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Scotron12
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 20, 2020 3:35 pm

PixelFlight wrote:
trini81 wrote:
https://www.msn.com/en-us/money/companies/how-boeings-responsibility-in-a-deadly-crash-got-buried/ar-BBZ8Saf

Interesting article on Boeing's history on dealing with accidents... "How Boeing’s Responsibility in a Deadly Crash ‘Got Buried’"

TK1951: Different systems but the same principle: primary flight control depending on a single sensor.
Redundancy is the key to improve safety.


I think the main thrust of the article was the length Boeing would go to deflect blame from Boeing and their products. So what...only 9 people died. Is the same mindset that pevails today...get this turkey in air at all costs!
 
morrisond
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 20, 2020 3:38 pm

PixelFlight wrote:
767333ER wrote:
To do a full FBW and avionics conversion would change a lot of the plane, the latter readily doing so. In order to convert to a 787 style FBW system all the cables would need to be removed, an extra hydraulic system added, the other two hydraulic systems changed, all the control “computers” changed (including that old hydraulic computer the thing has). Most of that is an undertaking they’ve never had to do before. There could be a chance the TC could stay the same, but then again what about it would be a 737 anymore? The fuselage and maybe the wings? It then becomes nearly as much 737 as the 737 is 707.

But what about converting only the stab trim to FBW first, possibly the 737-8/9 MAX already ?


Or you just train/retrain Pilots to remind them that the manual trim wheel may become ineffective above Vmo and that if Manual trim is needed reduce to normal operating speeds and make sure that the Autothrottle is not engaged at Take Off Go around thrust and if necessary use the rollercoaster maneuver to correct a severe mistrim.

They need to know these procedures anyways if they ever experienced a real trim runaway. However if your view is that that is so unlikely to happen so no need to train for it - then with MCAS V 2.0 the chances of that failing with the changes most likely to be implemented is so unlikely as well no need to train for that either and the Manual trim wheel is not an issue.
 
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PixelFlight
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 20, 2020 4:02 pm

morrisond wrote:
PixelFlight wrote:
767333ER wrote:
To do a full FBW and avionics conversion would change a lot of the plane, the latter readily doing so. In order to convert to a 787 style FBW system all the cables would need to be removed, an extra hydraulic system added, the other two hydraulic systems changed, all the control “computers” changed (including that old hydraulic computer the thing has). Most of that is an undertaking they’ve never had to do before. There could be a chance the TC could stay the same, but then again what about it would be a 737 anymore? The fuselage and maybe the wings? It then becomes nearly as much 737 as the 737 is 707.

But what about converting only the stab trim to FBW first, possibly the 737-8/9 MAX already ?


Or you just train/retrain Pilots to remind them that the manual trim wheel may become ineffective above Vmo and that if Manual trim is needed reduce to normal operating speeds and make sure that the Autothrottle is not engaged at Take Off Go around thrust and if necessary use the rollercoaster maneuver to correct a severe mistrim.

They need to know these procedures anyways if they ever experienced a real trim runaway. However if your view is that that is so unlikely to happen so no need to train for it - then with MCAS V 2.0 the chances of that failing with the changes most likely to be implemented is so unlikely as well no need to train for that either and the Manual trim wheel is not an issue.

I don't want to choose, I want the two: safety from design and safety from training. Trading between the two kill.
: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:
 
airhansa
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 20, 2020 4:06 pm

I still wouldn't support the plane why they still use an automated system (MCAS) to cover up flaws in the design. The plane should be designed to fly aerodynamically in manual mode without assitance from the autopilot. It should ideally also be able to fly on the autopilot without assistance from the pilots, but that's the icing not the cake. MCAS also puts the plane in a more dangerous situation: it forces the plane to dive (yes, it's called the stall recovery, but it's still not something you should do all the time). The solution to this entire controversy is to make the engines smaller and bin the stupid MCAS system.

A person earlier mentioned that automated systems are used all the time to do mundane jobs such as help parking, but the key thing is that the automated system is helping the pilot avoid mistakes, whereas MCAS is essentially covering up a mistake made by Boeing despite the pilot doing the right thing.

It's like driving a car that has wheels that eventually drive at an angle, but the "automated steering wheel" turns back so that angle doesn't matter.
 
Aptivaboy
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 20, 2020 4:12 pm

Given all of these issues, I'm seriously of the view that Boeing simply needs to move on - kill the MAX and move on to the NMA, NSA, or whatever they're calling it this week. For what they're spending in compensation, lawsuits, recertification and redesign, they should have just moved to a new airframe. Yes, hindsight is twenty-twenty, but that's essentially the reality. C'mon Boeing, time to fish or cut bait. If you can't get the MAX back in the air reasonably promptly, then move on. Offer impacted customers discounts on the new plane. Design a world beater. Become the leader in world aerospace that you once were.
 
kalvado
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 20, 2020 4:20 pm

airhansa wrote:
I still wouldn't support the plane why they still use an automated system (MCAS) to cover up flaws in the design. The plane should be designed to fly aerodynamically in manual mode without assitance from the autopilot. It should ideally also be able to fly on the autopilot without assistance from the pilots, but that's the icing not the cake. MCAS also puts the plane in a more dangerous situation: it forces the plane to dive (yes, it's called the stall recovery, but it's still not something you should do all the time). The solution to this entire controversy is to make the engines smaller and bin the stupid MCAS system.

A person earlier mentioned that automated systems are used all the time to do mundane jobs such as help parking, but the key thing is that the automated system is helping the pilot avoid mistakes, whereas MCAS is essentially covering up a mistake made by Boeing despite the pilot doing the right thing.

It's like driving a car that has wheels that eventually drive at an angle, but the "automated steering wheel" turns back so that angle doesn't matter.

One thing you need to understand: MCAS is there for EMERGENCY. If it activates, things are already going very wrong. Boeing estimated that 737 pilot can fly throughout their carreer without seeing MCAS by-design activation, and that sounds about right - once every few tens thousands hours. Hardly "cannot fly without computer help"
And I (yes, that was me) compared that to VSA - vehicle stability assistance, which kicks in for overspeed turns on icy road. Not with parking assistance you would use on a daily basis, but just that - emergency system which careful driver never sees in action. OK, again - shit happens even with the best of us, I (not the best driver, sure) saw VSA kicked in once or twice within past decade.
It is implementation of the system which is lacking for MAX.
Nobody really knows how good A planes behave in that situation - ok, nobody outside Airbus; because Airbus implemented proper envelope protection which (knock the wood!) is fairly reliable (that is, instead of rudimentary MCAS with false activation).
Bottom line: while undesired, MAX behavior is not a critical problem if handled with due attention.
 
planecane
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 20, 2020 4:22 pm

airhansa wrote:
I still wouldn't support the plane why they still use an automated system (MCAS) to cover up flaws in the design. The plane should be designed to fly aerodynamically in manual mode without assitance from the autopilot. It should ideally also be able to fly on the autopilot without assistance from the pilots, but that's the icing not the cake. MCAS also puts the plane in a more dangerous situation: it forces the plane to dive (yes, it's called the stall recovery, but it's still not something you should do all the time). The solution to this entire controversy is to make the engines smaller and bin the stupid MCAS system.

A person earlier mentioned that automated systems are used all the time to do mundane jobs such as help parking, but the key thing is that the automated system is helping the pilot avoid mistakes, whereas MCAS is essentially covering up a mistake made by Boeing despite the pilot doing the right thing.

It's like driving a car that has wheels that eventually drive at an angle, but the "automated steering wheel" turns back so that angle doesn't matter.


MCAS, when operating properly, does not "force the plane to dive." In introduces a mis-trim to cause it to take more force to lift the nose more. MCAS, operating properly, would never have caused a plane to dive or even for a pilot to notice it existed. The issue with MCAS was the botched fault tree analysis and allowing a single sensor failure to cause a potentially catastrophic runaway.

The need for and inclusion of MCAS is not the issue. Especially since it is only need for edge cases that aren't entered into very often, if at all, in normal service. As long as MCAS is fixed to only operate when and how it was originally intended, there is no issue with it.

STS on the NG is doing something similar. It just didn't have the authority and lack of a simple cutout (the column switches for STS) to cause a problem. Actually, STS activates in normal operation all the time so it is far more active than a properly functioning MCAS would ever be.
 
phollingsworth
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 20, 2020 4:32 pm

Revelation wrote:
phollingsworth wrote:
Boeing is currently paying the price for trying to retrofit safety criticality into an avionics suite that is not design to be safety critical. It is something that can be done, but basically requires rewriting the entire software stack to accomplish. Had Boeing gone for a rebuild of the underlying avionics on 737MAX in the first instance this would have been a much larger task upfront but would have made RTS a much simpler prospect, FBW or no FBW.

As per earlier posts, the stuff Boeing is doing now (going from active-standby pair to active-active pair) is not a rewrite of the entire stack, it's largely done so you do not have to rewrite the entire stack! The software stack itself is largely preserved, just some comparators are added around the edges, and just some more triggers for disengagement are added. In theory since you already have an active-standby pair the software already has some robustness with respect to rapid failover. The main issue becomes one of testing, and as we've seen with the issue reported last week about activating displays at start up time you often find some places where the software needs more hardening.

It's interesting to see the software audits being held in Cedar Rapids. It's as clear an indication one can get that the center of expertise with regard to the flight control software is at a vendor's site, which IMHO is an absurd position for Boeing to have put itself into.


By moving to the active-active setup with the comparison you add a fair amount of overhead and need for realtime scheduling that did not exist in the old system where the active-standby switch was done by the flight crew. The comparison is a lower order function that lit a warning indicator. Moving this into the software stack increases the issues with failures, bit-flips, etc. Hence the rewrites that have propagated out of this. The actual comparison check is fairly simple, it is the knock-on implications that are eating up time and manpower.
 
airhansa
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 20, 2020 4:52 pm

planecane wrote:
airhansa wrote:
I still wouldn't support the plane why they still use an automated system (MCAS) to cover up flaws in the design. The plane should be designed to fly aerodynamically in manual mode without assitance from the autopilot. It should ideally also be able to fly on the autopilot without assistance from the pilots, but that's the icing not the cake. MCAS also puts the plane in a more dangerous situation: it forces the plane to dive (yes, it's called the stall recovery, but it's still not something you should do all the time). The solution to this entire controversy is to make the engines smaller and bin the stupid MCAS system.

A person earlier mentioned that automated systems are used all the time to do mundane jobs such as help parking, but the key thing is that the automated system is helping the pilot avoid mistakes, whereas MCAS is essentially covering up a mistake made by Boeing despite the pilot doing the right thing.

It's like driving a car that has wheels that eventually drive at an angle, but the "automated steering wheel" turns back so that angle doesn't matter.


MCAS, when operating properly, does not "force the plane to dive." In introduces a mis-trim to cause it to take more force to lift the nose more. MCAS, operating properly, would never have caused a plane to dive or even for a pilot to notice it existed. The issue with MCAS was the botched fault tree analysis and allowing a single sensor failure to cause a potentially catastrophic runaway.

The need for and inclusion of MCAS is not the issue. Especially since it is only need for edge cases that aren't entered into very often, if at all, in normal service. As long as MCAS is fixed to only operate when and how it was originally intended, there is no issue with it.

STS on the NG is doing something similar. It just didn't have the authority and lack of a simple cutout (the column switches for STS) to cause a problem. Actually, STS activates in normal operation all the time so it is far more active than a properly functioning MCAS would ever be.


MCAS uses the horizontal fins to essentially push the plane nose down, with the idea being that the heavy engines cause the plane to fly at an angle-of-attack which could cause the plane to stall. MCAS essentially acts as a stall prevention system and in error situations it can push the nose down into a dive.

It would not be needed if the engines were reduced in size, or if Boeing had opted to redesign the plane. The autopilot is completely off when MCAS activates, but in fact the pilot should be the one controlling the horizontal fins and taking care about the angle-of-attack in manual mode. This is basically a plane that can't aerodynamically fly in a normal way.

Image
 
Dieuwer
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 20, 2020 4:55 pm

Aptivaboy wrote:
Given all of these issues, I'm seriously of the view that Boeing simply needs to move on - kill the MAX and move on to the NMA, NSA, or whatever they're calling it this week. For what they're spending in compensation, lawsuits, recertification and redesign, they should have just moved to a new airframe. Yes, hindsight is twenty-twenty, but that's essentially the reality. C'mon Boeing, time to fish or cut bait. If you can't get the MAX back in the air reasonably promptly, then move on. Offer impacted customers discounts on the new plane. Design a world beater. Become the leader in world aerospace that you once were.


For that you probably would need a massive culture change, from caring about short term results and big bonuses for management to having a long-term view and care about quality above profits.
 
kalvado
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 20, 2020 4:57 pm

airhansa wrote:
planecane wrote:
airhansa wrote:
I still wouldn't support the plane why they still use an automated system (MCAS) to cover up flaws in the design. The plane should be designed to fly aerodynamically in manual mode without assitance from the autopilot. It should ideally also be able to fly on the autopilot without assistance from the pilots, but that's the icing not the cake. MCAS also puts the plane in a more dangerous situation: it forces the plane to dive (yes, it's called the stall recovery, but it's still not something you should do all the time). The solution to this entire controversy is to make the engines smaller and bin the stupid MCAS system.

A person earlier mentioned that automated systems are used all the time to do mundane jobs such as help parking, but the key thing is that the automated system is helping the pilot avoid mistakes, whereas MCAS is essentially covering up a mistake made by Boeing despite the pilot doing the right thing.

It's like driving a car that has wheels that eventually drive at an angle, but the "automated steering wheel" turns back so that angle doesn't matter.


MCAS, when operating properly, does not "force the plane to dive." In introduces a mis-trim to cause it to take more force to lift the nose more. MCAS, operating properly, would never have caused a plane to dive or even for a pilot to notice it existed. The issue with MCAS was the botched fault tree analysis and allowing a single sensor failure to cause a potentially catastrophic runaway.

The need for and inclusion of MCAS is not the issue. Especially since it is only need for edge cases that aren't entered into very often, if at all, in normal service. As long as MCAS is fixed to only operate when and how it was originally intended, there is no issue with it.

STS on the NG is doing something similar. It just didn't have the authority and lack of a simple cutout (the column switches for STS) to cause a problem. Actually, STS activates in normal operation all the time so it is far more active than a properly functioning MCAS would ever be.


MCAS uses the horizontal fins to essentially push the plane nose down, with the idea being that the heavy engines cause the plane to fly at an angle-of-attack which could cause the plane to stall. MCAS essentially acts as a stall prevention system and in error situations it can push the nose down into a dive.

It would not be needed if the engines were reduced in size, or if Boeing had opted to redesign the plane. The autopilot is completely off when MCAS activates, but in fact the pilot should be the one controlling the horizontal fins and taking care about the angle-of-attack in manual mode. This is basically a plane that can't aerodynamically fly in a normal way.

Great. Now add the fact that MCAS activates at high AoA situations only. Some say MCAS happens only after stick shaker - aka warning that you're about to crash - is turned on.
 
planecane
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 20, 2020 4:57 pm

airhansa wrote:
planecane wrote:
airhansa wrote:
I still wouldn't support the plane why they still use an automated system (MCAS) to cover up flaws in the design. The plane should be designed to fly aerodynamically in manual mode without assitance from the autopilot. It should ideally also be able to fly on the autopilot without assistance from the pilots, but that's the icing not the cake. MCAS also puts the plane in a more dangerous situation: it forces the plane to dive (yes, it's called the stall recovery, but it's still not something you should do all the time). The solution to this entire controversy is to make the engines smaller and bin the stupid MCAS system.

A person earlier mentioned that automated systems are used all the time to do mundane jobs such as help parking, but the key thing is that the automated system is helping the pilot avoid mistakes, whereas MCAS is essentially covering up a mistake made by Boeing despite the pilot doing the right thing.

It's like driving a car that has wheels that eventually drive at an angle, but the "automated steering wheel" turns back so that angle doesn't matter.


MCAS, when operating properly, does not "force the plane to dive." In introduces a mis-trim to cause it to take more force to lift the nose more. MCAS, operating properly, would never have caused a plane to dive or even for a pilot to notice it existed. The issue with MCAS was the botched fault tree analysis and allowing a single sensor failure to cause a potentially catastrophic runaway.

The need for and inclusion of MCAS is not the issue. Especially since it is only need for edge cases that aren't entered into very often, if at all, in normal service. As long as MCAS is fixed to only operate when and how it was originally intended, there is no issue with it.

STS on the NG is doing something similar. It just didn't have the authority and lack of a simple cutout (the column switches for STS) to cause a problem. Actually, STS activates in normal operation all the time so it is far more active than a properly functioning MCAS would ever be.


MCAS uses the horizontal fins to essentially push the plane nose down, with the idea being that the heavy engines cause the plane to fly at an angle-of-attack which could cause the plane to stall. MCAS essentially acts as a stall prevention system and in error situations it can push the nose down into a dive.

It would not be needed if the engines were reduced in size, or if Boeing had opted to redesign the plane. The autopilot is completely off when MCAS activates, but in fact the pilot should be the one controlling the horizontal fins and taking care about the angle-of-attack in manual mode. This is basically a plane that can't aerodynamically fly in a normal way.

Image


A simplified graphic from The Air Current is not the gospel technical truth.

By your argument, the yaw damper shouldn't operate during manual flight. The pilot should be controlling the yaw in manual mode.
 
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 20, 2020 6:16 pm

phollingsworth wrote:
By moving to the active-active setup with the comparison you add a fair amount of overhead and need for realtime scheduling that did not exist in the old system where the active-standby switch was done by the flight crew. The comparison is a lower order function that lit a warning indicator. Moving this into the software stack increases the issues with failures, bit-flips, etc. Hence the rewrites that have propagated out of this. The actual comparison check is fairly simple, it is the knock-on implications that are eating up time and manpower.

You can't know this without a lot of detailed info we can presume the average a.net member does not have. For instance earlier in the thread it was suggested that the comparison would be done by the I/O processor thus would not tax the main processor, other than it having to be prepared to handle the indication that the comparison failed. The tradeoffs aren't hard to make for those who specialize in this work. The fact we haven't heard of a change in strategy and have heard of side issues such as the display startup issue suggest to me the active-active strategy is not currently being undermined by concerns such as lack of resources etc. While the fact that the software audit discovering a problem is a disappointment, the fact that the audit was held indicates progress along the announced path without any info about any change in direction.
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Aptivaboy
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 20, 2020 6:43 pm

For that you probably would need a massive culture change, from caring about short term results and big bonuses for management to having a long-term view and care about quality above profits.


Sadly, you're absolutely right. But... That cultural change may happen. I really do believe that as the lawsuits pile up, and perhaps criminal charges if certain accounts about investigations are to be believed, that change must happen for Boeing to survive in anything close to its current form. They're having commercial aircraft issues, space and defense issues, the list goes on. At some point, they must go back to being an engineering firm which makes great profits from said engineering; great products usually result in great profits. Hopefully, the current board possesses the wisdom to see that.
 
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 20, 2020 6:57 pm

kalvado wrote:
One thing you need to understand: MCAS is there for EMERGENCY. If it activates, things are already going very wrong. Boeing estimated that 737 pilot can fly throughout their carreer without seeing MCAS by-design activation, and that sounds about right - once every few tens thousands hours. Hardly "cannot fly without computer help"


Except that in two cases MCAS V1.0 activated when there wasn't an emergency, but rather faulty sensor data that fooled it into thinking there was an emergency. And we know the tragic result that followed.

What V2.0 has done to avoid this nobody yet has the full picture, although single-activation rather than repeated activation is apparently one of the correctives.

The flight test program will hopefully prove that V2.0 can't bite like V1.0. But it also must prove that the aircraft is manageable with MCAS deactivated in the case the computer detects a sensor reading mismatch and kicks MCAS offline.

Beech
 
morrisond
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 20, 2020 7:12 pm

airhansa wrote:
the idea being that the heavy engines cause the plane to fly at an angle-of-attack which could cause the plane to stall.
Image


You learn something new every day. Who knew the MAX's engines were mounted behind the center of gravity/center of lift....Good thing they mounted them even more forward then or the problem would have even been worse.

Yes - I know this is wrong. Much like the statement above it.
 
flipdewaf
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 20, 2020 7:34 pm

morrisond wrote:
PixelFlight wrote:
767333ER wrote:
To do a full FBW and avionics conversion would change a lot of the plane, the latter readily doing so. In order to convert to a 787 style FBW system all the cables would need to be removed, an extra hydraulic system added, the other two hydraulic systems changed, all the control “computers” changed (including that old hydraulic computer the thing has). Most of that is an undertaking they’ve never had to do before. There could be a chance the TC could stay the same, but then again what about it would be a 737 anymore? The fuselage and maybe the wings? It then becomes nearly as much 737 as the 737 is 707.

But what about converting only the stab trim to FBW first, possibly the 737-8/9 MAX already ?


Or you just train/retrain Pilots to remind them that the manual trim wheel may become ineffective above Vmo and that if Manual trim is needed reduce to normal operating speeds and make sure that the Autothrottle is not engaged at Take Off Go around thrust and if necessary use the rollercoaster maneuver to correct a severe mistrim.

Agreed, max specific training would probably go along way to helping bring it more in line with the safety record of other aircraft.

Fred



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Image
 
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par13del
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 20, 2020 8:02 pm

flipdewaf wrote:
Agreed, max specific training would probably go along way to helping bring it more in line with the safety record of other aircraft.
Fred
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Unfortunately, it is taking the FAA, EASA and the JTAR participants forever and a day to come up with what they want that training to be.....and since they included dual computer use the training just got MAX specific, will be interesting to see what they come up with.
 
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 20, 2020 8:23 pm

Aptivaboy wrote:
For what they're spending in compensation, lawsuits, recertification and redesign, they should have just moved to a new airframe. Yes, hindsight is twenty-twenty, but that's essentially the reality.

Yes, you are indeed engaging in hindsight. The actual reality is not the ones everyone can construct via hindsight, it's the one we're all in right now. Boeing has made commitments totalling many billion dollars to customers and partners, and set them on a path of action since the MAX was announced in 2011. Now they have no real option other than doing everything they can to get MAX back into service. Not doing so would cause a solid five plus more years of chaos for them and their partners and their customers.

planecane wrote:
MCAS, operating properly, would never have caused a plane to dive or even for a pilot to notice it existed. The issue with MCAS was the botched fault tree analysis and allowing a single sensor failure to cause a potentially catastrophic runaway.

Sad but true. It would have taken just a few people to resist the penny pinching management for a while and focus on the job at hand. Unfortunately this isn't what happened, and we're really not getting much insight into this aspect of the tragedy. Forkner et al are the focus of everyone's attention because their texts are so sensational, but the stuff they were doing was really secondary compared to the main job of producing a safe design and implementation for the 737 MAX. Hopefully someone with subpoena power is tuned in to the primary aspect of this tragedy.
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DenverTed
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 20, 2020 9:17 pm

What if Boeing gets the 800 or so MAX flying, and then make about 220 a year for 10 years for a total run of 3,000 aircraft. Is that a reality they are willing to comprehend, or is that so little to be unthinkable?
 
oschkosch
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 20, 2020 9:55 pm

DenverTed wrote:
What if Boeing gets the 800 or so MAX flying, and then make about 220 a year for 10 years for a total run of 3,000 aircraft. Is that a reality they are willing to comprehend, or is that so little to be unthinkable?
what if they don't is the more interesting question currently.

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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 7:27 am

PixelFlight wrote:
767333ER wrote:
To do a full FBW and avionics conversion would change a lot of the plane, the latter readily doing so. In order to convert to a 787 style FBW system all the cables would need to be removed, an extra hydraulic system added, the other two hydraulic systems changed, all the control “computers” changed (including that old hydraulic computer the thing has). Most of that is an undertaking they’ve never had to do before. There could be a chance the TC could stay the same, but then again what about it would be a 737 anymore? The fuselage and maybe the wings? It then becomes nearly as much 737 as the 737 is 707.

But what about converting only the stab trim to FBW first, possibly the 737-8/9 MAX already ?

Well that’s plausible, but I was responding to a reply that was suggesting that it may be a good idea to keep the 737 and just convert it to 787 flight deck and FBW. That’s a different situation than FBW trim. That’s doable just like the spoilers were doable... since the 1980s
Been on: 732 733 734 73G 738 752 763 A319 A320 A321 CRJ CR7 CRA/CR9 E145 E175 E190 F28 MD-82 MD-83 C172R C172S P2006T PA-28-180

2 ears for spatial hearing, 2 eyes for depth perception, 2 ears for balance... How did Boeing think 1 sensor was good enough?!
 
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 7:39 am

morrisond wrote:
PixelFlight wrote:
767333ER wrote:
To do a full FBW and avionics conversion would change a lot of the plane, the latter readily doing so. In order to convert to a 787 style FBW system all the cables would need to be removed, an extra hydraulic system added, the other two hydraulic systems changed, all the control “computers” changed (including that old hydraulic computer the thing has). Most of that is an undertaking they’ve never had to do before. There could be a chance the TC could stay the same, but then again what about it would be a 737 anymore? The fuselage and maybe the wings? It then becomes nearly as much 737 as the 737 is 707.

But what about converting only the stab trim to FBW first, possibly the 737-8/9 MAX already ?


Or you just train/retrain Pilots to remind them that the manual trim wheel may become ineffective above Vmo and that if Manual trim is needed reduce to normal operating speeds and make sure that the Autothrottle is not engaged at Take Off Go around thrust and if necessary use the rollercoaster maneuver to correct a severe mistrim.

They need to know these procedures anyways if they ever experienced a real trim runaway. However if your view is that that is so unlikely to happen so no need to train for it - then with MCAS V 2.0 the chances of that failing with the changes most likely to be implemented is so unlikely as well no need to train for that either and the Manual trim wheel is not an issue.

Like telling Toyota drivers how to fix their gas pedal rather than just fixing the issue itself. This do this, do that, and if not, perform specific maneuver is not a very good solution. It is asking too much in comparison to other aircraft that are currently flying off assembly lines. There should be some sort of standard of engineering proficiency and risk mitigation in the industry before we rely on taming of human factors and training to cover up the remaining Swiss cheese holes. The 737 MAX lowers the bar of this standard. Training can help, a lot, but it is much farther from being an infallible fix than actually fixing the problem is. Fixing the problem itself will undoubtedly be more effective. Like I always say, if it even were to save one life, it should be done. One human life is worth more than Boeing and their billions. We all get your position and now you are beating a dead horse, especially when inserting in such an opportunistic way almost as a pushy salesperson does completely out of context of our discussion I might add. We were basically talking about how many FBW modifications to the 737 you could realistically do and basically which would be the most important. If we were making commentaries specifically on the trim, the most no brainer way to actually remove the issue is not to add FBW, but to just allow for the auto flight trim modes to be reliably shut off without the motor being disconnected as well. That doesn’t require FBW and anyone making an argument counter to yours knows this.
Been on: 732 733 734 73G 738 752 763 A319 A320 A321 CRJ CR7 CRA/CR9 E145 E175 E190 F28 MD-82 MD-83 C172R C172S P2006T PA-28-180

2 ears for spatial hearing, 2 eyes for depth perception, 2 ears for balance... How did Boeing think 1 sensor was good enough?!
 
Agrajag
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 8:10 am

I am genuinely interest to know from those who regularly defend Boeing on these pages, when do you feel the Max should have been grounded, if at all?
The plural of anecdote is anecdotes, not data.
Slartibartfast had a point
 
benbeny
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 10:01 am

With almost $20B, why didn't Boeing kill this ugly frankenplane back in June, when they knew that this mess will cost a lot?

At least they should slap a new gear, make the pylon longer, and add slides, thus avoiding MCAS requirements?
 
WIederling
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 10:14 am

airhansa wrote:
Image


MCAS does not check on "steeply turning".

prerequisites:
Autopilot inactive
No Flaps.

===>> MCAS active.

single active AOA too high ( right or wrong )

===>> rabid action from MCAS.
Murphy is an optimist
 
airhansa
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 10:28 am

In a situation where the AOA instrument is malfunctioning and MCAS is turned off, would normal manual operation of the aircraft produce an angle-of-attack that could lead to a stall?

If yes then the problem is the structural design of the aircraft.
 
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 11:25 am

airhansa wrote:
In a situation where the AOA instrument is malfunctioning and MCAS is turned off, would normal manual operation of the aircraft produce an angle-of-attack that could lead to a stall?

If yes then the problem is the structural design of the aircraft.

It's an ongoing debate if it really could lead to a stall just because MCAS is disabled. Even the JATR is not conclusive about if the MCAS is a stall protection system:

https://www.skybrary.aero/bookshelf/books/5319.pdf
"Finding F3.5-C: The JATR team considers that the STS/MCAS and EFS
functions could be considered as stall identification systems or stall protection
systems, depending on the natural (unaugmented) stall characteristics of the
aircraft. From its data review, the JATR team was unable to completely rule out
the possibility that these augmentation systems function as a stall protection
system."

Argument for is that the gigantic effort to keep the MCAS should be because there is no way to just replace it by some unknown limitation.
Argument against is that a guy from Canadian regulator proposed to get ride of MCAS and replace it by some unknown limitation.

The real flight characteristic of the 737-8/9 MAX without augmentation is still largely unknown at this time. But as even the new MCAS could be disabled, I see no way how Boeing could avoid pilots training about the limitation of the 737-8/9 MAX flight characteristics without augmentation. We will see...
: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:
 
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 12:15 pm

I've readed so many times about the "heavy engines" of the 737MAX. Just curious: does somebody knows the weight of the CFM's used on the 737NG and weight of the LEAP engines used on the MAX to know really how many more weight is managing the 737MAX and their MCAS?
 
mjoelnir
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 12:21 pm

morrisond wrote:
PixelFlight wrote:
767333ER wrote:
To do a full FBW and avionics conversion would change a lot of the plane, the latter readily doing so. In order to convert to a 787 style FBW system all the cables would need to be removed, an extra hydraulic system added, the other two hydraulic systems changed, all the control “computers” changed (including that old hydraulic computer the thing has). Most of that is an undertaking they’ve never had to do before. There could be a chance the TC could stay the same, but then again what about it would be a 737 anymore? The fuselage and maybe the wings? It then becomes nearly as much 737 as the 737 is 707.

But what about converting only the stab trim to FBW first, possibly the 737-8/9 MAX already ?


Or you just train/retrain Pilots to remind them that the manual trim wheel may become ineffective above Vmo and that if Manual trim is needed reduce to normal operating speeds and make sure that the Autothrottle is not engaged at Take Off Go around thrust and if necessary use the rollercoaster maneuver to correct a severe mistrim.

They need to know these procedures anyways if they ever experienced a real trim runaway. However if your view is that that is so unlikely to happen so no need to train for it - then with MCAS V 2.0 the chances of that failing with the changes most likely to be implemented is so unlikely as well no need to train for that either and the Manual trim wheel is not an issue.


Or just fix that bloody trim wheel. Why flying around with something that is know that it really does not work since at least the 737 jurassic.

No reason to use substandard technology in a frame Boeing wants to be second most sold passenger aircraft in the world.

The list of exemptions to safety rules for the 737 is quite impressive. The answer by Boeing seems to be in most cases, it is expensive to fix.

Pay a little less to share holders and design frames, that do not fall out of the sky, would be a good start.
 
namezero111111
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 12:45 pm

Byron1976 wrote:
I've readed so many times about the "heavy engines" of the 737MAX. Just curious: does somebody knows the weight of the CFM's used on the 737NG and weight of the LEAP engines used on the MAX to know really how many more weight is managing the 737MAX and their MCAS?


Yes, someone knows for sure.
 
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glideslope
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 1:17 pm

planecane wrote:
airhansa wrote:
MCAS, when operating properly, does not "force the plane to dive." In introduces a mis-trim to cause it to take more force to lift the nose more. MCAS, operating properly, would never have caused a plane to dive or even for a pilot to notice it existed. The issue with MCAS was the botched fault tree analysis and allowing a single sensor failure to cause a potentially catastrophic runaway.

The need for and inclusion of MCAS is not the issue. Especially since it is only need for edge cases that aren't entered into very often, if at all, in normal service. As long as MCAS is fixed to only operate when and how it was originally intended, there is no issue with it.

STS on the NG is doing something similar. It just didn't have the authority and lack of a simple cutout (the column switches for STS) to cause a problem. Actually, STS activates in normal operation all the time so it is far more active than a properly functioning MCAS would ever be.


Correct. The Max is not an inherently unstable design. It was the implementation of MCAS with poorly written code from outsourcing, lack of training, lack of communication with pilots and companies, and Boeings unwillingness to to own up and fix things. Personally I don't see how the Max can fly again if MCAS is retained without a new Type Rating. The Max simply flys different enough from an NG to warrant this.

I'm starting to agree however that it is approaching the point where Boeing may need to think about cutting the program, ask for some Govt. assistance as other companies do ( :box: ) and design a new NB. It's the only way to truly recover from this.
To know your Enemy, you must become your Enemy.” Sun Tzu
 
dtw2hyd
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 1:28 pm

Byron1976 wrote:
I've readed so many times about the "heavy engines" of the 737MAX. Just curious: does somebody knows the weight of the CFM's used on the 737NG and weight of the LEAP engines used on the MAX to know really how many more weight is managing the 737MAX and their MCAS?


There are some good informative posts somewhere in this thread of distortion, you have to browse through. It appears the bigger diameter nacelle completely changed the airflow.

MAX project in layman terms
    Boeing and engine maker were working on building a perfect engine.
    Airbus showed its NEO.
    Boeing scrambled and strapped on bigger engines.
    Engineers started patching issue after issue as they appeared
    Meanwhile management kept switching to bottom dollar suppliers
    Engineers kept on patching
    By 2017 speed tape was holding enough to enter service.
    2018 speed tape peeled off.
Here we are
All posts are just opinions.
 
phollingsworth
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 1:46 pm

par13del wrote:
flipdewaf wrote:
Agreed, max specific training would probably go along way to helping bring it more in line with the safety record of other aircraft.
Fred
Sent from my iPhone using Tapatalk

Unfortunately, it is taking the FAA, EASA and the JTAR participants forever and a day to come up with what they want that training to be.....and since they included dual computer use the training just got MAX specific, will be interesting to see what they come up with.


They won't be able to sign-off with the final training requirement until the design authorisation side of things signs off on the changes. The reason for this is that while the changes are in flux there is a possibility that it will trigger significant changes in the training requirements. Remember, it is Boeing that proposes the training regime and the regulators sign off on it. Of course in consultation they may indicated that a given level will be unacceptable. However, they cannot really say anything definitive until they are ask specifically.

As for MAX specific. Yes, the training will be MAX specific in that pilots who have flown the NG will need additional training to fly the MAX. The real question is will this additional training be back compatible with the NG or will it required ongoing differences. For example, the removal of the aft column cutout requires changes to training for dealing with a nose-down trim runaway. If pilots can respond quickly enough to the runaway and only use the trim switches in all cases, then both MAX and NG training could be the same, if that didn't work for the NG, then a continuous difference would have to be maintained. Without know the exact changes, how they present, and how both the aircraft and crews react it is hard to know on which side of the line things will fall.
 
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 1:56 pm

767333ER wrote:
morrisond wrote:
PixelFlight wrote:
But what about converting only the stab trim to FBW first, possibly the 737-8/9 MAX already ?


Or you just train/retrain Pilots to remind them that the manual trim wheel may become ineffective above Vmo and that if Manual trim is needed reduce to normal operating speeds and make sure that the Autothrottle is not engaged at Take Off Go around thrust and if necessary use the rollercoaster maneuver to correct a severe mistrim.

They need to know these procedures anyways if they ever experienced a real trim runaway. However if your view is that that is so unlikely to happen so no need to train for it - then with MCAS V 2.0 the chances of that failing with the changes most likely to be implemented is so unlikely as well no need to train for that either and the Manual trim wheel is not an issue.

Like telling Toyota drivers how to fix their gas pedal rather than just fixing the issue itself. This do this, do that, and if not, perform specific maneuver is not a very good solution. It is asking too much in comparison to other aircraft that are currently flying off assembly lines. There should be some sort of standard of engineering proficiency and risk mitigation in the industry before we rely on taming of human factors and training to cover up the remaining Swiss cheese holes. The 737 MAX lowers the bar of this standard. Training can help, a lot, but it is much farther from being an infallible fix than actually fixing the problem is. Fixing the problem itself will undoubtedly be more effective. Like I always say, if it even were to save one life, it should be done. One human life is worth more than Boeing and their billions. We all get your position and now you are beating a dead horse, especially when inserting in such an opportunistic way almost as a pushy salesperson does completely out of context of our discussion I might add. We were basically talking about how many FBW modifications to the 737 you could realistically do and basically which would be the most important. If we were making commentaries specifically on the trim, the most no brainer way to actually remove the issue is not to add FBW, but to just allow for the auto flight trim modes to be reliably shut off without the motor being disconnected as well. That doesn’t require FBW and anyone making an argument counter to yours knows this.


Three things.

Runaway Trim NNC is basically common to all aircraft types and the ability to run this should not be considered abnormal or requiring test pilot skills. This is why I keep beating a dead horse as this is not MAX specific.

Second, the odds of converting the MAX to FBW or adding an additional system are about O - it would be a lot easier just to train the pilots.

Third - I agree with you - it's asinine if they don't go back to the NG trim switch configuration where they can defeat all the auto nannies and still have electric trim available. That may be one of the upshots of Boeing finally agreeing to training. As there could be differences training on the MAX so I believe this would be an acceptable solution again.

However on the above even if you still have electric trim available it may have not made a difference on the ET flight as even it may not be effective in all corners of the envelope or beyond the normal envelope - which is normal. So you still have to know that leaving Autothrottle engaged at TOGA thrust is a bad idea.

One of the theories on why ET did not bring the plane back into trim when they turned the electric trim back on is that it caused violent effects on the frame and in the cabin due to the excessive high speed - basically trying to throw the pilots to the ceiling and hence why they only used it briefly twice.

It could have made a difference earlier in the flight right after first and second MCAS activation before they exceeded Vmo - but then they still had electric trim available and could have simply returned it to in-trim before turning it off - just like there Company procedures told them to do so. As far as we know it still worked and as evidenced later in the flight it still did when they turned it back on.

It may have not made a difference on ET unfortunately .
 
Rustbelt
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 2:01 pm

Air Lease is saying "damaged" MAX brand should be dropped. This is echoing some of the posters here as well as president Trump suggesting Boeing to rebrand MAX.
https://www.yahoo.com/finance/news/boei ... 11028.html
 
dtw2hyd
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 2:03 pm

morrisond wrote:
Runaway Trim NNC is basically common to all aircraft types and the ability to run this should not be considered abnormal or requiring test pilot skills.


This is 2100th time we are reading this, yet no one is buying it. I wonder why?
All posts are just opinions.
 
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Byron1976
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 2:13 pm

dtw2hyd wrote:
Byron1976 wrote:
I've readed so many times about the "heavy engines" of the 737MAX. Just curious: does somebody knows the weight of the CFM's used on the 737NG and weight of the LEAP engines used on the MAX to know really how many more weight is managing the 737MAX and their MCAS?


There are some good informative posts somewhere in this thread of distortion, you have to browse through. It appears the bigger diameter nacelle completely changed the airflow.



Thanks for the suggestion, I've done a search on this thread, and no figures were found about the weight of the engines.
I know that aerodynamically bigger engines will make some influences on the behaviour or the airflow of any plane, but I was asking for weight figures, because I've readed so many times about the "heavy engines", that I wanted to know how heavier are these new engines to know how much is the difference that makes to be called "heavy engines".
 
Agrajag
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 2:14 pm

morrisond wrote:
767333ER wrote:
morrisond wrote:

Or you just train/retrain Pilots to remind them that the manual trim wheel may become ineffective above Vmo and that if Manual trim is needed reduce to normal operating speeds and make sure that the Autothrottle is not engaged at Take Off Go around thrust and if necessary use the rollercoaster maneuver to correct a severe mistrim.

They need to know these procedures anyways if they ever experienced a real trim runaway. However if your view is that that is so unlikely to happen so no need to train for it - then with MCAS V 2.0 the chances of that failing with the changes most likely to be implemented is so unlikely as well no need to train for that either and the Manual trim wheel is not an issue.

Like telling Toyota drivers how to fix their gas pedal rather than just fixing the issue itself. This do this, do that, and if not, perform specific maneuver is not a very good solution. It is asking too much in comparison to other aircraft that are currently flying off assembly lines. There should be some sort of standard of engineering proficiency and risk mitigation in the industry before we rely on taming of human factors and training to cover up the remaining Swiss cheese holes. The 737 MAX lowers the bar of this standard. Training can help, a lot, but it is much farther from being an infallible fix than actually fixing the problem is. Fixing the problem itself will undoubtedly be more effective. Like I always say, if it even were to save one life, it should be done. One human life is worth more than Boeing and their billions. We all get your position and now you are beating a dead horse, especially when inserting in such an opportunistic way almost as a pushy salesperson does completely out of context of our discussion I might add. We were basically talking about how many FBW modifications to the 737 you could realistically do and basically which would be the most important. If we were making commentaries specifically on the trim, the most no brainer way to actually remove the issue is not to add FBW, but to just allow for the auto flight trim modes to be reliably shut off without the motor being disconnected as well. That doesn’t require FBW and anyone making an argument counter to yours knows this.


Three things.

Runaway Trim NNC is basically common to all aircraft types and the ability to run this should not be considered abnormal or requiring test pilot skills. This is why I keep beating a dead horse as this is not MAX specific.

Second, the odds of converting the MAX to FBW or adding an additional system are about O - it would be a lot easier just to train the pilots.

Third - I agree with you - it's asinine if they don't go back to the NG trim switch configuration where they can defeat all the auto nannies and still have electric trim available. That may be one of the upshots of Boeing finally agreeing to training. As there could be differences training on the MAX so I believe this would be an acceptable solution again.

However on the above even if you still have electric trim available it may have not made a difference on the ET flight as even it may not be effective in all corners of the envelope or beyond the normal envelope - which is normal. So you still have to know that leaving Autothrottle engaged at TOGA thrust is a bad idea.

One of the theories on why ET did not bring the plane back into trim when they turned the electric trim back on is that it caused violent effects on the frame and in the cabin due to the excessive high speed - basically trying to throw the pilots to the ceiling and hence why they only used it briefly twice.

It could have made a difference earlier in the flight right after first and second MCAS activation before they exceeded Vmo - but then they still had electric trim available and could have simply returned it to in-trim before turning it off - just like there Company procedures told them to do so. As far as we know it still worked and as evidenced later in the flight it still did when they turned it back on.

It may have not made a difference on ET unfortunately .



Out of interest, in your view, when should the Max have been grounded, if at all?
The plural of anecdote is anecdotes, not data.
Slartibartfast had a point
 
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Revelation
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 2:16 pm

benbeny wrote:
With almost $20B, why didn't Boeing kill this ugly frankenplane back in June, when they knew that this mess will cost a lot?

Because they have billions of dollars invested in all the MAXes they've already built, not to mention all the investments they and their partners have made, nor all the commitments they've made to customers. In short killing the plane causes more problems than it solves and costs even more money than fixing the planes they've built and restarting production.

benbeny wrote:
At least they should slap a new gear, make the pylon longer, and add slides, thus avoiding MCAS requirements?

That would make it an all new type of airplane, which is the opposite of what their goals were with MAX.
Last edited by Revelation on Tue Jan 21, 2020 2:17 pm, edited 1 time in total.
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dtw2hyd
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 2:20 pm

Byron1976 wrote:
but I was asking for weight figures, because I've readed so many times about the "heavy engines", that I wanted to know how heavier are these new engines to know how much is the difference that makes to be called "heavy engines".


From Wiki

CFM56-7 - 5,216 lb
LEAP-1B - 6,130 lb
All posts are just opinions.
 
phollingsworth
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 2:48 pm

PixelFlight wrote:
airhansa wrote:
In a situation where the AOA instrument is malfunctioning and MCAS is turned off, would normal manual operation of the aircraft produce an angle-of-attack that could lead to a stall?

If yes then the problem is the structural design of the aircraft.

It's an ongoing debate if it really could lead to a stall just because MCAS is disabled. Even the JATR is not conclusive about if the MCAS is a stall protection system:

https://www.skybrary.aero/bookshelf/books/5319.pdf
"Finding F3.5-C: The JATR team considers that the STS/MCAS and EFS
functions could be considered as stall identification systems or stall protection
systems, depending on the natural (unaugmented) stall characteristics of the
aircraft. From its data review, the JATR team was unable to completely rule out
the possibility that these augmentation systems function as a stall protection
system."

Argument for is that the gigantic effort to keep the MCAS should be because there is no way to just replace it by some unknown limitation.
Argument against is that a guy from Canadian regulator proposed to get ride of MCAS and replace it by some unknown limitation.

The real flight characteristic of the 737-8/9 MAX without augmentation is still largely unknown at this time. But as even the new MCAS could be disabled, I see no way how Boeing could avoid pilots training about the limitation of the 737-8/9 MAX flight characteristics without augmentation. We will see...


It all depends on where the 'bad things' happen when MCAS is unavailable. In the case of the NG the use of 'super' STS for stall ID isn't a big deal for the cases where the aircraft is dispatched with only 1 of 2 AoA sensors, or Speed trim systems working. This is because the FAA doesn't view STS in the stall ID roll as critical and that the flight crew can rapidly ID a failure, compensate, and either switch to the alternate STS system or disable it. For EASA stall ID augmentation is critical to certification, but it is allowed to fail in flight as long as the rate is below a threshold a given threshold, for Major 1E-5 per hour. Keep in mind the FAA views that aircraft will only be operated between stall warning and stall roughly 1E-5 per flight hour. If MCAS is used to avoid a stall because of stall or post stall behaviours, then it becomes much more critical. In this case if the 737MAX does not exhibit low speed buffet and the stall warning system were out it could be a hazardous to catastrophic condition. EASA will want to see what the aircraft flies like as it approaches stall to decide for themselves which of the above it is. Hence the no MCAS flight ask.
 
mcdu
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 3:24 pm

kalvado wrote:
airhansa wrote:
planecane wrote:

MCAS, when operating properly, does not "force the plane to dive." In introduces a mis-trim to cause it to take more force to lift the nose more. MCAS, operating properly, would never have caused a plane to dive or even for a pilot to notice it existed. The issue with MCAS was the botched fault tree analysis and allowing a single sensor failure to cause a potentially catastrophic runaway.

The need for and inclusion of MCAS is not the issue. Especially since it is only need for edge cases that aren't entered into very often, if at all, in normal service. As long as MCAS is fixed to only operate when and how it was originally intended, there is no issue with it.

STS on the NG is doing something similar. It just didn't have the authority and lack of a simple cutout (the column switches for STS) to cause a problem. Actually, STS activates in normal operation all the time so it is far more active than a properly functioning MCAS would ever be.


MCAS uses the horizontal fins to essentially push the plane nose down, with the idea being that the heavy engines cause the plane to fly at an angle-of-attack which could cause the plane to stall. MCAS essentially acts as a stall prevention system and in error situations it can push the nose down into a dive.

It would not be needed if the engines were reduced in size, or if Boeing had opted to redesign the plane. The autopilot is completely off when MCAS activates, but in fact the pilot should be the one controlling the horizontal fins and taking care about the angle-of-attack in manual mode. This is basically a plane that can't aerodynamically fly in a normal way.

Great. Now add the fact that MCAS activates at high AoA situations only. Some say MCAS happens only after stick shaker - aka warning that you're about to crash - is turned on.


The stick shaker is not a "about to crash" warning. Stick shakers activate to alert pilots to the possibility of entering a stall if the AOA is not reduced.
 
phollingsworth
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 4:08 pm

glideslope wrote:
planecane wrote:
airhansa wrote:
MCAS, when operating properly, does not "force the plane to dive." In introduces a mis-trim to cause it to take more force to lift the nose more. MCAS, operating properly, would never have caused a plane to dive or even for a pilot to notice it existed. The issue with MCAS was the botched fault tree analysis and allowing a single sensor failure to cause a potentially catastrophic runaway.

The need for and inclusion of MCAS is not the issue. Especially since it is only need for edge cases that aren't entered into very often, if at all, in normal service. As long as MCAS is fixed to only operate when and how it was originally intended, there is no issue with it.

STS on the NG is doing something similar. It just didn't have the authority and lack of a simple cutout (the column switches for STS) to cause a problem. Actually, STS activates in normal operation all the time so it is far more active than a properly functioning MCAS would ever be.


Correct. The Max is not an inherently unstable design. It was the implementation of MCAS with poorly written code from outsourcing, lack of training, lack of communication with pilots and companies, and Boeings unwillingness to to own up and fix things. Personally I don't see how the Max can fly again if MCAS is retained without a new Type Rating. The Max simply flys different enough from an NG to warrant this.

I'm starting to agree however that it is approaching the point where Boeing may need to think about cutting the program, ask for some Govt. assistance as other companies do ( :box: ) and design a new NB. It's the only way to truly recover from this.


Except that all the evidence says that for the Normal and Operating flight envelope the MAX flies substantially the same as the NG. AS Planecane points out the NG, at the behest of the JAA (now EASA), has an AoA driven function in the Speed Trim System to force the aircraft nose-down in certain situations. This looks to operate in a continuous fashion driving the stab to the limits at a constant rate. Further, the Elevator feel mechanism is designed to make it quite hard for the pilot to reach the aft-cutout limit. This is systems is provided by two simplex systems in an active-monitor setting with a warning light if active disagrees with monitor. Note this disagree activated in the MTC log on the two JT flights, but for some reason the indicators in the cockpit didn't work.

MCAS in its original incarnation was to add manoeuvre stability (stick force per g), as such you don't want the elevator feel mechanism making it impossible to pull back as this makes the aircraft less/un-manoueverable. So Boeing disabled the aft column cutout. However, when Boeing moved it to the 1g case with the increased rates. The fact is that the rates for MCAS are the same as those in the flaps down condition. So what is the problem.
1. Boeing removed the aft-column cutout from the 1g STS/MCAS case. Given that the authority is faster and has a greater range this will delay countering and put the aircraft into a more severe miss-trim.
2. Boeing converted the continuous STS/AoA run to a cyclical one, further delaying the ID.

My guess is the higher rate and range have to do with the fact that the stall is even less identifiable in the MAX compared to the NG. There will be less buffet and the aircraft will have less nose-down tendency. Note: stab trim does not fix the control force issue, it makes it somewhat worse. This is done by the elevator feel system. The problem here is this seems to be solely driven the airspeed. So reasonable for column force to airspeed stability, but no good for column force to AoA stability near stall (this isn't required for anything other than stall ID).
 
phollingsworth
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 4:11 pm

Revelation wrote:
benbeny wrote:
With almost $20B, why didn't Boeing kill this ugly frankenplane back in June, when they knew that this mess will cost a lot?

Because they have billions of dollars invested in all the MAXes they've already built, not to mention all the investments they and their partners have made, nor all the commitments they've made to customers. In short killing the plane causes more problems than it solves and costs even more money than fixing the planes they've built and restarting production.

benbeny wrote:
At least they should slap a new gear, make the pylon longer, and add slides, thus avoiding MCAS requirements?

That would make it an all new type of airplane, which is the opposite of what their goals were with MAX.


Further, if all your did was make the gear longer and adjusted the pylons you wouldn't necessarily avoid the situations that brought MCAS about. The fact is they exist on all swept wing aircraft, and the greater the interaction between the nacelle and wing at high AoA the greater the need. The A300/A310 has an MCAS equivalent and so does the 767-2C, both have relatively smaller engines further away from the wing.
 
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seahawk
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 4:40 pm

Add the non functional AoA disagree warning to the list of reasons.
 
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767333ER
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 4:42 pm

morrisond wrote:
767333ER wrote:
morrisond wrote:

Or you just train/retrain Pilots to remind them that the manual trim wheel may become ineffective above Vmo and that if Manual trim is needed reduce to normal operating speeds and make sure that the Autothrottle is not engaged at Take Off Go around thrust and if necessary use the rollercoaster maneuver to correct a severe mistrim.

They need to know these procedures anyways if they ever experienced a real trim runaway. However if your view is that that is so unlikely to happen so no need to train for it - then with MCAS V 2.0 the chances of that failing with the changes most likely to be implemented is so unlikely as well no need to train for that either and the Manual trim wheel is not an issue.

Like telling Toyota drivers how to fix their gas pedal rather than just fixing the issue itself. This do this, do that, and if not, perform specific maneuver is not a very good solution. It is asking too much in comparison to other aircraft that are currently flying off assembly lines. There should be some sort of standard of engineering proficiency and risk mitigation in the industry before we rely on taming of human factors and training to cover up the remaining Swiss cheese holes. The 737 MAX lowers the bar of this standard. Training can help, a lot, but it is much farther from being an infallible fix than actually fixing the problem is. Fixing the problem itself will undoubtedly be more effective. Like I always say, if it even were to save one life, it should be done. One human life is worth more than Boeing and their billions. We all get your position and now you are beating a dead horse, especially when inserting in such an opportunistic way almost as a pushy salesperson does completely out of context of our discussion I might add. We were basically talking about how many FBW modifications to the 737 you could realistically do and basically which would be the most important. If we were making commentaries specifically on the trim, the most no brainer way to actually remove the issue is not to add FBW, but to just allow for the auto flight trim modes to be reliably shut off without the motor being disconnected as well. That doesn’t require FBW and anyone making an argument counter to yours knows this.


Three things.

Runaway Trim NNC is basically common to all aircraft types and the ability to run this should not be considered abnormal or requiring test pilot skills. This is why I keep beating a dead horse as this is not MAX specific.

Second, the odds of converting the MAX to FBW or adding an additional system are about O - it would be a lot easier just to train the pilots.

Third - I agree with you - it's asinine if they don't go back to the NG trim switch configuration where they can defeat all the auto nannies and still have electric trim available. That may be one of the upshots of Boeing finally agreeing to training. As there could be differences training on the MAX so I believe this would be an acceptable solution again.

However on the above even if you still have electric trim available it may have not made a difference on the ET flight as even it may not be effective in all corners of the envelope or beyond the normal envelope - which is normal. So you still have to know that leaving Autothrottle engaged at TOGA thrust is a bad idea.

One of the theories on why ET did not bring the plane back into trim when they turned the electric trim back on is that it caused violent effects on the frame and in the cabin due to the excessive high speed - basically trying to throw the pilots to the ceiling and hence why they only used it briefly twice.

It could have made a difference earlier in the flight right after first and second MCAS activation before they exceeded Vmo - but then they still had electric trim available and could have simply returned it to in-trim before turning it off - just like there Company procedures told them to do so. As far as we know it still worked and as evidenced later in the flight it still did when they turned it back on.

It may have not made a difference on ET unfortunately .

But it’s Boeing’s asininity before it’s the pilots screwing up. Fix the problem itself rather then bandaid it to allow them to get away with saving money. I do not wish to discuss what the crew did with this or that, we’ve heard it so many times already. The point is we weren’t even talking about whose fault is what and you still jump in out of nowhere blaming the crew for getting into a position where they couldn’t trim. That was not relevant to put chain of discussion. I try to avoid the blame game now because I’ve had enough and yet I get dragged into it again!
Been on: 732 733 734 73G 738 752 763 A319 A320 A321 CRJ CR7 CRA/CR9 E145 E175 E190 F28 MD-82 MD-83 C172R C172S P2006T PA-28-180

2 ears for spatial hearing, 2 eyes for depth perception, 2 ears for balance... How did Boeing think 1 sensor was good enough?!
 
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767333ER
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 4:43 pm

mjoelnir wrote:
Or just fix that bloody trim wheel. Why flying around with something that is know that it really does not work since at least the 737 jurassic.

No reason to use substandard technology in a frame Boeing wants to be second most sold passenger aircraft in the world.

The list of exemptions to safety rules for the 737 is quite impressive. The answer by Boeing seems to be in most cases, it is expensive to fix.

Pay a little less to share holders and design frames, that do not fall out of the sky, would be a good start.

When their billions are worth more than people’s lives...
Been on: 732 733 734 73G 738 752 763 A319 A320 A321 CRJ CR7 CRA/CR9 E145 E175 E190 F28 MD-82 MD-83 C172R C172S P2006T PA-28-180

2 ears for spatial hearing, 2 eyes for depth perception, 2 ears for balance... How did Boeing think 1 sensor was good enough?!
 
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PixelFlight
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 5:11 pm

phollingsworth wrote:
Further, if all your did was make the gear longer and adjusted the pylons you wouldn't necessarily avoid the situations that brought MCAS about. The fact is they exist on all swept wing aircraft, and the greater the interaction between the nacelle and wing at high AoA the greater the need. The A300/A310 has an MCAS equivalent and so does the 767-2C, both have relatively smaller engines further away from the wing.

Yes, the A300 and A310 have a Trimmable Horizontal Stabilizer (THS) controlled by two Flight Augmentation Computers (FAC), See page 72 of that document:
https://fr.scribd.com/doc/287051238/Airbus-27-A300-A310-Flight-Controls

But even in the A300 and A310, this was already a properly redundant system with 3 AoA sensors, 2 FACs, 2 electrical trim motors actuators + manual trim wheel backup, and 2 hydraulic power sources. The design was relatively good but suffered at the beginning from not disconnecting the AP on the THS in case of conflicting pilot action on the elevator. This was an identified problem with a software update available. Unfortunately, not installing the update soon enough caused China Airlines Flight 140 crash: https://en.wikipedia.org/wiki/China_Airlines_Flight_140
: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:
 
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par13del
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 5:14 pm

phollingsworth wrote:
Remember, it is Boeing that proposes the training regime and the regulators sign off on it.

It is thus no longer....

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