Interested
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 8:38 pm

MSPNWA wrote:
Interested wrote:

Do you know what the next procedure should be by the manual?


Yeah, fly the plane.


Aren't they trying to do that when they both pull the sticks back together and it doesn't work?
 
Interested
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 8:39 pm

Planetalk wrote:
There is another psychological factor to consider, which is that once you've followed the checklist and done what you think you're supposed to, and the plane still isn't controllable, you begin to wonder if something else is wrong. Can you trust anything at all? Should you be doing something else? You've done what you were told, the plane still isn't working, and last time this happened to someone very recently everybody died.

And from that point controlling your fear and panic and thinking rationally through the situation and sticking with the plan, aware you have very little sky between you and the ground, becomes very, very, difficult. On the whole it seems these pilots did a pretty decent job on that front, despite the assertions of a couple of macho-men here.


Are you saying they've run out of things to do on the checklist at this stage?

There's no more procedure to follow?

If so then surely gambling is allowed as procedure has failed them?
 
Chemist
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 8:44 pm

Interested wrote:
Chemist wrote:
MSPNWA wrote:

You're making assumptions that aren't in the report. We don't know if the manual trim truly didn't work, or if didn't they know enough about it/didn't execute it properly. If it's the former, then we have decades of design at question going back to the original 737. If it's the latter, which is very plausible looking at the report, we have a training/CRM issue.


My guess would be that they allowed themselves to severely overspeed which made manual trim difficult to impossible. Just a bit of throttle down might have made the difference (and that's assuming they still didn't manually/electrically trim to neutral, which it seems they never did).


Do you know what the next procedure should be by the manual?


No, but I do know that there is backup airspeed and procedures for maintaining proper speeds when you don't have good airspeed indication. Those procedures avoid overspeed.
 
bhill
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 8:45 pm

Question about MCAS circuit and the electric stab trim thumb switches. Are they on separate circuits? That is, if you power off MCAS, does that also make the thumb switches inoperable? And for the manual trim wheel, how much force is needed to move them at the velocity this airplane may have been traveling?
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legoguy
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 8:51 pm

Can somebody correct me if any of this is wrong... From following things so far, after the initial MCAS activation the pilots were able to hit the cut off switches as per the checklist and were able to get the aircraft to a roughly level flight at 5000 ft above the ground.

However at this point, they were struggling with holding the control column fully back to maintain the level flight as the aircraft trim was still in a negative position and the aircraft was also in an overspeed situation. So whilst technically in level flight, they had little control considering the full back positions of the control columns and the aircraft speed.

One of the pilots tried to manually adjust the trim however it seemingly had little to no effect. At this point, the trim cut out switches were potentially flipped back on so that one of the pilots could use the electric trim switch in order to regain some use of the control column. But after 5 seconds of doing this, MCAS activated again, this time fatally.
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hilram
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 8:53 pm

bhill wrote:
Question about MCAS circuit and the electric stab trim thumb switches. Are they on separate circuits? That is, if you power off MCAS, does that also make the thumb switches inoperable? And for the manual trim wheel, how much force is needed to move them at the velocity this airplane may have been traveling?

Unfortunately, you cannot “power off MCAS”. In order to disable MCAS you have to either a) disable electric trim (thumb switches) or b) extend flaps. The emergency MCAS bulletin issued by Boeing says a) disable electric trim.

All that is left to you then is cranking the manual trim wheels.

Turning electric trim back on will re-enable MCAS.
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kalvado
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 8:53 pm

bhill wrote:
Question about MCAS circuit and the electric stab trim thumb switches. Are they on separate circuits? That is, if you power off MCAS, does that also make the thumb switches inoperable? And for the manual trim wheel, how much force is needed to move them at the velocity this airplane may have been traveling?

You cannot power off MCAS, it is a piece of a code running on the main plane computer.
You can disconnect that computer from the trim wheel motors - but from what we know, on MAX you also loose thumb switches. Not the case on NG, though.
 
mzlin
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 8:53 pm

legoguy wrote:
Can somebody correct me if any of this is wrong... From following things so far, after the initial MCAS activation the pilots were able to hit the cut off switches as per the checklist and were able to get the aircraft to a roughly level flight at 5000 ft above the ground.

However at this point, they were struggling with holding the control column fully back to maintain the level flight as the aircraft trim was still in a negative position and the aircraft was also in an overspeed situation. So whilst technically in level flight, they had little control considering the full back positions of the control columns and the aircraft speed.

One of the pilots tried to manually adjust the trim however it seemingly had little to no effect. At this point, the trim cut out switches were potentially flipped back on so that one of the pilots could use the electric trim switch in order to regain some use of the control column. But after 5 seconds of doing this, MCAS activated again, this time fatally.


Yes you have it right as far as I can tell too

The unfortunate thing is the person who flipped on the electrical trim didn't continue to make manual electrical trim inputs to counteract MCAS
Last edited by mzlin on Thu Apr 04, 2019 8:57 pm, edited 1 time in total.
 
ikramerica
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 8:56 pm

Planetalk wrote:
So to sum up the key action of the pilots as compared to the checklist.

- They did trim up to counter the MCAS movement before hitting the trim cutout switch.
- They did try to use manual trim as the procedure states when they still couldn't control the aircraft.
- Manual trim didn't work.

What exactly could they have done except reengage electric trim at this point? Note the checklist has now ended. The same checklist various posters insisted the pilots obviously hadn't followed.

Reduce airspeed...
Of all the things to worry about... the Wookie has no pants.
 
Waterbomber2
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:00 pm

MSPNWA wrote:
XRAYretired wrote:
"At 05:40:35, the First-Officer called out “stab trim cut-out” two times. Captain agreed and FirstOfficer confirmed stab trim cut-out. "


Unfortunately that's not confirmation they flipped the cut-offs, only an assumption. We need FDR data for confirmation of the switch position. That piece is missing. It's inferred later here "At 05:40:41, approximately five seconds after the end of the ANU stabilizer motion, a third instance of AND automatic trim command occurred without any corresponding motion of the stabilizer, which is consistent with the stabilizer trim cutout switches were in the ‘’cutout’’ position", however. Strange how they wrote the report.


Not every switch's position is recorded in the FDR.
Sometimes you need to infer from how the aircraft reacts to certain commands and I suspect that this is the case.
 
ikramerica
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:01 pm

legoguy wrote:
Can somebody correct me if any of this is wrong... From following things so far, after the initial MCAS activation the pilots were able to hit the cut off switches as per the checklist and were able to get the aircraft to a roughly level flight at 5000 ft above the ground.

However at this point, they were struggling with holding the control column fully back to maintain the level flight as the aircraft trim was still in a negative position and the aircraft was also in an overspeed situation. So whilst technically in level flight, they had little control considering the full back positions of the control columns and the aircraft speed.

One of the pilots tried to manually adjust the trim however it seemingly had little to no effect. At this point, the trim cut out switches were potentially flipped back on so that one of the pilots could use the electric trim switch in order to regain some use of the control column. But after 5 seconds of doing this, MCAS activated again, this time fatally.

If this is the case they sadly crashed the plane. I hope its not. If they were level why didnt they finally reduce speed?

This was actually similar to the german flight. That was a higher altitude. But they tested things by reactivating the Airbus system that was trimming down. It immediately trimmed down again and they turned it off for good. In this case it involved turning off ADIRU 2 in addition to disabled #3. Not in the manual, no checklist, required ground based support to figure out.
Last edited by ikramerica on Thu Apr 04, 2019 9:06 pm, edited 1 time in total.
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TravelbyAir
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:02 pm

mzlin wrote:
legoguy wrote:
Can somebody correct me if any of this is wrong... From following things so far, after the initial MCAS activation the pilots were able to hit the cut off switches as per the checklist and were able to get the aircraft to a roughly level flight at 5000 ft above the ground.

However at this point, they were struggling with holding the control column fully back to maintain the level flight as the aircraft trim was still in a negative position and the aircraft was also in an overspeed situation. So whilst technically in level flight, they had little control considering the full back positions of the control columns and the aircraft speed.

One of the pilots tried to manually adjust the trim however it seemingly had little to no effect. At this point, the trim cut out switches were potentially flipped back on so that one of the pilots could use the electric trim switch in order to regain some use of the control column. But after 5 seconds of doing this, MCAS activated again, this time fatally.


Yes you have it right as far as I can tell too

The unfortunate thing is the person who flipped on the electrical trim didn't continue to make manual electrical trim inputs to counteract MCAS

This seems to be the heart of the issue. They knew there was too much nose down trim that they could not counter with the manual trim wheel or stick. They attempted, successfully, to counter SOME of the down trim with electric trim, but then it seems abandoned this approach, and left auto trim on which MCAS commanded down AGAIN. Why didn't they keep trimming up electrically to a manageable level, and then cut-out trim again? It seems trim was around 5.0 before MCAS kicked in nose down, and they couldn't control when under 2. Why not trim it up to around 4 or 5?
 
morrisond
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:03 pm

legoguy wrote:
Can somebody correct me if any of this is wrong... From following things so far, after the initial MCAS activation the pilots were able to hit the cut off switches as per the checklist and were able to get the aircraft to a roughly level flight at 5000 ft above the ground.

However at this point, they were struggling with holding the control column fully back to maintain the level flight as the aircraft trim was still in a negative position and the aircraft was also in an overspeed situation. So whilst technically in level flight, they had little control considering the full back positions of the control columns and the aircraft speed.

One of the pilots tried to manually adjust the trim however it seemingly had little to no effect. At this point, the trim cut out switches were potentially flipped back on so that one of the pilots could use the electric trim switch in order to regain some use of the control column. But after 5 seconds of doing this, MCAS activated again, this time fatally.


If you look at the traces it does not appear as though they were full back until the final few seconds of the flight. It looks like it was about half - Manual trim should been somewhat possible or if they reduced power (slowly) over a minute or so they should have been able to counteract the slight nose down moment from that - however it never appears they tried that.
 
Waterbomber2
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:04 pm

Interested wrote:
Planetalk wrote:
There is another psychological factor to consider, which is that once you've followed the checklist and done what you think you're supposed to, and the plane still isn't controllable, you begin to wonder if something else is wrong. Can you trust anything at all? Should you be doing something else? You've done what you were told, the plane still isn't working, and last time this happened to someone very recently everybody died.

And from that point controlling your fear and panic and thinking rationally through the situation and sticking with the plan, aware you have very little sky between you and the ground, becomes very, very, difficult. On the whole it seems these pilots did a pretty decent job on that front, despite the assertions of a couple of macho-men here.


Are you saying they've run out of things to do on the checklist at this stage?

There's no more procedure to follow?

If so then surely gambling is allowed as procedure has failed them?


The captain said screw the checklist, pitch up together. You can't do checklists and pitch up as if your life depends on it.
 
Interested
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:04 pm

ikramerica wrote:
legoguy wrote:
Can somebody correct me if any of this is wrong... From following things so far, after the initial MCAS activation the pilots were able to hit the cut off switches as per the checklist and were able to get the aircraft to a roughly level flight at 5000 ft above the ground.

However at this point, they were struggling with holding the control column fully back to maintain the level flight as the aircraft trim was still in a negative position and the aircraft was also in an overspeed situation. So whilst technically in level flight, they had little control considering the full back positions of the control columns and the aircraft speed.

One of the pilots tried to manually adjust the trim however it seemingly had little to no effect. At this point, the trim cut out switches were potentially flipped back on so that one of the pilots could use the electric trim switch in order to regain some use of the control column. But after 5 seconds of doing this, MCAS activated again, this time fatally.

If this is the case they sadly crashed the plane.


I think you mean MCAS crashed the plane?
 
legoguy
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:05 pm

ikramerica wrote:
Reduce airspeed...


By reducing the airspeed, wouldn't they also lose altitude which isn't ideal at 5000 ft in a mountainous area?

Regarding the manual trim, when they tried to adjust manually in the over speed situation, would the manual trim wheel even rotate? Or will it rotate but have zero effect?
Can you say 'Beer Can' without sounding like a Jamaican saying 'Bacon'?
 
Interested
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:08 pm

legoguy wrote:
ikramerica wrote:
Reduce airspeed...


By reducing the airspeed, wouldn't they also lose altitude which isn't ideal at 5000 ft in a mountainous area?

Regarding the manual trim, when they tried to adjust manually in the over speed situation, would the manual trim wheel even rotate? Or will it rotate but have zero effect?


So reducing airspeed isn't the procedure to follow next?

Does anybody know what the actual checklist says?

I'm not interested in what the armchair pilots think they should do. Im simply asking what the checklist would say?
 
ikramerica
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:13 pm

legoguy wrote:
ikramerica wrote:
Reduce airspeed...


By reducing the airspeed, wouldn't they also lose altitude which isn't ideal at 5000 ft in a mountainous area?

Regarding the manual trim, when they tried to adjust manually in the over speed situation, would the manual trim wheel even rotate? Or will it rotate but have zero effect?

Speed doesn't equal altitude. They were going too fast from the beginning.

But at higher speeds smaller adjustments have greater impact relative to time and speed does impact momentum.

The effort needed to counteract the pitch was related to speed.

Speed also reduces the time pilots have to think and adjust based on their actions.

Speed also increases stress level in a panic situation.

Slow it down.
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smartplane
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:13 pm

Finn350 wrote:
Apparently STAB TRIM CUTOUT switch positions are not recorded by the DFDR, and so they cannot directly identify the position of the switches.

Not recorded, because MCAS, as well as the pilots, can change.

Likely MCAS will turn out to have three settings - OFF (procedure yet to be disclosed by Boeing), ON and BACKGROUND (what is currently described as OFF). In certain flight conditions, MCAS can be provoked from BACKGROUND to ON, even intruding in conditions where it shouldn't, like flaps extended and autopilot on.
 
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Finn350
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:20 pm

smartplane wrote:
Finn350 wrote:
Apparently STAB TRIM CUTOUT switch positions are not recorded by the DFDR, and so they cannot directly identify the position of the switches.

Not recorded, because MCAS, as well as the pilots, can change.

Likely MCAS will turn out to have three settings - OFF (procedure yet to be disclosed by Boeing), ON and BACKGROUND (what is currently described as OFF). In certain flight conditions, MCAS can be provoked from BACKGROUND to ON, even intruding in conditions where it shouldn't, like flaps extended and autopilot on.


I don’t think so. When flaps are retracted or autopilot is connected, MCAS is disabled. If MCAS is enabled in manual flight due to high AoA reading, nose down trimming can be prevented by cutout switches (as the electrical motors controlling the trim have no power, no trimming occurs even if MCAS is sending nose down commands).
 
Waterbomber2
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:21 pm

ikramerica wrote:
Planetalk wrote:
So to sum up the key action of the pilots as compared to the checklist.

- They did trim up to counter the MCAS movement before hitting the trim cutout switch.
- They did try to use manual trim as the procedure states when they still couldn't control the aircraft.
- Manual trim didn't work.

What exactly could they have done except reengage electric trim at this point? Note the checklist has now ended. The same checklist various posters insisted the pilots obviously hadn't followed.

Reduce airspeed...


Mmmm you are pulling with full force and 94% N1 to stay level in a very narrow flight envelope.
If you reduce thrust in that setting your aircraft is going to pitch down because the engines are actually helping you to stay level.

Reducing thrust is easier said than done, that's very counter-intuitive.
Sorry but manual trim should remain operable through the entire flight envelope of an aircraft.

It looks like an ADIRS left failure (could be sensors, could be downstream) caused MCAS to trim down. They switched MCAS off but the increasing speed cornered the pilots in that they couldn't counteract with elevators nor trim up anymore. Reducing speed could have helped them regain control of the manual trim at the expense of altitude but that is a suicide mission. You don't know if manual trim is going to work again if you do reduce the speed.
So they tried to trim their way out, perhaps by reactivating electrical trim and then MCAS put them in their final dive.

I would probably have done the same in their position.
Last edited by Waterbomber2 on Thu Apr 04, 2019 9:23 pm, edited 1 time in total.
 
Planetalk
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:23 pm

Interested wrote:
legoguy wrote:
ikramerica wrote:
Reduce airspeed...


By reducing the airspeed, wouldn't they also lose altitude which isn't ideal at 5000 ft in a mountainous area?

Regarding the manual trim, when they tried to adjust manually in the over speed situation, would the manual trim wheel even rotate? Or will it rotate but have zero effect?


So reducing airspeed isn't the procedure to follow next?

Does anybody know what the actual checklist says?

I'm not interested in what the armchair pilots think they should do. Im simply asking what the checklist would say?


There is no next step on the checklist. It finishes with manual trim. Please stop reposting the same question over and over!
 
chicawgo
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:28 pm

mzlin wrote:
tphuang wrote:
I love all the armchair QB dissecting all of the pilots possible mistakes from the comfort of their home computer without impending death facing them.


Actually we do like to do that, because we are interested in learning more about civil aviation, including understanding the risks involved when getting on an airplane, and that is why we are on this site.


This may be the best post I've ever seen on this site.

I love all the self-righteous "parents" who frequently type holier-than-thou statements like this just to boost their own confidence and get affirming responses but add nothing to the actual conversation. Almost all of us are armchair QBs. That's why the site exists. Every comment like the above should be removed.
 
Interested
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:28 pm

Planetalk wrote:
Interested wrote:
legoguy wrote:

By reducing the airspeed, wouldn't they also lose altitude which isn't ideal at 5000 ft in a mountainous area?

Regarding the manual trim, when they tried to adjust manually in the over speed situation, would the manual trim wheel even rotate? Or will it rotate but have zero effect?


So reducing airspeed isn't the procedure to follow next?

Does anybody know what the actual checklist says?

I'm not interested in what the armchair pilots think they should do. Im simply asking what the checklist would say?


There is no next step on the checklist. It finishes with manual trim. Please stop reposting the same question over and over!


It took that long to get an actual answer

Three or four times I got told reduce airspeed was the next procedure. But as I suspected it wasn't. It's just what the posters thought might have helped. Or what they would do. I wasn't interested in opinion. Just fact.

There's a lot of experts on here. Who talk like they are quoting procedure when they aren't from my experience

At least I got the answer in the end
Last edited by Interested on Thu Apr 04, 2019 9:30 pm, edited 1 time in total.
 
Amexair
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:29 pm

Chemist wrote:
Interested wrote:
Chemist wrote:

My guess would be that they allowed themselves to severely overspeed which made manual trim difficult to impossible. Just a bit of throttle down might have made the difference (and that's assuming they still didn't manually/electrically trim to neutral, which it seems they never did).




You realize you need pitch to control the speed of the aircraft when IAS is unreliable. In this case, they were fighting to keep the aircraft pitch stable which means there goes any control you have over speed. Reducing thrust will result in further nose-down pitch.
Last edited by Amexair on Thu Apr 04, 2019 9:38 pm, edited 1 time in total.
 
TaromA380
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:30 pm

mzlin wrote:
The unfortunate thing is the person who flipped on the electrical trim didn't continue to make manual electrical trim inputs to counteract MCAS

… altogether with strangely not passing on the information about its reactivation.
… plus completely missing the excessive airspeed and the subsequent clackers - not even an acknowledgement.

This critical moment, would it be
- either a bad management at the worst moment - were they so perturbed by seeing how ineffective their cumulated manual trim efforts were, the specter of LionAir’s ending surely overshadowing the cockpit despite the briefly success of stabilizing their altitude ?
- either something else, not obvious to us right now, was interfering ?
 
DH106
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:35 pm

For all those asking why didn't the pilots reduce speed:- the aircraft's airspeed is inextricably linked to the pitch trim - you can't just throttle back and expect the speed to bleed off with no pitch trim change.The aerodynamics of a stable aircraft tries to maintain the same airspeed, thus throttling back produces a nose-down change in the pitch trim as the aircraft attempts to maintain the trimmed airspeed. Clearly, in this case, extra nose-down pitching due to a reduction in speed is not what the pilots needed.
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Waterbomber2
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:40 pm

There is one thing the flight crew could have done but it's a bit insane. They could have treated this as being out of CG (excessively fwd CG) and ordered pax in the first 3 rows to run back to the aft galley and stay there until further notice.
2 tons shifting from all the way in the front to all the way in the back would create sufficient momentum to pitch the aircraft up.

Again, not saying they should have done this as it's insane, but this may have been their last option.
And again, I suggest this with hindsight, time to see the data and gain awareness, no bells and whistles going off and from a comfy chair safely on the ground.
Last edited by Waterbomber2 on Thu Apr 04, 2019 9:46 pm, edited 2 times in total.
 
glideslope900
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:42 pm

Does anybody have a link to the preliminary report?
 
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Finn350
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:48 pm

glideslope900 wrote:
Does anybody have a link to the preliminary report?


http://www.ecaa.gov.et/documents/20435/ ... X+,(ET-AVJ).pdf
 
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sergegva
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:49 pm

mzlin wrote:

The pilots did things correctly until 05:43:00 but then they made the mistake of not counteracting MCAS after 05:43:20. And as stated above, I suspect one pilot acted alone to turn on electrical trim because there was no verbal discussion or callout or confirmation. (This would then be a CRM issue.) And whoever switched it on may not have realized that MCAS would come back. And finally neither pilot noticed the trim moving back down.


For me, that's the main mystery. And that's another thing in common with the Lion Air flight.

Clearly, the pilots of both flights had understood that they could counter the nose down/MCAS with manual electric trim imputs. It was working. And then suddenly they stopped doing it! In the Lion Air flight, it's already incomprehensible. But we know they didn't know what MCAS was. So we can still admit that, at one point, they tried something else "without realizing" that stopping to counter the MCAS would crash the plane. But here in the second crash? They deactivate the switch 35 secondes after the first MCAS imput, which is rather fast! Both pilots verbally reported "trim cut-out". And indeed, the MCAS stopped immediately. To me, it is obvious that they knew perfectly well that the MCAS was causing the problem, and they were following Boeing's procedure. Unfortunately, it appears that the aircraft was not controllable with manual trim controls because of its high speed.

From that point on, a rational behaviour, considering that slowing down the aircraft was risky at only 1500 m above ground level with unreliable airspeed, was to reactivate the electric trim and to manually counter each MCAS activation every 10 seconds with the manual electric trim, as the Lion Air pilots did for quite some time. And that's precisely what they seemed to have done right after the switch was reactivated, since a manual electric trim has been recorded. And then, they suddenly stopped! Why??! After having understood that the problem came from the MCAS, after having noticed that disabling the switch stopped the MCAS, it simply seems impossible to me that a pilot could have "forgotten" that reactivating the switch would reactivate the MCAS. Especially after the Lion Air accident! At that time, those two pilots probably had MCAS only in their mind!

We can put forward 99 hypotheses on why this sudden stop of counter-triming against MCAS had happened,had it happened in a single accident only. But twice the exact same omission?

Are there any technical reasons that could explain why, after a certain time / a certain number of uses / a certain configuration, the manual electric trim button stops working? For example, that the button breaks, to take a rather simplistic example?
Last edited by sergegva on Thu Apr 04, 2019 9:54 pm, edited 2 times in total.
 
tropical
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:54 pm

Whereas it is still possible that once the final report comes out it might rule human error might have been *partially* to blame (even though it is looking less likely by the day to me, but never mind that for now), surely it is beyond any doubt by now that Boeing will certainly shoulder a significant amount of the blame overall in this sorry saga?

In view of that, perhaps it is time for anyone still trying to find alternative (and increasingly desperate) scenarios that might suggest pilot error was responsible to reconsider and stop trying to shift the focus of the discussion to it. That Boeing has made a series of serious errors of judgment throughout the conception and implementation of the MAX is both undeniable and the root of the problem here. Even if deficient training or maintenance turned out to have played a part in either crash, it would still be a footnote to the core issue here.
 
afgeneral
Posts: 86
Joined: Sat Jul 02, 2016 2:43 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 9:57 pm

Waterbomber2 wrote:
There is one thing the flight crew could have done but it's a bit insane. They could have treated this as being out of CG (excessively fwd CG) and ordered pax in the first 3 rows to run back to the aft galley and stay there until further notice.
2 tons shifting from all the way in the front to all the way in the back would create sufficient momentum to pitch the aircraft up.

Again, not saying they should have done this as it's insane, but this may have been their last option.
And again, I suggest this with hindsight, time to see the data and gain awareness, no bells and whistles going off and from a comfy chair safely on the ground.


that's like saying pilots of an aircraft suffering from a fire should command passengers to start spitting and pissing on the fire until it is put out
 
tphuang
Posts: 3000
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 10:00 pm

chicawgo wrote:
mzlin wrote:
tphuang wrote:
I love all the armchair QB dissecting all of the pilots possible mistakes from the comfort of their home computer without impending death facing them.


Actually we do like to do that, because we are interested in learning more about civil aviation, including understanding the risks involved when getting on an airplane, and that is why we are on this site.


This may be the best post I've ever seen on this site.

I love all the self-righteous "parents" who frequently type holier-than-thou statements like this just to boost their own confidence and get affirming responses but add nothing to the actual conversation. Almost all of us are armchair QBs. That's why the site exists. Every comment like the above should be removed.


Right, nobody said you can't study or comment on it. That's your right, but the pilots were in a situation with very little margin for error, without full situation awareness and very little time on hand. So all these comments about how they could've saved the aircraft without actually being in their situation or they didn't do everything they could given the circumstances is entirely off base. Watching the entire replay makes a lot of great after the fact generals.
Last edited by tphuang on Thu Apr 04, 2019 10:01 pm, edited 1 time in total.
 
Waterbomber2
Posts: 381
Joined: Mon Feb 04, 2019 3:44 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 10:04 pm

tropical wrote:
Whereas it is still possible that once the final report comes out it might rule human error might have been *partially* to blame (even though it is looking less likely by the day to me, but never mind that for now), surely it is beyond any doubt by now that Boeing will certainly shoulder a significant amount of the blame overall in this sorry saga?

In view of that, perhaps it is time for anyone still trying to find alternative (and increasingly desperate) scenarios that might suggest pilot error was responsible to reconsider and stop trying to shift the focus of the discussion to it. That Boeing has made a series of serious errors of judgment throughout the conception and implementation of the MAX is both undeniable and the root of the problem here. Even if deficient training or maintenance turned out to have played a part in either crash, it would still be a footnote to the core issue here.


It definitely looks that way.
To me, a non-FBW aircraft that can't be trimmed manually within its flight envelope raises question marks.
 
Waterbomber2
Posts: 381
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 10:06 pm

afgeneral wrote:
Waterbomber2 wrote:
There is one thing the flight crew could have done but it's a bit insane. They could have treated this as being out of CG (excessively fwd CG) and ordered pax in the first 3 rows to run back to the aft galley and stay there until further notice.
2 tons shifting from all the way in the front to all the way in the back would create sufficient momentum to pitch the aircraft up.

Again, not saying they should have done this as it's insane, but this may have been their last option.
And again, I suggest this with hindsight, time to see the data and gain awareness, no bells and whistles going off and from a comfy chair safely on the ground.


that's like saying pilots of an aircraft suffering from a fire should command passengers to start spitting and pissing on the fire until it is put out


It certainly is.
So consider this as just a mental exercise to entertain all the options.
Last edited by Waterbomber2 on Thu Apr 04, 2019 10:15 pm, edited 1 time in total.
 
Interested
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Joined: Thu May 19, 2016 12:19 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 10:11 pm

Waterbomber2 wrote:
afgeneral wrote:
Waterbomber2 wrote:
There is one thing the flight crew could have done but it's a bit insane. They could have treated this as being out of CG (excessively fwd CG) and ordered pax in the first 3 rows to run back to the aft galley and stay there until further notice.
2 tons shifting from all the way in the front to all the way in the back would create sufficient momentum to pitch the aircraft up.

Again, not saying they should have done this as it's insane, but this may have been their last option.
And again, I suggest this with hindsight, time to see the data and gain awareness, no bells and whistles going off and from a comfy chair safely on the ground.


that's like saying pilots of an aircraft suffering from a fire should command passengers to start spitting and pissing on the fire until it is put out


It surely is.


Yep and in 2019 with a plane that should be state of the art

We've ended up with that suggestion as to how to save the plane

It says it all really!!
 
RickNRoll
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 10:14 pm

morrisond wrote:
My take on reading the accident report is that the flight was saveable until they turned the Electric Trim back on which reactivated MCAS which due to the high speed they were travelling at they were not able to recover from as the airspeed was excessive.

On Page 33 of the Accident report the Boeing Nov 6, 2018 Flight bulletin clearly says to not reengage the Electric Trim system for the remainder of the flight.
Did Boeing do a full test of this procedure before it was released? It appears to be critical to follow a critical path exactly or death is certain. Typically you would want to train crews on a simulator for such an event. Only there were no simulators available for such training. Boeing should have known it was not as simple as their simple check sheet made it out to be.

I believe the MAX should have been grounded after the lion air crash until a fully debugged and tested and trained procedure was available for all pilots of the MAX.
 
Interested
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 10:15 pm

tphuang wrote:
chicawgo wrote:
mzlin wrote:

Actually we do like to do that, because we are interested in learning more about civil aviation, including understanding the risks involved when getting on an airplane, and that is why we are on this site.


This may be the best post I've ever seen on this site.

I love all the self-righteous "parents" who frequently type holier-than-thou statements like this just to boost their own confidence and get affirming responses but add nothing to the actual conversation. Almost all of us are armchair QBs. That's why the site exists. Every comment like the above should be removed.


Right, nobody said you can't study or comment on it. That's your right, but the pilots were in a situation with very little margin for error, without full situation awareness and very little time on hand. So all these comments about how they could've saved the aircraft without actually being in their situation or they didn't do everything they could given the circumstances is entirely off base. Watching the entire replay makes a lot of great after the fact generals.


Not only that. These generals keep making simple statements about what SHOULD have happened and 5 minutes later someone else comes in and tells them why that wouldn't work

Yet until this report it was as simple as "why didn't they just flick the switch and fly the plane?"

Now it's "what was the best gamble to try when all the procedures and checklist have failed?"

Is there no end to how we question these pilots?

We've got to the stage of suggesting gambles??

And we can't even agree on them?

But we still want to say some of the blame lies with the pilots

Ok - I will say 5 per cent at most. And that's being generous to the plane they were flying and MCAS

Ps - have we stopped questioning the airline yet?? Have they done anything wrong?
 
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remcor
Posts: 366
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 10:19 pm

ikramerica wrote:
Planetalk wrote:
So to sum up the key action of the pilots as compared to the checklist.

- They did trim up to counter the MCAS movement before hitting the trim cutout switch.
- They did try to use manual trim as the procedure states when they still couldn't control the aircraft.
- Manual trim didn't work.

What exactly could they have done except reengage electric trim at this point? Note the checklist has now ended. The same checklist various posters insisted the pilots obviously hadn't followed.

Reduce airspeed...


You guys are saying REDUCE AIRSPEED like it's a given. So how would one reduce airspeed in the current situation?

Pitch up? Seems they were trying to do that as much as they could.

Reduce throttle? Ok fine. But that will cause the nose to pitch down, since it would reduce the net down-force on the stabilizer/elevator causing a pitch-down moment.

Normally, if one wants to reduce airspeed without changing altitude you need to do a combination of reducing throttle and nose-up trim/elevator. I'm no 737 pilot, but I know in my Cessna that if I'm at level flight and pull throttle the nose will pitch down, and to maintain altitude I must pull up and re-trim with a higher AOA.
Last edited by remcor on Thu Apr 04, 2019 10:23 pm, edited 1 time in total.
 
TaromA380
Posts: 290
Joined: Sun Sep 11, 2005 12:35 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 10:21 pm

tropical wrote:
Whereas it is still possible that once the final report comes out it might rule human error might have been *partially* to blame (even though it is looking less likely by the day to me, but never mind that for now), surely it is beyond any doubt by now that Boeing will certainly shoulder a significant amount of the blame overall in this sorry saga?

In view of that, perhaps it is time for anyone still trying to find alternative (and increasingly desperate) scenarios that might suggest pilot error was responsible to reconsider and stop trying to shift the focus of the discussion to it. That Boeing has made a series of serious errors of judgment throughout the conception and implementation of the MAX is both undeniable and the root of the problem here. Even if deficient training or maintenance turned out to have played a part in either crash, it would still be a footnote to the core issue here.

In the courts every concerned entity will fight to minimize their share in the accident and maximize the other’s involvement, the sky will be the limit in twisting every aspect to make it look as wished. It is part of universal humans going for their interests. Everything is polemical in this world, not only final accidents reports. Somewhere a balance of all vectors will be reached, but not before screaming loud all contradictory points of view.
There is even a philosophical saying "everyone is right".
Right now the medias seems to be focused on the first part of the report, where pilots did exactly what they were supposed to do. They already tell the whole story, when in fact it isn’t. The second part, starting at the reactivation without verbal acknowledgement, can be used as well for telling a different story. Even omitting the first part of the same report. We already saw how the same topic can be narrated and mass-perceived from one extreme to the other at short intervals.
 
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anfromme
Posts: 883
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 10:21 pm

smartplane wrote:
Finn350 wrote:
Apparently STAB TRIM CUTOUT switch positions are not recorded by the DFDR, and so they cannot directly identify the position of the switches.

Not recorded, because MCAS, as well as the pilots, can change.

Likely MCAS will turn out to have three settings - OFF (procedure yet to be disclosed by Boeing), ON and BACKGROUND (what is currently described as OFF). In certain flight conditions, MCAS can be provoked from BACKGROUND to ON, even intruding in conditions where it shouldn't, like flaps extended and autopilot on.
Actually, I would say - based on what we have learnt in the past few weeks - that MCAS is on or off.
The chief point is - contrary to what you would have thought after that AD last year, using the cutout switches as per runaway trim procedure does not actually turn MCAS off. It just disables the actuator motors MCAS controls. Which means that if you flip the switches back on, MCAS might just be in the middle of one of its cycles and thus immediately start having an effect on trim again as the motor responds to input again.
42
 
Interested
Posts: 647
Joined: Thu May 19, 2016 12:19 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 10:22 pm

remcor wrote:
ikramerica wrote:
Planetalk wrote:
So to sum up the key action of the pilots as compared to the checklist.

- They did trim up to counter the MCAS movement before hitting the trim cutout switch.
- They did try to use manual trim as the procedure states when they still couldn't control the aircraft.
- Manual trim didn't work.

What exactly could they have done except reengage electric trim at this point? Note the checklist has now ended. The same checklist various posters insisted the pilots obviously hadn't followed.

Reduce airspeed...


Yes but how would one reduce airspeed?

Pitch up? Seems they were trying to do that as much as they could.

Reduce throttle? Ok, but that will cause the nose to pitch down, since it would reduce the net down-force on the stabilizer/elevator causing a pitch-down moment.

Normally if you want to reduce airspeed without changing altitude you need to do a combination of reducing throttle and nose-up trim/elevator.


It's OK. The guys who suggested reduce airspeed have gone now

They must realise it couldn't work after all
 
Interested
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 10:25 pm

TaromA380 wrote:
tropical wrote:
Whereas it is still possible that once the final report comes out it might rule human error might have been *partially* to blame (even though it is looking less likely by the day to me, but never mind that for now), surely it is beyond any doubt by now that Boeing will certainly shoulder a significant amount of the blame overall in this sorry saga?

In view of that, perhaps it is time for anyone still trying to find alternative (and increasingly desperate) scenarios that might suggest pilot error was responsible to reconsider and stop trying to shift the focus of the discussion to it. That Boeing has made a series of serious errors of judgment throughout the conception and implementation of the MAX is both undeniable and the root of the problem here. Even if deficient training or maintenance turned out to have played a part in either crash, it would still be a footnote to the core issue here.

In the courts every concerned entity will fight to minimize their share in the accident and maximize the other’s involvement, the sky will be the limit in twisting every aspect to make it look as wished. It is part of universal humans going for their interests. Everything is polemical in this world, not only final accidents reports. Somewhere a balance of all vectors will be reached, but not before screaming loud all contradictory points of view.
There is even a philosophical saying "everyone is right".
Right now the medias seems to be focused on the first part of the report, where pilots did exactly what they were supposed to do. They already tell the whole story, when in fact it isn’t. The second part, starting at the reactivation without verbal acknowledgement, can be used as well for telling a different story. Even omitting the first part of the same report. We already saw how the same topic can be narrated and mass-perceived from one extreme to the other at short intervals.


But at that stage I think it's accepted they had no control over the plane and the Boeing procedures to reclaim control of the plane had failed?

So what else could they have gambled on

It appears reducing speed is not one of the gambles

What else could they try at this stage?

Aren't they doomed anyway by now?

They've tried the checklist repeatedly and its failed them?
 
sadiqutp
Posts: 277
Joined: Thu Sep 08, 2016 5:05 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 10:25 pm

I find it extremely disturbing the amount of focus is given to pilots actions rather than control systems...
You see, I am not saying the pilots did everything correctly or otherwise, I don't think the preliminary report give enough information to draw that conclusion.
But here is what I know.
1- MCAS is designed based on one input structure.. No redundancy.. That's on Boeing
2- This is not the first accident of the same cause, not only did Boeing relieved themselves of responsibility after the first one, but had failed to address it before it claimed other casualties. That's on Boeing
3- A new system was introduced to a new version of a series that would alter flight controls when AP is disengaged.. Pilots were neither informed nor trained to deal with new system.. That's on Boeing

I still think the actions of pilots should further be scrutinised, not for blame, but rather to improve training and safety.

I also believe, the conversation in here is extremely imbalanced and Boeing enthusiasts should admit that Boeing could've done better. I am sure the Max will be back in the air, but safely shouldn't be a compromise, again!

Until then, RIP to all those perished
 
spacecadet
Posts: 3416
Joined: Thu Sep 20, 2001 3:36 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 10:25 pm

remcor wrote:
You guys are saying REDUCE AIRSPEED like it's a given. So how would one reduce airspeed in the current situation?


Speed brakes, flaps, landing gear...

Not saying they had a way out of the situation, but as for this specific question, yes, there are ways to reduce airspeed in an airliner besides just reducing throttle and pitching up. Otherwise no airliner could ever land.
I'm tired of being a wanna-be league bowler. I wanna be a league bowler!
 
RickNRoll
Posts: 1726
Joined: Fri Jan 06, 2012 9:30 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 10:26 pm

zuckie13 wrote:
The two questions I'm left with are:

1) Why did they not reduce thrust?
2) After cutting out the electric trim, did they really try to move the trim manually (as in spinning the wheel), or did they try to "manually" move it with the switches on the control column? From my look at the data, I'm not convinced they moved the wheel (but cant' tell if because they didn't' try, or literally couldn't.

Would decelerating make manual pitch control easier?
A complex event like this really required time in a SIM. Most pilots would struggle to get it exactly right. Only there was no SIM that could give you an MCAS fail due to AoA error.

Boeing gave a promise that competent NG pilots could transition safely and quickly to the MAX after a simple video presentation. That would make introduction of the MAX cheap and efficient.

Boeing was wrong. And when they were shown to be wrong they doubled down. They came out with a lie that a simple procedure on a printed list would safe.

People are failing to distinguish between well known and rehearsed procedures would be the responsibility of the pilot. Ad hoc and untrained procedures are the responsibility of the manufacturer and airlines providing the plane to the pilots.
 
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remcor
Posts: 366
Joined: Thu Feb 16, 2006 9:25 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 10:29 pm

spacecadet wrote:
remcor wrote:
You guys are saying REDUCE AIRSPEED like it's a given. So how would one reduce airspeed in the current situation?


Speed brakes, flaps, landing gear...

Not saying they had a way out of the situation, but as for this specific question, yes, there are ways to reduce airspeed in an airliner besides just reducing throttle and pitching up. Otherwise no airliner could ever land.


Still, all would cause the nose to pitch down. Remember horizontal stabilizer is kind of like an upside-down wing. Reduce the airspeed flowing over it and it becomes less effective, and since the center of gravity is in front of the center of lift, the nose pitches down.

And I'm not saying that under no circumstances should they have done that - but some people (not necessarily you) have been saying this like it's a simple solution.

In fact one could make the opposite case and say an INCREASE in airspeed would - at a fixed elevator/trim configuration - cause a pitch up moment.
Last edited by remcor on Thu Apr 04, 2019 10:36 pm, edited 3 times in total.
 
RickNRoll
Posts: 1726
Joined: Fri Jan 06, 2012 9:30 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 10:29 pm

scbriml wrote:
qf789 wrote:
Here is Boeing's statement on the investigation preliminary report

http://www.boeing.com/commercial/737max ... /statement


"The preliminary report contains flight data recorder information indicating the airplane had an erroneous angle of attack sensor input that activated the Maneuvering Characteristics Augmentation System (MCAS) function during the flight, as it had during the Lion Air 610 flight."

That lays to rest any lingering doubts that MCAS was involved in both accidents and that the grounding wasn't justified.
Like i just said, from Boeing themselves.

"To ensure unintended MCAS activation will not occur again, Boeing has developed and is planning to release a software update to MCAS and an associated comprehensive pilot training and supplementary education program for the 737 MAX."
 
dragon6172
Posts: 1068
Joined: Sat Jul 14, 2007 9:56 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 04, 2019 10:30 pm

anfromme wrote:
smartplane wrote:
Finn350 wrote:
Apparently STAB TRIM CUTOUT switch positions are not recorded by the DFDR, and so they cannot directly identify the position of the switches.

Not recorded, because MCAS, as well as the pilots, can change.

Likely MCAS will turn out to have three settings - OFF (procedure yet to be disclosed by Boeing), ON and BACKGROUND (what is currently described as OFF). In certain flight conditions, MCAS can be provoked from BACKGROUND to ON, even intruding in conditions where it shouldn't, like flaps extended and autopilot on.
Actually, I would say - based on what we have learnt in the past few weeks - that MCAS is on or off.
The chief point is - contrary to what you would have thought after that AD last year, using the cutout switches as per runaway trim procedure does not actually turn MCAS off. It just disables the actuator motors MCAS controls. Which means that if you flip the switches back on, MCAS might just be in the middle of one of its cycles and thus immediately start having an effect on trim again as the motor responds to input again.

The AD and the Boeing bulletin make no comment about MCAS
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