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VV
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 1:03 pm

As for the force needed to move the horizontal stabilizer, I hope people know that usually the hinges are located very close to the line between the two centers of lift.

The jack screw is located with a sufficient distance from the hinges.

And finally the up and down movement is performed by a jackscrew.

That rubbish about the force needed to move the horizontal stabilizer is astonishing.

Have you guys jacked a car?
 
Planetalk
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 1:20 pm

barney captain wrote:
Groundings should be based on facts, and not driven by social media.

I'm off to work, carry on this without me.


You said you agree with the grounding. Which version of you am I talking with now?
 
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speedbored
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 1:21 pm

VV wrote:
That rubbish about the force needed to move the horizontal stabilizer is astonishing.

Astonishing, yes. Rubbish, definitely not; it has been confirmed by multiple independent simulator tests, like the one in the video. The manual trim wheel becomes unusable by most pilots at high speeds with significant amounts of nose-down trim and nose-up elevator.

Boeing even used to include a procedure to work around this in the pilot's manual.
 
Saintor
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 1:24 pm

PcarSBA wrote:
I read Björns report. I am still trying to understand why they did not back off the thrust at some point.

If I understand correctly the building IAS with its increasing aerodynamic loads narrowed the envelope more and more to where

- manual trim (spinning the wheel) became increasingly difficult to the point of being impossible
- MCAS input and/or trim switch inputs ozn the stabilier with cut-off switches engaged resulted in violent G-forces
- flaps re-engage was out off the question due to high speed
- blow-back reduced elevator authority

How many indicators did they have to realize (in their high-stress situation) they went beyond Vmo while thrust was still at almost 100%.


Well according to this link, manual trimming is possible up to 250 knots. Did the pilots know that? The test in the video was at 300. They were going 350+. It was not possible (if they tried, unsure).
https://www.reuters.com/article/us-ethi ... SKCN1RG2PP

If I understand this right, it would have been possible to reduce to sub 200 knots (or any possible speed compatible with flaps), and to deploy them (preventing probably the MCAS to act).
 
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scbriml
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 1:25 pm

VV wrote:
Why?

Because none of the two actors looks towards the instruments not toward the handle.


They're not actors, they're 737 pilots.

VV wrote:
That rubbish about the force needed to move the horizontal stabilizer is astonishing.

Have you guys jacked a car?


It's not rubbish. Try jacking up a car with 20 people standing on it... Let us know how that goes.

What is astonishing is that you seem to refuse to believe what you've been shown. There's none so blind as he who will not see.
Time flies like an arrow. Fruit flies like a banana!
There are 10 types of people in the World - those that understand binary and those that don't.
 
Planetalk
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 1:47 pm

barney captain wrote:
Groundings should be based on facts, and not driven by social media.

I'm off to work, carry on this without me.


You just said you agree it should be grounded. So social media was right no? Perhaps an example of it doing good in the world. Or your logic is the plane should have been grounded, but passengers should have kept quiet and flown on the plane you think should have been grounded, but then nothing would have made poor Boeing look bad, and then they wouldn't have had to ground it. But you said it should be grounded. Social media actually achieved what regulation couldn't.

Also note how when China first grounded it a large number of posters here said it was 'political'. A large number of those posters have now disappeared, and equally many posters who said they 'just needed to cut the trim switches'.

Sad to see how many people were here only to push propaganda, and then disappeared. Obviously people who had no actual interest in the causes of the accident, only muddying the waters, since they haven't posted at all since the facts got inconvenient.
Last edited by Planetalk on Sat Apr 13, 2019 2:10 pm, edited 1 time in total.
 
SimonL
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 1:54 pm

Saintor wrote:
PcarSBA wrote:
I read Björns report. I am still trying to understand why they did not back off the thrust at some point.

If I understand correctly the building IAS with its increasing aerodynamic loads narrowed the envelope more and more to where

- manual trim (spinning the wheel) became increasingly difficult to the point of being impossible
- MCAS input and/or trim switch inputs ozn the stabilier with cut-off switches engaged resulted in violent G-forces
- flaps re-engage was out off the question due to high speed
- blow-back reduced elevator authority

How many indicators did they have to realize (in their high-stress situation) they went beyond Vmo while thrust was still at almost 100%.


Well according to this link, manual trimming is possible up to 250 knots. Did the pilots know that? The test in the video was at 300. They were going 350+. It was not possible (if they tried, unsure).
https://www.reuters.com/article/us-ethi ... SKCN1RG2PP

If I understand this right, it would have been possible to reduce to sub 200 knots (or any possible speed compatible with flaps), and to deploy them (preventing probably the MCAS to act).


You cannot reduce the speed if you cannot trim the plane. Any decrease in speed will make the plane even more nose heavy. If you barely can hold it at 350 knots you wont be able to do it at 250.
 
Olddog
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 2:00 pm

If VV stands for Vero Venia, theses posts are not surprising :)
 
kalvado
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 2:04 pm

Planetalk wrote:
barney captain wrote:
Groundings should be based on facts, and not driven by social media.

I'm off to work, carry on this without me.


You just said you agree it should be grounded. So social media was right no? Perhaps an example of it doing good in the world. Or your logic is the plane should have been grounded, but passengers should have kept quiet and flown on the plane you think should have been grounded, but so nothing would have made poor Boeing look bad, and then they wouldn't have had to ground it. But you said it should be grounded. Social media actually achieved what regulation couldn't. Also note how when China first grounded it a large number of posters here said it was 'political'. A large number of those posters have now disappeared, and equally many posters who said they 'just needed to cut the trim switches'.

Sad to see how many people were here only to push propaganda, and then disappeared. Obviously people who had no actual interest in the causes of the accident, only muddying the waters, since they haven't posted at all since the facts got inconvenient.

And to make it worse: China was the first country to ground MAX. Accusing chinese regulators of bowing to social media is... well, lets say unexpected.
 
Planetalk
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 2:11 pm

kalvado wrote:
Planetalk wrote:
barney captain wrote:
Groundings should be based on facts, and not driven by social media.

I'm off to work, carry on this without me.


You just said you agree it should be grounded. So social media was right no? Perhaps an example of it doing good in the world. Or your logic is the plane should have been grounded, but passengers should have kept quiet and flown on the plane you think should have been grounded, but so nothing would have made poor Boeing look bad, and then they wouldn't have had to ground it. But you said it should be grounded. Social media actually achieved what regulation couldn't. Also note how when China first grounded it a large number of posters here said it was 'political'. A large number of those posters have now disappeared, and equally many posters who said they 'just needed to cut the trim switches'.

Sad to see how many people were here only to push propaganda, and then disappeared. Obviously people who had no actual interest in the causes of the accident, only muddying the waters, since they haven't posted at all since the facts got inconvenient.

And to make it worse: China was the first country to ground MAX. Accusing chinese regulators of bowing to social media is... well, lets say unexpected.


Indeed. Which should cause a few people to ask some questions of their own authorities. But brainwashing doesn't only happen in communist states...
 
MigPilot
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 2:15 pm

VV wrote:
As for the force needed to move the horizontal stabilizer, I hope people know that usually the hinges are located very close to the line between the two centers of lift.

The jack screw is located with a sufficient distance from the hinges.

And finally the up and down movement is performed by a jackscrew.

That rubbish about the force needed to move the horizontal stabilizer is astonishing.

Have you guys jacked a car?


http://www.avioesemusicas.com/wp-conten ... to-AOA.pdf

Note: Initially, higher control forces may be needed to overcome any stabilizer nose down trim already applied.….


You better tell Boeing their note is rubbish and totally unnecessary. No high control forces in the trim system possible. The jackscrew takes care of that. Thank god you cleared that up
 
OldAeroGuy
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 2:30 pm

WIederling wrote:
OldAeroGuy wrote:
maint123 wrote:
The lion air crash can be termed a accident due to ignorance but the ethiopian crash is criminal neglect.
Boeing was too busy deflecting and blaming the crew and maintenance to take a serious look at their plane.
Anyone defending them should also be made accessories to their actions.
I will repeat, laws of physics are unforgiving. You can't fool them.


Very bold statements to make since the FAA/Boeing issued Emergency Air Worthiness Directive 2018-23-51 on November 7, 2018.


Which apparently was unsuitable for the task. ( due to pervasive disinterest? no idea )
( I find this pronounced lack of deep thinking sticking out all over MCAS and the resulting crashes irritating.)


Except that:

1) The AD was not followed as the "STAB TRIM" switches were turned back on. The AD says clearly to turn them off and leave them off.
2) Airspeed was above Vmo

These are the two primary differences between ET302 and the Lion Air flight that also had an MCAS malfunction due to a false AoA vane signal and survived the experience.

While I agree that MCAS.v1 is a poorly implemented design, to say that Boeing's actions were criminal is a bit of uncalled for hyperbole.

I also curious about what laws of physics were so unforgiving.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
PlanesNTrains
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 2:52 pm

kalvado wrote:
Planetalk wrote:
barney captain wrote:
Groundings should be based on facts, and not driven by social media.

I'm off to work, carry on this without me.


You just said you agree it should be grounded. So social media was right no? Perhaps an example of it doing good in the world. Or your logic is the plane should have been grounded, but passengers should have kept quiet and flown on the plane you think should have been grounded, but so nothing would have made poor Boeing look bad, and then they wouldn't have had to ground it. But you said it should be grounded. Social media actually achieved what regulation couldn't. Also note how when China first grounded it a large number of posters here said it was 'political'. A large number of those posters have now disappeared, and equally many posters who said they 'just needed to cut the trim switches'.

Sad to see how many people were here only to push propaganda, and then disappeared. Obviously people who had no actual interest in the causes of the accident, only muddying the waters, since they haven't posted at all since the facts got inconvenient.

And to make it worse: China was the first country to ground MAX. Accusing chinese regulators of bowing to social media is... well, lets say unexpected.


It’s possible China was using [manipulating] social media to influence the grounding and not responding to it. It’s also likely that what BC is saying is “ground the plane when you have some solid information about the cause of the crash” versus “ground the plane due to public pressure influenced by social media”.

I’m not opining on whether I think any of that is what happened, but you’re attacking him as a pusher of propaganda when he likely just sees it differently than you. He comes at this as a long-time a.net member and 737 captain. Maybe he’s not as objective because of that experience, but I don’t think he deserves to have ulterior motives attributed to him.
-Dave


MAX’d out on MAX threads. If you are starting a thread, and it’s about the MAX - stop. There’s already a thread that covers it.
 
XRAYretired
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 3:04 pm

Saintor wrote:
PcarSBA wrote:
I read Björns report. I am still trying to understand why they did not back off the thrust at some point.

If I understand correctly the building IAS with its increasing aerodynamic loads narrowed the envelope more and more to where

- manual trim (spinning the wheel) became increasingly difficult to the point of being impossible
- MCAS input and/or trim switch inputs ozn the stabilier with cut-off switches engaged resulted in violent G-forces
- flaps re-engage was out off the question due to high speed
- blow-back reduced elevator authority

How many indicators did they have to realize (in their high-stress situation) they went beyond Vmo while thrust was still at almost 100%.


Well according to this link, manual trimming is possible up to 250 knots. Did the pilots know that? The test in the video was at 300. They were going 350+. It was not possible (if they tried, unsure).
https://www.reuters.com/article/us-ethi ... SKCN1RG2PP

If I understand this right, it would have been possible to reduce to sub 200 knots (or any possible speed compatible with flaps), and to deploy them (preventing probably the MCAS to act).


Don't know where the 250knots comes from. Is it in the manual? Anyway, just wanted to point out that they were passing through 250 before MCAS kicked in for its first cycle. On the second point, I understand there is nothing in the manuals, procedures or AD that tells them MCAS is inhibited with Flaps down.

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

Sat Apr 13, 2019 3:11 pm

OldAeroGuy wrote:
Except that:

1) The AD was not followed as the "STAB TRIM" switches were turned back on. The AD says clearly to turn them off and leave them off.

The AD also says to use the manual trim wheel. At the point that they discovered that that was not possible, they probably abandoned the checklist.
Or maybe they then moved on to the checklist footnote, using electric trim before the cutouts, which would require the switches to be turned back on.

IMO, had the footnote not been a confusing/contradictory footnote, but a mandatory part of the checklist, the ET flight might not have ended in a crash. The AD checklist, IMO, was negligently compiled.

OldAeroGuy wrote:
I also curious about what laws of physics were so unforgiving.

Newton's third law definitely seems to have come into play with the manual trim wheel.
 
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barney captain
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 3:25 pm

PlanesNTrains -

Exactly, and thank you!
Southeast Of Disorder
 
MSPNWA
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 3:43 pm

SimonL wrote:
You cannot reduce the speed if you cannot trim the plane. Any decrease in speed will make the plane even more nose heavy. If you barely can hold it at 350 knots you wont be able to do it at 250.


That statement isn't congruent with how an airplane works. In general, as speed increases, the control surface effectiveness decreases. One learns that the hard way with any simulator. I'd be willing to wager that they would have increased their pitch control at 250 knots versus 350 knots. You must reduce speed when at overspeed to have proper control of an aircraft. Why they didn't address their overspeed condition is a disturbing mystery.

scbriml wrote:
It's not rubbish. Try jacking up a car with 20 people standing on it... Let us know how that goes.

What is astonishing is that you seem to refuse to believe what you've been shown. There's none so blind as he who will not see.


You'll still be able to jack the car assuming it doesn't break first. Sounds like you haven't jacked a car. VV makes a great point about the mechanics of the trim.
 
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PW100
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 4:10 pm

flybucky wrote:
In hindsight, they had things semi-controlled (they gained 4000 ft in the past 2 mins). So they could have maintained that climb to get to at least 10,000 ft AGL, without touching anything like flaps, thrust, stab trim cutouts. Then call Maintenance for troubleshooting help. Then Maintenance could probably walk them through troubleshooting to reduce thrust, get speed down, and safely adjust the stab trim so they didn't need to pull back on the yoke. After all that was stable, then turn back to the airport.


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.
Immigration officer: "What's the purpose of your visit to the USA?" Spotter: "Shooting airliners with my Canon!"
 
PcarSBA
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 4:13 pm

To me it looks like by „flying the airplane“ their sole focus was on the attitude (using outside queues or AH) but they completely neglected the ever building air speed due to the thrust setting. That got them backed into a corner.
 
Saintor
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 4:16 pm

Newbie question here. I checked on google, trying to understand the purpose of trimming vs the nose-heavy nature of the 737 MAX. Why just pulling on the yoke wouldn't raise the nose via rear elevators? Sorry, it must be obvious for the pros.
 
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PW100
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 4:25 pm

flybucky wrote:
PW100 wrote:
I'm not sure if the trimming instruction would have changed anything with respect to the ET accident: the crew did do just that: uptrimming before cutting out electric trimming. In fact, the released FDR graphs shows the largest amount of uptrimming was right before the electric trimming was cut. The uptrim just did not reach the "neutral" condition.

It could be something else, something outside crew control. If the crew could not get more uptrim out of the electric (or manual crank) trimming, then a different procedure by Boeing (and AD mandated) would not have changed a thing. I find it believable that this could be related to Boeing delaying the release of "the MCAS fix".

Yes, one of the open questions after the Prelim Report is why did the pilots not use Electric Trim longer? Was it because Electric Trim was ineffective?

My theory is that Electric Trim was effective. The reason I think this is because if Electric Trim was ineffective, but they wanted to raise the stab trim, they would have kept holding the Electric Trim switch up, but we would see the Pitch Trim did not change. This was not the case anywhere in the FDR data. Even near the end of the flight, when they blipped the Electric Trim up at over 350 kts, the Pitch Trim did increase in response.

Yes. But they must have seen the trim wheel spinning as a result of thump uptirm.

If you go all the way back to the first couple of pages of this thread (and the Lionair thread), many conveyed the picture that the pilots must have seen the trim wheel turning down as a result of MCAS, and called out the pilots for not hitting the cut out switches.




So if Electric Trim was effective, why didn't they do it longer? My theory for the first time that MCAS kicked in (around 05:40:30), is that their primary concern was stalling, so they were focused on keeping thrust high and keeping the Pitch Attitude above 0 but not too high in case of stall. (And they did do that. Almost the entire flight they kept the Pitch Attitude between 0 and +10º.) So once they were able to hold Pitch Attitude above 0, they stopped Electric Trim and Cutout the Stab Trim altogether. Of course, after that Electric Trim was out of the equation.

I'm not with you on the stalling concern: they were still pulling back quite hard (if not very very hard) on the control column. That does not jive with stalling concern.



How about at the end of the flight, why did they only blip the Electric Trim? Possible theory:
1) Bjorn's analysis was that at 360 kts at the relatively low altitude, a tiny bit of trim input will result in a violent reaction.
2) Their Pitch Attitude was positive, so that was good enough for them.

1) This I can understand; short blimps on the thump. but why then stop after two, when they obviously much more? Still suggest something else was going on.
2) Pitch attitude positive, but with very much back force on the control column, can't understand how they would see that as "good enough".

Could there perhaps be a max torque limiter on the trim motor? When ANU trim exceeds some preset limit, could the trim signal be cut somewhere? And thus not tracing on FDR, despite pilots having the thump physically in uprim position?
Immigration officer: "What's the purpose of your visit to the USA?" Spotter: "Shooting airliners with my Canon!"
 
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PW100
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 4:40 pm

VV wrote:
I am not saying it is the pilot's fault, I am just saying that MCAS failure should have been relatively benign if the pilot identifies the issue and take the appropriate actions.


By the time MCAS first kicked in, they were already at 250 kts. By the second cycle of MCAS they were over 300 kts. It seems that they were already in the corner at that point, with heavy back column force, preventing the eclectic and manual trim getting the stabilizer to normal position.

It seems that they let the speed go up to 250 kts pretty quickly. Perhaps that was the result of stickshaker and unreliable airspeed. Up to the point of MCAS kicking in for the first time, things seems pretty well under control, with neutral control column. Only question is why they didn't reduce throttle prior to MCAS kicking in. The unreliable airspeed checklist asks for 74% N1 or something like that. Perhaps they were in the midst of doing just that (unreliable air speed checklist) when they were brutally interrupted by MCAS. And they turned their attention to pitch control (MCAS, AD Lionair) before speed control.

I'm sure the investigators will look closely at their procedures for auto throttle settings and speed management in general.
Immigration officer: "What's the purpose of your visit to the USA?" Spotter: "Shooting airliners with my Canon!"
 
WIederling
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 4:44 pm

Isn't electric "un-trimming" about as overwhelmed as the manual actuation?
Elevators in neutral and the tailplane is trimmable with small forces (as it is hinged around the CoL )
If you introduce large elevator deflection that is no longer the case.
The reaction forces that counter the trim state
aid further miss- trimming and counter trim corrections to neutral.
Murphy is an optimist
 
SimonL
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 4:47 pm

Saintor wrote:
Newbie question here. I checked on google, trying to understand the purpose of trimming vs the nose-heavy nature of the 737 MAX. Why just pulling on the yoke wouldn't raise the nose via rear elevators? Sorry, it must be obvious for the pros.



Trimming has the purpose of balance the downward force of the stabilisator with the upward force of the wing so that the nose stays level. its like a fine tuning of the elevators. since the amount of trim needed depends on a lot of things, speed is the most important one, planes have to be almost constantly retrimmed during flight. If the plane is out of trim it have to be compensated by the pilots in order to maintain the desired attitude, either by pushing or pulling the yoke but this can require a lot of force and they might not have the strength to do it for any longer period of time.
 
OldAeroGuy
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 4:53 pm

speedbored wrote:
OldAeroGuy wrote:
Except that:

1) The AD was not followed as the "STAB TRIM" switches were turned back on. The AD says clearly to turn them off and leave them off.

The AD also says to use the manual trim wheel. At the point that they discovered that that was not possible, they probably abandoned the checklist.
Or maybe they then moved on to the checklist footnote, using electric trim before the cutouts, which would require the switches to be turned back on.

IMO, had the footnote not been a confusing/contradictory footnote, but a mandatory part of the checklist, the ET flight might not have ended in a crash. The AD checklist, IMO, was negligently compiled.


The AD clearly states that:

1) Once the "STAB TRIM" cutoff switches are turned OFF, they are to remain OFF for the remainder of the flight.
2) Electrical stabilizer trim is to be used prior to using the "STAB TRIM" cutoff switches. This is not a footnote but is contained in the main body of the AD.

https://www.federalregister.gov/documen ... -airplanes

Once the AD is issued, it becomes part of the airplane certification basis. An airline then becomes responsible for training the crew to comply with the AD if the airline wishes to continue operating the airplane. When the crew turned "STAB TRIM" back ON, they were either not trained to leave them OFF or ignored their training.

At the point the crew elected to switch "STAB TRIM" OFF, the airplane was in nearly level flight at 1000' AGL, 94% N1 and 340 KIAS (Vmo) on the reliable right airspeed indicator. Pitch control was available as a climb to 7000' AGL was initiated with right airspeed stabilizing at 360 KIAS, above Vmo. Options other than switching "STAB TRIM" ON were available.

https://leehamnews.com/wp-content/uploa ... cifics.png

Under the stress of the situation, it can be understandable that the crew stepped outside the AD instructions. However, they could have also run the Unreliable Airspeed checklist to address exceeding Vmo. If they had done this, thrust would have been cutback to 70% N1 and airspeed would have been reduced. This in turn may have made it easier to trim the airplane manually.

As with any accident, there are multiple factors. For ET302, it appears the main ones were:

1) Erroneous AoA vane signal
2) Flawed Boeing MCAS.v1 logic
3) Crew not following training
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
Planetalk
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 5:02 pm

PlanesNTrains wrote:
kalvado wrote:
Planetalk wrote:

You just said you agree it should be grounded. So social media was right no? Perhaps an example of it doing good in the world. Or your logic is the plane should have been grounded, but passengers should have kept quiet and flown on the plane you think should have been grounded, but so nothing would have made poor Boeing look bad, and then they wouldn't have had to ground it. But you said it should be grounded. Social media actually achieved what regulation couldn't. Also note how when China first grounded it a large number of posters here said it was 'political'. A large number of those posters have now disappeared, and equally many posters who said they 'just needed to cut the trim switches'.

Sad to see how many people were here only to push propaganda, and then disappeared. Obviously people who had no actual interest in the causes of the accident, only muddying the waters, since they haven't posted at all since the facts got inconvenient.

And to make it worse: China was the first country to ground MAX. Accusing chinese regulators of bowing to social media is... well, lets say unexpected.


It’s possible China was using [manipulating] social media to influence the grounding and not responding to it. It’s also likely that what BC is saying is “ground the plane when you have some solid information about the cause of the crash” versus “ground the plane due to public pressure influenced by social media”.

I’m not opining on whether I think any of that is what happened, but you’re attacking him as a pusher of propaganda when he likely just sees it differently than you. He comes at this as a long-time a.net member and 737 captain. Maybe he’s not as objective because of that experience, but I don’t think he deserves to have ulterior motives attributed to him.


What this accident has shown again is something aviation was supposed to have learned long ago, it shouldn't require dead bodies to act when something is clearly wrong. And sometimes the precautionary principle is apt, and two planes of a new model crashing in strikingly similar circumstances is so statistically unlikely that alone practically justified a grounding. Anyway it seems we're all agreed the grounding was right so I really don't understand the problem. I don't think anyone in the world except President Trump was considering social media in their decision. It is for the US to ask itself why that was necessary.

For that reason I don't actually agree with those defending the Qantas airbus incidents because there was no loss of life. I don't think it is comparable to the Max incidents but 'nobody died so its all ok' should never be spoken in aviation.
 
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SheikhDjibouti
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 5:18 pm

MSPNWA wrote:
scbriml wrote:
It's not rubbish. Try jacking up a car with 20 people standing on it... Let us know how that goes.


You'll still be able to jack the car assuming it doesn't break first. Sounds like you haven't jacked a car.

UTTER RUBBISH!

For a start you haven't even enquired as to whether the jack is mechanical (scissor-jack) or hydraulic (trolley or bottle jack).

I have used both types, and probably more recently than you (unless you are a regular vehicle mechanic?)

But what is even more probable is, like most vehicle mechanics, you have never found yourself in a position where you tried to lift a vehicle with 20 people standing on it.

I have.

Or at least the next best thing; I have struggled to lift a 3½ tonne load (e.g. a fully loaded 4x4) using a the only thing available at the time - a 2 tonne Walmart trolley jack designed for a typical compact. Not my choice - this was only done as an emergency measure.

I have also used an old Ford scissor jack to raise one part of a small out-building.

Both of these tools worked admirably well within their normal range.
And both were physically capable of supporting loads beyond their normal limits; nothing broke or failed catastrophically. But the human link in the chain simply couldn't operate them in these extreme cases.
(In the case of the hydraulic jack, I resorted to using a 4ft extension bar to give me enough leverage, and even then it was tricky...)

Unless the equipment on the MAX was massively over-engineered for the job, and/or the gearing reduced, whilst it might not fail, it would be impossible to operate.

Given that the physical diameter of the trim wheel has been reduced since the original 737 Classic, whilst the MTOW and other specs have all increased (~doubled), the scenario posited by several reputable sources beats anything you can offer.
Nothing to see here; move along please.
 
Planetalk
Posts: 470
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 5:25 pm

OldAeroGuy wrote:
speedbored wrote:
OldAeroGuy wrote:
Except that:

1) The AD was not followed as the "STAB TRIM" switches were turned back on. The AD says clearly to turn them off and leave them off.

The AD also says to use the manual trim wheel. At the point that they discovered that that was not possible, they probably abandoned the checklist.
Or maybe they then moved on to the checklist footnote, using electric trim before the cutouts, which would require the switches to be turned back on.

IMO, had the footnote not been a confusing/contradictory footnote, but a mandatory part of the checklist, the ET flight might not have ended in a crash. The AD checklist, IMO, was negligently compiled.


The AD clearly states that:

1) Once the "STAB TRIM" cutoff switches are turned OFF, they are to remain OFF for the remainder of the flight.
2) Electrical stabilizer trim is to be used prior to using the "STAB TRIM" cutoff switches. This is not a footnote but is contained in the main body of the AD.

https://www.federalregister.gov/documen ... -airplanes

Once the AD is issued, it becomes part of the airplane certification basis. An airline then becomes responsible for training the crew to comply with the AD if the airline wishes to continue operating the airplane. When the crew turned "STAB TRIM" back ON, they were either not trained to leave them OFF or ignored their training.

At the point the crew elected to switch "STAB TRIM" OFF, the airplane was in nearly level flight at 1000' AGL, 94% N1 and 340 KIAS (Vmo) on the reliable right airspeed indicator. Pitch control was available as a climb to 7000' AGL was initiated with right airspeed stabilizing at 360 KIAS, above Vmo. Options other than switching "STAB TRIM" ON were available.

https://leehamnews.com/wp-content/uploa ... cifics.png

Under the stress of the situation, it can be understandable that the crew stepped outside the AD instructions. However, they could have also run the Unreliable Airspeed checklist to address exceeding Vmo. If they had done this, thrust would have been cutback to 70% N1 and airspeed would have been reduced. This in turn may have made it easier to trim the airplane manually.

As with any accident, there are multiple factors. For ET302, it appears the main ones were:

1) Erroneous AoA vane signal
2) Flawed Boeing MCAS.v1 logic
3) Crew not following training


This forun really needs to decide if it prefers pilots who think for themselves in emergencies, or checklist ticking robots.

As you say, under the stress of the situation their actions are understandable. And tbey got more right than I expect a good proportion of pilots from any part of the world would have done.

Some of the decisions made at Boeing however seem inexplicable. And weren't made under imminent threat of death. Only imminent threat of paying $$$$ to Southwest. Ok mayhe not so inexplicable considering the kind of people running the company now. Noone calling themselves an aviation enthusiast has an interest in sociopathic beancounters heading this company.
 
MSPNWA
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 5:46 pm

SheikhDjibouti wrote:
UTTER RUBBISH!


Woah, someone is triggered.

Glad you asked. I am a regular car mechanic. Will be using one again tomorrow. That's why I speak with confidence about it. It was a poor analogy, and I've called it out.

In order for the theory that trim was impossible to move with either the trim switches or manually to be valid, it implies that Boeing built a "jack" that as woefully below the safe "weight" limit necessary, and this flaw has been flying for decades. That's a theory that needs more than speculation to be plausible.
 
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PW100
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 5:50 pm

morrisond wrote:
morrisond wrote:
PW100 wrote:
Yes, the worldwide declining standards mainly seem to affect 737 MAX aircraft.
Perhaps Boeing should start informing pilots about the hidden systems, and manual back-up systems not working at some part of the flight envelope.

It is becoming quite tiring reading about the declining pilot standards (outside the US of A of course), in relation to the deaths of 350 people, when the root causes of both accidents are probably to be found mainly inside the US of A.


Do you have problems reading? Did I say outside the US? I said Worldwide and I specifically mentioned that training is deficient in North America as well.

I must confess, with these long threads, I sometimes loose track at some specific details. There is no discussion that some posters insinuate (some even state out blankly) that the declining standards mainly affect those outside the USA. If you are not one of those, I sincerely apologize.


Are you comfortable with the state of training worldwide?

Generally, I don't share the concerns that some have. Not saying that things could not be improved, but I feel that airline safety, and pilot proficiency specific, for most "third world operators" is not as bad as some would portray. I think it is at par with western standards 15 - 25 years ago. Which is not a bad thing, but could be improved. Considering the challenges in other sectors of society of those countries, I can forgive them for not reaching standards as practiced in USA and western Europe today.


It seems to me as though the last number of major accidents could have turned out better if better training existed. All the people bashing on Boeing conveniently forget that Airbus is establishing schools worldwide as they think Training Standards aren't what they should be.

All true of course.
But that does not take anything away that the MAX seems much more heavily affected, while other types are not, or to a much lesser extent.
Therefore the feeling keeps creeping up that this is a handle trying to takeaway some focus from the real issues at hand.

The MentourPilot video is very telling, and replicating the conditions of ET302, he found himself in such situation that hey had to hit the "Red Button" in the sim (and his fndings are confirmed by others). If one feels he also falls in the poorly trained group, then that can't be based on his basic training, basic pilot skills, and experience. If he isn't trained sufficiently on 737 MAX, then there is no way around that the manufacturer should have provided more details on how to operate the MAX.


It has not been established 100% that the backup systems did not work. There is some doubt that they were even tried.

Nothing has been 100% established. I'm not sure why you feel the need to emphasize such. Of course the opposite hasn't been demonstrated 100%, and that was what I was pointing at. Perhaps your words aree better than mine . . .
Immigration officer: "What's the purpose of your visit to the USA?" Spotter: "Shooting airliners with my Canon!"
 
OldAeroGuy
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 5:51 pm

Planetalk wrote:
This forun really needs to decide if it prefers pilots who think for themselves in emergencies, or checklist ticking robots.

As you say, under the stress of the situation their actions are understandable. And tbey got more right than I expect a good proportion of pilots from any part of the world would have done.


One of the things that they really got wrong though was a basic airmanship issue: speed control

Planetalk wrote:
Noone calling themselves an aviation enthusiast has an interest in sociopathic beancounters heading this company.


A bit too harsh.

While I'm not happy about MCAS.v1 implementation, there is some historical justification. MCAS is an electronic equivalent of prior stability augmentation systems.

Past stick pushers and stick nudgers have been triggered by single AoA vanes. The surprise for the MAX is the higher than expected vane signal failure rate.

Besides, sociopaths can do quite well in presidential elections.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
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PW100
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 5:55 pm

MSPNWA wrote:
SheikhDjibouti wrote:
UTTER RUBBISH!


Woah, someone is triggered.

Glad you asked. I am a regular car mechanic. Will be using one again tomorrow. That's why I speak with confidence about it. It was a poor analogy, and I've called it out.

In order for the theory that trim was impossible to move with either the trim switches or manually to be valid, it implies that Boeing built a "jack" that as woefully below the safe "weight" limit necessary, and this flaw has been flying for decades. That's a theory that needs more than speculation to be plausible.


That "theory" was apparently included in the operating manuals of earlier 737 versions. It even included instructions on how to handle such event (yoyo, or roller-coaster technique). Since then, the wheel size has been reduced, which would even increase the force required.

While we have don't have 100% certainty on this, I feel confident that this by now has assed the level of wild speculation . . .
Immigration officer: "What's the purpose of your visit to the USA?" Spotter: "Shooting airliners with my Canon!"
 
OldAeroGuy
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 6:00 pm

PW100 wrote:
The MentourPilot video is very telling, and replicating the conditions of ET302, he found himself in such situation that hey had to hit the "Red Button" in the sim (and his fndings are confirmed by others). If one feels he also falls in the poorly trained group, then that can't be based on his basic training, basic pilot skills, and experience. If he isn't trained sufficiently on 737 MAX, then there is no way around that the manufacturer should have provided more details on how to operate the MAX.


Two comments:

1) The FAA/Boeing did provide more details on how to operate the MAX via the Emergency AD. The Ethiopian pilots did not follow all the AD instructions.

2) If MentourPilot did follow what the Ethiopian pilots did and not follow the EAD, why would the result be different? It doesn't mean he is poorly trained. It would be more interesting to put him a MAX simulator and see how he would deal with the situation after being trained on the EAD.
Would he have allowed the airplane to accelerate to Vmo at 1000' AGL?
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
VV
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 6:25 pm

OldAeroGuy wrote:
PW100 wrote:
The MentourPilot video is very telling, and replicating the conditions of ET302, he found himself in such situation that hey had to hit the "Red Button" in the sim (and his fndings are confirmed by others). If one feels he also falls in the poorly trained group, then that can't be based on his basic training, basic pilot skills, and experience. If he isn't trained sufficiently on 737 MAX, then there is no way around that the manufacturer should have provided more details on how to operate the MAX.


Two comments:

1) The FAA/Boeing did provide more details on how to operate the MAX via the Emergency AD. The Ethiopian pilots did not follow all the AD instructions.


That's what I have understood so far.
 
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speedbored
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 6:27 pm

OldAeroGuy wrote:
The AD clearly states that:

1) Once the "STAB TRIM" cutoff switches are turned OFF, they are to remain OFF for the remainder of the flight.
2) Electrical stabilizer trim is to be used prior to using the "STAB TRIM" cutoff switches. This is not a footnote but is contained in the main body of the AD.

1) Yes, it does.
2) No, it does not say that and yes, it is a footnote that, to any reasonable reader, looks like an optional extra:

The AD procedure starts:
Disengage autopilot and control airplane pitch attitude with control column and main electric trim as required. If relaxing the column causes the trim to move, set stabilizer trim switches to CUTOUT. If runaway continues, hold the stabilizer trim wheel against rotation and trim the airplane manually.

Note: The 737-8/-9 uses a Flight Control Computer command of pitch trim to improve longitudinal handling characteristics. In the event of erroneous Angle of Attack (AOA) input, the pitch trim system can trim the stabilizer nose down in increments lasting up to 10 seconds.In the event an uncommanded nose down stabilizer trim is experienced on the 737-8/ -9, in conjunction with one or more of the indications or effects listed below, do the existing AFM Runaway Stabilizer procedure above, ensuring that the STAB TRIM CUTOUT switches are set to CUTOUT and stay in the CUTOUT position for the remainder of the flight.


So, if the pilots follow the AD, they are specifically told (the bolded text) to follow a procedure that does not include the use of electric trim.

Making use of electric trim is only mentioned in the final paragraph:
Initially, higher control forces may be needed to overcome any stabilizer nose down trim already applied. Electric stabilizer trim can be used to neutralize control column pitch forces before moving the STAB TRIM CUTOUT switches to CUTOUT. Manual stabilizer trim can be used before and after the STAB TRIM CUTOUT switches are moved to CUTOUT

The fact that this is not included in the "procedure above", and includes the wording "can be used" clearly suggests that this is optional.

I see absolutely no reason for blaming the pilots for switching electric trim back on to try this, and many reasons for blaming Boeing for the negligently written AD procedure.

OldAeroGuy wrote:
Options other than switching "STAB TRIM" ON were available.

I'd love to know exactly what else you think they could have done in the time they had left after the AD procedure failed them, while pulling as hard as they could on the yokes.
 
VV
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 6:28 pm

I agree the system could have been designed better.

However, the consequence of the failure should have not been an accident.

Perhaps the LionAir accident could have happened because the pilots did not know what to do, but the second accident? What the heck?

I still find the article below quite good.
https://www.nytimes.com/interactive/201 ... ckpit.html
 
GalebG4
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 8:13 pm

I still believe in Boeing, max 8 crashes unfortunately happened but this was chance for Boeing to show us how they can act in extremely hard situation.
I think that 737 max 8 is safe aircraft with “updated system”. Yes they should do review of certification, but in reality aircrafts can and should fly updated while review is being done by regulators.
 
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speedbored
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 8:16 pm

lifecomm wrote:
Do I understand MentourPilot correctly? At 2:20 he asks to trim the nose further down? And isn't that what the FO does? Exactly what does this prove - that if you allow the trim (or cause the trim) to move nose down there could be a point where you can't save the plane?

I believe that they were "for the sake of the exercise" trying to get the trim to the same amount of nose-down that the ET crew ended up with.

They failed to manage to push it to that much nose-down and could not subsequently move the trim back in the nose-up direction at all. And also worth noting that they still hit Vmo with 75% N1 while trying this.
 
lifecomm
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 8:34 pm

speedbored wrote:
lifecomm wrote:
Do I understand MentourPilot correctly? At 2:20 he asks to trim the nose further down? And isn't that what the FO does? Exactly what does this prove - that if you allow the trim (or cause the trim) to move nose down there could be a point where you can't save the plane?

I believe that they were "for the sake of the exercise" trying to get the trim to the same amount of nose-down that the ET crew ended up with.

They failed to manage to push it to that much nose-down and could not subsequently move the trim back in the nose-up direction at all. And also worth noting that they still hit Vmo with 75% N1 while trying this.

Thank you for the sanity check - I kept thinking, "what the heck are you doing?!"

So what am I missing? This video seems to demonstrate how pilot inaction (or "do not try this at home" stupidity) is deadly. Is this suppose to vindicate the pilots' actions? I am now (maybe) not as confused as why he would take this video down...
 
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speedbored
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 8:39 pm

lifecomm wrote:
speedbored wrote:
lifecomm wrote:
Do I understand MentourPilot correctly? At 2:20 he asks to trim the nose further down? And isn't that what the FO does? Exactly what does this prove - that if you allow the trim (or cause the trim) to move nose down there could be a point where you can't save the plane?

I believe that they were "for the sake of the exercise" trying to get the trim to the same amount of nose-down that the ET crew ended up with.

They failed to manage to push it to that much nose-down and could not subsequently move the trim back in the nose-up direction at all. And also worth noting that they still hit Vmo with 75% N1 while trying this.

Thank you for the sanity check - I kept thinking, "what the heck are you doing?!"

So what am I missing? This video seems to demonstrate how pilot inaction (or "do not try this at home" stupidity) is deadly. Is this suppose to vindicate the pilots' actions? I am now (maybe) not as confused as why he would take this video down...

They were trying to show how difficult the ET pilots would have found it to follow the AD procedure and get the aircraft back under control.
 
OldAeroGuy
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 9:19 pm

speedbored wrote:
OldAeroGuy wrote:
Options other than switching "STAB TRIM" ON were available.


I'd love to know exactly what else you think they could have done in the time they had left after the AD procedure failed them, while pulling as hard as they could on the yokes.


The airplane is way too fast. Pulling the throttles back to idle would have been a good choice. Here's why:

First, let's review where the airplane was when the "STAB TRIM" switches were turned back ON.

- 7000' AGL after about a 2 minute climb from 1500' AGL
- 360 KIAS- 20 knots over the 340 KIAS which was also achieved at 1500' AGL
- 92% N1 on both engines.

Three things are obvious:

1) Airplane is 20 knots over Vmo

2) Some pitch control is still available via the yoke. If it wasn't, the airplane would have accelerated more during its 5500' climb. Excess energy was being converted into climb rather than acceleration. This could only be done by controlling pitch attitude.

3)Thrust is still at takeoff level. This is about 5 minutes after the throttles were advanced for takeoff. Takeoff thrust time limit is 5 minutes.

At this point, even with trim difficulties, pulling the throttles back to reduce speed below Vmo is a logical action.

Slowing the airplane down may have helped with the high stick forces as well. At high speed, elevator blow down is reducing its effectiveness. More elevator effectiveness means less stick force.

At lower speeds, the manual trim wheels would probably worked better as well. Dynamic pressure at 360 KIAS is 65% higher than at 280 KIAS with a likewise reduction manual trim wheel effort.

The main unknown is the actual state of airplane trim speed. Since the pilots were able to control speed with elevator by climbing in a high thrust situation, they could probably also control speed until manual trim was available.

It's unfortunate the ET302 crew never made a thrust cutback.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
planecane
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 9:20 pm

speedbored wrote:

2) No, it does not say that and yes, it is a footnote that, to any reasonable reader, looks like an optional extra:

The AD procedure starts:
Disengage autopilot and control airplane pitch attitude with control column and main electric trim as required. If relaxing the column causes the trim to move, set stabilizer trim switches to CUTOUT. If runaway continues, hold the stabilizer trim wheel against rotation and trim the airplane manually.

Note: The 737-8/-9 uses a Flight Control Computer command of pitch trim to improve longitudinal handling characteristics. In the event of erroneous Angle of Attack (AOA) input, the pitch trim system can trim the stabilizer nose down in increments lasting up to 10 seconds.In the event an uncommanded nose down stabilizer trim is experienced on the 737-8/ -9, in conjunction with one or more of the indications or effects listed below, do the existing AFM Runaway Stabilizer procedure above, ensuring that the STAB TRIM CUTOUT switches are set to CUTOUT and stay in the CUTOUT position for the remainder of the flight.


So, if the pilots follow the AD, they are specifically told (the bolded text) to follow a procedure that does not include the use of electric trim.

Making use of electric trim is only mentioned in the final paragraph:
Initially, higher control forces may be needed to overcome any stabilizer nose down trim already applied. Electric stabilizer trim can be used to neutralize control column pitch forces before moving the STAB TRIM CUTOUT switches to CUTOUT. Manual stabilizer trim can be used before and after the STAB TRIM CUTOUT switches are moved to CUTOUT

The fact that this is not included in the "procedure above", and includes the wording "can be used" clearly suggests that this is optional.

I see absolutely no reason for blaming the pilots for switching electric trim back on to try this, and many reasons for blaming Boeing for the negligently written AD procedure.


The entire modified "Runaway Stabilizer" revision required by the AD is:
Runaway Stabilizer

Disengage autopilot and control airplane pitch attitude with control column and main electric trim as required. If relaxing the column causes the trim to move, set stabilizer trim switches to CUTOUT. If runaway continues, hold the stabilizer trim wheel against rotation and trim the airplane manually.

Note: The 737-8/-9 uses a Flight Control Computer command of pitch trim to improve longitudinal handling characteristics. In the event of erroneous Angle of Attack (AOA) input, the pitch trim system can trim the stabilizer nose down in increments lasting up to 10 seconds.

In the event an uncommanded nose down stabilizer trim is experienced on the 737-8/-9, in conjunction with one or more of the indications or effects listed below, do the existing AFM Runaway Stabilizer procedure above, ensuring that the STAB TRIM CUTOUT switches are set to CUTOUT and stay in the CUTOUT position for the remainder of the flight.

An erroneous AOA input can cause some or all of the following indications and effects:
• Continuous or intermittent stick shaker on the affected side only.
• Minimum speed bar (red and black) on the affected side only.
• Increasing nose down control forces. • IAS DISAGREE alert.
• ALT DISAGREE alert. • AOA DISAGREE alert (if the option is installed).
• FEEL DIFF PRESS light.
• Autopilot may disengage.
• Inability to engage autopilot.
Initially, higher control forces may be needed to overcome any stabilizer nose down trim already applied. Electric stabilizer trim can be used to neutralize control column pitch forces before moving the STAB TRIM CUTOUT switches to CUTOUT. Manual stabilizer trim can be used before and after the STAB TRIM CUTOUT switches are moved to CUTOUT.


As bolded, the "procedure above" most certainly says to use the "main electric trim as required." If the pilots follow the first two sentences in the procedure verbatim, the pilots should control the airplane pitch attitude with control column and main electric trim as required. Then, upon relaxing the control column, MCAS will kick in and the trim will move (the actual cause will be stopping the manual trim inputs). THEN it says to set the stabilizer trim switches to cutout.

In the case of the ET flight, they started following the procedure and then set the stabilizer trim switches to cutout before they got the pitch attitude under control. In the FDR plots, the stabilizer was clearly responding to the manual trim inputs right up until they set the switches to cutout.

The pilots did not follow the procedure exactly per the AD.

I don't put the blame of the crash on the pilots. The blame goes to the horrific implementation of MCAS response to a failed AoA sensor. However, based on the FDR plots, it is clear that if they had followed the first two sentences in the procedure verbatim, they would have saved the airplane.
 
morrisond
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 9:24 pm

PW100 wrote:
morrisond wrote:
morrisond wrote:


Do you have problems reading? Did I say outside the US? I said Worldwide and I specifically mentioned that training is deficient in North America as well.

I must confess, with these long threads, I sometimes loose track at some specific details. There is no discussion that some posters insinuate (some even state out blankly) that the declining standards mainly affect those outside the USA. If you are not one of those, I sincerely apologize.


Are you comfortable with the state of training worldwide?

Generally, I don't share the concerns that some have. Not saying that things could not be improved, but I feel that airline safety, and pilot proficiency specific, for most "third world operators" is not as bad as some would portray. I think it is at par with western standards 15 - 25 years ago. Which is not a bad thing, but could be improved. Considering the challenges in other sectors of society of those countries, I can forgive them for not reaching standards as practiced in USA and western Europe today.


It seems to me as though the last number of major accidents could have turned out better if better training existed. All the people bashing on Boeing conveniently forget that Airbus is establishing schools worldwide as they think Training Standards aren't what they should be.

All true of course.
But that does not take anything away that the MAX seems much more heavily affected, while other types are not, or to a much lesser extent.
Therefore the feeling keeps creeping up that this is a handle trying to takeaway some focus from the real issues at hand.

The MentourPilot video is very telling, and replicating the conditions of ET302, he found himself in such situation that hey had to hit the "Red Button" in the sim (and his fndings are confirmed by others). If one feels he also falls in the poorly trained group, then that can't be based on his basic training, basic pilot skills, and experience. If he isn't trained sufficiently on 737 MAX, then there is no way around that the manufacturer should have provided more details on how to operate the MAX.


It has not been established 100% that the backup systems did not work. There is some doubt that they were even tried.

Nothing has been 100% established. I'm not sure why you feel the need to emphasize such. Of course the opposite hasn't been demonstrated 100%, and that was what I was pointing at. Perhaps your words aree better than mine . . .



Thank you for your response.

I have not seen the Mentourpilot Video.

One question on it - after showing the trim wheel would be very difficult to move at high speed - did he replicate the exact same climb scenario with identical thrust settings, Horizontal stabilizer angle and showed that if he pulled back power it was impossible to save the airplane as the nose dipped too much as there was not enough elevator authority to compensate?

I have read 737 pilots state that the pitch change going from say 94-90% thrust is very small if anything at all at high speed.
 
morrisond
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 9:26 pm

planecane wrote:
speedbored wrote:

2) No, it does not say that and yes, it is a footnote that, to any reasonable reader, looks like an optional extra:

The AD procedure starts:
Disengage autopilot and control airplane pitch attitude with control column and main electric trim as required. If relaxing the column causes the trim to move, set stabilizer trim switches to CUTOUT. If runaway continues, hold the stabilizer trim wheel against rotation and trim the airplane manually.

Note: The 737-8/-9 uses a Flight Control Computer command of pitch trim to improve longitudinal handling characteristics. In the event of erroneous Angle of Attack (AOA) input, the pitch trim system can trim the stabilizer nose down in increments lasting up to 10 seconds.In the event an uncommanded nose down stabilizer trim is experienced on the 737-8/ -9, in conjunction with one or more of the indications or effects listed below, do the existing AFM Runaway Stabilizer procedure above, ensuring that the STAB TRIM CUTOUT switches are set to CUTOUT and stay in the CUTOUT position for the remainder of the flight.


So, if the pilots follow the AD, they are specifically told (the bolded text) to follow a procedure that does not include the use of electric trim.

Making use of electric trim is only mentioned in the final paragraph:
Initially, higher control forces may be needed to overcome any stabilizer nose down trim already applied. Electric stabilizer trim can be used to neutralize control column pitch forces before moving the STAB TRIM CUTOUT switches to CUTOUT. Manual stabilizer trim can be used before and after the STAB TRIM CUTOUT switches are moved to CUTOUT

The fact that this is not included in the "procedure above", and includes the wording "can be used" clearly suggests that this is optional.

I see absolutely no reason for blaming the pilots for switching electric trim back on to try this, and many reasons for blaming Boeing for the negligently written AD procedure.


The entire modified "Runaway Stabilizer" revision required by the AD is:
Runaway Stabilizer

Disengage autopilot and control airplane pitch attitude with control column and main electric trim as required. If relaxing the column causes the trim to move, set stabilizer trim switches to CUTOUT. If runaway continues, hold the stabilizer trim wheel against rotation and trim the airplane manually.

Note: The 737-8/-9 uses a Flight Control Computer command of pitch trim to improve longitudinal handling characteristics. In the event of erroneous Angle of Attack (AOA) input, the pitch trim system can trim the stabilizer nose down in increments lasting up to 10 seconds.

In the event an uncommanded nose down stabilizer trim is experienced on the 737-8/-9, in conjunction with one or more of the indications or effects listed below, do the existing AFM Runaway Stabilizer procedure above, ensuring that the STAB TRIM CUTOUT switches are set to CUTOUT and stay in the CUTOUT position for the remainder of the flight.

An erroneous AOA input can cause some or all of the following indications and effects:
• Continuous or intermittent stick shaker on the affected side only.
• Minimum speed bar (red and black) on the affected side only.
• Increasing nose down control forces. • IAS DISAGREE alert.
• ALT DISAGREE alert. • AOA DISAGREE alert (if the option is installed).
• FEEL DIFF PRESS light.
• Autopilot may disengage.
• Inability to engage autopilot.
Initially, higher control forces may be needed to overcome any stabilizer nose down trim already applied. Electric stabilizer trim can be used to neutralize control column pitch forces before moving the STAB TRIM CUTOUT switches to CUTOUT. Manual stabilizer trim can be used before and after the STAB TRIM CUTOUT switches are moved to CUTOUT.


As bolded, the "procedure above" most certainly says to use the "main electric trim as required." If the pilots follow the first two sentences in the procedure verbatim, the pilots should control the airplane pitch attitude with control column and main electric trim as required. Then, upon relaxing the control column, MCAS will kick in and the trim will move (the actual cause will be stopping the manual trim inputs). THEN it says to set the stabilizer trim switches to cutout.

In the case of the ET flight, they started following the procedure and then set the stabilizer trim switches to cutout before they got the pitch attitude under control. In the FDR plots, the stabilizer was clearly responding to the manual trim inputs right up until they set the switches to cutout.

The pilots did not follow the procedure exactly per the AD.

I don't put the blame of the crash on the pilots. The blame goes to the horrific implementation of MCAS response to a failed AoA sensor. However, based on the FDR plots, it is clear that if they had followed the first two sentences in the procedure verbatim, they would have saved the airplane.



That AD is pretty clear to me - i don't know how it could be misinterpreted.

I hope a big part of the investigation looks into whether whether or not Ethiopian Airlines properly trained there pilots on this.
 
OldAeroGuy
Posts: 3928
Joined: Sun Dec 05, 2004 6:50 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 9:32 pm

speedbored wrote:
lifecomm wrote:
speedbored wrote:
I believe that they were "for the sake of the exercise" trying to get the trim to the same amount of nose-down that the ET crew ended up with.

They failed to manage to push it to that much nose-down and could not subsequently move the trim back in the nose-up direction at all. And also worth noting that they still hit Vmo with 75% N1 while trying this.

Thank you for the sanity check - I kept thinking, "what the heck are you doing?!"

So what am I missing? This video seems to demonstrate how pilot inaction (or "do not try this at home" stupidity) is deadly. Is this suppose to vindicate the pilots' actions? I am now (maybe) not as confused as why he would take this video down...

They were trying to show how difficult the ET pilots would have found it to follow the AD procedure and get the aircraft back under control.


Except they did not perform the EAD procedure for "Runaway Stabilizer". Re-read the first paragraph.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
morrisond
Posts: 2945
Joined: Thu Jan 07, 2010 12:22 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 9:38 pm

o0OOO0oChris wrote:
Wow, that video clears up some things:
- At 2,5°, the pilot has to use all his force to control pitch. And he doesn`t even have the feel system , thinking they are approaching stall, adding a lot of force on top of that. So in the MCAS situation, pitch would not be controllable from 2.5° ND trim for one pilot.
- As the pilot has to use all his force to control the elevator, he can`t help the copilot to trimm back down.
- Below 2,5° ND, the copilot has to help the pilot to controll the elevator - but then he can`t trim it back up again.
- So they have to decide to run the stabilizer together or the elevator. Not a choice that leads to a good outcome below 5000 feet AGL
- It must be extremely frightening and shocking for a pilot to realize that the control is fading away from him slowely but shurely. Getting panicked is a high probablility in that environment and that is really bad for the decision making process. They didn`t have a red button to push.
- Both Pilots are male, tall and look fit. How would a small female pilot do in this situation? Are there limits on physical strength a pilot has to have to get type rated?
- It took quite a while using good crm and communication between the pilots to do the checklists and confirm the runaway trim before they cut out.


Except ET302 was 2.1-2.3 degrees Nose Up - not Nose down and Mentourpilot did nothing to control airspeed either.
 
Heinkel
Posts: 259
Joined: Sun Sep 08, 2013 6:15 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 9:57 pm

speedbored wrote:
Making use of electric trim is only mentioned in the final paragraph:
Initially, higher control forces may be needed to overcome any stabilizer nose down trim already applied. Electric stabilizer trim can be used to neutralize control column pitch forces before moving the STAB TRIM CUTOUT switches to CUTOUT. Manual stabilizer trim can be used before and after the STAB TRIM CUTOUT switches are moved to CUTOUT

The fact that this is not included in the "procedure above", and includes the wording "can be used" clearly suggests that this is optional.


Indeed. "Can be used" means it is optional. "Must be used" means that it is mandatory.
 
morrisond
Posts: 2945
Joined: Thu Jan 07, 2010 12:22 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 10:22 pm

PW100 wrote:
MSPNWA wrote:
SheikhDjibouti wrote:
UTTER RUBBISH!


Woah, someone is triggered.

Glad you asked. I am a regular car mechanic. Will be using one again tomorrow. That's why I speak with confidence about it. It was a poor analogy, and I've called it out.

In order for the theory that trim was impossible to move with either the trim switches or manually to be valid, it implies that Boeing built a "jack" that as woefully below the safe "weight" limit necessary, and this flaw has been flying for decades. That's a theory that needs more than speculation to be plausible.


That "theory" was apparently included in the operating manuals of earlier 737 versions. It even included instructions on how to handle such event (yoyo, or roller-coaster technique). Since then, the wheel size has been reduced, which would even increase the force required.

While we have don't have 100% certainty on this, I feel confident that this by now has assed the level of wild speculation . . .



Yes they changed the wheel size - but did they maintain the same number of turns to fully move the stabilizer? They may have changed the gearing which would make it easier to turn - but require more turns to do the same thing.

I'm looking but I can't find any references.
 
freakyrat
Posts: 2128
Joined: Fri Aug 22, 2008 1:04 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 10:28 pm

PcarSBA wrote:
To me it looks like by „flying the airplane“ their sole focus was on the attitude (using outside queues or AH) but they completely neglected the ever building air speed due to the thrust setting. That got them backed into a corner.


A MAX pilot that writes for the FlightGlobal website agrees and said the proper response to all that was going on would have been to retard the throttles and raise the speedbrakes which by slowing the aircraft would have allowed them to pull out of the nose down attitude with the elevators alone.

https://www.flightglobal.com/news/artic ... ns-457369/
 
Planetalk
Posts: 470
Joined: Thu Aug 27, 2015 5:12 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Sat Apr 13, 2019 11:07 pm

freakyrat wrote:
PcarSBA wrote:
To me it looks like by „flying the airplane“ their sole focus was on the attitude (using outside queues or AH) but they completely neglected the ever building air speed due to the thrust setting. That got them backed into a corner.


A MAX pilot that writes for the FlightGlobal website agrees and said the proper response to all that was going on would have been to retard the throttles and raise the speedbrakes which by slowing the aircraft would have allowed them to pull out of the nose down attitude with the elevators alone.

https://www.flightglobal.com/news/artic ... ns-457369/


Which is all well and good, but for all we know that pilot spent two weeks thinking about it sitting in a garden listening to the birds chirping before deciding that was the best course of action.

And since the very first paragraph is completely factually incorrect, I'm not going to take seriously anything else they say. We know MCAS was required for certification. And saying it isn't a safety feature is just bizarre, or some seriously stretched semantics.

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