Ethiopian Airlines plane crashes on way to Nairobi

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Re: Ethiopian Airlines plane crashes on way to Nairobi

Unread post by Horace Blok » Thu Mar 14, 2019 6:08 pm

I’m afraid I cannot accept that there were only two trim events and both ended up catastrophically. I wonder how many other trim events there were where the crew were able to save the day by following procedures by disengaging the switches? Has it been reported anywhere?
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Re: Ethiopian Airlines plane crashes on way to Nairobi

Unread post by Swartbok » Thu Mar 14, 2019 6:08 pm

jimdavis wrote:
Thu Mar 14, 2019 5:39 pm
JCO7 wrote:
Thu Mar 14, 2019 4:25 pm
jimdavis wrote:
Thu Mar 14, 2019 3:27 pm

It is hugely powerful and there is no way that the elevator will overcome it if it runs away to one of its extremes.

jim
The aircraft is supposed to be flyable on elevator only, regardless of stab position.

From Max 8 QRH (Stabiliser Trim Inoperative):
Thanks so much JCO7. My info came from a current airline captain, but if the QRH says otherwise - so be it! We live and learn. :D

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I’m not sure which QRH that comes from, I don’t dispute it as I don’t have my QRH with me right now but from experience it’s pretty much impossible to fly the elevator by hand with the stabilizer trimmed to the limit.

Maybe I need to eat more spinach

Actually just checked my QRH but don’t find that note
Last edited by Swartbok on Thu Mar 14, 2019 6:14 pm, edited 1 time in total.
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Re: Ethiopian Airlines plane crashes on way to Nairobi

Unread post by Deanw » Thu Mar 14, 2019 6:10 pm

Bushpilotzaa wrote:
Thu Mar 14, 2019 5:45 pm
https://pasteboard.co/I4Oz13y.jpg
That's comparing apples with bananas. The Lion Air date is 'complete' to the time of crash, whilst the Ethiopian FR24 data stops when the aircraft was out of range of FR24 ADBS receivers, but the aircraft actually carried on flying for a few more minutes prior to crashing.
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Re: Ethiopian Airlines plane crashes on way to Nairobi

Unread post by ddevos » Thu Mar 14, 2019 6:11 pm

Bushpilotzaa wrote:
Thu Mar 14, 2019 5:45 pm
https://pasteboard.co/I4Oz13y.jpg
That website is unsafe due to a trojan virus...
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Re: Ethiopian Airlines plane crashes on way to Nairobi

Unread post by JCO7 » Thu Mar 14, 2019 6:23 pm

Swartbok wrote:
Thu Mar 14, 2019 6:08 pm
jimdavis wrote:
Thu Mar 14, 2019 5:39 pm
JCO7 wrote:
Thu Mar 14, 2019 4:25 pm


The aircraft is supposed to be flyable on elevator only, regardless of stab position.

From Max 8 QRH (Stabiliser Trim Inoperative):
Thanks so much JCO7. My info came from a current airline captain, but if the QRH says otherwise - so be it! We live and learn. :D

jim
I’m not sure which QRH that comes from, I don’t dispute it as I don’t have my QRH with me right now but from experience it’s pretty much impossible to fly the elevator by hand with the stabilizer trimmed to the limit.

Maybe I need to eat more spinach

Actually just checked my QRH but don’t find that note
Hey Swartbok,

It's between step 9 and 10 of the Stabiliser Trim Inoperative checklist. In the Max 8, -800, -400 and -200 QRH's (so presumably the same applies to all 737's). Not saying it would be easy to fly but I'm thinking it may be a requirement of the certification process.
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Re: Ethiopian Airlines plane crashes on way to Nairobi

Unread post by JCO7 » Thu Mar 14, 2019 6:28 pm

Horace Blok wrote:
Thu Mar 14, 2019 6:08 pm
I’m afraid I cannot accept that there were only two trim events and both ended up catastrophically. I wonder how many other trim events there were where the crew were able to save the day by following procedures by disengaging the switches? Has it been reported anywhere?
Well on the Lion Air aircraft the same issue was snagged on the prior flight. But that crew seemed to cope. I believe they completed the flight using manual trim.

Also there are apparently a number of pilot reports on NASA's confidential reporting system where crews had similar issues.
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Re: Ethiopian Airlines plane crashes on way to Nairobi

Unread post by JCO7 » Thu Mar 14, 2019 6:35 pm

jimdavis wrote:
Thu Mar 14, 2019 5:52 pm
JCO7 wrote:
Thu Mar 14, 2019 5:20 pm

Now that is the interesting bit. Calculating G loads from FR24 data, it looks like some of the pitch events resulted in +/- 2G excursions (although the majority of the flight was <|0.5G|). So the G loads should not have been enough to seriously inhibit the pilots.

So, either it is a spectacularly mismanaged trim runaway (MCAS or otherwise), or something else went wrong.

The mechanics of the control system are identical (as far as I can find out) to the NG, so there are millions of flight hours without any issues.

No idea what else it could be?
Just bear in mind that an erroneous AoA input would have caused unreliable airspeed and probably stick shaker activation. This would have been the pilots' primary focus. Then MCAS subtly trims in the background, creating a horribly out of trim condition. The pilot could have even lowered the nose himself initially to recover from the non-existent stall. You now have a nose down attitude with excessive nose down trim being applied without your knowledge.

You may then realise the aircraft is not actually stalling and attempt to bring the attitude and thrust toward the Airspeed Unreliable recovery settings (4 degrees nose up/75% N1) but you require large elevator and trim inputs to achieve this. Just as you start getting control the MCAS activates again and continues to trim nose down. You are faced with erroneous speed indications, stick shaker activated and struggling to control the aircraft in pitch.

The only way out is to timeously move the stab trim switches to cutout, IF you realise under the stress of the situation that there is uncommanded trim being applied.

All easier said than done.
Very interesting JCO7. Do you think that crew would, in desperation, look outside and try to fly visually? Also could the attitude indicator have been effected by erroneous inputs form the pitot or AoA sensors? Would it not have been instinctive for the crew to resort to basic power and attitude flying?

jim
[/quote]

Jim the attitude info comes from the IRS's, so those would've been unaffected.

It is remarkable that both accidents occurred in VMC, which is indicative of the level of control difficulties they had.

Basic power and attitude flying is exactly what is required in an unreliable airspeed situation. But having observed many crews stuff it up in the sim I would not say it is instinctive to the average pilot of a modern jetliner. Add to that flight control issues and things get hairy quickly.
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Re: Ethiopian Airlines plane crashes on way to Nairobi

Unread post by Romeo E.T. » Thu Mar 14, 2019 6:37 pm

Swartbok wrote:
Thu Mar 14, 2019 6:08 pm
jimdavis wrote:
Thu Mar 14, 2019 5:39 pm
JCO7 wrote:
Thu Mar 14, 2019 4:25 pm


The aircraft is supposed to be flyable on elevator only, regardless of stab position.

From Max 8 QRH (Stabiliser Trim Inoperative):
Thanks so much JCO7. My info came from a current airline captain, but if the QRH says otherwise - so be it! We live and learn. :D

jim
I’m not sure which QRH that comes from, I don’t dispute it as I don’t have my QRH with me right now but from experience it’s pretty much impossible to fly the elevator by hand with the stabilizer trimmed to the limit.

Maybe I need to eat more spinach

Actually just checked my QRH but don’t find that note
Earlier today, two training Captains, tried in the simulator to see if the aircraft is flyable with far forward/nose down trim

the conclusion was that they could barely maintain S+L , with great effort
however
once the nose started downwards, it was impossible to bring it back up again

also take into account, the Stall Computer, that applies a hydraulic feel pressure that makes it more difficult to move the control column rearwards, when the Stall computer senses a stall, or near stall condition.

This feel pressure and forward MCAS trim makes the task of pulling back on the control column and recovering the aircraft once it starts a downward trajectory, nearly impossible
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Re: Ethiopian Airlines plane crashes on way to Nairobi

Unread post by Jasondn78 » Thu Mar 14, 2019 6:49 pm

I thought all the Max models were grounded, but there are a few flying around the USA still.

Are they returning to their hub / storage facility or are a few still flying passengers around?
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Re: Ethiopian Airlines plane crashes on way to Nairobi

Unread post by JCO7 » Thu Mar 14, 2019 6:57 pm

Romeo E.T. wrote:
Thu Mar 14, 2019 6:37 pm
Swartbok wrote:
Thu Mar 14, 2019 6:08 pm
jimdavis wrote:
Thu Mar 14, 2019 5:39 pm


Thanks so much JCO7. My info came from a current airline captain, but if the QRH says otherwise - so be it! We live and learn. :D

jim
I’m not sure which QRH that comes from, I don’t dispute it as I don’t have my QRH with me right now but from experience it’s pretty much impossible to fly the elevator by hand with the stabilizer trimmed to the limit.

Maybe I need to eat more spinach

Actually just checked my QRH but don’t find that note
Earlier today, two training Captains, tried in the simulator to see if the aircraft is flyable with far forward/nose down trim

the conclusion was that they could barely maintain S+L , with great effort
however
once the nose started downwards, it was impossible to bring it back up again

also take into account, the Stall Computer, that applies a hydraulic feel pressure that makes it more difficult to move the control column rearwards, when the Stall computer senses a stall, or near stall condition.

This feel pressure and forward MCAS trim makes the task of pulling back on the control column and recovering the aircraft once it starts a downward trajectory, nearly impossible
Yes I would imagine those added factors would make it impossible to fly. Out of interest, did they utilise thrust at all to try get the nose back up (pitch-up moment)?

In these accidents they did presumably have access to trim though - electric initially and, after disconnecting electric, the manual trim.
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Re: Ethiopian Airlines plane crashes on way to Nairobi

Unread post by jimdavis » Thu Mar 14, 2019 7:05 pm

Thanks Schultzie and JCO7. So my informant was correct! Very interesting. I suppose if they were both hauling back on their poles together, maybe it was indeed too late by then, and maybe neater felt they has a spare hand to tackle manual trimming. A terrifying thought! Let's hope the FDR and CVR have some clues.

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Re: Ethiopian Airlines plane crashes on way to Nairobi

Unread post by Swartbok » Thu Mar 14, 2019 7:11 pm

JCO7 wrote:
Thu Mar 14, 2019 6:23 pm
Swartbok wrote:
Thu Mar 14, 2019 6:08 pm
jimdavis wrote:
Thu Mar 14, 2019 5:39 pm


Thanks so much JCO7. My info came from a current airline captain, but if the QRH says otherwise - so be it! We live and learn. :D

jim
I’m not sure which QRH that comes from, I don’t dispute it as I don’t have my QRH with me right now but from experience it’s pretty much impossible to fly the elevator by hand with the stabilizer trimmed to the limit.

Maybe I need to eat more spinach

Actually just checked my QRH but don’t find that note
Hey Swartbok,

It's between step 9 and 10 of the Stabiliser Trim Inoperative checklist. In the Max 8, -800, -400 and -200 QRH's (so presumably the same applies to all 737's). Not saying it would be easy to fly but I'm thinking it may be a requirement of the certification process.
I double checked and you are quite correct about the checklist.
As Romeo ET said though I agree, practically I found it virtually impossible.
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Re: Ethiopian Airlines plane crashes on way to Nairobi

Unread post by mnmodels » Thu Mar 14, 2019 7:16 pm

Deanw wrote:
Thu Mar 14, 2019 6:10 pm
Bushpilotzaa wrote:
Thu Mar 14, 2019 5:45 pm
https://pasteboard.co/I4Oz13y.jpg
That's comparing apples with bananas. The Lion Air date is 'complete' to the time of crash, whilst the Ethiopian FR24 data stops when the aircraft was out of range of FR24 ADBS receivers, but the aircraft actually carried on flying for a few more minutes prior to crashing.
bucky_za wrote:
Thu Mar 14, 2019 2:21 pm
If this aircraft fly's differently to the previous one under certain circumstances, such as when the MCAS is disconnected,
would these different flight characteristics, such as the pitch up due to the new engine placement be programmed into the sim ?
Am I wrong to presume "no update to simulators" was required, considering the new aircraft is supposed to fly the same as the previous one,
which clearly it doesn't.

What is the possibility AirET managed to shut down the system as directed by Boeing after the previous crash,
and after regaining control our 8000 hour Pilot pulled up out of the dive, using dive recovery techniques no doubt practiced in the sim,
only to be caught out by the new pitch up characteristic on the MAX ending up in a stall that the MCAS is designed to prevent.

The various tracks as posted of the Altitude/Vspeed etc all show a big jump in altitude before going of Radar.
Does this proof that the pilots shut down electrical system trying to recover aircraft......explaining no ADBS
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Re: Ethiopian Airlines plane crashes on way to Nairobi

Unread post by JCO7 » Thu Mar 14, 2019 7:28 pm

mnmodels wrote:
Thu Mar 14, 2019 7:16 pm
Deanw wrote:
Thu Mar 14, 2019 6:10 pm
Bushpilotzaa wrote:
Thu Mar 14, 2019 5:45 pm
https://pasteboard.co/I4Oz13y.jpg
That's comparing apples with bananas. The Lion Air date is 'complete' to the time of crash, whilst the Ethiopian FR24 data stops when the aircraft was out of range of FR24 ADBS receivers, but the aircraft actually carried on flying for a few more minutes prior to crashing.
bucky_za wrote:
Thu Mar 14, 2019 2:21 pm
If this aircraft fly's differently to the previous one under certain circumstances, such as when the MCAS is disconnected,
would these different flight characteristics, such as the pitch up due to the new engine placement be programmed into the sim ?
Am I wrong to presume "no update to simulators" was required, considering the new aircraft is supposed to fly the same as the previous one,
which clearly it doesn't.

What is the possibility AirET managed to shut down the system as directed by Boeing after the previous crash,
and after regaining control our 8000 hour Pilot pulled up out of the dive, using dive recovery techniques no doubt practiced in the sim,
only to be caught out by the new pitch up characteristic on the MAX ending up in a stall that the MCAS is designed to prevent.

The various tracks as posted of the Altitude/Vspeed etc all show a big jump in altitude before going of Radar.
Does this proof that the pilots shut down electrical system trying to recover aircraft......explaining no ADBS
No Morne they would not have shut down the aircraft's electrical system. I think reference was made to the electrical trim system. The lack of FR data is probably spotty coverage in the area.
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Re: Ethiopian Airlines plane crashes on way to Nairobi

Unread post by Wingnutter » Thu Mar 14, 2019 8:34 pm

Unreliable airspeed on its own is a bit of a handful, especially when you have stick shakers / overspeed warnings going off - throw in an aeroplane that’s trying to trim the aeroplane to fly into the ground, and you’re looking at a very interesting day out indeed.

On the flip side, I would have thought that any 737 max crew would have the possibility of a trim runaway very much on their minds after the Lion Air crash and would have been on the stabiliser trim cutout switches at the first sign of anything amiss.
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