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rheinwaldner
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Wed Mar 27, 2019 7:36 am

ikramerica wrote:
rheinwaldner wrote:
ikramerica wrote:
Wonder what “compromises to safety” Boeing baked in to make the 767 and 757 similar. What design (safety) compromises they use the 767 cockpit section on the 777?

Simple: None!

You continue to overlook the evidence of decade long trouble free operations, which is overwhelming in case of 767 and 757. Not so with the MAX.

Yeah. Who says they have been trouble free?

Statistics. And with trouble I mean comparable trouble. As even the hysterical social media crowd seems to be getting the difference, I wonder why you cant see it.
Many things are difficult, all things are possible!
 
osiris30
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Wed Mar 27, 2019 7:42 am

speedbored wrote:
osiris30 wrote:
Overspeed leads to STS (or pilots) trimming nose down (as airspeed increases, the lift would increase and the AC would pitch up). As speed increases authority from the yoke starts to fail under 'blowback' as we have seen discussed here. Aircraft trim if not adjusted starts to win out over defeated elevators. AC noses over... Pilots (still confused by all the noises in cockpit, etc.) take their eyes off the ball... at their altitude, there is very little reaction time, and re-trimming from a heavy extent won't have an immediate impact on forward motion due to inertia.

IMO, a more likely scenario is that the failed AoA sensor triggered both an airspeed flag and stick shaker which, along with the pilots' own perception of the aircraft's AoA (including the view out of the window) made the pilots believe that the problem was that the aircraft was flying too slowly, so they took the standard actions to rectify that. This led to overspeed which then contributed to things rapidly spiralling out of control later due to the actions of MCAS.

Had they been presented with an AoA sensor disagree indication as well as, or instead of the airspeed flag, I suspect that they would have come to a totally different conclusion and might have been able to maintain control.

Seems to me that this will ultimately boil down to a combination of the AoA disagree flag being a costly optional extra, and the negligently bad MCAS implementation.

osiris30 wrote:
I remain unconvinced that automation had to play a role in this crash. I can think of many reasons why this plane crashed without MCAS.

I have to admire your commitment to this opinion but the publicly available information, along with comments from, and actions by, the authorities which have seen additional non-public data, firmly support a conclusion that both crashes have almost identical causes, and are MCAS related.


Well, frankly there isn't very much publically available information. If we were in a courtroom right now there would be no judgment against MCAS as everything thus far is incredibly circumstantial. If it turns out MCAS did it I shan't protest in the slightest, but with what we have now, that is a jump and a half. The actions by the authorities were all taken before the FDR and CVR were even read, some were the day of the accident.
I don't care what you think of my opinion. It's my opinion, so have a nice day :)
 
WIederling
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Wed Mar 27, 2019 7:50 am

osiris30 wrote:
If we were in a courtroom right now there would be no judgment against MCAS as everything thus far is incredibly circumstantial. If it turns out MCAS did it I shan't protest in the slightest, but with what we have now, that is a jump and a half. The actions by the authorities were all taken before the FDR and CVR were even read, some were the day of the accident.


Safety ( or any other case of unintended "function" ) related dissemination do not happen in a courtroom.

Usually you start out with most everything being suspect and than
build a chain of trust that things work as expected. analysis and testing.
( analysis in scope of rare occurrences tends to show better results than hands on testing.)

In court you do the inverse.
Everybody is not guilty and you build a chain of guilt/cause ...
Murphy is an optimist
 
jollo
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Wed Mar 27, 2019 8:04 am

speedbored wrote:
IMO, a more likely scenario is that the failed AoA sensor triggered both an airspeed flag and stick shaker which, along with the pilots' own perception of the aircraft's AoA (including the view out of the window) made the pilots believe that the problem was that the aircraft was flying too slowly, so they took the standard actions to rectify that. This led to overspeed which then contributed to things rapidly spiralling out of control later due to the actions of MCAS.

Had they been presented with an AoA sensor disagree indication as well as, or instead of the airspeed flag, I suspect that they would have come to a totally different conclusion and might have been able to maintain control.

Seems to me that this will ultimately boil down to a combination of the AoA disagree flag being a costly optional extra, and the negligently bad MCAS implementation.


I agree with your assessment and prediction, Sir. We'll see.

I will repeat myself adding that if on an AoA disagree condition, in addition to displaying a warning light to pilots, the system had simply disabled MCAS (instead of requiring pilots to manually cut off electric stab trim) we would very likely not be having this thread. Note: this would not have been a good, or even "good enough" flight envelope protection implementation, but at least it would avoid an obvious and potentially catastrophic failure mode. I cannot believe this very basic principle was never even considered during the whole design and development of the MAX: nobody is *that* bad, and certainly not Boeing engineers. I suspect that it was considered at some point, then overridden for some reason.
 
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speedbored
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Wed Mar 27, 2019 10:16 am

jollo wrote:
I suspect that it was considered at some point, then overridden for some reason.

I suspect that the "reason" will ultimately be that far too much of Boeing senior management these days is people recruited externally for their qualifications (e.g. MBAs) and accountancy skills, and far too few people recruited from within with engineering, design, test, flying, or operational knowledge and skills.

In my experience, people "from the coal face" with lots of real-world knowledge and skills, almost always want, and know how, to do the job properly. Accountants and MBAs often make decisions based purely on short-term financials.
 
XRAYretired
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Wed Mar 27, 2019 11:08 am

 
WIederling
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Wed Mar 27, 2019 11:52 am

speedbored wrote:
jollo wrote:
I suspect that it was considered at some point, then overridden for some reason.

I suspect that the "reason" will ultimately be that far too much of Boeing senior management these days is people recruited externally for their qualifications (e.g. MBAs) and accountancy skills, and far too few people recruited from within with engineering, design, test, flying, or operational knowledge and skills.

In my experience, people "from the coal face" with lots of real-world knowledge and skills, almost always want, and know how, to do the job properly. Accountants and MBAs often make decisions based purely on short-term financials.


They make decision on what they think they understand. That does not reach very far ( time, scope ).
And they are more prone to fall for legal logic than for "real hard physical in your face logic".
:: underpinning here is the fully incompatible concepts behind
"law" in scope of legal affairs ( artifical rule : intentionally kill somebody and you may get away with a good lawyer )
and the
"law" in scope of Science ( observed regular behavior : like unsupported things falling down in earth gravity field showing predictable acceleration ...)
Murphy is an optimist
 
RickNRoll
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Wed Mar 27, 2019 11:53 am

osiris30 wrote:
WIederling wrote:
osiris30 wrote:
We have no data from the FDR or CVR yet. (so no hard evidence on any instrument or system malfunctions yet... it is all speculation).. nor does anyone apparently which is starting to be a bit troubling. I would have expected the CEO of Ethiopian would have seen the data by now.


Was the satellite based ADS-B collection ( a superset of the FR24 data ) made public ? ( Haven't seen it, but .. )


It was not. But the most that data will show is oscillations in altitude. There are lots of other causes that could bring that about especially in an overspeed condition (blowback has been discussed numerous times). Given the CG on the MAX (that we are always talking about), high thrust may cause a nose up incidence on the airframe, at high-speed control surfaces may be unable to counteract, till the plane climbs a bit and bleeds speed then the surfaces come back in and result in a dramatic nose down. On ADS-B data it could look a LOT like MCAS, without being MCAS at all.
They have all the data and grounded the MAX, even though we don't have all the data.
 
morrisond
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Wed Mar 27, 2019 12:12 pm

jollo wrote:
speedbored wrote:
IMO, a more likely scenario is that the failed AoA sensor triggered both an airspeed flag and stick shaker which, along with the pilots' own perception of the aircraft's AoA (including the view out of the window) made the pilots believe that the problem was that the aircraft was flying too slowly, so they took the standard actions to rectify that. This led to overspeed which then contributed to things rapidly spiralling out of control later due to the actions of MCAS.

Had they been presented with an AoA sensor disagree indication as well as, or instead of the airspeed flag, I suspect that they would have come to a totally different conclusion and might have been able to maintain control.

Seems to me that this will ultimately boil down to a combination of the AoA disagree flag being a costly optional extra, and the negligently bad MCAS implementation.


I agree with your assessment and prediction, Sir. We'll see.

I will repeat myself adding that if on an AoA disagree condition, in addition to displaying a warning light to pilots, the system had simply disabled MCAS (instead of requiring pilots to manually cut off electric stab trim) we would very likely not be having this thread. Note: this would not have been a good, or even "good enough" flight envelope protection implementation, but at least it would avoid an obvious and potentially catastrophic failure mode. I cannot believe this very basic principle was never even considered during the whole design and development of the MAX: nobody is *that* bad, and certainly not Boeing engineers. I suspect that it was considered at some point, then overridden for some reason.


Do the backup instruments have an independent air source? Assuming that they do - the first thing a good pilot would do would be to check that for confirmation. If it showed normal speed that's when they should have started shutting off the electronic helpers.
 
jayunited
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Wed Mar 27, 2019 1:46 pm

I don't know if this article has been posted on this thread yet and I don' t have time to go through all 73 pages. But it is very interesting and offers some perspective on what could have happened to JT610 and ET302.. Figure 2A in the article also contains information from the JT610's flight data recorder released by the Indonesian authorities.

The guy who wrote the article says he is a pilot and brings up some very interesting views on Boeings MCAS system and how something called blowback could have contributed to both crashes.

https://leehamnews.com/2019/03/22/bjorn ... sh-part-2/
 
flybucky
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Wed Mar 27, 2019 3:36 pm

jayunited wrote:
I don't know if this article has been posted on this thread yet and I don' t have time to go through all 73 pages.
https://leehamnews.com/2019/03/22/bjorn ... sh-part-2/

Search results for "blowback" in this thread: search.php?keywords=blowback&t=1417519&sf=msgonly

The Search feature at the top of the page is quite useful:

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

Wed Mar 27, 2019 5:32 pm

mandala499 wrote:
PW100 wrote:
Some questions on my side:
1) When MCAS was active during the 10 seconds, is electric trimming on the control column inhibited for that 10 second period?
2) So in that scenario, is electric trimming only available to the pilots during a 5 second window?
3) If control column is already heavy, and the pilot just misses the 5 second window, will he have to wait another full 10 seconds before electric trimming is available again?
4) If the pilot is using electric trimming in the 5 second window, will his trimming be stopped by MCAS kicking in again?

1. No, it isn't.
1.1. When MCAS activates it will command a nose down trim of up to 2.5degs and takes up to 9.26 seconds.
1.2. If MCAS detects the AOA has gone below the MCAS activation threshold while moving the stabilizer trim, it will stop.
1.3. If MCAS goes for the full 2.5 degs (9.26 secs), and aircraft AOA is still above the MCAS activation threshold, it will stop for 5 seconds before reactivating.
1.4. Application of trim is available and overrides MCAS inputs which will inhibit MCAS for a few seconds. If I remember correctly it inhibits it for about 10 seconds. If after 10 seconds AOA remains above MCAS activation threshold, MCAS will activate again. (Go to loop 1.1 - 1.3)
2. See 1.4
3. See 1.4
4. See 1.4


Backseater wrote:
My understanding is that you can stop the current action of MCAS at any time by up trimming with the column switches or manually holding or turning the stab wheel.
That’s why the Lion air Captain was succesful halting and negating each MCAS action until he handed control over to the F/O.


OK Thanks guys. Makes sense.
I read somewhere that MCAS overruled pilot trimming, but apparently just poor journalist at work.
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Backseater
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Wed Mar 27, 2019 9:04 pm

MCAS did not just appear with the MAX.
Here is a quote from Aviation Daily (25 March 2019):
"Both the KC-767 and KC-46 fleets delivered to air forces in Italy, Japan and the U.S. rely on the MCAS to adjust for pitch trim changes during refueling operations.

In the 1980s, Boeing’s engineers considered using a pitch augmentation system for the commercial version of the 767, but dropped the idea after finding that vortex generators provided adequate control.

By 2011, Boeing had already delivered KC-767s to Italy and Japan fitted with the first version of MCAS. The use of the system then spread as Boeing won the Air Force’s KC-46 contract in February and launched the 737 Max 8 in August.

But Boeing designed the integration on the KC-767 and KC-46 slightly differently than on the 737 Max family.

The single-aisle airliner uses one angle of attack vane — either the captain’s or first officer’s — to generate the data used by the flight computer to activate the MCAS.

By comparison, the KC-767 and KC-46 are designed to use two sensor inputs to feed angle of attack data, Boeing says".
 
jollo
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Wed Mar 27, 2019 11:20 pm

morrisond wrote:
jollo wrote:
speedbored wrote:
IMO, a more likely scenario is that the failed AoA sensor triggered both an airspeed flag and stick shaker which, along with the pilots' own perception of the aircraft's AoA (including the view out of the window) made the pilots believe that the problem was that the aircraft was flying too slowly, so they took the standard actions to rectify that. This led to overspeed which then contributed to things rapidly spiralling out of control later due to the actions of MCAS.

Had they been presented with an AoA sensor disagree indication as well as, or instead of the airspeed flag, I suspect that they would have come to a totally different conclusion and might have been able to maintain control.

Seems to me that this will ultimately boil down to a combination of the AoA disagree flag being a costly optional extra, and the negligently bad MCAS implementation.


I agree with your assessment and prediction, Sir. We'll see.

I will repeat myself adding that if on an AoA disagree condition, in addition to displaying a warning light to pilots, the system had simply disabled MCAS (instead of requiring pilots to manually cut off electric stab trim) we would very likely not be having this thread. Note: this would not have been a good, or even "good enough" flight envelope protection implementation, but at least it would avoid an obvious and potentially catastrophic failure mode. I cannot believe this very basic principle was never even considered during the whole design and development of the MAX: nobody is *that* bad, and certainly not Boeing engineers. I suspect that it was considered at some point, then overridden for some reason.


Do the backup instruments have an independent air source? Assuming that they do - the first thing a good pilot would do would be to check that for confirmation. If it showed normal speed that's when they should have started shutting off the electronic helpers.


All the pitots were almost certainly working fine: it was the single faulty AoA source in use that caused the airspeed flag. Remember the ET crew (and the Lion Air crew as well) had no AoA display at all: that's an extra only offered by Boeing as an option, and their airline didn't buy it (possibly on the assumption that if it's an option, then it's not essential for safety, but more probably considering that hundreds of NGs operated safely for years without AoA displays; alas, wihout a MCAS as well). Also, consider that pilots have no way of knowing which AoA sensor is in use at any given moment. If you're flattering youself thinking "I'm a GOOD PILOT and I would have figured it out right away", I think you're underestimating what an awful hand those guys were dealt.
Last edited by jollo on Wed Mar 27, 2019 11:29 pm, edited 1 time in total.
 
jollo
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Wed Mar 27, 2019 11:26 pm

Backseater wrote:
MCAS did not just appear with the MAX.
Here is a quote from Aviation Daily (25 March 2019):
"...But Boeing designed the integration on the KC-767 and KC-46 slightly differently than on the 737 Max family.

The single-aisle airliner uses one angle of attack vane — either the captain’s or first officer’s — to generate the data used by the flight computer to activate the MCAS.

By comparison, the KC-767 and KC-46 are designed to use two sensor inputs to feed angle of attack data, Boeing says".


Well, it's nice to get confimation at last. Now, KC-767 / KC-46 customers (ITAF, USAF, etc.) have no problems acknowledging that their crews need type-specific training, and lots of it: i bet MCAS inop is an integral part of the syllabus. On the other hand, 737 MAX customers were sold the fiction that no difference training from NG would be required. So no MCAS inop training, and better still no mention of MCAS at all, otherwise someone will sooner or later ask why there's a new system but no training for it. Therefore MCAS needs to be silently always on. But with only two AoA sensors you cannot implement a fail-safe architecture, and if you add a third AoA sensor people is bound to notice... Things have been snowballing downslope ever since.
 
maint123
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Mar 28, 2019 12:34 am

What really surprises me is that it's claimed that the flight prior to the crashed lion air flight was flown fully manually for most of its duration.
Means the pilots were using a handwheel to move the control surfaces. And in full manual mode their must be several other auto or help features bypassed.
And I can bet flying like this and even landing manually must be a once in a life time experience for most pilots.
How come this didn't raise a major stink in the airline or with Boeing.? Majority of the pilots would never have to face a similar situation ever in their lifetimes. Maybe I am wrong and pilots are used to flying and landing fully manually ?
Something is off. The stink should have been much stronger after the previous flight.
 
smartplane
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Mar 28, 2019 2:29 am

Backseater wrote:
MCAS did not just appear with the MAX.
Here is a quote from Aviation Daily (25 March 2019):
"Both the KC-767 and KC-46 fleets delivered to air forces in Italy, Japan and the U.S. rely on the MCAS to adjust for pitch trim changes during refueling operations.

In the 1980s, Boeing’s engineers considered using a pitch augmentation system for the commercial version of the 767, but dropped the idea after finding that vortex generators provided adequate control.

By 2011, Boeing had already delivered KC-767s to Italy and Japan fitted with the first version of MCAS. The use of the system then spread as Boeing won the Air Force’s KC-46 contract in February and launched the 737 Max 8 in August.

But Boeing designed the integration on the KC-767 and KC-46 slightly differently than on the 737 Max family.

Is this Boeing trying to flatter MCAS by association with STS, which is surely what is referred to in the 767?
 
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Finn350
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Mar 28, 2019 6:36 am

smartplane wrote:
Backseater wrote:
MCAS did not just appear with the MAX.
Here is a quote from Aviation Daily (25 March 2019):
"Both the KC-767 and KC-46 fleets delivered to air forces in Italy, Japan and the U.S. rely on the MCAS to adjust for pitch trim changes during refueling operations.

In the 1980s, Boeing’s engineers considered using a pitch augmentation system for the commercial version of the 767, but dropped the idea after finding that vortex generators provided adequate control.

By 2011, Boeing had already delivered KC-767s to Italy and Japan fitted with the first version of MCAS. The use of the system then spread as Boeing won the Air Force’s KC-46 contract in February and launched the 737 Max 8 in August.

But Boeing designed the integration on the KC-767 and KC-46 slightly differently than on the 737 Max family.

Is this Boeing trying to flatter MCAS by association with STS, which is surely what is referred to in the 767?


Apparently 767 tanker versions have MCAS due to different weight distribution

http://www.airforcemag.com/Features/Pag ... ystem.aspx
 
WIederling
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Mar 28, 2019 7:43 am

Backseater wrote:
MCAS did not just appear with the MAX.
..............................

That is quite interesting. Explains a bit of the "design taste" of "found in some drawer, could work"
that we see with MCAS implementation on the 737.
Murphy is an optimist
 
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scbriml
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Mar 28, 2019 8:14 am

smartplane wrote:
Is this Boeing trying to flatter MCAS by association with STS, which is surely what is referred to in the 767?


Possibly. Do the KC-767/KC-46 manuals refer specifically to "MCAS"?

WIederling wrote:
That is quite interesting. Explains a bit of the "design taste" of "found in some drawer, could work"
that we see with MCAS implementation on the 737.


If it was, someone will have to explain why they decided to change it from using data from both AOA sensor to just a single one on the 737MAX?
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Jouhou
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Mar 28, 2019 8:54 am

scbriml wrote:
smartplane wrote:
Is this Boeing trying to flatter MCAS by association with STS, which is surely what is referred to in the 767?


Possibly. Do the KC-767/KC-46 manuals refer specifically to "MCAS"?

WIederling wrote:
That is quite interesting. Explains a bit of the "design taste" of "found in some drawer, could work"
that we see with MCAS implementation on the 737.


If it was, someone will have to explain why they decided to change it from using data from both AOA sensor to just a single one on the 737MAX?


I doubt they changed it from 2 to 1. If the KC was the first use of the concept, and the max system was developed later, they probably for some reason had to start from scratch and did it in a half assed manner.

I do think the military would absolutely demand redundancy from them. It's sort of a big deal on the military side of things.
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afriwing
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Mar 28, 2019 10:05 am

Jouhou wrote:

I do think the military would absolutely demand redundancy from them. It's sort of a big deal on the military side of things.


Only that 2 AoA sensors is barely adequate redundancy for civil aviation, it's not truly a fail safe setup. You practically need 3 sensors to ascertain which one is faulty. Which begs the question, will we see a 3rd AoA sensor as part of the 737MAX fix? If not then the risk would've been "reduced" but not eliminated.
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jollo
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Mar 28, 2019 10:44 am

scbriml wrote:
If it was, someone will have to explain why they decided to change it from using data from both AOA sensor to just a single one on the 737MAX?


A 2-channel architecture can only be used to detect unreliable inputs, but doesn't tell you which channel is good and which has failed (well, there are ways to identify the failed sensor within a certain probability, but for real fail-safe operations you need at least 3 independent inputs). Therefore, 2 channels are only good to drive an AoA disagree flag (which the KC-46 has and the MAX can have - as an option). I have no explicit references to USAF or ITAF procedures, but I bet that SOP is to disable MCAS on an AoA disagree warning (either manually or automatically, I don't know) - and to rely on training to handle the plane safely without MCAS.

The problem with the MAX is that MCAS needed to be hidden, and no training was even available (let alone mandatory) to handle the plane safely without MCAS. Therefore what are you going to do with 2 AoA channels? I would have loved to be a fly on the wall of that Boeing office were this discussion must have been had. I can almost picture someone - speculation here - coming up with the bright idea "hey, we've already got STS acting on a single channel with logic to alternate port and starbord inputs - let's piggy-back MCAS on the same architecture". Quick, cheap, apparently reasonable...
 
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PixelFlight
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Mar 28, 2019 11:15 pm

jollo wrote:
scbriml wrote:
If it was, someone will have to explain why they decided to change it from using data from both AOA sensor to just a single one on the 737MAX?


A 2-channel architecture can only be used to detect unreliable inputs, but doesn't tell you which channel is good and which has failed (well, there are ways to identify the failed sensor within a certain probability, but for real fail-safe operations you need at least 3 independent inputs). Therefore, 2 channels are only good to drive an AoA disagree flag (which the KC-46 has and the MAX can have - as an option). I have no explicit references to USAF or ITAF procedures, but I bet that SOP is to disable MCAS on an AoA disagree warning (either manually or automatically, I don't know) - and to rely on training to handle the plane safely without MCAS.

The problem with the MAX is that MCAS needed to be hidden, and no training was even available (let alone mandatory) to handle the plane safely without MCAS. Therefore what are you going to do with 2 AoA channels? I would have loved to be a fly on the wall of that Boeing office were this discussion must have been had. I can almost picture someone - speculation here - coming up with the bright idea "hey, we've already got STS acting on a single channel with logic to alternate port and starbord inputs - let's piggy-back MCAS on the same architecture". Quick, cheap, apparently reasonable...

Certainly that the MCAS command was implemented aside of the STS command because this was the simplest thing to do. But this simplicity could also be motivated by the goal to keep the same type rating. An other implementation would have required more change is the software and triggering more safety assessment activity for the certification. The single sensors context in manual flight mode already existed for the STS command for years without big trouble, so yes, it was probably hard to object to add the MCAS command in the same context.

That said, sensors filtering from a flight dynamic predictor would not only allow to downplay erratic sensors but allow to estimate usable missing value.
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
XRAYretired
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 29, 2019 8:42 am

https://www.wsj.com/articles/investigat ... 1553836204

Officials investigating the fatal crash of a Boeing Co. 737 MAX in Ethiopia have reached a preliminary conclusion that a suspect flight-control feature automatically activated before the plane nose-dived into the ground, according to people briefed on the matter, the first findings based on data retrieved from the flight’s black boxes.
The emerging consensus among investigators, one of these people said, was relayed during a high-level briefing at the Federal Aviation Administration on Thursday, and is the strongest indication...
 
flybucky
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 29, 2019 8:49 am

maint123 wrote:
What really surprises me is that it's claimed that the flight prior to the crashed lion air flight was flown fully manually for most of its duration. Means the pilots were using a handwheel to move the control surfaces. And in full manual mode their must be several other auto or help features bypassed.

How come this didn't raise a major stink in the airline or with Boeing.?

That's a good question. I've heard that pilots like to practice manual landings sometimes to keep their skills sharp. But I don't think that means *full* manual, like hand cranking the trim wheel. I assume they still do "manual" trim with the Electric Trim switch.

I wonder if the flight before JT610 tried to use the other automatic flight systems with the Stab Trim switches off (like Autothrottle, auto navigation, ?) I have no idea if those are possible with the Stab Trim switches off.
 
flybucky
Posts: 376
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 29, 2019 9:14 am

afriwing wrote:
Only that 2 AoA sensors is barely adequate redundancy for civil aviation, it's not truly a fail safe setup. You practically need 3 sensors to ascertain which one is faulty.

Yes, you need 3 sensors for true fail safe, but 2 sensors is good enough to determine if one of them is faulty. Then you can disable systems that rely solely on AOA (or you can rely on other inputs).

Will we see a 3rd AoA sensor as part of the 737MAX fix? If not then the risk would've been "reduced" but not eliminated.

Boeing has already presented their MCAS fix, and it does not include a 3rd AOA sensor.

Even 3 AOA sensors only reduces the risk and does not eliminate it. Airbus had at least 2 incidents where 2 of the AOA sensors froze and gave the same invalid input, outvoting the 3rd AOA sensor (which was the valid one!). The computer forced the plane to pitch down, which could not be compensated even with full stick back.

2008 A320 acceptance flight - crashed into the sea with no survivors.
2014 A321 Lufthansa 1829 - dropped 4000 ft before the pilots disconnected the ADR and recovered the flight.
 
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Jouhou
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 29, 2019 9:15 am

flybucky wrote:
maint123 wrote:
What really surprises me is that it's claimed that the flight prior to the crashed lion air flight was flown fully manually for most of its duration. Means the pilots were using a handwheel to move the control surfaces. And in full manual mode their must be several other auto or help features bypassed.

How come this didn't raise a major stink in the airline or with Boeing.?

That's a good question. I've heard that pilots like to practice manual landings sometimes to keep their skills sharp. But I don't think that means *full* manual, like hand cranking the trim wheel. I assume they still do "manual" trim with the Electric Trim switch.

I wonder if the flight before JT610 tried to use the other automatic flight systems with the Stab Trim switches off (like Autothrottle, auto navigation, ?) I have no idea if those are possible with the Stab Trim switches off.


I'm not sure how well other automated systems would work with messed up speed indications...
情報
 
flybucky
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 29, 2019 9:18 am

From https://www.reuters.com/article/us-ethi ... SKCN1RA0E1

Investigators looking into a Boeing 737 MAX crash have reached a preliminary conclusion that an anti-stall system was activated before the plane hit the ground, the Wall Street Journal reported on Friday, citing people briefed on the matter.

U.S. safety investigators have reviewed data from the “black boxes” that were aboard Ethiopian Airlines Flight 302, four people briefed on the investigation told Reuters on Thursday. A preliminary report is expected as early as next week, the U.S. officials said.
 
Paolo18
Posts: 29
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 29, 2019 9:53 am

So it was mcas that killed these innocent people.
Well done Boeing...

https://www.bbc.com/news/business-47745191
 
morrisond
Posts: 2664
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 29, 2019 10:20 am

Paolo18 wrote:
So it was mcas that killed these innocent people.
Well done Boeing...

https://www.bbc.com/news/business-47745191


No - in this case the pilots should shoulder a lot more of the responsibility. This was a known issue at the time of the crash (MCAS doing weird things) and the pilots should have done all they could to learn about the issue and know how to get around it (turn off trim switches).
 
morrisond
Posts: 2664
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 29, 2019 10:22 am

flybucky wrote:
maint123 wrote:
What really surprises me is that it's claimed that the flight prior to the crashed lion air flight was flown fully manually for most of its duration. Means the pilots were using a handwheel to move the control surfaces. And in full manual mode their must be several other auto or help features bypassed.

How come this didn't raise a major stink in the airline or with Boeing.?

That's a good question. I've heard that pilots like to practice manual landings sometimes to keep their skills sharp. But I don't think that means *full* manual, like hand cranking the trim wheel. I assume they still do "manual" trim with the Electric Trim switch.

I wonder if the flight before JT610 tried to use the other automatic flight systems with the Stab Trim switches off (like Autothrottle, auto navigation, ?) I have no idea if those are possible with the Stab Trim switches off.


Any pilot Flying any aircraft should be able to land in full manual mode - it is not that hard. Full stop. If they can't they should not be in the cockpit.

They are there in case the Automated Helpers fail.

Manual trim is no big thing.
 
pugman211
Posts: 524
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 29, 2019 10:26 am

The question is, was MCAS the root cause? Or was MCAS the final nail that caused the irretrievably condition? It certainly caused the latter part imo.
 
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airkas1
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 29, 2019 10:44 am

Please correct me if I'm wrong though, but..
MCAS is the common factor in both crashes. The Lion Air crash was caused by a faulty AoA sensor, but that doesn't have to be the trigger in this crash (which is not known yet AFAIK). So in theory, there could be 2 different triggers for MCAS to activate? And the recent software update only fixes the faulty info scenario(?). So also in theory, another fix might be needed if the trigger in this crash is not faulty info or pilot error?
 
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SheikhDjibouti
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 29, 2019 10:46 am

morrisond wrote:
Paolo18 wrote:
So it was mcas that killed these innocent people.
Well done Boeing...

https://www.bbc.com/news/business-47745191


No - in this case the pilots should shoulder a lot more of the responsibility. This was a known issue at the time of the crash (MCAS doing weird things) and the pilots should have done all they could to learn about the issue and know how to get around it (turn off trim switches).

On what planet did you see this?
I don't recall Boeing speaking out loudly about MCAS issues
In fact I would say the reverse is true, as is evidenced by the decision to insist the MAX was still safe to fly.
And that was after the second crash. :banghead:

q.v. Ministry of Truth, George Orwell, 1984.
Nothing to see here; move along please.
 
mjoelnir
Posts: 9391
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 29, 2019 11:21 am

morrisond wrote:
Paolo18 wrote:
So it was mcas that killed these innocent people.
Well done Boeing...

https://www.bbc.com/news/business-47745191


No - in this case the pilots should shoulder a lot more of the responsibility. This was a known issue at the time of the crash (MCAS doing weird things) and the pilots should have done all they could to learn about the issue and know how to get around it (turn off trim switches).


Boeing is responsible for the abbreviated training regime. And if you do not want to talk about Boeing in this case, than it is the FAA and EASA, as the two most important regulators.

https://www.reuters.com/article/us-ethi ... SKCN1RA0DP

Regulators knew before crashes that 737 MAX trim control was confusing in some conditions: document

quote: EASA and the U.S. Federal Aviation Administration (FAA) ultimately determined that set-up was safe enough for the plane to be certified, with the European agency citing training plans and the relative rarity of conditions requiring the trim wheel.

A training regime was part of the certification for MCAS. Real training on MCAS and failure situations, zero. Boeing was hiding MCAS.

IMO Boeing, the FAA and EASA have blood on their hands, by not grounding the MAX directly when it was recognized that the Lion Air crash was connected to MCAS.
 
AEROFAN
Posts: 1848
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 29, 2019 11:36 am

https://www.wsj.com/articles/investigat ... 1553836204

"Investigators Believe Boeing 737 MAX Stall-Prevention Feature Activated in Ethiopian Crash..."
“You are not entitled to your opinion. You are entitled to your informed opinion. No one is entitled to be ignorant.” ~Harlan Ellison~
 
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Finn350
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 29, 2019 11:41 am

pugman211 wrote:
The question is, was MCAS the root cause? Or was MCAS the final nail that caused the irretrievably condition? It certainly caused the latter part imo.


MCAS activation is certainly not the root cause of the either accident. However, the original design of the MCAS may very well be root cause for both of these accidents (or contributing factors at the very least).
 
zoom321
Posts: 46
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 29, 2019 11:46 am

morrisond wrote:
Paolo18 wrote:
So it was mcas that killed these innocent people.
Well done Boeing...

https://www.bbc.com/news/business-47745191


No - in this case the pilots should shoulder a lot more of the responsibility. This was a known issue at the time of the crash (MCAS doing weird things) and the pilots should have done all they could to learn about the issue and know how to get around it (turn off trim switches).

Given the lower altitude here than Lion, the pilots had much less time to identify the issue and shut MCAS before it became irrecoverable.
 
ExDubai
Posts: 229
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 29, 2019 12:01 pm

The EASA document Reuter’s referring to:
https://www.easa.europa.eu/sites/defaul ... S%2010.pdf

Issue 10, Page 15.

Interesting reading:
Furthermore, the additional crew procedures and training material will clearly explain to pilots the situations where use of the trim wheel may be needed due to lack of trim authority with the wheel mounted switches.
Last edited by ExDubai on Fri Mar 29, 2019 12:31 pm, edited 1 time in total.
Better to reign in hell than serve in heaven
 
Pluto707
Posts: 37
Joined: Sun Mar 10, 2019 2:59 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 29, 2019 12:25 pm

Official declaration seems to be published within a few days.... i wonder how the declaration will be transformed in a manner that Boeing gets a shelter against lawsuits that could wipe them out....
Last edited by Pluto707 on Fri Mar 29, 2019 12:27 pm, edited 1 time in total.
 
aaexecplat
Posts: 511
Joined: Tue Sep 29, 2009 2:49 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 29, 2019 12:26 pm

morrisond wrote:
flybucky wrote:
maint123 wrote:
What really surprises me is that it's claimed that the flight prior to the crashed lion air flight was flown fully manually for most of its duration. Means the pilots were using a handwheel to move the control surfaces. And in full manual mode their must be several other auto or help features bypassed.

How come this didn't raise a major stink in the airline or with Boeing.?

That's a good question. I've heard that pilots like to practice manual landings sometimes to keep their skills sharp. But I don't think that means *full* manual, like hand cranking the trim wheel. I assume they still do "manual" trim with the Electric Trim switch.

I wonder if the flight before JT610 tried to use the other automatic flight systems with the Stab Trim switches off (like Autothrottle, auto navigation, ?) I have no idea if those are possible with the Stab Trim switches off.


Any pilot Flying any aircraft should be able to land in full manual mode - it is not that hard. Full stop. If they can't they should not be in the cockpit.

They are there in case the Automated Helpers fail.

Manual trim is no big thing.


Are you a commercial pilot?
 
aaexecplat
Posts: 511
Joined: Tue Sep 29, 2009 2:49 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 29, 2019 12:28 pm

flybucky wrote:
From https://www.reuters.com/article/us-ethi ... SKCN1RA0E1

Investigators looking into a Boeing 737 MAX crash have reached a preliminary conclusion that an anti-stall system was activated before the plane hit the ground, the Wall Street Journal reported on Friday, citing people briefed on the matter.

U.S. safety investigators have reviewed data from the “black boxes” that were aboard Ethiopian Airlines Flight 302, four people briefed on the investigation told Reuters on Thursday. A preliminary report is expected as early as next week, the U.S. officials said.


Can we now please dispense with the non-sense spewed here for weeks that MCAS may not have been involved in the ET crash and focus on what likely happened?
 
PixelPilot
Posts: 563
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 29, 2019 1:03 pm

SheikhDjibouti wrote:
morrisond wrote:
Paolo18 wrote:
So it was mcas that killed these innocent people.
Well done Boeing...

https://www.bbc.com/news/business-47745191


No - in this case the pilots should shoulder a lot more of the responsibility. This was a known issue at the time of the crash (MCAS doing weird things) and the pilots should have done all they could to learn about the issue and know how to get around it (turn off trim switches).

On what planet did you see this?
I don't recall Boeing speaking out loudly about MCAS issues
In fact I would say the reverse is true, as is evidenced by the decision to insist the MAX was still safe to fly.
And that was after the second crash. :banghead:

q.v. Ministry of Truth, George Orwell, 1984.


ET boss himself said those pilots were trained on MCAS. Stop banging your head against the wall. IT will make you even less objective.
From what we know, something happened that in the end activated MCAS but at that point if they were trained like ET is stating they should have had no problem disconnecting it and flying manually. I bet on this. ET stated they will continue working with boeing and they have faith in them. You don't drop the tone in event like this (especially when entire world went to war against B) unless you realized that fault is somewhere in the middle.
There's a lot more here apparently. MCAS was just the final straw if we are to believe that this article is 100% true.
 
Pluto707
Posts: 37
Joined: Sun Mar 10, 2019 2:59 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 29, 2019 1:17 pm

Is my summary correct ? Upcoming software will cutout MCAS in case of any disagree of input data, in earlier version this was not possible as there was only one data-input used to check AoA info
 
XRAYretired
Posts: 870
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 29, 2019 1:44 pm

Pluto707 wrote:
Is my summary correct ? Upcoming software will cutout MCAS in case of any disagree of input data, in earlier version this was not possible as there was only one data-input used to check AoA info


Essentially yes. Suggest you refer to the Lion Air thread, its covered in some detail there.


Ray
 
morrisond
Posts: 2664
Joined: Thu Jan 07, 2010 12:22 am

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 29, 2019 1:55 pm

SheikhDjibouti wrote:
morrisond wrote:
Paolo18 wrote:
So it was mcas that killed these innocent people.
Well done Boeing...

https://www.bbc.com/news/business-47745191


No - in this case the pilots should shoulder a lot more of the responsibility. This was a known issue at the time of the crash (MCAS doing weird things) and the pilots should have done all they could to learn about the issue and know how to get around it (turn off trim switches).

On what planet did you see this?
I don't recall Boeing speaking out loudly about MCAS issues
In fact I would say the reverse is true, as is evidenced by the decision to insist the MAX was still safe to fly.
And that was after the second crash. :banghead:

q.v. Ministry of Truth, George Orwell, 1984.


Here you go - Fleetwide Bulletin issued on Nov .6, 2018

Is this good enough for you?

https://theaircurrent.com/aviation-safe ... air-crash/

How is the bulletin not clear?

I am not a commercial pilot but I do hold a Private Pilots license.
Last edited by morrisond on Fri Mar 29, 2019 2:01 pm, edited 1 time in total.
 
barney captain
Posts: 2337
Joined: Tue Nov 06, 2001 5:47 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 29, 2019 2:00 pm

Stating the MCAS was active is not at all the same as saying it was malfunctioning - as in the case with Lion Air.

If the flaps wear inadvertently raised instead of the gear (I've seen it nearly happen) it's quite possible the MCAS was fighting to keep the aircraft from stalling, and doing exactly what it was designed to do.

The word choice matters.
Southeast Of Disorder
 
zoom321
Posts: 46
Joined: Sat Mar 09, 2019 3:05 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 29, 2019 2:04 pm

Which is worse for B ? Another crash by mcas triggered by bad sensors or a real stall so severe, due to Max's inherent aerodynamic instability, that neither the pilots nor mcas could recover ?
 
jollo
Posts: 395
Joined: Mon Aug 08, 2011 7:24 pm

Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Mar 29, 2019 2:11 pm

[code][/code]
Pluto707 wrote:
Is my summary correct ? Upcoming software will cutout MCAS in case of any disagree of input data, in earlier version this was not possible as there was only one data-input used to check AoA info


This is my understanding also, and matches my expectation. I also expect that "MCAS cutout" effected by the software update will only disable MCAS control actions, leaving electric stab trim switches on the wheel operative (as opposed to manually setting the STAB TRIM switches to CUTOUT, which completely disables the electric stab trim actuator).

I also expect specific training to be mandated for safe handling of near-stall conditions with MCAS inoperative (with an AoA disagree flag).

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