilot to figure it out, similar to JT043. It was also probably a good decision not to turn back while they were diagnosing the problem.

Please understand that this incident was only possible once the aircraft end it climb and start the flat cruse flight. To be lethal, this incident must have both:
1) froze 2 sensors at low altitude
_AND_
2) stop climbing at low altitude.
But sensors are hard to froze at low altitude. I don't say it's impossible to froze 2 sensors at low altitude, but this make this already rare event even more unlikely at low altitude.
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
planecane
Posts: 1579
Joined: Thu Feb 09, 2017 4:58 pm

Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 10:21 am

mjoelnir wrote:
Interested wrote:
mjoelnir wrote:
I think Boeing needs to have a hard look at the whole trim system. Perhaps the combination of old grandfathered design and modern additions went a step to far.

The problem for Boeing will be, that that will lead to more differences between the NG and MAX, resulting in more training needed. Something that seems to be a absolut no way at Boeing Management.


You have to assume that there's no choice but for Boeing to cover the cost and inconvenience of whatever training may be needed. It's obviously better than not being able to produce and deliver these planes any more. It may of course make them less desirable to order in the future and less profitable but there's going to have to be some pain here for Boeing both short and long term. They've messed up it will cost them for sure.

But I still can't help thinking it's like putting an elastoplast on a cancer

The only reason we need MCAS and now extra training is because the initial plane design is unsafe without both or either

I've no doubt if this plane wasn't already certified and so huge an investment and project but was just at the design stage knowing what we know now it wouldn't continue

There surely has to be some doubts about it continuing even as we are?

But if it doesn't then what a huge gap needs filling in the airline industry


That is why I hope that regulators do not let Boeing get away with a quick fix software fix, but rather insist on a redesign of the complete trim system on the MAX. If it is near impossible to manually, after using the cutout switches, trim the frame fast enough to survive, than cutting electrical trim seems to be recipe for disaster rather than a safe move.

I expect Boeing to fight the need for a redesign all the way.


As time goes on, we are starting to pass the point of logic in some of the responses. Isn't it completely impossible to manually trim a 757 or 767 after using the cutout switches since they don't have a trim wheel?

The point of the software fix is to limit MCAS total trim inputs and especially to only have it activate one time per event. If the "quick fix" software fix stops MCAS from causing a runaway trim then why does the entire trim system need to be redesigned? With the limitation of MCAS to one activation per stall event, the pilots can just trim to where they have elevator authority before using the cutout switches, if those switches are still necessary. In the new software, it would require BOTH AoA sensors to fail AND read similar to eachother for MCAS to activate in an unintended scenario.

The trim system that you want them to redesign has been flying around on the 737 since 1967 and the near impossibility to manually trim after using the cutout switches has never caused an issue. I think over 10,000 aircraft and 50+ years of flights is enough to say that the trim system is perfectly safe the way it is. MCAS is another system that controlls the trim system. THAT is the problem, not the trim system itself.

Let's all calm down a little. The implementation of MCAS was obviously very flawed with respect to the reacton to bad sensor data. When the sensors are working properly, MCAS is not an issue and all this hyperbole about it being required for stability and therefore shouldn't have been allowed is ridiculous. Any Airbus starting with the A320 requires software systems to fly at all. Same with the 777 and 787.

Had Boeing simply limited MCAS to one activation per event from the beginning, neither of these crashes would have happened regardless of the reliance on one AoA sensor. MCAS would have pitched the nose down 2.5 degrees. The pilots would have said "what the hell is the trim doing" and hit the thumb switch to re-trim back to where it was and gone on their merry way. Even if another "event" happened several minutes later, they would have done the same thing.

With the constant application of trim down by MCAS, it created a confusing/panicked situation and was able to lead to a full nose down pitch rather quickly. As long as the "quick fix" can be proven to regulators to be written properly to have MCAS turn off in the event of AoA disagree, limit it to one activation per event and limit the total authority to 2.5 degrees, it will be approved and the MAX will be just as safe as the NG (assuming nothing else was added without informing the pilots).
 
flybucky
Posts: 376
Joined: Tue Apr 17, 2018 7:44 pm

Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 10:38 am

PixelFlight wrote:
Please understand that this incident was only possible once the aircraft end it climb and start the flat cruse flight. To be lethal, this incident must have both:
1) froze 2 sensors at low altitude
_AND_
2) stop climbing at low altitude.
But sensors are hard to froze at low altitude. I don't say it's impossible to froze 2 sensors at low altitude, but this make this already rare event even more unlikely at low altitude.

GXL888T: At FL320, AOA sensors 1 and 2 froze and stayed frozen for the remainder of the flight. Due to the frozen sensors, Alpha protection did not kick in, and the plane stalled around 3000-4000 ft altitude (AOA still frozen) and crashed. It may be rare, but it definitely can happen.

http://avherald.com/h?article=410c9cec
http://www.aviation-accidents.net/xl-ai ... t-gxl888t/
 
XRAYretired
Posts: 870
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Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 10:47 am

planecane wrote:
mjoelnir wrote:
Interested wrote:

You have to assume that there's no choice but for Boeing to cover the cost and inconvenience of whatever training may be needed. It's obviously better than not being able to produce and deliver these planes any more. It may of course make them less desirable to order in the future and less profitable but there's going to have to be some pain here for Boeing both short and long term. They've messed up it will cost them for sure.

But I still can't help thinking it's like putting an elastoplast on a cancer

The only reason we need MCAS and now extra training is because the initial plane design is unsafe without both or either

I've no doubt if this plane wasn't already certified and so huge an investment and project but was just at the design stage knowing what we know now it wouldn't continue

There surely has to be some doubts about it continuing even as we are?

But if it doesn't then what a huge gap needs filling in the airline industry


That is why I hope that regulators do not let Boeing get away with a quick fix software fix, but rather insist on a redesign of the complete trim system on the MAX. If it is near impossible to manually, after using the cutout switches, trim the frame fast enough to survive, than cutting electrical trim seems to be recipe for disaster rather than a safe move.

I expect Boeing to fight the need for a redesign all the way.


As time goes on, we are starting to pass the point of logic in some of the responses. Isn't it completely impossible to manually trim a 757 or 767 after using the cutout switches since they don't have a trim wheel?

The point of the software fix is to limit MCAS total trim inputs and especially to only have it activate one time per event. If the "quick fix" software fix stops MCAS from causing a runaway trim then why does the entire trim system need to be redesigned? With the limitation of MCAS to one activation per stall event, the pilots can just trim to where they have elevator authority before using the cutout switches, if those switches are still necessary. In the new software, it would require BOTH AoA sensors to fail AND read similar to eachother for MCAS to activate in an unintended scenario.

The trim system that you want them to redesign has been flying around on the 737 since 1967 and the near impossibility to manually trim after using the cutout switches has never caused an issue. I think over 10,000 aircraft and 50+ years of flights is enough to say that the trim system is perfectly safe the way it is. MCAS is another system that controlls the trim system. THAT is the problem, not the trim system itself.

Let's all calm down a little. The implementation of MCAS was obviously very flawed with respect to the reacton to bad sensor data. When the sensors are working properly, MCAS is not an issue and all this hyperbole about it being required for stability and therefore shouldn't have been allowed is ridiculous. Any Airbus starting with the A320 requires software systems to fly at all. Same with the 777 and 787.

Had Boeing simply limited MCAS to one activation per event from the beginning, neither of these crashes would have happened regardless of the reliance on one AoA sensor. MCAS would have pitched the nose down 2.5 degrees. The pilots would have said "what the hell is the trim doing" and hit the thumb switch to re-trim back to where it was and gone on their merry way. Even if another "event" happened several minutes later, they would have done the same thing.

With the constant application of trim down by MCAS, it created a confusing/panicked situation and was able to lead to a full nose down pitch rather quickly. As long as the "quick fix" can be proven to regulators to be written properly to have MCAS turn off in the event of AoA disagree, limit it to one activation per event and limit the total authority to 2.5 degrees, it will be approved and the MAX will be just as safe as the NG (assuming nothing else was added without informing the pilots).


Just a point - in support.

In this case:- "In the new software, it would require BOTH AoA sensors to fail AND read similar to each other for MCAS to activate in an unintended scenario." They would have to fail high and activation would be limited to one iteration.

I have not seen a case that would require use of the cut out with the described fix installed.

Ray
 
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BoeingVista
Posts: 2060
Joined: Mon Jan 12, 2009 9:54 am

Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 10:48 am

flybucky wrote:
seahawk wrote:

BoeingVista wrote:
WSJ has been briefed on the preliminary ET302 report, not great for Boeing as pilots did initially follow the new Boeing MCAS drill but they still couldn't get the plane to clmb so they flipped the electric trim motor back on and the rest is history

Would proof the blowback effect.

Not exactly. The blowback effect that Bjorn wrote about was in regards to full elevator input (yoke pulled full back) not being able to counter stabilizer full nose down at higher speeds.

This WSJ article is about the pilots hitting the Stabilizer Trim Cutouts and attempting to use the manual trim wheel, which controls the stabilizers, not elevators. This may be more related to stabilizer trim load preventing manual trim wheel usage. https://www.satcom.guru/2019/04/stabili ... range.html


You cant seriously be suggesting that the pilots didn't try to pull back fully on the stick to try and get the aircraft to climb knowing that a previous 737MAX flight had gone in nose down and killed everyone aboard?!?
BV
 
maint123
Posts: 396
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Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 10:48 am

Let the max be flown exclusively in US airspace by American Airlines using American pilots, for a year or so, to prove the reliability of MAX. This way the doubts about non American pilots and maintenance of the planes will be taken care of. As things stand now with new revelations about the plane coming out everyday, most non Americans would not feel safe in this plane.
 
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BoeingVista
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Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 10:52 am

planecane wrote:
The point of the software fix is to limit MCAS total trim inputs and especially to only have it activate one time per event. If the "quick fix" software fix stops MCAS from causing a runaway trim then why does the entire trim system need to be redesigned?


Because we don't know what demons MCAS was implemented to tame and whether taming MCAS lets the demon back out of the bag.
BV
 
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seahawk
Posts: 9682
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Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 10:53 am

flybucky wrote:
seahawk wrote:

BoeingVista wrote:
WSJ has been briefed on the preliminary ET302 report, not great for Boeing as pilots did initially follow the new Boeing MCAS drill but they still couldn't get the plane to clmb so they flipped the electric trim motor back on and the rest is history

Would proof the blowback effect.

Not exactly. The blowback effect that Bjorn wrote about was in regards to full elevator input (yoke pulled full back) not being able to counter stabilizer full nose down at higher speeds.

This WSJ article is about the pilots hitting the Stabilizer Trim Cutouts and attempting to use the manual trim wheel, which controls the stabilizers, not elevators. This may be more related to stabilizer trim load preventing manual trim wheel usage. https://www.satcom.guru/2019/04/stabili ... range.html


It matches known characteristics of the 737. Even on the NG it is known that pitch control with the elevator is sometimes not achieving the desired quick response and using the stab to support is recommended. We also know that manual trimming of the stab at high speeds and and elevator input is not possible. Standard procedure would be to reduce thrust and then trim the stab with the elevator in neutral position, but if trimmed nose down by the MCAS and at low altitude there is probably not enough time for that.
 
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BoeingVista
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Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 11:15 am

And it gets worse. The WSJ briefing may have been yet more Boeing disaster management. Investegators are investigating if MCAS behaves more like HAL.

Boeing anti-stall software on a doomed Ethiopian Airlines jet re-engaged as many as four times after the crew initially turned it off due to suspect data from an airflow sensor, two people familiar with the matter said.

It was not immediately clear whether the crew had chosen to re-deploy the system, which pushes the nose of the Boeing 737 Max downwards, but one person with knowledge of the matter said investigators were studying the possibility that the software had kicked in again without human intervention.

---------------------- Snip -----------------------------------

Investigators are studying whether there are any conditions under which MCAS could re-activate itself automatically, without the pilots reversing the cutout manoeuvre. Boeing is in the midst of upgrading the software while adding extra training.


https://www.theguardian.com/business/20 ... repeatedly
BV
 
mjoelnir
Posts: 9396
Joined: Sun Feb 03, 2013 11:06 pm

Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 11:18 am

planecane wrote:
mjoelnir wrote:
Interested wrote:

You have to assume that there's no choice but for Boeing to cover the cost and inconvenience of whatever training may be needed. It's obviously better than not being able to produce and deliver these planes any more. It may of course make them less desirable to order in the future and less profitable but there's going to have to be some pain here for Boeing both short and long term. They've messed up it will cost them for sure.

But I still can't help thinking it's like putting an elastoplast on a cancer

The only reason we need MCAS and now extra training is because the initial plane design is unsafe without both or either

I've no doubt if this plane wasn't already certified and so huge an investment and project but was just at the design stage knowing what we know now it wouldn't continue

There surely has to be some doubts about it continuing even as we are?

But if it doesn't then what a huge gap needs filling in the airline industry


That is why I hope that regulators do not let Boeing get away with a quick fix software fix, but rather insist on a redesign of the complete trim system on the MAX. If it is near impossible to manually, after using the cutout switches, trim the frame fast enough to survive, than cutting electrical trim seems to be recipe for disaster rather than a safe move.

I expect Boeing to fight the need for a redesign all the way.


As time goes on, we are starting to pass the point of logic in some of the responses. Isn't it completely impossible to manually trim a 757 or 767 after using the cutout switches since they don't have a trim wheel?

The point of the software fix is to limit MCAS total trim inputs and especially to only have it activate one time per event. If the "quick fix" software fix stops MCAS from causing a runaway trim then why does the entire trim system need to be redesigned? With the limitation of MCAS to one activation per stall event, the pilots can just trim to where they have elevator authority before using the cutout switches, if those switches are still necessary. In the new software, it would require BOTH AoA sensors to fail AND read similar to eachother for MCAS to activate in an unintended scenario.

The trim system that you want them to redesign has been flying around on the 737 since 1967 and the near impossibility to manually trim after using the cutout switches has never caused an issue. I think over 10,000 aircraft and 50+ years of flights is enough to say that the trim system is perfectly safe the way it is. MCAS is another system that controlls the trim system. THAT is the problem, not the trim system itself.

Let's all calm down a little. The implementation of MCAS was obviously very flawed with respect to the reacton to bad sensor data. When the sensors are working properly, MCAS is not an issue and all this hyperbole about it being required for stability and therefore shouldn't have been allowed is ridiculous. Any Airbus starting with the A320 requires software systems to fly at all. Same with the 777 and 787.

Had Boeing simply limited MCAS to one activation per event from the beginning, neither of these crashes would have happened regardless of the reliance on one AoA sensor. MCAS would have pitched the nose down 2.5 degrees. The pilots would have said "what the hell is the trim doing" and hit the thumb switch to re-trim back to where it was and gone on their merry way. Even if another "event" happened several minutes later, they would have done the same thing.

With the constant application of trim down by MCAS, it created a confusing/panicked situation and was able to lead to a full nose down pitch rather quickly. As long as the "quick fix" can be proven to regulators to be written properly to have MCAS turn off in the event of AoA disagree, limit it to one activation per event and limit the total authority to 2.5 degrees, it will be approved and the MAX will be just as safe as the NG (assuming nothing else was added without informing the pilots).


Because the entire trim system seems to be a joke. The only reason it is like it is, seems to be grandfathering. If the resolution to all trim problems is throwing the cut out switches and than being hardly able to trim manually with the wheels and only with tricks and under certain conditions, why keep it that way?
Just because pilots 60 years ago had to use a kludge of a trim system, why not making the live of pilots today easier, with a well thought out easy to use system?

Why rely on the manual trim wheels? Why not have redundancy in the electrical trim? And especially why is there no switch automatic trim off for the guys that love everything manually?
 
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SheikhDjibouti
Posts: 2289
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Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 11:54 am

achmafooma wrote:
I keep imagining that I'm driving down the freeway and I have my cruise control set at 65, and the car starts accelerating in apparently random 10s spurts. I don't keep tweaking it back down with the speedometer controls. I don't start paging through the manual. I certainly don't start questioning whether the manual's instructions about dealing with "continuous" cruise control problems applies to "intermittent" cruise control problems. The first thing I do is turn the darn cruise control off!
That analogy was a good start, but rather over-simplified the situation. (Just like the Cessna pilot up thread who insists it is all so simple...)

Your cruise control might be at 65, but your speedometer is totally blacked out. If you cannot work out what speed you are doing, what is the cruise control using for data?

Whilst you are puzzling over that, the steering wheel is shaking madly, as if you have a tire with a puncture or a loose wheel, and tbh you are more concerned with the possibility of a blow out, so whether or not you are maintaining 65 mph is not even your biggest worry.

And somebody keeps randomly turning on the radio, LOUD, featuring a traffic report warning you of an accident ahead. This also disrupts your thought process.

Plus nobody driving a car with a fault ever stated paging through the manual to find out what was wrong; they would pull over first and take their time. Not an option in a 737. :shakehead:

..
I was going to add more, but then I saw flybucky's excellent submission, and he really nailed it. :bigthumbsup:

flybucky wrote:
It's not that simple as that. Let me continue your analogy put try to paint a more accurate picture:

First of all, you never set the cruise. You are driving manually at 65 mph, and all of the sudden, the car starts to accelerate intermittently. Since you never set the cruise, you don't think of it first thing. The first thing you think of is maybe the gas pedal is malfunctioning. You immediately take your foot off the gas, but that doesn't seem to do anything. Next you try braking, and that does help somewhat, but when you let go of the brake, it starts accelerating again. Also, you know that when you tap the brake, it always disconnects the cruise, so it can't be the cruise.

Then, your steering wheel starts shaking like a jackhammer and an audible alarm repeatedly blares, "Do not drive below 55 mph"...….

Brilliant.
Nothing to see here; move along please.
 
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PixelFlight
Posts: 1026
Joined: Thu Nov 08, 2018 11:09 pm

Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 12:12 pm

flybucky wrote:
PixelFlight wrote:
Please understand that this incident was only possible once the aircraft end it climb and start the flat cruse flight. To be lethal, this incident must have both:
1) froze 2 sensors at low altitude
_AND_
2) stop climbing at low altitude.
But sensors are hard to froze at low altitude. I don't say it's impossible to froze 2 sensors at low altitude, but this make this already rare event even more unlikely at low altitude.

GXL888T: At FL320, AOA sensors 1 and 2 froze and stayed frozen for the remainder of the flight. Due to the frozen sensors, Alpha protection did not kick in, and the plane stalled around 3000-4000 ft altitude (AOA still frozen) and crashed. It may be rare, but it definitely can happen.

http://avherald.com/h?article=410c9cec
http://www.aviation-accidents.net/xl-ai ... t-gxl888t/

Yes, but on this GXL888T all the sensors was damaged on the ground prior to the flight _AND_ the test pilot was trying to flight far outside of the established safety procedure.
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
WIederling
Posts: 9348
Joined: Sun Sep 13, 2015 2:15 pm

Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 12:30 pm

PixelFlight wrote:
flybucky wrote:
http://avherald.com/h?article=410c9cec
http://www.aviation-accidents.net/xl-ai ... t-gxl888t/

Yes, but on this GXL888T all the sensors was damaged on the ground prior to the flight _AND_ the test pilot was trying to flight far outside of the established safety procedure.


doing something he wasn't really allowed to do ( not a test pilot )
and at an altitude that left no leeway to act on problems.
More like the Habsheim accident that at its core was caused by bravado.
Murphy is an optimist
 
planecane
Posts: 1579
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Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 12:44 pm

mjoelnir wrote:
planecane wrote:
mjoelnir wrote:

That is why I hope that regulators do not let Boeing get away with a quick fix software fix, but rather insist on a redesign of the complete trim system on the MAX. If it is near impossible to manually, after using the cutout switches, trim the frame fast enough to survive, than cutting electrical trim seems to be recipe for disaster rather than a safe move.

I expect Boeing to fight the need for a redesign all the way.


As time goes on, we are starting to pass the point of logic in some of the responses. Isn't it completely impossible to manually trim a 757 or 767 after using the cutout switches since they don't have a trim wheel?

The point of the software fix is to limit MCAS total trim inputs and especially to only have it activate one time per event. If the "quick fix" software fix stops MCAS from causing a runaway trim then why does the entire trim system need to be redesigned? With the limitation of MCAS to one activation per stall event, the pilots can just trim to where they have elevator authority before using the cutout switches, if those switches are still necessary. In the new software, it would require BOTH AoA sensors to fail AND read similar to eachother for MCAS to activate in an unintended scenario.

The trim system that you want them to redesign has been flying around on the 737 since 1967 and the near impossibility to manually trim after using the cutout switches has never caused an issue. I think over 10,000 aircraft and 50+ years of flights is enough to say that the trim system is perfectly safe the way it is. MCAS is another system that controlls the trim system. THAT is the problem, not the trim system itself.

Let's all calm down a little. The implementation of MCAS was obviously very flawed with respect to the reacton to bad sensor data. When the sensors are working properly, MCAS is not an issue and all this hyperbole about it being required for stability and therefore shouldn't have been allowed is ridiculous. Any Airbus starting with the A320 requires software systems to fly at all. Same with the 777 and 787.

Had Boeing simply limited MCAS to one activation per event from the beginning, neither of these crashes would have happened regardless of the reliance on one AoA sensor. MCAS would have pitched the nose down 2.5 degrees. The pilots would have said "what the hell is the trim doing" and hit the thumb switch to re-trim back to where it was and gone on their merry way. Even if another "event" happened several minutes later, they would have done the same thing.

With the constant application of trim down by MCAS, it created a confusing/panicked situation and was able to lead to a full nose down pitch rather quickly. As long as the "quick fix" can be proven to regulators to be written properly to have MCAS turn off in the event of AoA disagree, limit it to one activation per event and limit the total authority to 2.5 degrees, it will be approved and the MAX will be just as safe as the NG (assuming nothing else was added without informing the pilots).


Because the entire trim system seems to be a joke. The only reason it is like it is, seems to be grandfathering. If the resolution to all trim problems is throwing the cut out switches and than being hardly able to trim manually with the wheels and only with tricks and under certain conditions, why keep it that way?
Just because pilots 60 years ago had to use a kludge of a trim system, why not making the live of pilots today easier, with a well thought out easy to use system?

Why rely on the manual trim wheels? Why not have redundancy in the electrical trim? And especially why is there no switch automatic trim off for the guys that love everything manually?


How is it a joke if it has worked fine for 50+ years on 10,000+ aircraft? Doesn't the A320 have some kind of very limited manual backup if the entire FBW system fails? I've read (supposedly posted by pilots who fly them) that there are cutout switches on the 757 and 767 and there are scenarios where they are used. Those aircraft have no trim once you hit the cutout so why is that better?
 
marcelh
Posts: 1047
Joined: Wed Jun 19, 2013 12:43 pm

Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 1:03 pm

PixelFlight wrote:
flybucky wrote:
PixelFlight wrote:
Please understand that this incident was only possible once the aircraft end it climb and start the flat cruse flight. To be lethal, this incident must have both:
1) froze 2 sensors at low altitude
_AND_
2) stop climbing at low altitude.
But sensors are hard to froze at low altitude. I don't say it's impossible to froze 2 sensors at low altitude, but this make this already rare event even more unlikely at low altitude.

GXL888T: At FL320, AOA sensors 1 and 2 froze and stayed frozen for the remainder of the flight. Due to the frozen sensors, Alpha protection did not kick in, and the plane stalled around 3000-4000 ft altitude (AOA still frozen) and crashed. It may be rare, but it definitely can happen.

http://avherald.com/h?article=410c9cec
http://www.aviation-accidents.net/xl-ai ... t-gxl888t/

Yes, but on this GXL888T all the sensors was damaged on the ground prior to the flight _AND_ the test pilot was trying to flight far outside of the established safety procedure.

What are you trying to tell us?
 
mjoelnir
Posts: 9396
Joined: Sun Feb 03, 2013 11:06 pm

Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 1:15 pm

planecane wrote:
mjoelnir wrote:
planecane wrote:

As time goes on, we are starting to pass the point of logic in some of the responses. Isn't it completely impossible to manually trim a 757 or 767 after using the cutout switches since they don't have a trim wheel?

The point of the software fix is to limit MCAS total trim inputs and especially to only have it activate one time per event. If the "quick fix" software fix stops MCAS from causing a runaway trim then why does the entire trim system need to be redesigned? With the limitation of MCAS to one activation per stall event, the pilots can just trim to where they have elevator authority before using the cutout switches, if those switches are still necessary. In the new software, it would require BOTH AoA sensors to fail AND read similar to eachother for MCAS to activate in an unintended scenario.

The trim system that you want them to redesign has been flying around on the 737 since 1967 and the near impossibility to manually trim after using the cutout switches has never caused an issue. I think over 10,000 aircraft and 50+ years of flights is enough to say that the trim system is perfectly safe the way it is. MCAS is another system that controlls the trim system. THAT is the problem, not the trim system itself.

Let's all calm down a little. The implementation of MCAS was obviously very flawed with respect to the reacton to bad sensor data. When the sensors are working properly, MCAS is not an issue and all this hyperbole about it being required for stability and therefore shouldn't have been allowed is ridiculous. Any Airbus starting with the A320 requires software systems to fly at all. Same with the 777 and 787.

Had Boeing simply limited MCAS to one activation per event from the beginning, neither of these crashes would have happened regardless of the reliance on one AoA sensor. MCAS would have pitched the nose down 2.5 degrees. The pilots would have said "what the hell is the trim doing" and hit the thumb switch to re-trim back to where it was and gone on their merry way. Even if another "event" happened several minutes later, they would have done the same thing.

With the constant application of trim down by MCAS, it created a confusing/panicked situation and was able to lead to a full nose down pitch rather quickly. As long as the "quick fix" can be proven to regulators to be written properly to have MCAS turn off in the event of AoA disagree, limit it to one activation per event and limit the total authority to 2.5 degrees, it will be approved and the MAX will be just as safe as the NG (assuming nothing else was added without informing the pilots).


Because the entire trim system seems to be a joke. The only reason it is like it is, seems to be grandfathering. If the resolution to all trim problems is throwing the cut out switches and than being hardly able to trim manually with the wheels and only with tricks and under certain conditions, why keep it that way?
Just because pilots 60 years ago had to use a kludge of a trim system, why not making the live of pilots today easier, with a well thought out easy to use system?

Why rely on the manual trim wheels? Why not have redundancy in the electrical trim? And especially why is there no switch automatic trim off for the guys that love everything manually?


How is it a joke if it has worked fine for 50+ years on 10,000+ aircraft? Doesn't the A320 have some kind of very limited manual backup if the entire FBW system fails? I've read (supposedly posted by pilots who fly them) that there are cutout switches on the 757 and 767 and there are scenarios where they are used. Those aircraft have no trim once you hit the cutout so why is that better?


Because for 50 years the automatic was not actively trying to kill the pilots and passengers.

The MAX is not the NG, so pointing to prior safety statistics is about a senseless as can be.

And what has the A320 to do with it, they are not dropping every few month out of the sky like the MAX

I call something a joke when is a joke. Just because something has been the same for 60 years, is no reason to keep it the same. A trim run away, as one sees on the nice youtube videos is not done on the simulator with a broken AoA sensor, MCAS engaging, stick shaker turned on, stall warning sounding and unreliable airspeed indication and very near to the ground. I like to see those guys turning the hand wheel with full elevator engaged and 2.5% trim the wrong way. Perhaps pilots have been lucky for years, because no automation was trying to kill them.

Turning the trim automatic off, STS and MCAS, only together with manual electrical trim, why?
 
User avatar
Polot
Posts: 10741
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Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 1:23 pm

mjoelnir wrote:
planecane wrote:
mjoelnir wrote:

Because the entire trim system seems to be a joke. The only reason it is like it is, seems to be grandfathering. If the resolution to all trim problems is throwing the cut out switches and than being hardly able to trim manually with the wheels and only with tricks and under certain conditions, why keep it that way?
Just because pilots 60 years ago had to use a kludge of a trim system, why not making the live of pilots today easier, with a well thought out easy to use system?

Why rely on the manual trim wheels? Why not have redundancy in the electrical trim? And especially why is there no switch automatic trim off for the guys that love everything manually?


How is it a joke if it has worked fine for 50+ years on 10,000+ aircraft? Doesn't the A320 have some kind of very limited manual backup if the entire FBW system fails? I've read (supposedly posted by pilots who fly them) that there are cutout switches on the 757 and 767 and there are scenarios where they are used. Those aircraft have no trim once you hit the cutout so why is that better?


Because for 50 years the automatic was not actively trying to kill the pilots and passengers.

The MAX is not the NG, so pointing to prior safety statistics is about a senseless as can be.

And what has the A320 to do with it, they are not dropping every few month out of the sky like the MAX

I call something a joke when is a joke. Just because something has been the same for 60 years, is no reason to keep it the same. A trim run away, as one sees on the nice youtube videos is not done on the simulator with a broken AoA sensor, MCAS engaging, stick shaker turned on, stall warning sounding and unreliable airspeed indication and very near to the ground. I like to see those guys turning the hand wheel with full elevator engaged and 2.5% trim the wrong way. Perhaps pilots have been lucky for years, because no automation was trying to kill them.

Turning the trim automatic off, STS and MCAS, only together with manual electrical trim, why?

That suggests a problem with the automation system/software/logic, not the entire trim system.

You are basically suggesting that it is just “luck” that pilots haven’t crashed 737s left and right because of the trim system prior to the automation, which is a ridiculous claim when the 737’s total flight hours are considered.
Last edited by Polot on Wed Apr 03, 2019 1:34 pm, edited 2 times in total.
 
planecane
Posts: 1579
Joined: Thu Feb 09, 2017 4:58 pm

Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 1:28 pm

mjoelnir wrote:
planecane wrote:
mjoelnir wrote:

Because the entire trim system seems to be a joke. The only reason it is like it is, seems to be grandfathering. If the resolution to all trim problems is throwing the cut out switches and than being hardly able to trim manually with the wheels and only with tricks and under certain conditions, why keep it that way?
Just because pilots 60 years ago had to use a kludge of a trim system, why not making the live of pilots today easier, with a well thought out easy to use system?

Why rely on the manual trim wheels? Why not have redundancy in the electrical trim? And especially why is there no switch automatic trim off for the guys that love everything manually?


How is it a joke if it has worked fine for 50+ years on 10,000+ aircraft? Doesn't the A320 have some kind of very limited manual backup if the entire FBW system fails? I've read (supposedly posted by pilots who fly them) that there are cutout switches on the 757 and 767 and there are scenarios where they are used. Those aircraft have no trim once you hit the cutout so why is that better?


Because for 50 years the automatic was not actively trying to kill the pilots and passengers.

The MAX is not the NG, so pointing to prior safety statistics is about a senseless as can be.

And what has the A320 to do with it, they are not dropping every few month out of the sky like the MAX

I call something a joke when is a joke. Just because something has been the same for 60 years, is no reason to keep it the same. A trim run away, as one sees on the nice youtube videos is not done on the simulator with a broken AoA sensor, MCAS engaging, stick shaker turned on, stall warning sounding and unreliable airspeed indication and very near to the ground. I like to see those guys turning the hand wheel with full elevator engaged and 2.5% trim the wrong way. Perhaps pilots have been lucky for years, because no automation was trying to kill them.

Turning the trim automatic off, STS and MCAS, only together with manual electrical trim, why?


None of that indicates that the entire trim system needs to be redesigned. The problem is MCAS activating due to a single bad AoA sensor. The scenario that you are suggesting won't happen after the software changes (assuming the software is written properly).

Here is a statistical tidbit for those worried about the "quick fix" software. If the failure rate of a single AoA sensor causing MCAS to activate is 1 in 50,000 flights (reasonable estimate based on the MAX crash rate), the failure of both sensors to cause MCAS to activate would be 1 in 2.5 BILLION flights. Since one of the main changes is disabling MCAS on AoA disagree, I think that that failure rate falls under acceptable risk, especially since other changes limit the authority and number of activations so that even if you are on that 1 in 2.5 billion flight the pilots should be able to recover.
 
Nils75cz
Posts: 20
Joined: Mon Mar 25, 2019 10:18 pm

Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 1:41 pm

Imagine driving, suddenly the car starts steering itself in a dangerous direction. You now have to turn a switch off and then use the manual window lever to correct the steering. That's MCAS. Not an appropriate system to me.
 
texl1649
Posts: 1414
Joined: Thu Aug 02, 2007 5:38 am

Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 1:46 pm

The sensor on the JT610 flight was known not to be working/was installed incorrectly, but it was dispatched anyway.

The pilots on the ET flight disengaged MCAS but then re-engaged it. Bjorn/Ferpe @ Leeham has a good piece out this am on what is known/isn't based on some more recent news. It's not very good news, for a short term fix, which may be why Boeing is punting "a few more weeks" for now on timelines to submit something.
 
mjoelnir
Posts: 9396
Joined: Sun Feb 03, 2013 11:06 pm

Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 1:49 pm

planecane wrote:
mjoelnir wrote:
planecane wrote:

How is it a joke if it has worked fine for 50+ years on 10,000+ aircraft? Doesn't the A320 have some kind of very limited manual backup if the entire FBW system fails? I've read (supposedly posted by pilots who fly them) that there are cutout switches on the 757 and 767 and there are scenarios where they are used. Those aircraft have no trim once you hit the cutout so why is that better?


Because for 50 years the automatic was not actively trying to kill the pilots and passengers.

The MAX is not the NG, so pointing to prior safety statistics is about a senseless as can be.

And what has the A320 to do with it, they are not dropping every few month out of the sky like the MAX

I call something a joke when is a joke. Just because something has been the same for 60 years, is no reason to keep it the same. A trim run away, as one sees on the nice youtube videos is not done on the simulator with a broken AoA sensor, MCAS engaging, stick shaker turned on, stall warning sounding and unreliable airspeed indication and very near to the ground. I like to see those guys turning the hand wheel with full elevator engaged and 2.5% trim the wrong way. Perhaps pilots have been lucky for years, because no automation was trying to kill them.

Turning the trim automatic off, STS and MCAS, only together with manual electrical trim, why?


None of that indicates that the entire trim system needs to be redesigned. The problem is MCAS activating due to a single bad AoA sensor. The scenario that you are suggesting won't happen after the software changes (assuming the software is written properly).

Here is a statistical tidbit for those worried about the "quick fix" software. If the failure rate of a single AoA sensor causing MCAS to activate is 1 in 50,000 flights (reasonable estimate based on the MAX crash rate), the failure of both sensors to cause MCAS to activate would be 1 in 2.5 BILLION flights. Since one of the main changes is disabling MCAS on AoA disagree, I think that that failure rate falls under acceptable risk, especially since other changes limit the authority and number of activations so that even if you are on that 1 in 2.5 billion flight the pilots should be able to recover.


So you never see a reason to redesign something to lighten the load of the pilot rather than adding to it?

Why does a manual override, the trim wheel, not work under any conditions? Under all the stress the pilot is put under by the malfunctioning automatic, he has to think about in what conditions he can use the trim wheel lightening the load on the trim?

Why do you have to switch off the manual electrical trim to switch off automatic trim?

Perhaps you need a reason to keep a kludge of a system, other than it has been always like this.

Regarding the sensor. None of the sensors in this two accidents came just near to a lifetime of 1 in 50,000 hours. The sensors were all a few month old, so if this frames would have been flying for 24 hours in 4 month, that gives us inside of 3,000 hours usage, most likely around 1,000 in reality.
If you tell me that is statistical unsound, you can not point either to 1 in 50,000 hours, that catches only the sensors that failed in a high position, we can have hundreds of sensors failing in a low position without triggering MCAS.
 
mjoelnir
Posts: 9396
Joined: Sun Feb 03, 2013 11:06 pm

Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 1:52 pm

texl1649 wrote:
The sensor on the JT610 flight was known not to be working/was installed incorrectly, but it was dispatched anyway.

The pilots on the ET flight disengaged MCAS but then re-engaged it. Bjorn/Ferpe @ Leeham has a good piece out this am on what is known/isn't based on some more recent news. It's not very good news, for a short term fix, which may be why Boeing is punting "a few more weeks" for now on timelines to submit something.


I think you go slightly far with this declaration. There is also the information out there that the sensor was actually changed between the flights. The mechanic on the flight having done it.
 
User avatar
Polot
Posts: 10741
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Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 2:10 pm

mjoelnir wrote:
planecane wrote:
mjoelnir wrote:

Because for 50 years the automatic was not actively trying to kill the pilots and passengers.

The MAX is not the NG, so pointing to prior safety statistics is about a senseless as can be.

And what has the A320 to do with it, they are not dropping every few month out of the sky like the MAX

I call something a joke when is a joke. Just because something has been the same for 60 years, is no reason to keep it the same. A trim run away, as one sees on the nice youtube videos is not done on the simulator with a broken AoA sensor, MCAS engaging, stick shaker turned on, stall warning sounding and unreliable airspeed indication and very near to the ground. I like to see those guys turning the hand wheel with full elevator engaged and 2.5% trim the wrong way. Perhaps pilots have been lucky for years, because no automation was trying to kill them.

Turning the trim automatic off, STS and MCAS, only together with manual electrical trim, why?


None of that indicates that the entire trim system needs to be redesigned. The problem is MCAS activating due to a single bad AoA sensor. The scenario that you are suggesting won't happen after the software changes (assuming the software is written properly).

Here is a statistical tidbit for those worried about the "quick fix" software. If the failure rate of a single AoA sensor causing MCAS to activate is 1 in 50,000 flights (reasonable estimate based on the MAX crash rate), the failure of both sensors to cause MCAS to activate would be 1 in 2.5 BILLION flights. Since one of the main changes is disabling MCAS on AoA disagree, I think that that failure rate falls under acceptable risk, especially since other changes limit the authority and number of activations so that even if you are on that 1 in 2.5 billion flight the pilots should be able to recover.


So you never see a reason to redesign something to lighten the load of the pilot rather than adding to it?

Why does a manual override, the trim wheel, not work under any conditions? Under all the stress the pilot is put under by the malfunctioning automatic, he has to think about in what conditions he can use the trim wheel lightening the load on the trim?

Why do you have to switch off the manual electrical trim to switch off automatic trim?

Perhaps you need a reason to keep a kludge of a system, other than it has been always like this.

Regarding the sensor. None of the sensors in this two accidents came just near to a lifetime of 1 in 50,000 hours. The sensors were all a few month old, so if this frames would have been flying for 24 hours in 4 month, that gives us inside of 3,000 hours usage, most likely around 1,000 in reality.
If you tell me that is statistical unsound, you can not point either to 1 in 50,000 hours, that catches only the sensors that failed in a high position, we can have hundreds of sensors failing in a low position without triggering MCAS.

Again, everything you are suggesting points to issues with the automation system, not the entire trim system. You even lay direct blame on the automation system (“under all the stress the pilot is put under by the malfunctioning automatic”) while trying to blame the trim system.

The answer isn’t redesign the trim system, it’s redesign the automation so if it fails the pilot can still manually trim the plane to where they want it. MCAS was never fully releasing control and letting the pilots do what they want and expected from the plane.
 
mjoelnir
Posts: 9396
Joined: Sun Feb 03, 2013 11:06 pm

Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 2:45 pm

Polot wrote:
mjoelnir wrote:
planecane wrote:

None of that indicates that the entire trim system needs to be redesigned. The problem is MCAS activating due to a single bad AoA sensor. The scenario that you are suggesting won't happen after the software changes (assuming the software is written properly).

Here is a statistical tidbit for those worried about the "quick fix" software. If the failure rate of a single AoA sensor causing MCAS to activate is 1 in 50,000 flights (reasonable estimate based on the MAX crash rate), the failure of both sensors to cause MCAS to activate would be 1 in 2.5 BILLION flights. Since one of the main changes is disabling MCAS on AoA disagree, I think that that failure rate falls under acceptable risk, especially since other changes limit the authority and number of activations so that even if you are on that 1 in 2.5 billion flight the pilots should be able to recover.


So you never see a reason to redesign something to lighten the load of the pilot rather than adding to it?

Why does a manual override, the trim wheel, not work under any conditions? Under all the stress the pilot is put under by the malfunctioning automatic, he has to think about in what conditions he can use the trim wheel lightening the load on the trim?

Why do you have to switch off the manual electrical trim to switch off automatic trim?

Perhaps you need a reason to keep a kludge of a system, other than it has been always like this.

Regarding the sensor. None of the sensors in this two accidents came just near to a lifetime of 1 in 50,000 hours. The sensors were all a few month old, so if this frames would have been flying for 24 hours in 4 month, that gives us inside of 3,000 hours usage, most likely around 1,000 in reality.
If you tell me that is statistical unsound, you can not point either to 1 in 50,000 hours, that catches only the sensors that failed in a high position, we can have hundreds of sensors failing in a low position without triggering MCAS.

Again, everything you are suggesting points to issues with the automation system, not the entire trim system. You even lay direct blame on the automation system (“under all the stress the pilot is put under by the malfunctioning automatic”) while trying to blame the trim system.

The answer isn’t redesign the trim system, it’s redesign the automation so if it fails the pilot can still manually trim the plane to where they want it. MCAS was never fully releasing control and letting the pilots do what they want and expected from the plane.


So not being able to use the manual trim wheel when there are high loads on elevator or tail plane does not come under kludge? Having to push or pull on the stick to lighten the load on the trim, to be able to move the wheels, does not distract the pilot in the middle of saving the frame? That is for me a definition of a kludge system. Something making it more difficult for the pilot to survive rather than easier.

Why not bring the ability to just switch off the automatic?

Just so Boeing can say you need only a 1 hour i-pad training from NG to MAX, because Boeing has promised Southwest that no simulator training would be necessary.
 
ArgentoSystems
Posts: 315
Joined: Sun Mar 24, 2019 12:05 am

Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 3:02 pm

maint123 wrote:
Let the max be flown exclusively in US airspace by American Airlines using American pilots, for a year or so, to prove the reliability of MAX. This way the doubts about non American pilots and maintenance of the planes will be taken care of. As things stand now with new revelations about the plane coming out everyday, most non Americans would not feel safe in this plane.


That would not prove much. Too few MAXes in USA. They might as well not have any accidents even with no changes.
 
jollo
Posts: 396
Joined: Mon Aug 08, 2011 7:24 pm

Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 3:03 pm

mjoelnir wrote:
Turning the trim automatic off, STS and MCAS, only together with manual electrical trim, why?


Now, this is an interesting question.

We all know that the MAX's stab trim system is not going to be "completely re-designed": this would add unforeseen risks, not reduce them. However, the reason for the Runaway Stabilizer NNC to be designed the way it is seems to be a legacy of the past.

Cutting an automatic controller off the control loop should be a separate option than completely disabling the actuator/servo. Both are useful options, but address distinct contingencies.

That's why under the STAB TRIM CUTOFF label the 737 NG (and the Classic as well, AFAIK) has 2 distinct switches: AUTOPILOT and MAIN ELECT. Switching the AUTOPILOT switch to CUTOFF only deactivates autopilot stabilizer trim operation, leaving the electric trim manual switches on the yoke operative, whereas switching the MAIN ELECT switch to CUTOFF completely kills electric trim at the actuator level.

Questions:
1) what happens if MAIN ELECT is switched to CUTOFF but AUTOPILOT is left on NORMAL? I expect the autopilot would sense an inop trim and disengage? This setting seems to make little sense anyway
2) what happens to STS when AUTOPILOT is switched to CUTOFF but MAIN ELECT is left on NORMAL? Would STS be disconnected as well, since it's an automation? Or would it continue to operate because STS is not the A/P?

Interestingly, in the MAX the switches have been relabeled to PRI (for PRImary) and B/U (for Back/Up).

Questions:
3) Anyone cares to explain the logic for the new names? Have the functions been changed as well (I expect not, otherwhise the "no difference training" argument would not have held)?
4) What happens to STS and MCAS if PRI is switched to CUTOFF but B/U is left on NORMAL?

From an ergonomics point of view, I would recommend one switch (let's call it AUTO, to avoid confusions) to disable all automatic controllers (A/P, Speed Trim, Mach Trim and MCAS) thus letting the pilot retain exclusive control of electric trim, and another switch (let's call it MANUAL) to cut off the electric trim actuator altogether - ideally, the AUTO switch should be slaved to the MANUAL switch, because the AUTO=NORMAL + MANUAL=CUTOFF configuration would be inconsistent.

Then the Stabilizer Runaway NNC could be broken out in distinct steps:
...
If the runaway continues after the autopilot is disengaged:
STAB TRIM CUTOUT - AUTO switch ........... CUTOUT
If the runaway continues:
Stabilizer....................................................... Neutral (using electric trim switches)
STAB TRIM CUTOUT - MANUAL switch ...... CUTOUT
...

Would this sequence make sense? Wording and naming would have to be revised, of course...
Last edited by jollo on Wed Apr 03, 2019 3:13 pm, edited 2 times in total.
 
achmafooma
Posts: 12
Joined: Wed Jul 29, 2015 10:30 pm

Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 3:08 pm

BoeingVista wrote:
WSJ has been briefed on the preliminary ET302 report, not great for Boeing as pilots did initially follow the new Boeing MCAS drill but they still couldn't get the plane to clmb so they flipped the electric trim motor back on and the rest is history

The pilots on Ethiopian Airlines Flight 302 initially reacted to the emergency by shutting off power to electric motors driven by the automated system, these people said, but then appear to have re-engaged the system to cope with a persistent steep nose-down angle. It wasn’t immediately clear why the pilots turned the automated system back on instead of continuing to follow Boeing’s standard emergency checklist, but government and industry officials said the likely reason would have been because manual controls to raise the nose didn’t achieve the desired results.

After first cranking a manual wheel in the cockpit that controls the same movable surfaces on the plane’s tail that MCAS had affected, the pilots turned electric power back on, one of these people said. They began to use electric switches to try to raise the plane’s nose, according to these people. But the electric power also reactivated MCAS, allowing it to continue its strong downward commands, the people said.


https://www.wsj.com/articles/ethiopian- ... 1554263276

If this report is accurate, it would change things (at least from my perspective). If you cut off the electric trim and the plane is still uncontrollable then that shifts a lot of the responsibility back over to Boeing that I might otherwise have assigned to the pilots. Is this possibly that the trim was far out of whack due to MCAS and they did not get it back to a near-neutral position before cutting the power? I saw a YouTube vid of MentourPilot in a 737 sim replicating a similar situation, and I was surprised by how much he had to crank that wheel. First he asked the FO to do it, but the FO was giving a fairly slow adjustment, so the CA reached down and really cranked the thing. The whole vid is worth watching but here's the part I'm talking about: https://youtu.be/xixM_cwSLcQ?t=1071

flybucky wrote:
achmafooma wrote:
I also have a very hard time understanding why the pilots didn't cut-out the electric trim.

I keep imagining that I'm driving down the freeway and I have my cruise control set at 65, and the car starts accelerating in apparently random 10s spurts. I don't keep tweaking it back down with the speedometer controls. I don't start paging through the manual. I certainly don't start questioning whether the manual's instructions about dealing with "continuous" cruise control problems applies to "intermittent" cruise control problems. The first thing I do is turn the darn cruise control off!

But as hard as I've tried to be empathetic with the crews on these flights, this just seems like a no-brainer to me. Auto-trim goes crazy, turn off auto-trim.

It's not that simple as that. Let me continue your analogy put try to paint a more accurate picture:

First of all, you never set the cruise. You are driving manually at 65 mph, and all of the sudden, the car starts to accelerate intermittently. Since you never set the cruise, you don't think of it first thing. The first thing you think of is maybe the gas pedal is malfunctioning. You immediately take your foot off the gas, but that doesn't seem to do anything. Next you try braking, and that does help somewhat, but when you let go of the brake, it starts accelerating again. Also, you know that when you tap the brake, it always disconnects the cruise, so it can't be the cruise.

Then, your steering wheel starts shaking like a jackhammer and an audible alarm repeatedly blares, "Do not drive below 55 mph" (this is my poor analogy for the stall warning). Maybe there is a runaway semi truck on your tail going 55 mph, so if you drive too slow, it'll pancake you. So now you're afraid to brake too much, and also checking your rearview mirror, but you don't see a truck. Then you go back to looking down at the gas pedal, trying to see what's wrong with it. Meanwhile, you didn't realize that the speed has increased to 85 mph, and there is a curve coming up. You slam on the brakes but it's too late, you've driven off a cliff.

Turns out that it was the cruise control that had activated after all. But it didn't occur to you because you never set the cruise (STS and MCAS operate during manual flying, not autopilot). And you had been braking, which should have disconnected the cruise (In 737 NG, if you counter Speed Trim System by pulling on the yoke, STS will stop. In 737 MAX, yoke will not stop MCAS.) Instead, you thought it was the gas pedal and fixated on that. The other alarms and shaking added to the confusion. By the way, there was no semi truck behind you, the sensor was faulty. You could have just braked and came to a stop safely.

Not the greatest analogy, but basically the point is that human factors are a real issue in safety, including pilot fixation.

Thank you. No analogy can be perfect but this comes pretty close, I think. Really helps to put it into perspective for me. Thank you for the article link as well.

XRAYretired wrote:
Best analogy I've read. brilliant. You been up all night working on it?

Ray

I hope he didn't stay up late on my account!

SheikhDjibouti wrote:
That analogy was a good start, but rather over-simplified the situation. (Just like the Cessna pilot up thread who insists it is all so simple...)

Your cruise control might be at 65, but your speedometer is totally blacked out. If you cannot work out what speed you are doing, what is the cruise control using for data?

Whilst you are puzzling over that, the steering wheel is shaking madly, as if you have a tire with a puncture or a loose wheel, and tbh you are more concerned with the possibility of a blow out, so whether or not you are maintaining 65 mph is not even your biggest worry.

And somebody keeps randomly turning on the radio, LOUD, featuring a traffic report warning you of an accident ahead. This also disrupts your thought process.

Plus nobody driving a car with a fault ever stated paging through the manual to find out what was wrong; they would pull over first and take their time. Not an option in a 737. :shakehead:

..
I was going to add more, but then I saw flybucky's excellent submission, and he really nailed it. :bigthumbsup:

Thank you. Yeah, the part in my analogy about paging through the manual was the biggest stretch in the car v. plane comparison. I was trying to contrive a similar scenario that is "in my world" as it were. Now that you mention it, I actually did get a strange warning light I wasn't familiar with in my car a couple months ago, and I actually did pull out the manual (after I had parked) to try and figure it out. But like you said, pulling off into a gas station or to the shoulder of the highway isn't an option in the air. I guess I was just underestimating the number of things going on and the confusion that it all must have caused.
 
xwb565
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Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 3:24 pm

Leeham in co operation with MentourPilot paints a picture of what might have happened

http://leehamnews.com/2019/04/03/et302- ... more-29790
 
StTim
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Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 3:24 pm

I have just read the latest Leeham news article on this. How scary that you know the issue, you follow the instructions and yet it is still impossible to recover the plane.

Blooming scary and really unforgivable in the modern world?
 
Interested
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Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 3:34 pm

mjoelnir wrote:
Interested wrote:
mjoelnir wrote:
I think Boeing needs to have a hard look at the whole trim system. Perhaps the combination of old grandfathered design and modern additions went a step to far.

The problem for Boeing will be, that that will lead to more differences between the NG and MAX, resulting in more training needed. Something that seems to be a absolut no way at Boeing Management.


You have to assume that there's no choice but for Boeing to cover the cost and inconvenience of whatever training may be needed. It's obviously better than not being able to produce and deliver these planes any more. It may of course make them less desirable to order in the future and less profitable but there's going to have to be some pain here for Boeing both short and long term. They've messed up it will cost them for sure.

But I still can't help thinking it's like putting an elastoplast on a cancer

The only reason we need MCAS and now extra training is because the initial plane design is unsafe without both or either

I've no doubt if this plane wasn't already certified and so huge an investment and project but was just at the design stage knowing what we know now it wouldn't continue

There surely has to be some doubts about it continuing even as we are?

But if it doesn't then what a huge gap needs filling in the airline industry


That is why I hope that regulators do not let Boeing get away with a quick fix software fix, but rather insist on a redesign of the complete trim system on the MAX. If it is near impossible to manually, after using the cutout switches, trim the frame fast enough to survive, than cutting electrical trim seems to be recipe for disaster rather than a safe move.

I expect Boeing to fight the need for a redesign all the way.


Unless Boeing has a long term death wish on their business they have to take the safest option now

What's the point of battling short term to get the planes back in the air if we are still left with a potentially catastrophic risk for future passengers

They need to take a long term view as well

There must be some wise heads at Boeing who realise this in amongst all the staff they employ?
Last edited by Interested on Wed Apr 03, 2019 3:36 pm, edited 1 time in total.
 
mjoelnir
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Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 3:35 pm

As I say redesign the complete trim system. Manual trim should work in any condition, also with a high load. Automatic trimming should be able to be shut off without disabling manual electric trim.
 
Amiga500
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Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 3:39 pm

StTim wrote:
I have just read the latest Leeham news article on this. How scary that you know the issue, you follow the instructions and yet it is still impossible to recover the plane.

Blooming scary and really unforgivable in the modern world?



Ah, but 'murican pilots with superior training to Johnny Foreigner would have dealt with it. :rolleyes:
 
Interested
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Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 3:42 pm

planecane wrote:
mjoelnir wrote:
Interested wrote:

You have to assume that there's no choice but for Boeing to cover the cost and inconvenience of whatever training may be needed. It's obviously better than not being able to produce and deliver these planes any more. It may of course make them less desirable to order in the future and less profitable but there's going to have to be some pain here for Boeing both short and long term. They've messed up it will cost them for sure.

But I still can't help thinking it's like putting an elastoplast on a cancer

The only reason we need MCAS and now extra training is because the initial plane design is unsafe without both or either

I've no doubt if this plane wasn't already certified and so huge an investment and project but was just at the design stage knowing what we know now it wouldn't continue

There surely has to be some doubts about it continuing even as we are?

But if it doesn't then what a huge gap needs filling in the airline industry


That is why I hope that regulators do not let Boeing get away with a quick fix software fix, but rather insist on a redesign of the complete trim system on the MAX. If it is near impossible to manually, after using the cutout switches, trim the frame fast enough to survive, than cutting electrical trim seems to be recipe for disaster rather than a safe move.

I expect Boeing to fight the need for a redesign all the way.


As time goes on, we are starting to pass the point of logic in some of the responses. Isn't it completely impossible to manually trim a 757 or 767 after using the cutout switches since they don't have a trim wheel?

The point of the software fix is to limit MCAS total trim inputs and especially to only have it activate one time per event. If the "quick fix" software fix stops MCAS from causing a runaway trim then why does the entire trim system need to be redesigned? With the limitation of MCAS to one activation per stall event, the pilots can just trim to where they have elevator authority before using the cutout switches, if those switches are still necessary. In the new software, it would require BOTH AoA sensors to fail AND read similar to eachother for MCAS to activate in an unintended scenario.

The trim system that you want them to redesign has been flying around on the 737 since 1967 and the near impossibility to manually trim after using the cutout switches has never caused an issue. I think over 10,000 aircraft and 50+ years of flights is enough to say that the trim system is perfectly safe the way it is. MCAS is another system that controlls the trim system. THAT is the problem, not the trim system itself.

Let's all calm down a little. The implementation of MCAS was obviously very flawed with respect to the reacton to bad sensor data. When the sensors are working properly, MCAS is not an issue and all this hyperbole about it being required for stability and therefore shouldn't have been allowed is ridiculous. Any Airbus starting with the A320 requires software systems to fly at all. Same with the 777 and 787.

Had Boeing simply limited MCAS to one activation per event from the beginning, neither of these crashes would have happened regardless of the reliance on one AoA sensor. MCAS would have pitched the nose down 2.5 degrees. The pilots would have said "what the hell is the trim doing" and hit the thumb switch to re-trim back to where it was and gone on their merry way. Even if another "event" happened several minutes later, they would have done the same thing.

With the constant application of trim down by MCAS, it created a confusing/panicked situation and was able to lead to a full nose down pitch rather quickly. As long as the "quick fix" can be proven to regulators to be written properly to have MCAS turn off in the event of AoA disagree, limit it to one activation per event and limit the total authority to 2.5 degrees, it will be approved and the MAX will be just as safe as the NG (assuming nothing else was added without informing the pilots).


So whats happening with software on 737 Max is more like what is needed on 777 and 787?

So why was this plane allowed to be grandfathered based on 737?
 
Interested
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Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 3:52 pm

planecane wrote:
mjoelnir wrote:
planecane wrote:

How is it a joke if it has worked fine for 50+ years on 10,000+ aircraft? Doesn't the A320 have some kind of very limited manual backup if the entire FBW system fails? I've read (supposedly posted by pilots who fly them) that there are cutout switches on the 757 and 767 and there are scenarios where they are used. Those aircraft have no trim once you hit the cutout so why is that better?


Because for 50 years the automatic was not actively trying to kill the pilots and passengers.

The MAX is not the NG, so pointing to prior safety statistics is about a senseless as can be.

And what has the A320 to do with it, they are not dropping every few month out of the sky like the MAX

I call something a joke when is a joke. Just because something has been the same for 60 years, is no reason to keep it the same. A trim run away, as one sees on the nice youtube videos is not done on the simulator with a broken AoA sensor, MCAS engaging, stick shaker turned on, stall warning sounding and unreliable airspeed indication and very near to the ground. I like to see those guys turning the hand wheel with full elevator engaged and 2.5% trim the wrong way. Perhaps pilots have been lucky for years, because no automation was trying to kill them.

Turning the trim automatic off, STS and MCAS, only together with manual electrical trim, why?


None of that indicates that the entire trim system needs to be redesigned. The problem is MCAS activating due to a single bad AoA sensor. The scenario that you are suggesting won't happen after the software changes (assuming the software is written properly).

Here is a statistical tidbit for those worried about the "quick fix" software. If the failure rate of a single AoA sensor causing MCAS to activate is 1 in 50,000 flights (reasonable estimate based on the MAX crash rate), the failure of both sensors to cause MCAS to activate would be 1 in 2.5 BILLION flights. Since one of the main changes is disabling MCAS on AoA disagree, I think that that failure rate falls under acceptable risk, especially since other changes limit the authority and number of activations so that even if you are on that 1 in 2.5 billion flight the pilots should be able to recover.


1 in 50,000 times a sensor fails?

So youve got that figure based on Max Crash rate?

Does Max crash every time a sensor fails ? Or have you accounted for some not crashing?
 
StTim
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Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 4:00 pm

Amiga500 wrote:
StTim wrote:
I have just read the latest Leeham news article on this. How scary that you know the issue, you follow the instructions and yet it is still impossible to recover the plane.

Blooming scary and really unforgivable in the modern world?



Ah, but 'murican pilots with superior training to Johnny Foreigner would have dealt with it. :rolleyes:


Very true. To quote Bjorn Fehrm in the article (Fair use)

"Today we know the crowing from Western pilots, “Typical third world crews,” was not called for. Anyone who has tried a correctly set up MCAS situation in a simulator is more muted."
 
frmrCapCadet
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Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 4:11 pm

Situational awareness would seem to require a visual display of what the plane itself is doing - us non pilots find it confusing as to how much varying things automation both Airbus and Boeing provide. These varieties of automation are given various different names. I am surprised that these sorts of things do not have standard names. Seemingly the plane changes what it is doing without a clear depiction of just what is doing.

I do think the various government aviation regulatory bodies should be looking in enforcing standard regarding automation and nomenclature. MCAS as I understand it is an extreme stabilizer automation - shouldn't the pilots know that it is happening via standard displays? Check lists of course require memorization, but entire manuals cannot be word for word memorized. If a pilot knows that MCAS has taken over it would/should be somewhat trivial to react properly when it is happening erroneously.
Buffet: the airline business...has eaten up capital...like..no other (business)
 
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BoeingVista
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Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 4:23 pm

StTim wrote:
Amiga500 wrote:
StTim wrote:
I have just read the latest Leeham news article on this. How scary that you know the issue, you follow the instructions and yet it is still impossible to recover the plane.

Blooming scary and really unforgivable in the modern world?



Ah, but 'murican pilots with superior training to Johnny Foreigner would have dealt with it. :rolleyes:


Very true. To quote Bjorn Fehrm in the article (Fair use)

"Today we know the crowing from Western pilots, “Typical third world crews,” was not called for. Anyone who has tried a correctly set up MCAS situation in a simulator is more muted."


That video does not look like fun, Boeing hung the ET302 crew out to dry that day. No regulator is going to approve a procedure that requires stick forward bunting a potentially MTOW aircraft at 1000ft to stop an aircraft intent on killing everyone on board killing everyone on board, especially in EU where a lot of airports are in heavily built up areas. Boeing had better have a plan B that does not involve manufacturing MAX's.
BV
 
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PixelFlight
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Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 4:28 pm

marcelh wrote:
PixelFlight wrote:
flybucky wrote:
GXL888T: At FL320, AOA sensors 1 and 2 froze and stayed frozen for the remainder of the flight. Due to the frozen sensors, Alpha protection did not kick in, and the plane stalled around 3000-4000 ft altitude (AOA still frozen) and crashed. It may be rare, but it definitely can happen.

http://avherald.com/h?article=410c9cec
http://www.aviation-accidents.net/xl-ai ... t-gxl888t/

Yes, but on this GXL888T all the sensors was damaged on the ground prior to the flight _AND_ the test pilot was trying to flight far outside of the established safety procedure.

What are you trying to tell us?

That multiple frozen _undamaged_ AoA sensors is very very unlikely at low altitude. The GLX888T was more about maintenance error that damaged all sensors and pilot error that performed ultra-extreme flight without safety margin in case where the test it was doing will fail. The established procedure for that test was to make it a higher altitude in order to allow to perform a stall recovery in the case the test fail. The test failed but a recovery was impossible due to very low altitude. A normal flight would have not stalled, even with the multiple defective AoA sensors.

Adding multiple sensors of the same type don't add redundancy in case of common failure, and GXL888T is scary because it was a AoA common failure mode due to a single maintenance error while cleaning the aircraft. I think that the AoA sensors redundancy is actually not up to where is should be, even on a 4 AoA sensors A350. Flight dynamic predictive filters is a solution to identify and reject multiple AoA fault.
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
dk1967
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Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 4:37 pm

xwb565 wrote:
Leeham in co operation with MentourPilot paints a picture of what might have happened

http://leehamnews.com/2019/04/03/et302- ... more-29790


And that was a 737NG sim? Also, video is now unavailable.
 
mwmav8r01
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Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 4:53 pm

morrisond wrote:
I found this almost crash report of Lufthansa 1829. You can't design around some of this stuff. Stuff breaks. The crew reacted appropriately and the Aircraft was saved. It sounds like the crew was facing some of the same issues the MAX flights were.

On 5 November 2014, Lufthansa Flight 1829, an Airbus A321 was flying from Bilbao to Munich when the aircraft, while on autopilot, lowered the nose into a descent reaching 4000 fpm. The uncommanded pitch-down was caused by two angle of attack sensors that were jammed in their positions, causing the fly by wire protection to believe the aircraft entered a stall while it climbed through FL310. The Alpha Protection activated, forcing the aircraft to pitch down, which could not be corrected even by full stick input. The crew disconnected the related Air Data Units and were able to recover the aircraft.


Stop replying to Interested. They have an ax to grind. I cant handle a thread with more responses from 1 person.

Your analysis is spot on. Yes a tweak is needed but traing and even following CURRENT trim runaway procedure likely would have prevented this.

Its not a 1 spot blame.
 
mwmav8r01
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Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 4:56 pm

Bradin wrote:
I am not sure if everyone understands what MCAS is or if we can agree what MCAS is. Some of the more recent posts makes it sound like the MCAS is a piece of hardware. However based on everything I've read and how I've interpreted it, MCAS is a piece of software. Not a piece of hardware.

Does anyone else interpret it differently? Or do we all agree on the same definition of what MCAS is?


Its an auto trim function. There are multiple autotrim functions in the NG. More than the Classic and more than the Jurrasic. Technology changes.
 
Interested
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Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 5:06 pm

mwmav8r01 wrote:
morrisond wrote:
I found this almost crash report of Lufthansa 1829. You can't design around some of this stuff. Stuff breaks. The crew reacted appropriately and the Aircraft was saved. It sounds like the crew was facing some of the same issues the MAX flights were.

On 5 November 2014, Lufthansa Flight 1829, an Airbus A321 was flying from Bilbao to Munich when the aircraft, while on autopilot, lowered the nose into a descent reaching 4000 fpm. The uncommanded pitch-down was caused by two angle of attack sensors that were jammed in their positions, causing the fly by wire protection to believe the aircraft entered a stall while it climbed through FL310. The Alpha Protection activated, forcing the aircraft to pitch down, which could not be corrected even by full stick input. The crew disconnected the related Air Data Units and were able to recover the aircraft.


Stop replying to Interested. They have an ax to grind. I cant handle a thread with more responses from 1 person.

Your analysis is spot on. Yes a tweak is needed but traing and even following CURRENT trim runaway procedure likely would have prevented this.

Its not a 1 spot blame.


No axe to grind at all. Other than seeing the right things happen from now on.

Just be grateful I don't know anyone killed in one of these crashes as then you would see me with an axe to grind

I must say one thing that has motivated me to post more is the constant attempts by various posters to either excuse or deflect blame from Boeing on to the pilots etc

The more they have done that the more I've been inclined to post

Works both ways
 
Interested
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Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 5:08 pm

mwmav8r01 wrote:
morrisond wrote:
I found this almost crash report of Lufthansa 1829. You can't design around some of this stuff. Stuff breaks. The crew reacted appropriately and the Aircraft was saved. It sounds like the crew was facing some of the same issues the MAX flights were.

On 5 November 2014, Lufthansa Flight 1829, an Airbus A321 was flying from Bilbao to Munich when the aircraft, while on autopilot, lowered the nose into a descent reaching 4000 fpm. The uncommanded pitch-down was caused by two angle of attack sensors that were jammed in their positions, causing the fly by wire protection to believe the aircraft entered a stall while it climbed through FL310. The Alpha Protection activated, forcing the aircraft to pitch down, which could not be corrected even by full stick input. The crew disconnected the related Air Data Units and were able to recover the aircraft.


Stop replying to Interested. They have an ax to grind. I cant handle a thread with more responses from 1 person.

Your analysis is spot on. Yes a tweak is needed but traing and even following CURRENT trim runaway procedure likely would have prevented this.

Its not a 1 spot blame.


350 plus people dead - "a tweak is needed"

That says it all and that's why I will keep posting.
 
WIederling
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Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 5:11 pm

mwmav8r01 wrote:
Stop replying to Interested. They have an ax to grind. I cant handle a thread with more responses from 1 person.

Your analysis is spot on. Yes a tweak is needed but traing and even following CURRENT trim runaway procedure likely would have prevented this.

Its not a 1 spot blame.


What Schopenhauer couldn't know about : "argue via moderator"?

it is a two spot blame:
Boeing doing that MCAS "thingy"
Boeing handing out a remedy that killed even faster.
Good thing the software patch hasn't had contact with the unwashed public.

The ET crew seems to have followed the Boeing advisory "how to handle MCAS misbehaving" issued after the Lion Air crash.
It killed them even faster.
Murphy is an optimist
 
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PW100
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Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 5:11 pm

dk1967 wrote:
xwb565 wrote:
Leeham in co operation with MentourPilot paints a picture of what might have happened

http://leehamnews.com/2019/04/03/et302- ... more-29790


And that was a 737NG sim? Also, video is now unavailable.


Can't access that video either from my location (Netherlands).

Why do I have this feeling that mighty Boeing legal is hard at work here? Free speech anyone?
Immigration officer: "What's the purpose of your visit to the USA?" Spotter: "Shooting airliners with my Canon!"
 
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PixelFlight
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Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 5:14 pm

mjoelnir wrote:
I call something a joke when is a joke. Just because something has been the same for 60 years, is no reason to keep it the same. A trim run away, as one sees on the nice youtube videos is not done on the simulator with a broken AoA sensor, MCAS engaging, stick shaker turned on, stall warning sounding and unreliable airspeed indication and very near to the ground. I like to see those guys turning the hand wheel with full elevator engaged and 2.5% trim the wrong way.

What you describes is very important, because too many information (even from Boeing) only describes that the pilot have to hit two switches if the stab trim wheels turn abnormally. Without all the context this let too many peoples thinking that the cockpit is a quiet place without anything distracting but the wheels that turn so rarely that the pilot can evaluate each of there move. As you describes, this is a very wrong representation of the context. This was a scary place full of alarms messages, aural warnings, very noisy and annoying stick shaker, where the stab trim wheels turn so often that the pilots didn't take attention so there are used to it. On a very good design, the only event would have been an informative message that a single AoA sensor failed and that the FCC selected an other AoA sensor.
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
Etika
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Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 5:19 pm

PW100 wrote:
dk1967 wrote:
xwb565 wrote:
Leeham in co operation with MentourPilot paints a picture of what might have happened

http://leehamnews.com/2019/04/03/et302- ... more-29790


And that was a 737NG sim? Also, video is now unavailable.


Can't access that video either from my location (Netherlands).

Why do I have this feeling that mighty Boeing legal is hard at work here? Free speech anyone?


I don't know happened to the video, but I was able to watch it through hour ago, but now can't reach it. So, it certainly is not due to location limitation.

Also, it seems that the mention of the video has been removed from that article of Leeham News. No other reference to the removal anywhere that I can find from either Leeham or MentourPilot... Apparently it has been removed due to demand by MentourPilot's employer. That was some fast action by them...
 
StTim
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Re: B737MAX Grounded Worldwide

Wed Apr 03, 2019 5:22 pm

Video has been removed at the request of the pilots employer!

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