WIederling
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 10:07 am

SteinarN wrote:
If this latest development turns out to be the cause for the accident then this would be very difficult for the pilots to avoid?
If so, is this the first time a modern passenger airline have flown itself into the ground leaving little room for the pilots to avoid the disaster?


reported remedy:
... if not counteracted by pilot trimming the aircraft and disconnecting the stabilizer trim system.

use the 10 sec intermission period. fix trim and then cut power . voila.
Murphy is an optimist
 
mjoelnir
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 10:11 am

That is some news about possible technical problems on the 737-8 could have caused the accident. If that is the case, some of the posters here who have been damning the pilots, airline or service level of that airline, perhaps need to eat some crow and wait next time for the investigation.
 
uta999
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 10:13 am

Perhaps a simple App on an iPad (based on SatNav) satellite data could be created, that gives (approx) airspeed and an artificial horizon, and then outputs both to a small HUD in between the pilots.
Your computer just got better
 
SteinarN
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 10:31 am

WIederling wrote:
SteinarN wrote:
If this latest development turns out to be the cause for the accident then this would be very difficult for the pilots to avoid?
If so, is this the first time a modern passenger airline have flown itself into the ground leaving little room for the pilots to avoid the disaster?


reported remedy:
... if not counteracted by pilot trimming the aircraft and disconnecting the stabilizer trim system.

use the 10 sec intermission period. fix trim and then cut power . voila.


Would this be a memory procedure for the pilots? They would need to react very quickly and have learned beforehand exactly what to do.
So, the next question, have the pilots on 737 Max learned that suddenly "uncommanded" pitch down of the aircraft and "uncommanded" forward motion with large force by the control column needs to be counteracted by pushing those trim switches immediately?
 
log0008
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 10:32 am

uta999 wrote:
Perhaps a simple App on an iPad (based on SatNav) satellite data could be created, that gives (approx) airspeed and an artificial horizon, and then outputs both to a small HUD in between the pilots.


GPS ground speed has nothing to do with airspeed
 
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Finn350
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 10:39 am

WIederling wrote:
SteinarN wrote:
If this latest development turns out to be the cause for the accident then this would be very difficult for the pilots to avoid?
If so, is this the first time a modern passenger airline have flown itself into the ground leaving little room for the pilots to avoid the disaster?


reported remedy:
... if not counteracted by pilot trimming the aircraft and disconnecting the stabilizer trim system.

use the 10 sec intermission period. fix trim and then cut power . voila.


Based on the Aircurrent article, the time to react is actually 5 seconds.

It will be interesting to see whether the direct cause of the accident will be pilot error or system design (the other will then be contributory factor, if the news reports about the trim system are true).

According to the official familiar with the bulletin, Boeing warns operators that the angle of attack issue can occur during only manual flight. The erroneous AOA input can pitch the aircraft's stabilizer trim down for up to 10 seconds as a time.

The plane maker is expected to caution pilots to use the electric stabilizer trim to reverse the downward stabilizer trim, but the nose-over can begin again five seconds after those switches are released, the official added.


Source: https://theaircurrent.com/aviation-safe ... air-crash/
 
SteinarN
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 10:54 am

And further, what if this happens at say 500 ft just after takeoff? I certainly wouldnt be a pilot, or passenger for that matter, on that aircraft, even if I had memorized the correct action.
 
XT6Wagon
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 10:54 am

uta999 wrote:
Perhaps a simple App on an iPad (based on SatNav) satellite data could be created, that gives (approx) airspeed and an artificial horizon, and then outputs both to a small HUD in between the pilots.


Plane with a stall speed of 130 knots is moving at a ground speed of 200 knots with a tail wind of 71 knots. Math says complex aluminum tube will play lawn dart. Its why windshear areas are so dangerous as planes move from going slow with a solid headwind to a going too slow with the sudden new tailwind. Plane keeps its momentum (ground speed) while wings lose the critical air speed needed for flight.

So unless you have a good way to accurately measure tail wind, you can't use GPS for "low" speed flight. And higher speeds/altitude you run the risk of finding too much of either. Also coffin corner where you find both right next to stall speed.
 
Amiga500
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 11:04 am

Eikie wrote:
Amiga500 wrote:
Erebus wrote:

You mean this thing:
https://goo.gl/images/fvj858

Which is allready on every (modern) airplane.


I was about to ask... if its on every modern plane - and I assume supplying AoA information to the pilots - how are they then conspiring to stall the damn aircraft?

A quick google later and...

viewtopic.php?t=774161


Optional, only a few airlines have it and only on a few planes. There is even an example there of someone having to use it due to triple failure of airspeed indicators.


If I were asked, I would strongly recommend that the FAA and EASA mandate its incorporation everywhere and that pilots know how to use it.
 
konrad
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 11:05 am

I find it strange that conditions for such an important malfunction have not occurred earlier, in test flying or in any of the hundreds of daily 737 MAX flights.
 
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seahawk
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 11:09 am

That will be interesting to see and we might see the first problems of the not fully digital system core of the 737.
 
Amiga500
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 11:11 am

trpmb6 wrote:
I believe you just described the Airbus Backup Speed Scale system. (BUSS) that has been discussed here.

I'm not familiar with how the Airbus BUSS system works, but I assume it involves measuring angle of attack by determining the angle of the streamline with the wing. (cough - by definition that would be angle of attack :mrgreen: ) Probably have naca scoops on the wing or some other method. I may post in the technical forum about this topic just to get a better understanding personally.


That sounds like it runs through some convoluted process to infer speed.

I'm talking about simple stuff - AoA only - and should be constantly displayed. Wouldn't be hard to add a blip to the artificial horizon or maybe cleaner, a vertical scale running beside it.
 
WIederling
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 11:35 am

Amiga500 wrote:
I'm talking about simple stuff - AoA only - and should be constantly displayed. Wouldn't be hard to add a blip to the artificial horizon or maybe cleaner, a vertical scale running beside it.


The issue appears to not be loss of airspeed information but faulty indication ( of AoA?) that leads into
erroneous trim commands _that are "difficult to get away from".

to wit:
* Remedy is taking away power from electric trim.
* But you first have to fix trim ( electric actuation only :-)
Murphy is an optimist
 
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Finn350
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 11:37 am

konrad wrote:
I find it strange that conditions for such an important malfunction have not occurred earlier, in test flying or in any of the hundreds of daily 737 MAX flights.


I can understand how it has not come up in actual flying previously, if it requires a certain set of malfunctions, but how has it not come up in the system design phase?
 
dragon6172
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 11:47 am

konrad wrote:
I find it strange that conditions for such an important malfunction have not occurred earlier, in test flying or in any of the hundreds of daily 737 MAX flights.

It has come up on prior flights. The flight right before the accident flight actually. Those pilots were able to follow the procedure and continue the flight.
Phrogs Phorever
 
Amiga500
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 11:56 am

WIederling wrote:
Amiga500 wrote:
I'm talking about simple stuff - AoA only - and should be constantly displayed. Wouldn't be hard to add a blip to the artificial horizon or maybe cleaner, a vertical scale running beside it.


The issue appears to not be loss of airspeed information but faulty indication ( of AoA?) that leads into
erroneous trim commands _that are "difficult to get away from".

to wit:
* Remedy is taking away power from electric trim.
* But you first have to fix trim ( electric actuation only :-)



So basically a trim "RESET & OFF" button.
 
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SomebodyInTLS
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 12:41 pm

log0008 wrote:
uta999 wrote:
Perhaps a simple App on an iPad (based on SatNav) satellite data could be created, that gives (approx) airspeed and an artificial horizon, and then outputs both to a small HUD in between the pilots.


GPS ground speed has nothing to do with airspeed


I think we need to have a new a.net emoticon of someone holding this as a banner...
"As with most things related to aircraft design, it's all about the trade-offs and much more nuanced than A.net likes to make out."
 
ranold76
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 12:45 pm

WIederling wrote:

reported remedy:
... if not counteracted by pilot trimming the aircraft and disconnecting the stabilizer trim system.

use the 10 sec intermission period. fix trim and then cut power . voila.


That's if you even have 10 seconds available..
Wow. Not sure I'll be on a MAX until a real solution is implemented imo.
 
estorilm
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 1:05 pm

MatthewDB wrote:

estorilm wrote:

I think it needs to be looked at as a requirement for new model certifications.


Did the 737MAX get a new certificate, or is it still legacy?


We are definitely on the same page! FWIW I think the MAX is still grandfathered in for almost every aspect of its type certificate. My additional point about the systems was that AB has actually developed and implemented such a safety system, and has it as standard equipment on some of their models now (which is smart, since I think the other systems in the plane require all the data anyways).

Requiring the MAX series to have such a system is probably unrealistic, due to the vast array of additional computer systems required - even so, all such systems are already certified for the airframes that AB has the BUSS system on, while I don't think any such systems (capable of the calculations/display/data processing) are certified on a Boeing product minus the 787.
 
dragon6172
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 1:10 pm

ranold76 wrote:
WIederling wrote:

reported remedy:
... if not counteracted by pilot trimming the aircraft and disconnecting the stabilizer trim system.

use the 10 sec intermission period. fix trim and then cut power . voila.


That's if you even have 10 seconds available..
Wow. Not sure I'll be on a MAX until a real solution is implemented imo.

Same system is on NG's also. Better avoid them, too. :roll:

And, looks like it is on 737 Classic's also. May as well avoid the whole type.
Last edited by dragon6172 on Wed Nov 07, 2018 1:32 pm, edited 1 time in total.
Phrogs Phorever
 
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hOMSaR
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 1:21 pm

SomebodyInTLS wrote:
log0008 wrote:
uta999 wrote:
Perhaps a simple App on an iPad (based on SatNav) satellite data could be created, that gives (approx) airspeed and an artificial horizon, and then outputs both to a small HUD in between the pilots.


GPS ground speed has nothing to do with airspeed


I think we need to have a new a.net emoticon of someone holding this as a banner...


And maybe a second one that says airplanes already have GPS.
The plural of Airbus is Airbuses. Airbii is not a word.
There is no 787-800, nor 787-900 or 747-800. It's 787-8, 787-9, and 747-8.
A321neoLR is also unnecessary. It's simply A321LR.
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groundbird
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 1:32 pm

Would this have covered it?
"'What's it doing now?' click, click, click."
 
CeddP
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 1:48 pm

groundbird wrote:
Would this have covered it?
"'What's it doing now?' click, click, click."


The STS is only active during manual flying… :roll:
The bulletin Boeing just released states in bold it's applicable to manual flight only
 
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scbriml
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 2:07 pm

CeddP wrote:
The bulletin Boeing just released states in bold it's applicable to manual flight only


If airspeed indication has been lost and the autopilot switched off they would be manual, no?
Time flies like an arrow. Fruit flies like a banana!
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WIederling
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 2:08 pm

dragon6172 wrote:
And, looks like it is on 737 Classic's also. May as well avoid the whole type.


Trim actively controlled by AoA bypassing pilot input ?
Murphy is an optimist
 
dragon6172
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 2:21 pm

WIederling wrote:
dragon6172 wrote:
And, looks like it is on 737 Classic's also. May as well avoid the whole type.


Trim actively controlled by AoA bypassing pilot input ?

It doesn't bypass pilot input. If the pilot made a trim input it would stop automatically trimming. There is also a procedure to disconnect the electrical trim function, which is why the memo / alert from Boeing warns pilots to follow the established procedure.
Phrogs Phorever
 
CeddP
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 2:24 pm

scbriml wrote:
CeddP wrote:
The bulletin Boeing just released states in bold it's applicable to manual flight only


If airspeed indication has been lost and the autopilot switched off they would be manual, no?


Indeed.

What's interesting now is FCOM 9.20.10 are exactly identical on NG and MAX. Read page 12 here for a summary http://www.737ng.co.uk/B_NG-Flight_Controls.pdf
That being said, Boeing bulletin is so far only applicable to MAXs. So something has to be different somewhere…?
 
ikramerica
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 2:28 pm

SteinarN wrote:
If this latest development turns out to be the cause for the accident then this would be very difficult for the pilots to avoid?
If so, is this the first time a modern passenger airline have flown itself into the ground leaving little room for the pilots to avoid the disaster?

Proper training, even difference training between NG and Max would make very clear that this can occur and corrected if system is turned off. Which would circle back to Lion training practices or pilot error.
Of all the things to worry about... the Wookie has no pants.
 
Trin
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 3:00 pm

stratclub wrote:
Erebus wrote:
Interesting development. Question I have is, if such issues have surfaced on other MAXes flying even if they were not immediately detected, or if this particular Lion Air aircraft presented the first known instance of such a problem.

Holy crap. No issues has been officially identified yet. The supposed source for this fake news remained anonymous. If people buy into unsubstantiated fake news the journalist's payday is assured. Watch for the slim possibility of a teeny tiny retraction on the last page if the reporting was not factual and correct.


FACT: Boeing have issued an Operations Bulletin addressing the issues (mentioned in this article and many others across media this morning) that they are positing contributed to this incident.

FACT: The more times you say "fake news" in a post, the less serious you will be taken. There's actually probably an algorithm out there that deals with this that perhaps some of our more technical-minded members can provide you with.

Trin
 
Trin
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 3:23 pm

ikramerica wrote:
SteinarN wrote:
If this latest development turns out to be the cause for the accident then this would be very difficult for the pilots to avoid?
If so, is this the first time a modern passenger airline have flown itself into the ground leaving little room for the pilots to avoid the disaster?

Proper training, even difference training between NG and Max would make very clear that this can occur and corrected if system is turned off. Which would circle back to Lion training practices or pilot error.


Most on here know far more than I do - but here's MY thing. Pilots are human beings with inherent flaws and inherent reaction speeds. Attempts at integrating the pilots INTO these (immensely complicated) machines and their (just as complicated) computer systems are always going to fail and MUST always allow for errors, reaction times, and the possibility of panic. You cannot place blame (or the expectation of it) solely at the feet of the humans who are expected to fly these airplanes. At some point you have to look into your designed man-machine interfaces and systems testing and ask yourself if you are designing an unsafe vehicle just because you are expecting too much of humans traveling hundreds of miles per hour at ~5,000ft. No matter how many items and checklists they commit to memory.

Trin
 
jeffrey0032j
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 3:24 pm

Trin wrote:
stratclub wrote:
Erebus wrote:
Interesting development. Question I have is, if such issues have surfaced on other MAXes flying even if they were not immediately detected, or if this particular Lion Air aircraft presented the first known instance of such a problem.

Holy crap. No issues has been officially identified yet. The supposed source for this fake news remained anonymous. If people buy into unsubstantiated fake news the journalist's payday is assured. Watch for the slim possibility of a teeny tiny retraction on the last page if the reporting was not factual and correct.


FACT: Boeing have issued an Operations Bulletin addressing the issues (mentioned in this article and many others across media this morning) that they are positing contributed to this incident.

FACT: The more times you say "fake news" in a post, the less serious you will be taken. There's actually probably an algorithm out there that deals with this that perhaps some of our more technical-minded members can provide you with.

Trin

I see it as Boeing suggesting that it may be a training issue but in a nicer way so as not to displease a large customer. Hence it was worded clearly as a reminder to follow established procedures.
 
jeffrey0032j
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 3:28 pm

Trin wrote:
ikramerica wrote:
SteinarN wrote:
If this latest development turns out to be the cause for the accident then this would be very difficult for the pilots to avoid?
If so, is this the first time a modern passenger airline have flown itself into the ground leaving little room for the pilots to avoid the disaster?

Proper training, even difference training between NG and Max would make very clear that this can occur and corrected if system is turned off. Which would circle back to Lion training practices or pilot error.


Most on here know far more than I do - but here's MY thing. Pilots are human beings with inherent flaws and inherent reaction speeds. Attempts at integrating the pilots INTO these (immensely complicated) machines and their (just as complicated) computer systems are always going to fail and MUST always allow for errors, reaction times, and the possibility of panic. You cannot place blame (or the expectation of it) solely at the feet of the humans who are expected to fly these airplanes. At some point you have to look into your designed man-machine interfaces and systems testing and ask yourself if you are designing an unsafe vehicle just because you are expecting too much of humans traveling hundreds of miles per hour at ~5,000ft. No matter how many items and checklists they commit to memory.

Trin

And potentially let a plane dive off by it's computers without knowing the real cause ever? Like QF72? The cause was an error in the ADIRU but the cause OF the error was never known.
 
ranold76
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 3:38 pm

dragon6172 wrote:
ranold76 wrote:
WIederling wrote:

reported remedy:
... if not counteracted by pilot trimming the aircraft and disconnecting the stabilizer trim system.

use the 10 sec intermission period. fix trim and then cut power . voila.


That's if you even have 10 seconds available..
Wow. Not sure I'll be on a MAX until a real solution is implemented imo.

Same system is on NG's also. Better avoid them, too. :roll:

And, looks like it is on 737 Classic's also. May as well avoid the whole type.


So essentially you're saying it's unique to Lion Air, their training and pilot error then?
Because I haven't see other MAXs, NGs and classics falling from the sky like this one did...
 
dragon6172
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 4:10 pm

ranold76 wrote:
dragon6172 wrote:
ranold76 wrote:

That's if you even have 10 seconds available..
Wow. Not sure I'll be on a MAX until a real solution is implemented imo.

Same system is on NG's also. Better avoid them, too. :roll:

And, looks like it is on 737 Classic's also. May as well avoid the whole type.


So essentially you're saying it's unique to Lion Air, their training and pilot error then?
Because I haven't see other MAXs, NGs and classics falling from the sky like this one did...

Maybe because other pilots who encountered the problem followed established procedures? The previous flight pilots seemed to do ok.

Boeing bulletin supposed text:
This bulletin directs flight crews to existing procedures to address this condition. In the event of erroneous AOA data, the pitch trim system can trim the stabilizer nose down in increments lasting up to 10 seconds. The nose down stabilizer trim movement can be stopped and reversed with the use of the electric stabilizer trim switches but may restart 5 seconds after the electric stabilizer trim switches are released. Repetitive cycles of uncommanded nose down stabilizer continue to occur unless the stabilizer trim system is deactivated through use of both STAB TRIM CUTOUT switches in accordance with the existing procedures in the Runaway Stabilizer NNC. It is possible for the stabilizer to reach the nose down limit unless the system inputs are counteracted completely by pilot trim inputs and both STAB TRIM CUTOUT switches are moved to CUTOUT.

Additionally, pilots are reminded that an erroneous AOA 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.
- Inability to engage autopilot.
- Automatic disengagement of autopilot.
- IAS DISAGREE alert.
- ALT DISAGREE alert.
- AOA DISAGREE alert (if the AOA indicator option is installed)
- FEEL DIFF PRESS light.

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


So, pending further investigation, the pilots would have always had control of the aircraft. If the stab was being trimmed the wrong way by the computers, all the pilot had to do was make inputs to counteract the problem until the cutout switch could be flipped.
Phrogs Phorever
 
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7BOEING7
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 4:10 pm

dragon6172 wrote:
WIederling wrote:
dragon6172 wrote:
And, looks like it is on 737 Classic's also. May as well avoid the whole type.


Trim actively controlled by AoA bypassing pilot input ?

It doesn't bypass pilot input. If the pilot made a trim input it would stop automatically trimming. There is also a procedure to disconnect the electrical trim function, which is why the memo / alert from Boeing warns pilots to follow the established procedure.


737NG -- If the stab trim starts to go nose down, the first thing a pilot will instinctively do if flying manually (which is a requirement for this to happen) is pull back on the control column which will stop the runaway. He will then trim nose up which will also prevent further nose down movement and then per memory will select both Stab Trim Cutout switches to the CUTOUT position -- this is not some long drawn out procedure and was part of every 737 simulator recurrent training I went thru. The cause may be MAX related but the corrective action appears to be the same.


Sounds like this was just one of their problems however and I'm guessing this didn't occur on the previous flight(s) or the flight crew would have noted operating the stab trim in manual in the write ups.
 
Noshow
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 4:11 pm

So, pending further investigation, the pilots would have always had control of the aircraft.


We don't know that yet. Flying day VMC there must have been a reason to lose control and crash.
Last edited by Noshow on Wed Nov 07, 2018 4:19 pm, edited 2 times in total.
 
WIederling
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 4:12 pm

ranold76 wrote:
So essentially you're saying it's unique to Lion Air, their training and pilot error then?
Because I haven't see other MAXs, NGs and classics falling from the sky like this one did...


We would have seen reports of similar issues none the less, wouldn't we?

Something in the setup must have changed for the MAX !?

The issue with preemptive fingerpointing is that for the
one finger pointing at the hapless incompetent
4 fingers may well point at the real cause :-)
Murphy is an optimist
 
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PW100
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 4:15 pm

mandala499 wrote:
I managed to get bits of the previous post flight maintenance reports from various sources. It looks like the unreliable airspeed indications from the last 4 flights may not have been caused by a single generated warning/fault on the sensor detection (ie: not purely a pitot issue).Am now getting info (which needs confirmation) that over the past week, whenever a problem occur, it would appear, get rectified according to the FIM and TSM, then fly again, get the same warning, fix it again, then the aircraft would generate a different problem. If this is true then the guys on the ground had little chance to pick up on them as a "repetitive problem" (which would require a different kind of troubleshooting). When taking a step back, it does appear that this may be an ADR issue (not a sensor input to the ADR, but the ADR itself). The major problem with this, is the STS (Speed Trim System)... which if taking erroneous ADR feeds, could lead to...

So, this morning we had a shocker... if true then... (Am still trying to get to the depths of it)
https://www.bloomberg.com/news/articles ... 7-max-jets
"erroneous readings from a flight-monitoring system can cause the planes to aggressively dive"

and now... this too:
https://theaircurrent.com/aviation-safe ... air-crash/

I guess this is going to be a looooooong case for everyone to deal with...


So essentially this may suggest that there may have been two problems:
1) Unreliable air speed captain side;
2) ADR/STS issue

Each of these problems may be intermittent in character. From a (ground) trouble shoot point of view, this could be a real nightmare, as the effects of each fault may impact the other one. One might even "camouflage" symptoms of the other problem.

Fault 2) may not be noticeable, or somehow hidden, until autopilot disconnects - because of 1) - and then STS puts elevator trim full down. At 5000 ft, these guys in the pointing end had very little time to realize what was going on before it was too late.

Was the electrical disconnecting of STS already a memory item?
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kalvado
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 4:29 pm

zeke wrote:

Image

If @zeke's reconstruction is correct, then they could have nose-down problem at least twice, with first one @500 sec being recovered - but the second one occurred two minutes later. Maybe some before.
Is it possible that the dive damaged something in flight control? Large airfoil load while being actuated or something?
 
mandala499
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 4:34 pm

WIederling wrote:
We would have seen reports of similar issues none the less, wouldn't we?

We didn't see reports of A330 ADIRUs going bonkers and turned the airliner into a Stuka bomber until the Qantas ones... after how many years? :)

7BOEING7 wrote:
737NG -- If the stab trim starts to go nose down, the first thing a pilot will instinctively do if flying manually (which is a requirement for this to happen) is pull back on the control column which will stop the runaway. He will then trim nose up which will also prevent further nose down movement and then per memory will select both Stab Trim Cutout switches to the CUTOUT position -- this is not some long drawn out procedure and was part of every 737 simulator recurrent training I went thru. The cause may be MAX related but the corrective action appears to be the same.

Has anyone done the above (with a startle effect, ie: not telling the pilot what the instructor is about to throw at him) in a sim with unreliable airspeed and possibly with AOA disagree on top of that?
When losing situational awareness, pray Cumulus Granitus isn't nearby !
 
CeddP
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 4:43 pm

7BOEING7 wrote:
737NG -- If the stab trim starts to go nose down, the first thing a pilot will instinctively do if flying manually (which is a requirement for this to happen) is pull back on the control column which will stop the runaway.

Does that even apply to STS operation ? At acceleration altitude for exemple, as you push control column to decrease pitch and accelerate, you always have the STS annoyingly trimming nose up until trimming nose down yourself with trim switches… I reckon the forward movement of the column is quite subtle, but it makes me wonder if the "anti-runaway" feature apply to STS operation ?
 
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7BOEING7
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 4:52 pm

mandala499 wrote:
WIederling wrote:
We would have seen reports of similar issues none the less, wouldn't we?

We didn't see reports of A330 ADIRUs going bonkers and turned the airliner into a Stuka bomber until the Qantas ones... after how many years? :)

7BOEING7 wrote:
737NG -- If the stab trim starts to go nose down, the first thing a pilot will instinctively do if flying manually (which is a requirement for this to happen) is pull back on the control column which will stop the runaway. He will then trim nose up which will also prevent further nose down movement and then per memory will select both Stab Trim Cutout switches to the CUTOUT position -- this is not some long drawn out procedure and was part of every 737 simulator recurrent training I went thru. The cause may be MAX related but the corrective action appears to be the same.

Has anyone done the above (with a startle effect, ie: not telling the pilot what the instructor is about to throw at him) in a sim with unreliable airspeed and possibly with AOA disagree on top of that?


That's why I said it was probably not their only problem but again if the airplane is pitching nose down, you're going to pull back to correct it thereby stopping (until you release the column) the runaway. It was probably elbows and a**holes in the cockpit by then so ….
 
frmrCapCadet
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 4:54 pm

https://www.seattletimes.com/business/b ... nose-dive/

I don't think this link has been posted. Dominic Gates gives an easy to understand article on what can happen, and what needs to be done to correct it.
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7BOEING7
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 4:56 pm

CeddP wrote:
7BOEING7 wrote:
737NG -- If the stab trim starts to go nose down, the first thing a pilot will instinctively do if flying manually (which is a requirement for this to happen) is pull back on the control column which will stop the runaway.

Does that even apply to STS operation ? At acceleration altitude for exemple, as you push control column to decrease pitch and accelerate, you always have the STS annoyingly trimming nose up until trimming nose down yourself with trim switches… I reckon the forward movement of the column is quite subtle, but it makes me wonder if the "anti-runaway" feature apply to STS operation ?


Boeing is referencing that procedure in the bulletin.
 
djm18
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 4:58 pm

I had thought that the issues on the prior flights were only related to the Air Speed Indicator. However, this article seems to imply that the AoA sensors on the flight the night before were not in agreement, which would explain why one sensor was replaced. And the pilots on the flight the night before the crash were in fact able to manage through a sudden dive after take off. It seems quite amazing that the pilot managed through that flight at night with this problem.

https://www.abc.net.au/news/2018-11-08/ ... h/10475468

Lion Air's first two attempts to address the airspeed indicator problem did not work, and for the Boeing 737 MAX 8 plane's second-to-last flight on October 28, the angle of attack sensors were replaced, Mr Tjahjono said.

On that flight, from Bali to Jakarta, the pilot's and co-pilot's sensors disagreed.

The two-month-old plane went into a sudden dive minutes after take-off, which the pilots were able to recover from. They decided to fly on to Jakarta at a lower-than-normal altitude.

Indonesian investigators said their flight procedure recommendations to Boeing were based on how the flight crew responded to problems on the Bali to Jakarta flight.
 
dragon6172
Posts: 928
Joined: Sat Jul 14, 2007 9:56 am

Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 5:09 pm

7BOEING7 wrote:
CeddP wrote:
7BOEING7 wrote:
737NG -- If the stab trim starts to go nose down, the first thing a pilot will instinctively do if flying manually (which is a requirement for this to happen) is pull back on the control column which will stop the runaway.

Does that even apply to STS operation ? At acceleration altitude for exemple, as you push control column to decrease pitch and accelerate, you always have the STS annoyingly trimming nose up until trimming nose down yourself with trim switches… I reckon the forward movement of the column is quite subtle, but it makes me wonder if the "anti-runaway" feature apply to STS operation ?


Boeing is referencing that procedure in the bulletin.

Assuming full nose down trim, can you hold the aircraft level with just aft control column pressure? If so, any guesses on the force required to do so?
Phrogs Phorever
 
buzzard302
Posts: 76
Joined: Sat Jun 06, 2015 12:06 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 5:24 pm

It doesn't take much study to realize this plane probably should have been taken out of service until the problem was resolved. I wonder if the final crew had any reservations about the plane before this ill fated flight.
 
hivue
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 5:35 pm

Disclaimer: Not an aeronautical engineer or involved in aviation.
The trimmable horizontal stabilizer wanting to jump in and pitch the nose down in the event it thinks AoA is excessive only when the autopilot is off sounds to me a lot like flight control law. How much alpha protection -- and other contemporary levels of automation (maybe a lot more in the case of the MAX) -- can be added to non-FBW airplanes without resulting in diminishing returns/a less safe airplane?
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
pygmalion
Posts: 833
Joined: Thu Jun 29, 2006 12:47 am

Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 5:38 pm

yes, the aircraft is fully controllable with full nose down or nose up trim. Control forces are not that high. The trim switches still work but the system would keep trying until you cycled the stab trim cutout switches. its not that different from a Cessna 172/182 with electric trim.
 
Trin
Posts: 132
Joined: Mon May 02, 2011 4:45 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Wed Nov 07, 2018 5:41 pm

mandala499 wrote:
Has anyone done the above (with a startle effect, ie: not telling the pilot what the instructor is about to throw at him) in a sim with unreliable airspeed and possibly with AOA disagree on top of that?


I surely would like to know the answer to that, also. Seeing as the safety of each flight is so closely tied to having accurate airspeed/AoA information fed into the ADIRU, one would certainly HOPE that all pilots plonked into a sim to train would have a mandatory training for ALL loss-of-air-data scenarios thrown at them with the startle effect. Would be pretty much useless to only give the scenario to them in the sim with prior warning, which doesn't account for unexpected and conflicting messages/readouts/warnings, and low-altitude problems with little height to pad your recovery.

Again - man-machine interface. Seems like we need to do a MUCH better job at understanding the limitations of it. Because there will ALWAYS be limitations.

Trin

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