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Ed 737 Max Crashes (was Shutdown caused Boeing crash.)

JoeMorgue said:
Of American based airlines:

Alaska Air has 32 on order, but is not currently flying any.
American Airlines has 100 on order, has 22 in its fleet.
Ryan Air has 135 on order, but is not currently flying any.Southwest has 280 on order, has 31 in its fleet.
United has 136 on order, has 14 in its fleet.
2 have been delivered to individuals/companies for use as personal or corporate jets. I assume they would be affected by the grounding.

I cannot find any carrier world wide that is flying only the 737 Max (some small budget carriers only fly one make/model of plane to keep costs down.)
Click to expand...

Ryan Air is an Irish airline.
 
I came across this speculation by a friend and fellow pilot, that I found well-informed and I thought I’d share.

***Warning contains my own uninformed speculation... I am posting it ONLY to see if people agree or disagree... ***

It seems clear to me that a chain of well known information could give us a possible explanation and the reasons for the recent 737 max 8 crashes.

Overall its the problem of adding envelope protection and automation to an older Boeing aircraft design that, unlike Airbus, was never designed for fly by wire automation, and an addition that is against the normal design philosophy of the manufacturer - - - Boeing.

Airbus has had fly by wire and computer based flight controls designed in from the begining, Boeing however have never before really embraced this idea.

While the lunar module and many agile fighter jets would be unstable without fly by wire, Boeing have normally designed aircraft that fly 'naturally'..

This can be seen clearly in the design of the pilot interface to the aircraft, a big old fashioned yoke in the Boeing and a small side stick like a games controller in the Airbus and the Apollo era lunar module.... .

But here's the problem, when Boeing added bigger engines and other changes like fuselage length to the 737-max series they upset the natural flight characteristics, engines needed to be more forward in a different position, and had more thrust. I heard Boeing found this affected control, badly, at some edges of the flight envelope including the full power stall characteristics of the aircraft.

Pilots who practice full power stalls know they are scary at the best of times. This aircraft was apparantly even more scary, so much so that it could probably not have been certified.

So automation shy Boeing were forced to depend on Airbus style software protection to prevent these edges of the flight envelope ever being reached.

Hense the MCAS system was born, an override that would automatically forward trim the aircraft at high angles of attack approaching the stall in this configuration, flaps up full power, ( you know like the climb phase close to the ground just after take off) to eliminate the possibility of the stall...

Trouble is, the airframe was designed years ago. The trim on the 737 trims the angle of the WHOLE tail stabiliser.... not just the elevators. Yes that 'wing at the back' actually changes its position relative to the fusalage... its whole angle.... this is actually a very powerful, coarse control input in the wrong hands.... .. the pilot controlled elevator for pitch control at the back is only part of this whole flying surface... so I imagine that trim can, at full defection, be a stronger force than elevator input.

So a faulty angle of attack sensor could trigger this forward stabiliser trim if it detects a phantom stall... . Boeing say this is what happened in the first lion Air crash... a faulty sensor.. but they blamed pilot training... really?

So what actually happens? Well every 10 seconds or so, unless the whole trim system is disabled, the MCAS forces the nose down using this very powerful stabiliser trim, to avoid the phantom stall.

You can imagine a pilot fighting this in two ways, pulling back on that big yoke, and trimming backwards to reverse the false input, but every time he does the system kicks in again and undoes his fixes... there are two additional problems the poor pilot faces... .

Firstly because the aircraft thinks its stalling it starts shaking this yoke. imagine pulling to save your life on a yoke that is shaking, it's like the aircraft is disobeying wanting to nose down and still want you to fight it. But hang on... secondarily the Yoke has an artifical feedback system designed to give flying the plane a more natural 'feel' for pilots. This system can make the controls feel stiffer at high speed for example and looser at low speed, even though, like the steering wheel of a car the controls are power assisted.... in a stall guess what? this artificial feedback system kicks in to make it very hard to pull back on the yoke... its stiffens as if to say 'don't do that'...

So we have runaway trim, moving the whole rear stabiliser into a dangerous nose down flight position... possibly faster that the pilot can fix it, a shaking stick, and a yoke that actively resists pilot input to pull back! Even if the pilots disconnected the trim system (as per Boeing 'fix'...) its likely to be left in a nose heavy trim position... which takes time to fix...

Then the poor pilot has to try and pull up, using a small (relatively speaking) elevator, against a stiff, artificially resistant pressure on the yoke, possibly with a shaking stick.... all close to the ground?

I can imagine easily how a runaway nose down trim, resistant and shaking controls and nose down path of the aircraft could quick result in loss of control, and ground impact, whatever the pilot did. Too little time to fight the disobedient aircraft..

To avoid it I guess they would need to very quickly identify what is happening (how can they when the problem has never been practiced?) disconnect the auto trim, manually fix the trim position quick enough to regain elevator authority, all while the stick is shaking and refusing or resisting to be pulled back?

I think this must qualify as a design flaw, that results on trying to add automation and envelope protection onto an aircraft concept and pilot interface where so many other design decisions have assumed automation is not present.

Thank goodness they have grounded the aircraft. Finally. But what can Boeing do to fix it? I suggest replacing MCAS with a good old fashioned Stall Warning horn, and let the pilots fly.. put a placard on the console saying 'Full power stalls prohibited'.. what else can they do?

Discuss?

Attribution: http://about.me/ianvalentine
 
https://www.nytimes.com/2019/03/19/podcasts/the-daily/boeing-737-max-ethiopia-crash.html

Short version is that this plane was made to compete with a similar sized Airbus plane, which is more fuel-efficient than earlier models of the 737. The selling point was that pilots who already know how to fly the 737 won't need any retraining or flight simulator time. They even decided that pilots didn't need to know about the new MCAS system, so when they ran into problems, the pilots didn't even know that the system existed or that it was what was causing the problem.
 
Pilot Who Hitched a Ride Saved Lion Air 737 Day Before Deadly Crash

"As the Lion Air crew fought to control their diving Boeing Co. 737 Max 8, they got help from an unexpected source: an off-duty pilot who happened to be riding in the cockpit.

That extra pilot, who was seated in the cockpit jumpseat, correctly diagnosed the problem and told the crew how to disable a malfunctioning flight-control system and save the plane, according to two people familiar with Indonesia’s investigation.

The next day, under command of a different crew facing what investigators said was an identical malfunction, the jetliner crashed into the Java Sea killing all 189 aboard."​

Doesn't look good for Lion Air.
 
Doesn't look good for Boeing either. An extra pilot who didn't have his hands full during a busy part of the flight just after takeoff was able to sit back and diagnose the root cause of the problem and the solution.
 
Fast Eddie B said:
I came across this speculation by a friend and fellow pilot, that I found well-informed and I thought I’d share.

***Warning contains my own uninformed speculation... I am posting it ONLY to see if people agree or disagree... ***




So automation shy Boeing were forced to depend on Airbus style software protection to prevent these edges of the flight envelope ever being reached.

Hense the MCAS system was born, an override that would automatically forward trim the aircraft at high angles of attack approaching the stall in this configuration, flaps up full power, ( you know like the climb phase close to the ground just after take off) to eliminate the possibility of the stall...

Trouble is, the airframe was designed years ago. The trim on the 737 trims the angle of the WHOLE tail stabiliser.... not just the elevators. Yes that 'wing at the back' actually changes its position relative to the fusalage... its whole angle.... this is actually a very powerful, coarse control input in the wrong hands.... .. the pilot controlled elevator for pitch control at the back is only part of this whole flying surface... so I imagine that trim can, at full defection, be a stronger force than elevator input.

So a faulty angle of attack sensor could trigger this forward stabiliser trim if it detects a phantom stall... . Boeing say this is what happened in the first lion Air crash... a faulty sensor.. but they blamed pilot training... really?

So what actually happens? Well every 10 seconds or so, unless the whole trim system is disabled, the MCAS forces the nose down using this very powerful stabiliser trim, to avoid the phantom stall.

You can imagine a pilot fighting this in two ways, pulling back on that big yoke, and trimming backwards to reverse the false input, but every time he does the system kicks in again and undoes his fixes... there are two additional problems the poor pilot faces... .

Firstly because the aircraft thinks its stalling it starts shaking this yoke. imagine pulling to save your life on a yoke that is shaking, it's like the aircraft is disobeying wanting to nose down and still want you to fight it. But hang on... secondarily the Yoke has an artifical feedback system designed to give flying the plane a more natural 'feel' for pilots. This system can make the controls feel stiffer at high speed for example and looser at low speed, even though, like the steering wheel of a car the controls are power assisted.... in a stall guess what? this artificial feedback system kicks in to make it very hard to pull back on the yoke... its stiffens as if to say 'don't do that'...

So we have runaway trim, moving the whole rear stabiliser into a dangerous nose down flight position... possibly faster that the pilot can fix it, a shaking stick, and a yoke that actively resists pilot input to pull back! Even if the pilots disconnected the trim system (as per Boeing 'fix'...) its likely to be left in a nose heavy trim position... which takes time to fix...

Then the poor pilot has to try and pull up, using a small (relatively speaking) elevator, against a stiff, artificially resistant pressure on the yoke, possibly with a shaking stick.... all close to the ground?

I can imagine easily how a runaway nose down trim, resistant and shaking controls and nose down path of the aircraft could quick result in loss of control, and ground impact, whatever the pilot did. Too little time to fight the disobedient aircraft..

To avoid it I guess they would need to very quickly identify what is happening (how can they when the problem has never been practiced?) disconnect the auto trim, manually fix the trim position quick enough to regain elevator authority, all while the stick is shaking and refusing or resisting to be pulled back?

I think this must qualify as a design flaw, that results on trying to add automation and envelope protection onto an aircraft concept and pilot interface where so many other design decisions have assumed automation is not present.

Thank goodness they have grounded the aircraft. Finally. But what can Boeing do to fix it? I suggest replacing MCAS with a good old fashioned Stall Warning horn, and let the pilots fly.. put a placard on the console saying 'Full power stalls prohibited'.. what else can they do?

Discuss?

Attribution: http://about.me/ianvalentine
Click to expand...

All airliners use that type of trim system by rotating the horizontal stabiliser up and down.

All modern Boeing airliners are fly by wire, even though they retain the yoke. The difference to Airbus fbw is that Boeing still gives the pilots more direct control of the plane, they can fly it into a stall of they really want. They yoke gives simulated force feedback while the sidestick doesn't.

MCAS does break with historic Boeing design philosophy in that it will help to prevent a stall by dropping the nose by moving the horizontal stabiliser. It does this so that the force on the control column will stay the same. Otherwise the effect of the engines at near full power at an unstable balance point makes the pilot feel a control column that is counterintuitively feeling lighter even though the plane is about to stall.

It's all a mess and there is no elegance of a design philosophy there, just an ugly hack. And not just an ugly hack, but one that has been done badly.
 
a_unique_person said:
Doesn't look good for Boeing either. An extra pilot who didn't have his hands full during a busy part of the flight just after takeoff was able to sit back and diagnose the root cause of the problem and the solution.
Click to expand...

I wonder if the pilots who saved that plane made any effort or had any mechanism to communicate their experience to the other Lion pilots: "Hey, we almost died! If the plane does this, flips these switches quick!"
 
smartcooky said:
Oh, I agree.

The point I'm making is that, if it was a faulty MCAS (which is starting to look more and more likely*) then the problem could have been overcome by disabling it (there is no way to actually turn the MCAS off).

There are two possible ways to do that (well three actually, but I won't go into the third as it gets complicated)

1. Lower the flaps to Flaps 1. MCAS is supposed to only be enabled with the flaps in the fully retracted position.

2. Turn the Stab Trim switches to OFF. This disables the horizontal stabilizer's automatic trim completely, and reverts to manual trim so that even if the MCAS is still erroneously detecting a stall, it cannot send trim inputs to the FCS.

[qimg]https://www.dropbox.com/s/yntgr47fa9ihlzt/MCAS-Disable.jpg?raw=1[/qimg]

*Update

https://www.washingtonpost.com/worl...2dda3c0df52_story.html?utm_term=.56baceff2f62

Investigators found a device known as a jackscrew in the wreckage. The jackscrew, used to set the trim that raises and lowers the plane’s nose, indicates the jet was configured to dive, according to John Cox, a former pilot and an airline-safety consultant with the Washington-based aviation-safety consulting firm Safety Operating Systems.​

Also, CNN are reporting that the pilot reported control system problems almost immediately after takeoff... about the time when the flaps are retracted. Also, that ATC tracked the aircraft pitching up and down wildly, and accelerating and decelerating.

This is definitely looking like a flight control system problem.
Click to expand...

Sometimes switching off the auto-pilot is more complicated;
https://www.youtube.com/watch?v=UgkyrW2NiwM
 
The FAA certification process is under review.
https://www.bbc.co.uk/news/business-47633085
The problem is that whilst the FAA has previously been 'trusted' to certify US aircraft their processes now seems to be under question. European aviation authorities will probably want more detailed supervision of the FAA certification process or will require re-certification. The 'self-certification' process where manufacturers carry out their own checks on behalf of the FAA is likely to be reviewed. This may get caught up in the current fashion for trade wars. The Canadians may see an opportunity to hit back at Boeing following Boeing's actions against Bombardier. Potentially all new US manufactured aircraft will have their safety credentials questioned.
 
Planigale said:
The FAA certification process is under review.
https://www.bbc.co.uk/news/business-47633085
The problem is that whilst the FAA has previously been 'trusted' to certify US aircraft their processes now seems to be under question. European aviation authorities will probably want more detailed supervision of the FAA certification process or will require re-certification. The 'self-certification' process where manufacturers carry out their own checks on behalf of the FAA is likely to be reviewed. This may get caught up in the current fashion for trade wars. The Canadians may see an opportunity to hit back at Boeing following Boeing's actions against Bombardier. Potentially all new US manufactured aircraft will have their safety credentials questioned.
Click to expand...

Please the administration will put a stop to all such intrusive regulations.
 
a_unique_person said:
All airliners use that type of trim system by rotating the horizontal stabiliser up and down.

All modern Boeing airliners are fly by wire, even though they retain the yoke. The difference to Airbus fbw is that Boeing still gives the pilots more direct control of the plane, they can fly it into a stall of they really want. They yoke gives simulated force feedback while the sidestick doesn't.

MCAS does break with historic Boeing design philosophy in that it will help to prevent a stall by dropping the nose by moving the horizontal stabiliser. It does this so that the force on the control column will stay the same. Otherwise the effect of the engines at near full power at an unstable balance point makes the pilot feel a control column that is counterintuitively feeling lighter even though the plane is about to stall.

It's all a mess and there is no elegance of a design philosophy there, just an ugly hack. And not just an ugly hack, but one that has been done badly.
Click to expand...

I pretty much go along with most of this and the excerpt you posted, except this bit.

"Even if the pilots disconnected the trim system (as per Boeing 'fix'...) its likely to be left in a nose heavy trim position... which takes time to fix... "

Not if I understand MCAS functionality correctly.

Switching off the stab trim does not disconnect the trim and leave the elevator in a fixed position, it turns off the autopilot inputs to the trim system. This means the trim system is returned to manual control, and the pilot is no longer fighting against the autopilot.
 
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a_unique_person said:
All modern Boeing airliners are fly by wire, even though they retain the yoke.
Click to expand...

Are you sure? Over on SGU someone just put forth that the 737 Max series still uses cables, rods and hydraulics for flight controls.

Or were you excluding the 737 Max as not being “modern”? It’s kind of a hybrid, with very old roots but lots of modern tech tacked on.

This, from Quora: Every newly designed Boeing aircraft since the Boeing 777, which came out in 1995, has fly-by-wire controls. Legacy aircraft which still sell, like the long-in-the-tooth 737, the new version of the 747, and any 767 still being manufactured (for the military or civilian use), are still non-fly-by-wire.
 
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Bob001 said:
I wonder if the pilots who saved that plane made any effort or had any mechanism to communicate their experience to the other Lion pilots: "Hey, we almost died! If the plane does this, flips these switches quick!"
Click to expand...
And how quickly considering most airlines try to keep their planes in the air for as much of the time as possible.
 
Fast Eddie B said:
Are you sure? Over on SGU someone just put forth that the 737 Max series still uses cables, rods and hydraulics for flight controls.

Or were you excluding the 737 Max as not being “modern”? It’s kind of a hybrid, with very old roots but lots of modern tech tacked on.

This, from Quora: Every newly designed Boeing aircraft since the Boeing 777, which came out in 1995, has fly-by-wire controls. Legacy aircraft which still sell, like the long-in-the-tooth 737, the new version of the 747, and any 767 still being manufactured (for the military or civilian use), are still non-fly-by-wire.
Click to expand...


The 737Max is not modern. The only FBW on it is the spoilers.
 
a_unique_person said:
Doesn't look good for Boeing either. An extra pilot who didn't have his hands full during a busy part of the flight just after takeoff was able to sit back and diagnose the root cause of the problem and the solution.
Click to expand...

Sure, it doesn't in any way absolve Boeing. But this is the first significant indicator that the airline did something wrong, in addition to Boeing.
 
Hmm. I'm not 100% sure this means the airline did anything wrong as such. The incident when the off-duty pilot saved the day only happened the day before.

Those pilots would have no idea that is was a systemic problem. On landing at the destination airport, they would have reported it as a fault with the trim system or autopilot when they filled in the flight log, and then one of two things would happen.

Firstly, if there was a Lion Air maintenance facility at the destination airport, the ground crew would diagnose the fault to try to determine the cause. I am an aeronautical engineer by trade, specialising in avionics and I know how long these things take. Flight control systems are very, very complicated, with a lot of interacting connections and complex feedback loops. You could do several hours, even days of testing and still never find what caused the problem, because you cannot accurately replicate the in-flight problem on the ground. Sometimes it will take an actual test flight to do this.

Alternatively, if there was no Lion Air maintenance facility, the aircraft would be tagged with a defect, and flown back to its home airport with the Stab Trim switches off, and the fault would be investigated there.

The idea that the airline could do all this, and determine that the fault was not an isolated one due to a mechanical defect on this particular aircraft, but a systemic one attributable to a faulty design and could happen to any of their aircraft, and then put a warning out to, not only all their own pilots, but to everyone flying this aircraft type, in the space of only 24 hours, is just ludicrous.

ETA: AIUI, the off-duty pilot didn't already "know" what to do, but together, the three of them worked it out. Having the extra guy in the cockpit diagnosing the problem while the other two were battling the flight controls was probably the key factor in saving the aircraft.



Its also worth noting that the pilots in the Lion Air aircraft that crashed, were scrambling though the QRH and the flight manuals trying to understand why their aircraft was pitching down. They clearly did not know and Boeing failed to put that information in their manuals.

https://www.abc.net.au/news/2019-03...nsulting-handbook-when-plane-crashed/10922820
 
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