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kalvado
Posts: 2664
Joined: Wed Mar 01, 2006 4:29 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Mon Apr 15, 2019 3:58 pm

morrisond wrote:

I wouldn't disagree - making airplanes safer is a good idea - but even the most perfectly designed plane can have things fail - that is why we need pilots until Artificial Intelligence can handle non-normal situations (probably a lot better than pilots).

We should be expecting more out of pilots these days in unusual situations vs less as Automation has made the job a lot easier and instead of decreasing training hours - maintain them or increase them so Pilots have time to get comfortable and familiar with things in the SIM going wrong so if they are faced with them in real life - the odds of a successful outcome are a lot higher.

Yes and no.
Consider it as a finite pool of money and resources (and everything is finite, of course) which can be allocated towards system improvement or training improvement, but you have to choose.
Up until now, allocation towards software, hardware and maintenance seemingly provided better return (not as $$, but as prevented accident) than advanced pilot training. At least that is IMHO the state of affairs with limited pilot training and certification requirements (limited and too low is basically what you say, from my perspective) and extensive automation.
It is always OK to do re-evaluation and see if automation spending entered the range of diminishing return and pilots training may be a better investment. I am not sure if that is the case, but I am not sure it is NOT the case. Accident rate charts - which are the best piece of hard data we have - point towards automation still being a better approach. But it is really about resource fractions allocation. It cannot be 100:0 apparently. In finite pool, though, spending more on one thing means spending less on the other.
Last edited by kalvado on Mon Apr 15, 2019 3:59 pm, edited 1 time in total.
 
dragon6172
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Mon Apr 15, 2019 3:59 pm

SheikhDjibouti wrote:
So at the exact point when MCAS is supposed to function (correctly) to assist a pilot approaching a possible high AoA/stall, the Boeing software is handcuffing the pilots by disabling the electric trim switches. THIS IS SURELY MADNESS :o
The pilots can only trim down to 4.0 i.e. about 1 degree nose down.
Then the pilots sit there with their thumbs on the thumb switch, frustrated that they are unable to take it any further, and presumably just waiting & hoping that MCAS rocks up and adds another 2.5 deg of AND because they no longer have control of the aircraft. :banghead:

Help me! I must have got this wrong!!! :cry2:

Do you have so little faith in pilots to think they would simply hold the trim switch and not PUSH THE CONTROL COLUMN? Actually, I would be interested to know if any approach to stall procedures include anything about trimming the aircraft.
Phrogs Phorever
 
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SheikhDjibouti
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Mon Apr 15, 2019 4:14 pm

VV wrote:
I am pretty sure you can see the trim wheel turn when the MCAS gives the order to trim.

I recall there's a painting on that wheel to enhance the visibility when it's turning.

This much is true. How many youtube videos did you watch before that outstanding insight came to you? :boxedin:
(Not counting the one where you presumed MentourPilot and his trainee were both "actors") :roll:

You can also see the wheel moving as a result of STS commands

And autopilot (autotrim) commands

And ….if the guy in the other seat presses his/her thumb switch, often without any fanfare or major announcement.

I've heard 737 jockeys comment that in certain busy phases of flight, e.g. immediately after take-off, the trim wheel is spinning backwards and forwards like crazy.

You get to the stage where it is merely background and you tend to ignore it. (their words, not mine)

Having said that, ALL pilots are trained to watch for runaway stabilizer trim, and that is where the white mark definitely plays a part.
I am less certain at what point exactly MAX pilots are going to notice it is specifically MCAS... :scratchchin:

This is where a simple confirmation light, and/or verbal warning, would be so very useful.
"Warning, M-CAS!!. Warning M-CAS!!"

Perhaps someone could suggest this to Boeing..... :duck:
Nothing to see here; move along please.
 
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aerolimani
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Mon Apr 15, 2019 4:21 pm

9Patch wrote:
Leeham news goes there:

Training is a factor in the MAX crashes

It’s fair to say that the four pilots were probably trapped into making mistakes. Boeing didn’t tell the airlines about the MCAS, so no training was possible. But mistakes were made by pilots, nevertheless.

Those who pointed to poorer training in Third World countries aren’t wrong.


Pilot skills and training in the First World are extraordinary. The accident rates in the US, Canada and First World Europe have been lower than anywhere else since the dawn of modern aviation.


That the definition of the “average pilot” may need a rethink is a thesis that has emerged from these two MAX accidents.

It looks like a thesis that has merit.

posting.php?mode=reply&f=3&t=1417519

https://leehamnews.com/2019/04/15/train ... x-crashes/

It’s important to note that this is a Scott Hamilton opinion column, and not a “news” article.
 
OldAeroGuy
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Mon Apr 15, 2019 4:55 pm

rheinwaldner wrote:
OldAeroGuy wrote:
The airplane is way too fast. Pulling the throttles back to idle would have been a good choice.

Having unreliable speed indications? Insisting on the strict compliance to the stab runaway NNC and the AD on one hand and asking to set zero thrust while having lost reliable speed indications sounds like comical to me.


So you think that's OK to leave the overspeed condition unaddressed?

Dealing with overspeed is a memory item and it doesn't entail leaving thrust at the takeoff setting.

Even running the "Unreliable Airspeed" memory drill at this point and cutting thrust to 70% rather than leaving it at 92% would have been a better response than violating the EAD and restoring "STAB TRIM".
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
morrisond
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Mon Apr 15, 2019 5:04 pm

kalvado wrote:
morrisond wrote:

I wouldn't disagree - making airplanes safer is a good idea - but even the most perfectly designed plane can have things fail - that is why we need pilots until Artificial Intelligence can handle non-normal situations (probably a lot better than pilots).

We should be expecting more out of pilots these days in unusual situations vs less as Automation has made the job a lot easier and instead of decreasing training hours - maintain them or increase them so Pilots have time to get comfortable and familiar with things in the SIM going wrong so if they are faced with them in real life - the odds of a successful outcome are a lot higher.

Yes and no.
Consider it as a finite pool of money and resources (and everything is finite, of course) which can be allocated towards system improvement or training improvement, but you have to choose.
Up until now, allocation towards software, hardware and maintenance seemingly provided better return (not as $$, but as prevented accident) than advanced pilot training. At least that is IMHO the state of affairs with limited pilot training and certification requirements (limited and too low is basically what you say, from my perspective) and extensive automation.
It is always OK to do re-evaluation and see if automation spending entered the range of diminishing return and pilots training may be a better investment. I am not sure if that is the case, but I am not sure it is NOT the case. Accident rate charts - which are the best piece of hard data we have - point towards automation still being a better approach. But it is really about resource fractions allocation. It cannot be 100:0 apparently. In finite pool, though, spending more on one thing means spending less on the other.


The Pool does not have to be finite though. Worldwide legislation that mandates Pilots spend 3 hours per month in a SIM to practice situations like these would add a total of $5 to an airplane ticket.

If you can design the Perfect airplane that never breaks or has a parts failure then great - no more training needed but then neither are pilots.
 
kalvado
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Mon Apr 15, 2019 5:21 pm

morrisond wrote:
kalvado wrote:
morrisond wrote:

I wouldn't disagree - making airplanes safer is a good idea - but even the most perfectly designed plane can have things fail - that is why we need pilots until Artificial Intelligence can handle non-normal situations (probably a lot better than pilots).

We should be expecting more out of pilots these days in unusual situations vs less as Automation has made the job a lot easier and instead of decreasing training hours - maintain them or increase them so Pilots have time to get comfortable and familiar with things in the SIM going wrong so if they are faced with them in real life - the odds of a successful outcome are a lot higher.

Yes and no.
Consider it as a finite pool of money and resources (and everything is finite, of course) which can be allocated towards system improvement or training improvement, but you have to choose.
Up until now, allocation towards software, hardware and maintenance seemingly provided better return (not as $$, but as prevented accident) than advanced pilot training. At least that is IMHO the state of affairs with limited pilot training and certification requirements (limited and too low is basically what you say, from my perspective) and extensive automation.
It is always OK to do re-evaluation and see if automation spending entered the range of diminishing return and pilots training may be a better investment. I am not sure if that is the case, but I am not sure it is NOT the case. Accident rate charts - which are the best piece of hard data we have - point towards automation still being a better approach. But it is really about resource fractions allocation. It cannot be 100:0 apparently. In finite pool, though, spending more on one thing means spending less on the other.


The Pool does not have to be finite though. Worldwide legislation that mandates Pilots spend 3 hours per month in a SIM to practice situations like these would add a total of $5 to an airplane ticket.

If you can design the Perfect airplane that never breaks or has a parts failure then great - no more training needed but then neither are pilots.


Well, $5 here and $5 there.. Even then, 3 hours is a pretty finite number. You also have to take into account 3% drop in pilot productivity on top of those $5, which probably doubles the estimate.
But I am not talking primarily about the cost itself, it is about justified expenses. Human life cost is a few (2-5-10) million dollars for such estimates.
You suggest $5 per ticket in an industry which currently has 1 crash in 20M flights, or about $100M spending per saved life at most, more like $200-500M. There will be more cost-efficient ways to save lives. Better security comes to mind as airborne explosions do happen. Healthcare maybe up there as well.
You need a MUCH higher crash rate to justify $5 per ticket for existing safety issues.
 
MrBretz
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Mon Apr 15, 2019 5:39 pm

freakyrat wrote:
Ok folks after reading all the reports and opinions about this accident one that I read sticks out. Mainly that thius aircraft could have been initially saved with the correct pilot actions. The aircraft lost AOA sensor data due to a possible bird strike ripping the sensor vane off of the aircraft. This happened moments after takeoff. The aircraft was climbing out with 100% of N1 power with flaps extended when the Captain's stick shaker activated due to loss of the sensor followerd by an overspeed alarm. The correct procedure which should be ingrained in every pilots memory would have been to reduce power to leave the flaps down, reduce backpressure on the control column to a 10% nose up on the PFD and reduce power to 85% of N1. All of which this crew did not do. From what I understand when reading about MCAS is that it doesn't operate with flaps extended. Should have, would have in hindsight. The crew should have corrected the overspeed situation, left the flaps extended and returned to the airport. MCAS would not have activated in this siutation. When they raised the flaps up MCAS kicked in and the series of trim events leading to an out of control airplane and subsequent crash occured. I'm just throwing this out there as it is one 737 pilots opinion that I read. Yes MCAS as it currently is designed is a poor system and software and hardware fixes should correct it so this never happens again. Also better pilot training in the SIM and more hands on flying will improve pilot skills so they can correctly respond to problem situations.


This rings of truth to me. What does everyone else think?
 
freakyrat
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Mon Apr 15, 2019 5:41 pm

I forgot to throw in in my post above that the 737 pilot also said the pilots should have raised the speedbrakes.
 
xmp125a
Posts: 292
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Mon Apr 15, 2019 5:54 pm

MrBretz wrote:
freakyrat wrote:
Also better pilot training in the SIM and more hands on flying will improve pilot skills so they can correctly respond to problem situations.


This rings of truth to me. What does everyone else think?


Perhaps this has to be said again and again: the main objective in development of 737MAX was that no sim time is required to transition from 737NG to 737MAX. This had a number of consequences, which forced the engineers into dangerous and outright stupid decisions that lead us where we are now.

If you strip "no sim time" requirement then only minor adjustments on the 737MAX are needed to make it a very safe airplane. Because if you require SOME simulator time for transition, then following becomes solved overnight:

- AoA disagree can become standard equipment. With no sim time it cannot be sold as standard part of a certified aircraft!
- "MCAS off" button can be added to the cockpit and situation that happened with Ethiopian can be solved with flick of a switch without taking care that plane is electrically trimmed before flicking the switch.

I am still sure that most of the people here do not understand what a clusterfuck was the original requirement that no sim time is needed. It prevented the logical and necessary safety equipment to be installed in the cockpit!
 
mandala499
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Mon Apr 15, 2019 5:56 pm

MRMR12 wrote:

Oh no, it's that guy who accused me in public of being a "disinformant on the payroll of Boeing"... LOL... (No, I did not mean MRMR12)
When losing situational awareness, pray Cumulus Granitus isn't nearby !
 
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PixelFlight
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Mon Apr 15, 2019 5:59 pm

MRMR12 wrote:
First post here :), this post says it could not be AoA senbsor since so many other systems where affected? Mostly about Lion Air but says even ET302 had similar errors?

Boeing does not understand the cause of this 737MAX problem themselves.

Because the AOA sensor on the Lion Air aircraft was replaced after it flew JT775 and was BITE tested twice before the crash flight (JT610) we can be confident that JT610’s crash was not caused by a faulty AOA sensor.

Boeing’s software patch however is entirely based on Boeing’s belief that the AOA sensor was the cause.

Boeing seems to lack engineering competence for reasons which I can only guess at. Both Boeing and FAA are locked in a form of psychosis of denial.

It now turns out Lion Air 737MAX in flights on three days before the accident suffered multiple failures that cannot be attributed to MCAS nor to AOA sensor.

For example failure of the Left PFD, failure of the Left Radar altimeter, Left anti-ice, Left AOA sensor and activation of the Left Stick Shaker. Ethiopian ET302 is reported by Flight Global to have suffered similar instrument failures on left side instruments & systems.

These systems cannot be influenced by the AOA sensor, nor by MCAS. They suggest the root cause is either a voltage instability in the Left DC bus relay or a TRU failure.

Voltage irregularity for example could affect how the data is signaled from the AOA sensor to the ADIRU/DFDAU along the ARINC 429 data bus by altering signal encoding.


Link: https://www.quora.com/Why-doesn-t-Boeing-fix-the-MCAS-software-immediately Simon Gunson

We are a few to have speculated that the AoA sensors was maybe not defective but that something other was wrong, including the power supply. Yet the article have only indirect arguments about a DC bus issue. I would be surprised that the DC voltage of that bus was not monitored and/or recorded on the FDR. While it's possible that a false contact impacted only a segment of the bus outside of the voltage probe, the span of the listed issues is curious.
: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:
 
fadecfault
Posts: 164
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Mon Apr 15, 2019 6:17 pm

mandala499 wrote:
MRMR12 wrote:

Oh no, it's that guy who accused me in public of being a "disinformant on the payroll of Boeing"... LOL... (No, I did not mean MRMR12)

I think it's obvious to one with 737 technical experience that he has no idea what he is talking about. Its disturbing people actually believe what he says when he has no credentials to back it up.
The views and opinions written here are my own and do not reflect those of my employer.
 
XRAYretired
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Mon Apr 15, 2019 6:23 pm

MrBretz wrote:
freakyrat wrote:
Ok folks after reading all the reports and opinions about this accident one that I read sticks out. Mainly that thius aircraft could have been initially saved with the correct pilot actions. The aircraft lost AOA sensor data due to a possible bird strike ripping the sensor vane off of the aircraft. This happened moments after takeoff. The aircraft was climbing out with 100% of N1 power with flaps extended when the Captain's stick shaker activated due to loss of the sensor followerd by an overspeed alarm. The correct procedure which should be ingrained in every pilots memory would have been to reduce power to leave the flaps down, reduce backpressure on the control column to a 10% nose up on the PFD and reduce power to 85% of N1. All of which this crew did not do. From what I understand when reading about MCAS is that it doesn't operate with flaps extended. Should have, would have in hindsight. The crew should have corrected the overspeed situation, left the flaps extended and returned to the airport. MCAS would not have activated in this siutation. When they raised the flaps up MCAS kicked in and the series of trim events leading to an out of control airplane and subsequent crash occured. I'm just throwing this out there as it is one 737 pilots opinion that I read. Yes MCAS as it currently is designed is a poor system and software and hardware fixes should correct it so this never happens again. Also better pilot training in the SIM and more hands on flying will improve pilot skills so they can correctly respond to problem situations.


This rings of truth to me. What does everyone else think?


No, not really, there are lots of bits out of order and assumptions that are not suported by the Preliminary.

Ray
 
OldAeroGuy
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Mon Apr 15, 2019 6:25 pm

mandala499 wrote:
MRMR12 wrote:

Oh no, it's that guy who accused me in public of being a "disinformant on the payroll of Boeing"... LOL... (No, I did not mean MRMR12)


Mr Gunson also posted on Quora initially that MCAS was added to the MAX because Boeing test pilots couldn't make the airplane takeoff or land. When I asked him why MCAS only worked Flaps Up, he told me that wasn't true and then took down his original post.

I'd be very careful about quoting or using him as a source.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
XRAYretired
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Mon Apr 15, 2019 6:28 pm

PixelFlight wrote:
MRMR12 wrote:
First post here :), this post says it could not be AoA senbsor since so many other systems where affected? Mostly about Lion Air but says even ET302 had similar errors?

Boeing does not understand the cause of this 737MAX problem themselves.

Because the AOA sensor on the Lion Air aircraft was replaced after it flew JT775 and was BITE tested twice before the crash flight (JT610) we can be confident that JT610’s crash was not caused by a faulty AOA sensor.

Boeing’s software patch however is entirely based on Boeing’s belief that the AOA sensor was the cause.

Boeing seems to lack engineering competence for reasons which I can only guess at. Both Boeing and FAA are locked in a form of psychosis of denial.

It now turns out Lion Air 737MAX in flights on three days before the accident suffered multiple failures that cannot be attributed to MCAS nor to AOA sensor.

For example failure of the Left PFD, failure of the Left Radar altimeter, Left anti-ice, Left AOA sensor and activation of the Left Stick Shaker. Ethiopian ET302 is reported by Flight Global to have suffered similar instrument failures on left side instruments & systems.

These systems cannot be influenced by the AOA sensor, nor by MCAS. They suggest the root cause is either a voltage instability in the Left DC bus relay or a TRU failure.

Voltage irregularity for example could affect how the data is signaled from the AOA sensor to the ADIRU/DFDAU along the ARINC 429 data bus by altering signal encoding.


Link: https://www.quora.com/Why-doesn-t-Boeing-fix-the-MCAS-software-immediately Simon Gunson

We are a few to have speculated that the AoA sensors was maybe not defective but that something other was wrong, including the power supply. Yet the article have only indirect arguments about a DC bus issue. I would be surprised that the DC voltage of that bus was not monitored and/or recorded on the FDR. While it's possible that a false contact impacted only a segment of the bus outside of the voltage probe, the span of the listed issues is curious.

There is not anything in the write up that ties up with anything in either of the Preliminary Reports as far as I can see.

Ray
 
PStechPaul
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Mon Apr 15, 2019 7:26 pm

It seems that there have been many more anomalies and failures involving left side instrumentation, than those on the right side. It might prove useful to research the maintenance logs as well as FDRs to explore the possibility of a meaningful correlation. There was some question about the mounting of the AoA vane that might make it more easily damaged, or perhaps installed incorrectly, and perhaps more so for the left side.

If there was unreliable data coming from the left side, perhaps it appeared to the ET302 pilots that they had trimmed the aircraft properly when the trim was actually 2.3-2.5 units, and their brief application of manual electric trim (or manual wheel trim) was intended to be minor corrections. But then they may have realized that they were actually in excessive AND trim, and in a dive, which was unrecoverable.
 
RedBob
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Mon Apr 15, 2019 7:32 pm

OldAeroGuy wrote:
So you think that's OK to leave the overspeed condition unaddressed?


In both Lion Air flights the speed was higher than it should be, and no special notes were made of it either in investigation or in Boeing's responses.
 
morrisond
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Mon Apr 15, 2019 7:36 pm

OldAeroGuy wrote:
rheinwaldner wrote:
OldAeroGuy wrote:
The airplane is way too fast. Pulling the throttles back to idle would have been a good choice.

Having unreliable speed indications? Insisting on the strict compliance to the stab runaway NNC and the AD on one hand and asking to set zero thrust while having lost reliable speed indications sounds like comical to me.


So you think that's OK to leave the overspeed condition unaddressed?

Dealing with overspeed is a memory item and it doesn't entail leaving thrust at the takeoff setting.

Even running the "Unreliable Airspeed" memory drill at this point and cutting thrust to 70% rather than leaving it at 92% would have been a better response than violating the EAD and restoring "STAB TRIM".


Quite right - An overspeed is almost as bad (and potentially worse as parts of the plane and control surfaces can rip off) as an underspeed causing the airplane to stall and if not corrected fall out of the sky.

Thrust must be maintained in the appropriate range or very bad things can happen.
 
morrisond
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Mon Apr 15, 2019 7:47 pm

RedBob wrote:
OldAeroGuy wrote:
So you think that's OK to leave the overspeed condition unaddressed?


In both Lion Air flights the speed was higher than it should be, and no special notes were made of it either in investigation or in Boeing's responses.


I'm trying to find a copy of the pre-lim report with the actual speed traces. Do you have one?
 
rheinwaldner
Posts: 1856
Joined: Wed Jan 02, 2008 4:58 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Mon Apr 15, 2019 7:51 pm

OldAeroGuy wrote:
So you think that's OK to leave the overspeed condition unaddressed?

Dealing with overspeed is a memory item and it doesn't entail leaving thrust at the takeoff setting.

Even running the "Unreliable Airspeed" memory drill at this point and cutting thrust to 70% rather than leaving it at 92% would have been a better response than violating the EAD and restoring "STAB TRIM".

Of course overspeed was a huge problem for them.

But - as the high thrust helped to push the nose up, are you sure that the nose down moment resulting from the thrust reduction would not have created a huge problem in itself? Do you have evidence that the struggle to keep barely their altitude would not have resulted in a descent, which potentially would not have been survivable in itself?
Many things are difficult, all things are possible!
 
flybucky
Posts: 376
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Mon Apr 15, 2019 7:54 pm

freakyrat wrote:
The aircraft was climbing out with 100% of N1 power with flaps extended when the Captain's stick shaker activated due to loss of the sensor followerd by an overspeed alarm. The correct procedure which should be ingrained in every pilots memory would have been to reduce power to leave the flaps down, reduce backpressure on the control column to a 10% nose up on the PFD and reduce power to 85% of N1.

Here's the timeline related to stall warnings and overspeed:

5:38:45 Captain's stick shaker activates (before they even cross the end of the runway) and stays on.
5:40:45 Airspeed reaches Vmo 350 kts.
5:41:20 Overspeed clacker activates.
5:43:45 end of FDR

The overspeed clacker did not activate until ~2.5 mins after the stick shaker. So I think the pilots were focused on preventing stall and not overspeed. Since they didn't have enough altitude to pitch down to prevent stall, they let the thrust remain at max to gain altitude while preventing stall. Also, they had unreliable AOA, airspeed, altitude, and flight director pitch bar. So they probably were not sure whether they can trust the airspeed indicator or overspeed clacker.
 
barney captain
Posts: 2332
Joined: Tue Nov 06, 2001 5:47 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Mon Apr 15, 2019 8:04 pm

xmp125a wrote:

Perhaps this has to be said again and again: the main objective in development of 737MAX was that no sim time is required to transition from 737NG to 737MAX. This had a number of consequences, which forced the engineers into dangerous and outright stupid decisions that lead us where we are now.

If you strip "no sim time" requirement then only minor adjustments on the 737MAX are needed to make it a very safe airplane. Because if you require SOME simulator time for transition, then following becomes solved overnight:

- AoA disagree can become standard equipment. With no sim time it cannot be sold as standard part of a certified aircraft!
- "MCAS off" button can be added to the cockpit and situation that happened with Ethiopian can be solved with flick of a switch without taking care that plane is electrically trimmed before flicking the switch.

I am still sure that most of the people here do not understand what a clusterfuck was the original requirement that no sim time is needed. It prevented the logical and necessary safety equipment to be installed in the cockpit!


It appears that you don't understand that it wasn't a "requirement" for no sim time - but a reality. No MAX sims existed when the first MAX's were delivered. The exact same thing was true when the NG's first rolled out - it is not uncommon. When the NG's first showed up at WN, we were required to do 3 touch and go's in an empty aircraft with a Check Airman - because we didn't have an NG sim yet. The same thing could have been done with the MAX if they felt it was warrented. There were FAR more differences between the classics and the NG, than between the NG and the MAX.
Southeast Of Disorder
 
XRAYretired
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Mon Apr 15, 2019 8:05 pm

PStechPaul wrote:
It seems that there have been many more anomalies and failures involving left side instrumentation, than those on the right side. It might prove useful to research the maintenance logs as well as FDRs to explore the possibility of a meaningful correlation. There was some question about the mounting of the AoA vane that might make it more easily damaged, or perhaps installed incorrectly, and perhaps more so for the left side.

If there was unreliable data coming from the left side, perhaps it appeared to the ET302 pilots that they had trimmed the aircraft properly when the trim was actually 2.3-2.5 units, and their brief application of manual electric trim (or manual wheel trim) was intended to be minor corrections. But then they may have realized that they were actually in excessive AND trim, and in a dive, which was unrecoverable.

If its AOA-L at fault, its Left side instruments that are affected, ergo, right instruments are not. There is only one trim indicator. The apparent problems on ET610 and ET302 do not appear to the same.

Ray
 
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PW100
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Mon Apr 15, 2019 9:14 pm

planecane wrote:
PW100 wrote:
planecane wrote:
The first attempt they only held the switch for maybe 3 seconds. Then 5 seconds later MCAS commanded to almost full nose down. Then they we trimming and the trim was moving ANU but they hit the cutoff switches after about 9 seconds. The last two commands they tried were only a second or less each. It is possible that due to over speed the electric motor didn't move the stabilizer but they didn't hold the switch very long.

The proper procedure would have been to keep pressing the trim switch on the first attempt until the forces we're balanced and then hit the cutoff. That is what the procedure says to do and they didn't. They allowed MCAS to activate again after the first manual trim. They cut off electric trim before they finished trimming the second time.

Do wo know for a fact that they didn't?
Could the system have stopped trimming**, while the pilot(s) kept pressing the thump switch?
** Perhaps because of overload? Is there an overload cut-out on the trim motor?

The FDR traces shows the command. Based on the block diagram posted at some point the only thing that cuts off power to the command signal is the cutout switches.
The other line on the chart shows the stabilizer trim position.

Yes,, I did realize that.
I was wondering whether there was an overload protection feature on the electric trimming motor. If so, it might also cut out the thump switch signal to the FDR, depending on where the FDR picks up the signal. Do you know if there is such a feature?
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OldAeroGuy
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Mon Apr 15, 2019 11:18 pm

flybucky wrote:
freakyrat wrote:
The aircraft was climbing out with 100% of N1 power with flaps extended when the Captain's stick shaker activated due to loss of the sensor followerd by an overspeed alarm. The correct procedure which should be ingrained in every pilots memory would have been to reduce power to leave the flaps down, reduce backpressure on the control column to a 10% nose up on the PFD and reduce power to 85% of N1.

Here's the timeline related to stall warnings and overspeed:

5:38:45 Captain's stick shaker activates (before they even cross the end of the runway) and stays on.
5:40:45 Airspeed reaches Vmo 350 kts.
5:41:20 Overspeed clacker activates.
5:43:45 end of FDR

The overspeed clacker did not activate until ~2.5 mins after the stick shaker. So I think the pilots were focused on preventing stall and not overspeed. Since they didn't have enough altitude to pitch down to prevent stall, they let the thrust remain at max to gain altitude while preventing stall. Also, they had unreliable AOA, airspeed, altitude, and flight director pitch bar. So they probably were not sure whether they can trust the airspeed indicator or overspeed clacker.


If the pilots were focused on preventing a stall, why did they retract the flaps at 5:39:45?

Flap retraction at low altitude with stall warning activated seems like a questionable action.

At 5:39:45, it appears that there was already a 20 KIAS difference between the Left and Right airspeed. Rather than retracting flaps, performing the "Unreliable Airspeed - Flaps Down" checklist would have been a high priority, either at 1500' AGL or 5000' AGL after a constant attitude climb.

While the Right overspeed clacker was noted on the CVR at 5:41:20, it had probably been going off since Right airspeed had exceeded 340KIAS at around 5:40:45. At that point, after wrestling with MCAS, the airplane was still at about 1500' AGL but Right IAS is at Vmo.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
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SheikhDjibouti
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Mon Apr 15, 2019 11:21 pm

Dragon - I feel we are 98% in agreement for a change. :bigthumbsup:
dragon6172 wrote:
Xrayretired wrote:
At 05:39:57, the Captain advised again the First-Officer to request to maintain runway heading and that they are having flight control problems.
What was the flight control problem at this point? There had not been any MCAS inputs yet. Up to this point there was stick shaker, Anti-ice Master Caution, and the autopilot had just kicked off at 5:39:55.

Two possibilities here
Option A) Maybe the message to ATC should have said "we are having instrument problems" ?
Personally I feel that is nitpicking; they didn't know at the time that every word they uttered would become the subject of detailed debate for years afterwards.
Option B) How about the following, from 33 seconds earlier...
At 05:39:22 and about 1,000 feet the left autopilot (AP) was engaged... the flaps were retracted and the pitch trim position decreased to 4.6 units.
Six seconds after the autopilot engagement, there were small amplitude roll oscillations accompanied by lateral acceleration, rudder oscillations and slight heading changes. These oscillations continued also after the autopilot was disengaged.
Surely that would qualify as "flight control problems"?
Again, this is all pre-MCAS, but it wouldn't leave me thinking this is Lion Air #2.

dragon6172 wrote:
If I make the assumption that this was said in conjunction with the first MCAS input around the 05:40:00, does that mean the pilots had properly diagnosed that they had a situation similar to LionAir, and if so why not trim to neutral and turn off electric trim IAW the AD now instead of waiting 30-40 seconds and two AND / MNU trim cycles.
Highly unlikely IMO; see alternative options above.

PW100 wrote:
The uptrim just did not reach the "neutral" condition. And we do not know why that is.

dragon6172 wrote:
It didn't reach neutral because the switch wasn't held long enough. Why wasn't the switch held long enough is the question. I do not think it is incompetence. I think it may come down to something physical or mental. In other words, if you are suddenly pulling 15-20 lb force to maintain level flight, then MCAS kicks in for round two and you are pulling 25-30 lb force, when you trim nose up you may stop around the 15-20 lb force mark cause that is what feels normal.
Most excellent summary there. :bigthumbsup:
I am reminded of a stage act (or was it a lecture on human biology?) where a volunteer was asked to push against a solid object, and then that object was removed. The situation was probably more contrived than I have described, it may have involved a blindfold too, but the upshot was they were disorientated and hence over-compensated (and probably fell on their face at some point)

dragon6172 wrote:
Another thing to think is how long does a pilot normally hold the trim switch? It would appear that they would have to hold the trim switch for 15-20 seconds to return to neutral. All other manual inputs earlier in the takeoff sequence are in the 2-3 second range. Trimming for 15-20 seconds probably doesn't seem normal. Easy to see why a pilot may stop trimming, especially when the forces on the controls maybe don't seem to be improving.
Another most excellent possible explanation. You're on a roll here. :bigthumbsup: x2

PW100 wrote:
That semi-controlled may not have been sustainable for much longer, if the crew needed most of their physical strength to keep the nose up. Having seen the infamous MentourPilot video, it can be very understandable that workload was so high that communication with Maintenance would have become very difficult.

dragon6172 wrote:
Most of their physical strength may be an exaggeration. Even in the video you mention, it is only one pilot who is holding the control column.
I am slightly puzzled by this counter-argument of yours. Whilst in theory two pilots can share the control column load, the Capt was hampered and his muscles weakened by the stick shaker which must be akin to operating a pneumatic jack-hammer. {Go on then, ask the question; the answer is yes, I have.... a long time ago :D )

And whilst the second pilot is assisting the first, who is left to read the manuals and attempt to move the trim wheel?
In the Mentour pilot video, at some point the trainee clearly lets go of the control column in order to get two hands on the trim wheel.
Not only that, but I suspect Petter was easing the column forward simply to allow the trainee full access to the trim wheel. This was not an option on ET302.
And finally there is the testimony from the FO on ET043.

dragon6172 wrote:
It is my understanding that AT engaged will not allow exceeding Vmo. This can be seen in the FDR plots. Once the LH (master FCC in this case) reaches Vmo, there is a slight reduction in N1.
And another :checkmark:
I'm laughing now because a whole month and 2700 posts ago, we were banging heads over whether they had exceeded Vmo, and if they had, whether it was by a significant margin. I cannot find where I first flagged up that auto-throttle was supposed to mitigate overspeed as far as it could. As it turns out, anything over 230 kts can bring handling problems in the wrong circumstances. :o

xmp125a wrote:
So perhaps "fiddle with the trim and never let 5 seconds elapse" would be far better advice (since you don't lose electric control), but I understand that sounds ridicolous for EAD for a modern airplane.

dragon6172 wrote:
This is essentially what LionAir crew did for 7 minutes. MCAS trims down, pilot trims up. Repeat 20 times.
Absolutely.
The final death dive came about because ET302 took their eye off the ball for ..... a whole NINE seconds.
A few pages back we had our own discussion here on a.net as to whether MCAS activated five or ten seconds after the previous thumb switch blip. Maybe the pilots on ET302 falsely remembered it was 10 seconds? One of the posters here claimed they didn't need to know this detail anyway.

In that respect, the first five seconds were just like the previous two minutes, difficult and puzzling, but the pilots must have thought they were still just about ok.
And then seemingly out of the blue there were four seconds of MCAS trim.... just four seconds and it was effectively all over.!

I still get a sick feeling just imagining this incredibly short period in the cockpit.
Nothing to see here; move along please.
 
OldAeroGuy
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Mon Apr 15, 2019 11:52 pm

rheinwaldner wrote:
OldAeroGuy wrote:
So you think that's OK to leave the overspeed condition unaddressed?

Dealing with overspeed is a memory item and it doesn't entail leaving thrust at the takeoff setting.

Even running the "Unreliable Airspeed" memory drill at this point and cutting thrust to 70% rather than leaving it at 92% would have been a better response than violating the EAD and restoring "STAB TRIM".

Of course overspeed was a huge problem for them.

But - as the high thrust helped to push the nose up, are you sure that the nose down moment resulting from the thrust reduction would not have created a huge problem in itself? Do you have evidence that the struggle to keep barely their altitude would not have resulted in a descent, which potentially would not have been survivable in itself?


At 5:43:00, ET302 crew were not struggling to keep their altitude. They had just climbed from 1500' AGL to 6500' AGL. IAS-R had just increased slightly to 360 KIAS, 20 KIAS over Vmo. The airplane was in almost level flight.

The QRH says reduce thrust to reduce overspeed. Under these conditions, a thrust reduction may have had little impact on pitch attitude due to high aerodynamic forces. Reducing speed would made it easier to use manual trim. With over 5000' of altitude to assess the effect of a significant thrust reduction, it would have been a viable option to restoring electric stab trim.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
ikramerica
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Tue Apr 16, 2019 2:01 am

OldAeroGuy wrote:
rheinwaldner wrote:
OldAeroGuy wrote:
So you think that's OK to leave the overspeed condition unaddressed?

Dealing with overspeed is a memory item and it doesn't entail leaving thrust at the takeoff setting.

Even running the "Unreliable Airspeed" memory drill at this point and cutting thrust to 70% rather than leaving it at 92% would have been a better response than violating the EAD and restoring "STAB TRIM".

Of course overspeed was a huge problem for them.

But - as the high thrust helped to push the nose up, are you sure that the nose down moment resulting from the thrust reduction would not have created a huge problem in itself? Do you have evidence that the struggle to keep barely their altitude would not have resulted in a descent, which potentially would not have been survivable in itself?


At 5:43:00, ET302 crew were not struggling to keep their altitude. They had just climbed from 1500' AGL to 6500' AGL. IAS-R had just increased slightly to 360 KIAS, 20 KIAS over Vmo. The airplane was in almost level flight.

The QRH says reduce thrust to reduce overspeed. Under these conditions, a thrust reduction may have had little impact on pitch attitude due to high aerodynamic forces. Reducing speed would made it easier to use manual trim. With over 5000' of altitude to assess the effect of a significant thrust reduction, it would have been a viable option to restoring electric stab trim.

This is what I was saying 20, 40 pages ago. Many don’t want to believe that pilot error probably caused this crash with failure to properly implementing the trim cutoff only being the final act.

They had reached enough altitude to remember that they shouldn’t be at TO thrust. Yet they remained over Vmo because they didn’t ever reduce thrust. They were level and somewhat under control, why not reduce thrust just a little to see what happens? People harp on them only having 4 seconds to make the right move but thats because they were moving so quickly.

I still wonder if the PF had too much to do because the 200 hour FO was simply of little or no use in a panic, and ultimately things were forgotten or done wrong because they were panicked, and the aircraft was screaming at them in various ways all at once.

The 3 AF pilots crashed the A330 because they implemented things wrong and they were panicked because the aircraft was screaming at them. I question the value of multiple warnings going off simultaneously. I can’t see it doing anything but adding to stress, confusion and panic.
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planecane
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Tue Apr 16, 2019 3:23 am

PW100 wrote:
planecane wrote:
PW100 wrote:
Do wo know for a fact that they didn't?
Could the system have stopped trimming**, while the pilot(s) kept pressing the thump switch?
** Perhaps because of overload? Is there an overload cut-out on the trim motor?

The FDR traces shows the command. Based on the block diagram posted at some point the only thing that cuts off power to the command signal is the cutout switches.
The other line on the chart shows the stabilizer trim position.

Yes,, I did realize that.
I was wondering whether there was an overload protection feature on the electric trimming motor. If so, it might also cut out the thump switch signal to the FDR, depending on where the FDR picks up the signal. Do you know if there is such a feature?

In all the information I can find online, there is no reference to any overload protection except for the circuit breaker. I can't 100% say one doesn't exist but I would assume it would have been mentioned in the preliminary report if it did.
 
rheinwaldner
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Tue Apr 16, 2019 5:27 am

barney captain wrote:
There were FAR more differences between the classics and the NG, than between the NG and the MAX.

If that was the attitude of the ET pilots (a glaring unawareness about really safety relevant differences of the MAX), it could explain to some degrees, why they were not able to handle the situation with a good outcome. I have seen Western MAX pilots first denying the existence of MCAS even after ET went down, then denying that MCAS played a role in both crashes at all. That attitude worries me. Attentive readers of Peter Lemmes or Ferpes blogs know MCAS better, than those MAX pilots, who strictly rely on Boeings memos. Its better the aircraft wait on the ground until the pilots catch up with their training and learn the highly relevant differences.

Why do I say this? Because the crash statistic after 300 delivered NGs clearly shows, that there were not FAR more differences between classics and NG. At least not hazardous ones.
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jagraham
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Tue Apr 16, 2019 5:49 am

rheinwaldner wrote:
barney captain wrote:
There were FAR more differences between the classics and the NG, than between the NG and the MAX.

If that was the attitude of the ET pilots (a glaring unawareness about really safety relevant differences of the MAX), it could explain to some degrees, why they were not able to handle the situation with a good outcome. I have seen Western MAX pilots first denying the existence of MCAS even after ET went down, then denying that MCAS played a role in both crashes at all. That attitude worries me. Attentive readers of Peter Lemmes or Ferpes blogs know MCAS better, than those MAX pilots, who strictly rely on Boeings memos. Its better the aircraft wait on the ground until the pilots catch up with their training and learn the highly relevant differences.

Why do I say this? Because the crash statistic after 300 delivered NGs clearly shows, that there were not FAR more differences between classics and NG. At least not hazardous ones.


Perhaps a compromise is in order?

It remains to be seen if there are FAR more differences between classic and NG vs NG and MAX, but
Boeing's intention was that the MAX would fly like the NG. However, it is now clear that the MAX does not fly like the NG in certain critical situations.
What is not clear is why? (why the MAX does not fly like the NG)
 
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zeke
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Tue Apr 16, 2019 5:50 am

OldAeroGuy wrote:
Flap retraction at low altitude with stall warning activated seems like a questionable action.


So is putting the autopilot on.

I was not there so I don’t know what was going through their minds, from reading the preliminary report there seems to be some nonchalance from the crew regarding the initial events immediately after takeoff.

Has there been a history of stick shaker activation events after takeoff?

It is a bizarre reaction by the two lion air flights and this flight with the crews reaction to stick shaker immediately after liftoff.
Last edited by zeke on Tue Apr 16, 2019 5:55 am, edited 1 time in total.
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PcarSBA
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Tue Apr 16, 2019 5:53 am

ikramerica wrote:
I still wonder if the PF had too much to do because the 200 hour FO was simply of little or no use in a panic, and ultimately things were forgotten or done wrong because they were panicked, and the aircraft was screaming at them in various ways all at once.


On the 200h PNF aspect I find it noteworthy that it wasn’t the PF calling out STAB TRIM CUTOUT but the 200h PNF. This makes me wonder if the experienced captain even realized they had an MCAS issue. I believe it was it the PNF.

What further speaks for that theory is when the PF is asking if electric trim was available at 5:41:46. I’d say the PNF was more use than what the 200h suggests but maybe cultural aspects prevented him from taking a more active role. Just saying.
 
xmp125a
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Tue Apr 16, 2019 6:20 am

barney captain wrote:
It appears that you don't understand that it wasn't a "requirement" for no sim time - but a reality. No MAX sims existed when the first MAX's were delivered. The exact same thing was true when the NG's first rolled out - it is not uncommon. When the NG's first showed up at WN, we were required to do 3 touch and go's in an empty aircraft with a Check Airman - because we didn't have an NG sim yet. The same thing could have been done with the MAX if they felt it was warrented. There were FAR more differences between the classics and the NG, than between the NG and the MAX.


No, you are wrong regarding the first part of the post.

1) Of course there was reality that there were few MAX simulators. But whose fault is that? Boeing's!
2) The contract with WN stipulated heavy penalties per delivered plane ($1M) if plane required pilots to have sim time to go from NG to MAX. https://www.washingtonpost.com/business ... hers-dont/ That was also reason why they did not consider MAX simulators to be a necessity.
3) Even after LionAir crash Boeing was adamant to avoid simulator time to avoid penalties.
4) As an engineer with experience regarding the people knocking on my door with impossible ideas which they already sold (but never checked whether they can be built), II can imagine what was the design process for Boeing 737MAX:

a) Management is caught sleeping at the wheel and even in 2010 they insist they will make new plane instead of reinventing 737
b) Management is rudely awakened by Airbus A320Neo announcement in 2011 with larger and much more efficient LEAP engines
c) Some idiot at Boeing Sales sells non-existing plane to Southwest with a stipulation that no sim time will be required or $1M fine PER DELIVERED AIRCRAFT will apply.
d) "no sim time" is one of the (unofficial) requirements for the design and Boeing engineers are set in to "Go, Go, Go" mode, with only half of the time that would be available for such a task. And since no sim time was what was needed to outpace Airbus 737neo, i can only speculate how the meetings of engineers and managers went:

Q: we have bigger engines, do we lift the airframe from the ground to accommodate them?
A: that would prevent common type certification and require simulation time. NO.
Q: ok, we mounted the engines forward, but now the aircraft has a tendency to pitch up in the valid part of the flight envelope
A: fix it goddamit!
Q: ok, we added software module to flight computer, we call it "MCAS" for "Maneuvering Characteristics Augmentation System", but we have trouble using both AoA sensors when A/C is turning...
A: then use one
Q: Ok, we are using only one sensor, but we should really add the indication about sensor failure (AoA disagree)
A: that would require simulation time. NO. Offer the sensor as add-on, that would be ok regarding the certification.
Q: Ok, but pilots would have to be trained in disabling MCAS anyway ... requiring sim time?
A: REMOVE the goddamned stuff from the pilot manuals! They don't have to know about MCAS, after all the plane flies the same as 737NG (they forgot MCAS acronym in the list though)
A: Ok, now we have aircraft that does not require sim time. Thank you all!

5) The 737MAX fiasco is much more than MCAS. It is a systemic failure at Boeing. I fully expect few people going to jail, and I assume most of them won't be engineers.

Any investigation which will look solely into MCAS and certification, and not into the systemic failures at Boeing will not result in safe 777 upgrade, because the system Boeing had for decades was broken, hopefully not destroyed in rushed design of 737MAX. I think NOW Boing understands that and the CEO's utterance "We own this" had exactly the purpose of acknowledging that MAX resulted from the number of systemic problems.
 
sgrow787
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Tue Apr 16, 2019 6:27 am

Two points that infer a ADIRU issue, and not a sensor issue:

(1) Both the Lion Air and Ethiopian crash reported right-side airspeed greater than left side. However both crashes also reported left-side AOA angle higher than right side. This is inconsistent with a faulty AOA, which would cause a computed airspeed HIGHER than what it would otherwise normally be. One can derive a proof of that by comparing a positive incident angle case to a zero incident angle case.

ET302 Preliminary report:

“Also, the airspeed, altitude and flight director pitch bar values from the left side noted deviating from the corresponding right side values. The left side values were lower than the right side values until near the end of the recording. “

JT610 Preliminary report:

The FDR data shows right-side computed airspeed greater than left-side for the entire flight.

(2) For the Ethiopian crash, the FDR data at 05:43:27 and 05:43:37 shows intermittent good data for AOA, altitude, and airspeed. Analyzing the data graphs, one can see these blips lining up with Vertical Acceleration falling to zero or less than zero. This would be consistent with a bad data and/or power bus connection that would respond to a change in acceleration forces.

https://imgur.com/0NUgCud

Edit: There also appears to be a change in Roll attitude at those two blips. The 'IR' in ADIRU is for Inertial Reference data, which is based off of an internal gyro. I believe the autopilot would have to be ON in order for the FCC to command a Roll to stay level with (what it thinks is) a level horizon line.
Just one sensor,
Oh just one se-en-sor,
Just one sensor,
Ooh ooh oo-ooh
Oo-oo-ooh.
 
rheinwaldner
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Tue Apr 16, 2019 6:58 am

OldAeroGuy wrote:
rheinwaldner wrote:
Of course overspeed was a huge problem for them.

But - as the high thrust helped to push the nose up, are you sure that the nose down moment resulting from the thrust reduction would not have created a huge problem in itself? Do you have evidence that the struggle to keep barely their altitude would not have resulted in a descent, which potentially would not have been survivable in itself?


At 5:43:00, ET302 crew were not struggling to keep their altitude. They had just climbed from 1500' AGL to 6500' AGL. IAS-R had just increased slightly to 360 KIAS, 20 KIAS over Vmo.

The climb was extremely shallow and even after the trim cutout vertical speed became negative for some times. Pitch control was absolutely a struggle.

See also the Accel Vert (g) graph. During the entire flight Accel Vert never stabilized. Wild spikes to negative g`s occurred in any phase of the flight. It was a rollercoaster climb with an average climb rate just barely pointing upwards.

OldAeroGuy wrote:
The QRH says reduce thrust to reduce overspeed.

Quote precisely the applicable section. Because overspeed can't be neither detected nor handled as long as unreliable airspeed has not been resolved. Pilots need to rely on the memory items for unreliable airspeed, which promise to keep the aircraft from overspeed.

Which is the next unsolvable issue they faced: The official Boeing memory items for unreliable airspeed would have crashed their flights entirely without the help of MCAS]. At least they were not dumb enough, to set 75% thrust/4° pitch right after departure @MTOW from this high airport. So they had to deviate from the official Boeing unreliable airspeed NNC right from the start. After that point they were left on their own and asking them with hindsight to apply selected Boeing procedures, while others did not work as advertised is imo just arrogant.

OldAeroGuy wrote:
Under these conditions, a thrust reduction may have had little impact on pitch attitude due to high aerodynamic forces.

So, you have no evidence (that the shallow climb would not have resulted in descent, taking away all the time needed to analyze and resolve the issues). Maybe they did not take away thrust because they also missed that evidence? Trail and error is no option. Also stick shaker is not the feedback from the aircraft, that naturally would trigger the reflex to reduce thrust.
Many things are difficult, all things are possible!
 
MRMR12
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Tue Apr 16, 2019 7:00 am

mandala499 wrote:
MRMR12 wrote:

Oh no, it's that guy who accused me in public of being a "disinformant on the payroll of Boeing"... LOL... (No, I did not mean MRMR12)


Yes, there are many "experts" out there speculation a lot. Waiting for the final report and hopefully it says what really happened.
 
HaulSudson
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Tue Apr 16, 2019 7:21 am

OldAeroGuy wrote:
rheinwaldner wrote:
OldAeroGuy wrote:
So you think that's OK to leave the overspeed condition unaddressed?

Dealing with overspeed is a memory item and it doesn't entail leaving thrust at the takeoff setting.

Even running the "Unreliable Airspeed" memory drill at this point and cutting thrust to 70% rather than leaving it at 92% would have been a better response than violating the EAD and restoring "STAB TRIM".

Of course overspeed was a huge problem for them.

But - as the high thrust helped to push the nose up, are you sure that the nose down moment resulting from the thrust reduction would not have created a huge problem in itself? Do you have evidence that the struggle to keep barely their altitude would not have resulted in a descent, which potentially would not have been survivable in itself?


At 5:43:00, ET302 crew were not struggling to keep their altitude. They had just climbed from 1500' AGL to 6500' AGL. IAS-R had just increased slightly to 360 KIAS, 20 KIAS over Vmo. The airplane was in almost level flight.

The QRH says reduce thrust to reduce overspeed. Under these conditions, a thrust reduction may have had little impact on pitch attitude due to high aerodynamic forces. Reducing speed would made it easier to use manual trim. With over 5000' of altitude to assess the effect of a significant thrust reduction, it would have been a viable option to restoring electric stab trim.


And if it still crashed, you'd join in the celebrations over here that the pilots did not follow the checklist and that they must get the blame for catering a perfectly fine plane.

Unfortunately Boeing seems to have enough information not to support these incompetent pilot dreams any longer.
 
WIederling
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Tue Apr 16, 2019 7:31 am

hivue wrote:
morrisond wrote:
Is there a better description that talks about the need for increasing control column force as speed increase vs getting close to the stall?


I think the requirement applies to scaling the control column force for both nose up and nose down column movement. The pilot needs the right feedback (even if it is contrived) from the control column whenever maneuvering.


If it is just for "feel right" on the MAX why did they not work MCAS functionality into the "feel unit" ?

IMU there is a very real hard reason to have MCAS work on tailplane incidence.
Boeing's description reproduced by 737.co.uk site is a circuitous lie.
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XRAYretired
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Tue Apr 16, 2019 7:52 am

sgrow787 wrote:
Two points that infer a ADIRU issue, and not a sensor issue:

(1) Both the Lion Air and Ethiopian crash reported right-side airspeed greater than left side. However both crashes also reported left-side AOA angle higher than right side. This is inconsistent with a faulty AOA, which would cause a computed airspeed HIGHER than what it would otherwise normally be. One can derive a proof of that by comparing a positive incident angle case to a zero incident angle case.

ET302 Preliminary report:

“Also, the airspeed, altitude and flight director pitch bar values from the left side noted deviating from the corresponding right side values. The left side values were lower than the right side values until near the end of the recording. “

JT610 Preliminary report:

The FDR data shows right-side computed airspeed greater than left-side for the entire flight.

(2) For the Ethiopian crash, the FDR data at 05:43:27 and 05:43:37 shows intermittent good data for AOA, altitude, and airspeed. Analyzing the data graphs, one can see these blips lining up with Vertical Acceleration falling to zero or less than zero. This would be consistent with a bad data and/or power bus connection that would respond to a change in acceleration forces.

https://imgur.com/0NUgCud

Edit: There also appears to be a change in Roll attitude at those two blips. The 'IR' in ADIRU is for Inertial Reference data, which is based off of an internal gyro. I believe the autopilot would have to be ON in order for the FCC to command a Roll to stay level with (what it thinks is) a level horizon line.


The narrative you present (1) appear to support AOA failing high to me?. I think you need to present your proof. In, (2) AOA value appears to follow the 'g' apparently consistent with AOA internal mass aligning with the force vector consistent with no vane attached.


Ray
 
sgrow787
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Joined: Fri May 16, 2014 8:12 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Tue Apr 16, 2019 8:46 am

XRAYretired wrote:
The narrative you present (1) appear to support AOA failing high to me?. I think you need to present your proof. In, (2) AOA value appears to follow the 'g' apparently consistent with AOA internal mass aligning with the force vector consistent with no vane attached.

Ray


You're grasping if you think this is about a bird strike. Two crashes with similar if not exact data. Lion Air replaced the AOA and it didn't fix their issue.

The proof on expected airspeed is what you are referring to (since AOA is a base parameter, meaning none of the other parameters affect it, but AOA can affect airspeed computation).

In normal operation:
With a working good AOA value, the measured incident air pressure (Px) is divided by the cosine of the incident angle, in order to calculate the magnitude of the air pressure vector (P), which is the vector in the direction opposite of airplane travel. Since the cosine of angles between 0 and 90 is between 1 and 0, we can say that dividing by cosine is equivalent to multiplying by a scale factor greater than 1. Hence, in normal operation, in high angle of attack, the AOA purpose is to bring UP the measured pitot air pressure for calculation of computed airspeed. Without the AOA, the measured air pressure at the pitot tube (and the corresponding computed airspeed) would decrease, giving a false indication.

With a faulty AOA reading high (positive incident angle):
The ADIRU that computes airspeed from AOA would "think" the measured pitot air pressure was incident (Px) rather than (P), and because Px = P when there is no actual AOA (or when Px "approaches" P for low AOA), then by the logic above, the AOA factor would bring UP that Px to a value LARGER than P. And the computed airspeed would be higher than otherwise.

You can google "vector components" to see the right-triangle and the associated equations.

In conclusion, since the computed airspeed is higher on the side with the failed AOA reading high, then the same on the other (good) side is LOWER, not higher.
Just one sensor,
Oh just one se-en-sor,
Just one sensor,
Ooh ooh oo-ooh
Oo-oo-ooh.
 
barney captain
Posts: 2332
Joined: Tue Nov 06, 2001 5:47 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Tue Apr 16, 2019 9:20 am

zeke wrote:
OldAeroGuy wrote:
Flap retraction at low altitude with stall warning activated seems like a questionable action.


So is putting the autopilot on.

I was not there so I don’t know what was going through their minds, from reading the preliminary report there seems to be some nonchalance from the crew regarding the initial events immediately after takeoff.

Has there been a history of stick shaker activation events after takeoff?

It is a bizarre reaction by the two lion air flights and this flight with the crews reaction to stick shaker immediately after liftoff.


This.

The continuing theme in this giant fur ball remains -

The pilots tasked with actually operating these machines are of one mindset.

Those who read and believe everything from the 'paid to sell you news' journalists are of another.

Those of us who are willing to put our asses in the seat have been trivialized. Cyber-pilots have nothing to lose.

And THAT is why Anet has lost so much of it's relevance.
Southeast Of Disorder
 
XRAYretired
Posts: 870
Joined: Fri Mar 15, 2019 11:21 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Tue Apr 16, 2019 9:23 am

sgrow787 wrote:
XRAYretired wrote:
The narrative you present (1) appear to support AOA failing high to me?. I think you need to present your proof. In, (2) AOA value appears to follow the 'g' apparently consistent with AOA internal mass aligning with the force vector consistent with no vane attached.

Ray


You're grasping if you think this is about a bird strike. Two crashes with similar if not exact data. Lion Air replaced the AOA and it didn't fix their issue.

The proof on expected airspeed is what you are referring to (since AOA is a base parameter, meaning none of the other parameters affect it, but AOA can affect airspeed computation).

In normal operation:
With a working good AOA value, the measured incident air pressure (Px) is divided by the cosine of the incident angle, in order to calculate the magnitude of the air pressure vector (P), which is the vector in the direction opposite of airplane travel. Since the cosine of angles between 0 and 90 is between 1 and 0, we can say that dividing by cosine is equivalent to multiplying by a scale factor greater than 1. Hence, in normal operation, in high angle of attack, the AOA purpose is to bring UP the measured pitot air pressure for calculation of computed airspeed. Without the AOA, the measured air pressure at the pitot tube (and the corresponding computed airspeed) would decrease, giving a false indication.

With a faulty AOA reading high (positive incident angle):
The ADIRU that computes airspeed from AOA would "think" the measured pitot air pressure was incident (Px) rather than (P), and because Px = P when there is no actual AOA (or when Px "approaches" P for low AOA), then by the logic above, the AOA factor would bring UP that Px to a value LARGER than P. And the computed airspeed would be higher than otherwise.

You can google "vector components" to see the right-triangle and the associated equations.

In conclusion, since the computed airspeed is higher on the side with the failed AOA reading high, then the same on the other (good) side is LOWER, not higher.


I dont grasp at anything, me old mate. I ask to improve my understanding and ability to arrive at my own intepretation of events based on all the inputs in the thread.

Ray
 
User avatar
zeke
Posts: 14890
Joined: Thu Dec 14, 2006 1:42 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Tue Apr 16, 2019 9:38 am

barney captain wrote:
This.

The continuing theme in this giant fur ball remains -

The pilots tasked with actually operating these machines are of one mindset.

Those who read and believe everything from the 'paid to sell you news' journalists are of another.

Those of us who are willing to put our asses in the seat have been trivialized. Cyber-pilots have nothing to lose.

And THAT is why Anet has lost so much of it's relevance.


BC,

I don’t like second guessing what is going through other pilots minds when they are not around to defend themselves.

Can you think of a reason why the two lion air flights and this flight seemed to ignore the stick shaker ?

I don’t understand why none of the crews performed the airspeed unreliable memory items. All I could think of was this was something which they had seen before and turned out to be a false positive.

I think we would all welcome your constructive input as you are a current MAX Captain.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
sgrow787
Posts: 434
Joined: Fri May 16, 2014 8:12 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Tue Apr 16, 2019 9:43 am

XRAYretired wrote:

I dont grasp at anything, me old mate. I ask to improve my understanding and ability to arrive at my own intepretation of events based on all the inputs in the thread.

Ray


Grasp this. If you had intentions to understand, you would have looked at the FDR data and responded with a question or two (your G force for a vaneless AOA is an obvious joke). You would have correctly referred to my observation of airspeed computations. Then you used the word 'narrative'. What I wrote was an observation of facts. A narrative is connecting facts with speculation.
Just one sensor,
Oh just one se-en-sor,
Just one sensor,
Ooh ooh oo-ooh
Oo-oo-ooh.
 
XRAYretired
Posts: 870
Joined: Fri Mar 15, 2019 11:21 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Tue Apr 16, 2019 10:02 am

sgrow787 wrote:
XRAYretired wrote:

I dont grasp at anything, me old mate. I ask to improve my understanding and ability to arrive at my own intepretation of events based on all the inputs in the thread.

Ray


Grasp this. If you had intentions to understand, you would have looked at the FDR data and responded with a question or two (your G force for a vaneless AOA is an obvious joke). You would have correctly referred to my observation of airspeed computations. Then you used the word 'narrative'. What I wrote was an observation of facts. A narrative is connecting facts with speculation.


Oh dear. If only I'd known 'narrative' was an offensive word in some parts.
 
barney captain
Posts: 2332
Joined: Tue Nov 06, 2001 5:47 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Tue Apr 16, 2019 11:30 am

zeke wrote:
barney captain wrote:
This.

The continuing theme in this giant fur ball remains -

The pilots tasked with actually operating these machines are of one mindset.

Those who read and believe everything from the 'paid to sell you news' journalists are of another.

Those of us who are willing to put our asses in the seat have been trivialized. Cyber-pilots have nothing to lose.

And THAT is why Anet has lost so much of it's relevance.


BC,

I don’t like second guessing what is going through other pilots minds when they are not around to defend themselves.

Can you think of a reason why the two lion air flights and this flight seemed to ignore the stick shaker ?

I don’t understand why none of the crews performed the airspeed unreliable memory items. All I could think of was this was something which they had seen before and turned out to be a false positive.

I think we would all welcome your constructive input as you are a current MAX Captain.


Zeke -

Fantastic questions from a revered professional.

The answer is - I don't have the faintest notion. None of us do.

And therein lies the point that so many fail to grasp - we don't have all the data. However, so many have drawn hard lines in the sand without it.

You and I have been around far too long to fall prey to early conclusions based on partial information. This is an emotional topic and I understand that. Lives have been lost, and that deserves the utmost scrutiny. It also deserves reason and pragmatic accountability.

My guess is simply that they were overwhelmed. Lots of bad things happening all at one time. What I dont understand is the fact that (at least in the case of ET) they were daytime VFR - and the aircraft stayed at maximum N1 all the way to impact. And I completely agree, I don't want to throw stones at a crew who isn't around to defend themselves. I simply don't understand it - yet.

What I do know is this, we had reinforced training on the MAX after the JT crash. It emphasized the emergency AD and it's procedures. I would be comfortable flying the MAX tomorrow.

Everything we learn in the sim is how to manage an aircraft when systems break, Systems do break. Prior to the MAX, there were 5 failures that could cause uncommanded trim movement. The MAX added a sixth. It didn't matter what the cause was, the procedure was still the same - Stab Trim Cutoff Switches - Off.

I know these guys had their hands full, and there's no doubt they did all that they could. It pains me to think of what they and their passengers went through, and I await the final report before taking a stand.

Respectfully,

BC
Southeast Of Disorder
 
Tristarsteve
Posts: 3658
Joined: Tue Nov 22, 2005 11:04 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Tue Apr 16, 2019 11:41 am

[quote="WIederling"
If it is just for "feel right" on the MAX why did they not work MCAS functionality into the "feel unit" ?

IMU there is a very real hard reason to have MCAS work on tailplane incidence.
Boeing's description reproduced by 737.co.uk site is a circuitous lie.[/quote]

The elevator feel computor is a mechanical computor. The inputs are pitot from two elevator pitot heads on the fin, and stab position through a mechanical link. There is no electrics in there, it is all done with springs and bellows, and the output is hydraulic pressure on the elevator trim mechanism.
To put MCAS in would mean starting again.
 
FluidFlow
Posts: 638
Joined: Wed Apr 10, 2019 6:39 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Tue Apr 16, 2019 11:44 am

barney captain wrote:

[...]

Respectfully,

BC


Sorry for the strange quote. As you seem to be familiar with the MAX, I would like to ask you a technical question:

Do you know at which AoA MCAS is supposed to be triggered?

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