Moderators: jsumali2, richierich, ua900, PanAm_DC10, hOMSaR

 
dragon6172
Posts: 1141
Joined: Sat Jul 14, 2007 9:56 am

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Thu Mar 14, 2019 10:10 pm

smartplane wrote:
RickNRoll wrote:
There is a warning system on the 737Max that warns if the AoA sensors disagree. It's an Optional Extra.

Certification loophole. Optional extras are discounted from grandfathering formula. If standard, questions would be asked why, whats changed from earlier models.....................

Are you trying to say these optional extras were not made standard to hide MCAS from certifying authority or operators?
 
RickNRoll
Posts: 1889
Joined: Fri Jan 06, 2012 9:30 am

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Thu Mar 14, 2019 10:37 pm

WIederling wrote:
smartplane wrote:
RickNRoll wrote:
There is a warning system on the 737Max that warns if the AoA sensors disagree. It's an Optional Extra.

Certification loophole. Optional extras are discounted from grandfathering formula. If standard, questions would be asked why, whats changed from earlier models.....................


Interesting to know. ( who ordered the option and did they get a hint to better order that too ? )


Southwest ordered them.

https://theaircurrent.com/aviation-safe ... max-fleet/
 
RickNRoll
Posts: 1889
Joined: Fri Jan 06, 2012 9:30 am

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Thu Mar 14, 2019 10:41 pm

https://twitter.com/jonostrower/status/ ... 40?lang=en

All "optional" equipment that Lion didn't order.
 
DDR
Posts: 1767
Joined: Sat Sep 28, 2013 11:09 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Thu Mar 14, 2019 10:45 pm

RickNRoll wrote:
There is a warning system on the 737Max that warns if the AoA sensors disagree. It's an Optional Extra.


For the love of God, why would it be optional?
 
WIederling
Posts: 10041
Joined: Sun Sep 13, 2015 2:15 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Thu Mar 14, 2019 10:46 pm

RickNRoll wrote:


that the same outfit that moved MCAS to pilot training?
If yes how did they get the intelligence?

reading Ostrower: they ordered that option after the Lion Air crash. ( end of November 2018 )

but I seem to remember that one US airline had the MCAS info from the getgo.
who was it?
 
SteinarN
Posts: 243
Joined: Mon Dec 29, 2014 1:26 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Fri Mar 15, 2019 12:52 am

WIederling wrote:
RickNRoll wrote:


that the same outfit that moved MCAS to pilot training?
If yes how did they get the intelligence?

reading Ostrower: they ordered that option after the Lion Air crash. ( end of November 2018 )

but I seem to remember that one US airline had the MCAS info from the getgo.
who was it?


I dont remember having read about one US airline. However, Brazilian aothorities demanded Boeing put the MCAS description in the manuals for the pilots. So pilots in any Brazilian airlines would at least have access to that basic MCAS description making them avare of its existence at least.

Regarding optional AoA display and disagree messages. If grandfathering clauses forced Boeing to make those cocpit messages and displays optional and Boeing really felt they should have been there to help the pilots, then why did Boeing charge something like 100.000 US$ for that option? Instead of offer them for say one or ten US$?
The answer is obviously that Boeing wished to keep that system under the radar of the pilots for whatever reason.
 
User avatar
SheikhDjibouti
Posts: 2348
Joined: Sat Sep 30, 2017 4:59 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Fri Mar 15, 2019 1:01 am

SteinarN wrote:
Brazilian aothorities demanded Boeing put the MCAS description in the manuals for the pilots. So pilots in any Brazilian airlines would at least have access to that basic MCAS description making them avare of its existence at least.

Regarding optional AoA display and disagree messages. If grandfathering clauses forced Boeing to make those cocpit messages and displays optional and Boeing really felt they should have been there to help the pilots, then why did Boeing charge something like 100.000 US$ for that option? Instead of offer them for say one or ten US$?
The answer is obviously that Boeing wished to keep that system under the radar of the pilots for whatever reason.


I had that exact thought myself; make it an option to keep it below FAA radar, but make it cheap enough everybody would take it anyway.

I suspect the answer is that the engineers at Boeing did the first part, and the accountants at Boeing screwed up the second.
 
hayzel777
Posts: 701
Joined: Wed Mar 16, 2016 3:18 am

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Fri Mar 15, 2019 1:23 am

WIederling wrote:
RickNRoll wrote:


that the same outfit that moved MCAS to pilot training?
If yes how did they get the intelligence?

reading Ostrower: they ordered that option after the Lion Air crash. ( end of November 2018 )

but I seem to remember that one US airline had the MCAS info from the getgo.
who was it?

I believe it was AA.

EDIT: https://viewfromthewing.boardingarea.co ... know-more/

APA says AA was the only one to have one indicator for each pilot from the get go.
 
mandala499
Posts: 6600
Joined: Wed Aug 29, 2001 8:47 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Fri Mar 15, 2019 1:46 am

With all this Max saga unfolding... why can't Boeing just come up with a temporary fix like:
1. Make AOA disagree warning mandatory
2. If "AOA DISAGREE" comes up after take off, do not retract flaps to UP, and land ASAP.
3. If "AOA DISAGREE" comes up at any other time, LAND ASAP, consider flights with flaps 1 or more.

Yes the above are overly simplified, and I believe while crude, would save lives, and save the Max... BUT, the downside is, such a procedure, might not save Boeing from a lot of liability lawsuits, because it admits a flaw in an explicit way...
 
LDRA
Posts: 493
Joined: Fri Jan 15, 2016 3:01 am

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Fri Mar 15, 2019 2:08 am

mandala499 wrote:
With all this Max saga unfolding... why can't Boeing just come up with a temporary fix like:
1. Make AOA disagree warning mandatory
2. If "AOA DISAGREE" comes up after take off, do not retract flaps to UP, and land ASAP.
3. If "AOA DISAGREE" comes up at any other time, LAND ASAP, consider flights with flaps 1 or more.

Yes the above are overly simplified, and I believe while crude, would save lives, and save the Max... BUT, the downside is, such a procedure, might not save Boeing from a lot of liability lawsuits, because it admits a flaw in an explicit way...


Current AOA DISAGREE logic fault threshold is 10deg difference between two sensors. That tolerance threshold may be too wide to completely prevent false activation of MCAS, especially under low speed high grossweight condition(actual AoA on the high side). I believe MCAS activation is around ~15deg AoA? So if aircraft is flying around with 5degree actual AoA, current AOA DISAGREE logic would not trigger on false activation of MCAS

Also current AOA DISAGREE logic may not be certified to assurance level needed for flight control
 
smartplane
Posts: 1914
Joined: Fri Aug 03, 2018 9:23 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Fri Mar 15, 2019 2:54 am

dragon6172 wrote:
smartplane wrote:
RickNRoll wrote:
There is a warning system on the 737Max that warns if the AoA sensors disagree. It's an Optional Extra.

Certification loophole. Optional extras are discounted from grandfathering formula. If standard, questions would be asked why, whats changed from earlier models.....................

Are you trying to say these optional extras were not made standard to hide MCAS from certifying authority or operators?

I'm saying optional extras are not included in the grandfather eligibility process. If some of the cockpit optional extras were standard, they would be included in the assessment of grandfathering eligibility. Presumably optional extras are also excluded from the common type rating assessment as well.
 
User avatar
7BOEING7
Posts: 3039
Joined: Fri Oct 12, 2012 5:28 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Fri Mar 15, 2019 3:22 am

hayzel777 wrote:
WIederling wrote:
RickNRoll wrote:


that the same outfit that moved MCAS to pilot training?
If yes how did they get the intelligence?

reading Ostrower: they ordered that option after the Lion Air crash. ( end of November 2018 )

but I seem to remember that one US airline had the MCAS info from the getgo.
who was it?

I believe it was AA.

EDIT: https://viewfromthewing.boardingarea.co ... know-more/

APA says AA was the only one to have one indicator for each pilot from the get go.


AA was the first to have AOA displays in their 777’s when they first got them and then pushed Boeing to provide them for the 737NG’s.
 
RickNRoll
Posts: 1889
Joined: Fri Jan 06, 2012 9:30 am

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Fri Mar 15, 2019 7:30 am

LDRA wrote:
mandala499 wrote:
With all this Max saga unfolding... why can't Boeing just come up with a temporary fix like:
1. Make AOA disagree warning mandatory
2. If "AOA DISAGREE" comes up after take off, do not retract flaps to UP, and land ASAP.
3. If "AOA DISAGREE" comes up at any other time, LAND ASAP, consider flights with flaps 1 or more.

Yes the above are overly simplified, and I believe while crude, would save lives, and save the Max... BUT, the downside is, such a procedure, might not save Boeing from a lot of liability lawsuits, because it admits a flaw in an explicit way...


Current AOA DISAGREE logic fault threshold is 10deg difference between two sensors. That tolerance threshold may be too wide to completely prevent false activation of MCAS, especially under low speed high grossweight condition(actual AoA on the high side). I believe MCAS activation is around ~15deg AoA? So if aircraft is flying around with 5degree actual AoA, current AOA DISAGREE logic would not trigger on false activation of MCAS

Also current AOA DISAGREE logic may not be certified to assurance level needed for flight control


That's not going to go well for the certification of the new software then..
 
mandala499
Posts: 6600
Joined: Wed Aug 29, 2001 8:47 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Sun Mar 17, 2019 4:46 am

LDRA wrote:
Current AOA DISAGREE logic fault threshold is 10deg difference between two sensors. That tolerance threshold may be too wide to completely prevent false activation of MCAS, especially under low speed high grossweight condition(actual AoA on the high side). I believe MCAS activation is around ~15deg AoA? So if aircraft is flying around with 5degree actual AoA, current AOA DISAGREE logic would not trigger on false activation of MCAS

Also current AOA DISAGREE logic may not be certified to assurance level needed for flight control

The question is, would my oversimplified solution work as an interim solution?
10deg maybe too wide, but if it detects more than 10deg difference and generate the AOA DISAGREE, the proposed oversimplified procedure would still provide safeguard against MCAS activation, because the idea is "how to prevent MCAS from activation when AOA DISAGREE appears"...

Am not talking about whether the threshold is adequate enough...

So, can the oversimplified modification help or not?
 
User avatar
zeke
Posts: 17261
Joined: Thu Dec 14, 2006 1:42 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Sun Mar 17, 2019 5:49 am

While there is only two physical AOA sensors, each sensor has two resolvers, the resolvers are basically the raw AOA values. In reality there is presently 4 AOA values which could be compared.

There could be a local comparison on the sensor as each resolver should agree with each other, if one resolver is saying 10 degrees and the other 2.5 degrees you know that physical AOA sensor is suspect as the two resolvers don’t closely agree.
 
WIederling
Posts: 10041
Joined: Sun Sep 13, 2015 2:15 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Sun Mar 17, 2019 10:19 am

zeke wrote:
While there is only two physical AOA sensors, each sensor has two resolvers, the resolvers are basically the raw AOA values. In reality there is presently 4 AOA values which could be compared.

There could be a local comparison on the sensor as each resolver should agree with each other, if one resolver is saying 10 degrees and the other 2.5 degrees you know that physical AOA sensor is suspect as the two resolvers don’t closely agree.


is that two independent resolvers working on the same vane or just a twinned output driver?

( how do they accomodate the left right swap? swap resolvers too, with one resolver handing out the complement of the other ersolver?)
 
aaexecplat
Posts: 558
Joined: Tue Sep 29, 2009 2:49 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Sun Mar 17, 2019 11:42 am

zeke wrote:
While there is only two physical AOA sensors, each sensor has two resolvers, the resolvers are basically the raw AOA values. In reality there is presently 4 AOA values which could be compared.

There could be a local comparison on the sensor as each resolver should agree with each other, if one resolver is saying 10 degrees and the other 2.5 degrees you know that physical AOA sensor is suspect as the two resolvers don’t closely agree.
Great info. Thanks.

Sent from my SM-T810 using Tapatalk
 
User avatar
PixelFlight
Posts: 1033
Joined: Thu Nov 08, 2018 11:09 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Sun Mar 17, 2019 3:02 pm

https://www.seattletimes.com/business/b ... air-crash/

Aside of the FAA safety assessment activity delegation to Boeing scandal, I found this regarding MCAS:

The original Boeing document provided to the FAA included a description specifying a limit to how much the system could move the horizontal tail — a limit of 0.6 degrees, out of a physical maximum of just less than 5 degrees of nose-down movement. That limit was later increased after flight tests showed that a more powerful movement of the tail was required to avert a high-speed stall, when the plane is in danger of losing lift and spiraling down. After the Lion Air Flight 610 crash, Boeing for the first time provided to airlines details about MCAS. Boeing’s bulletin to the airlines stated that the limit of MCAS’s command was 2.5 degrees.

That number was new to FAA engineers who had seen 0.6 degrees in the safety assessment. “The FAA believed the airplane was designed to the 0.6 limit, and that’s what the foreign regulatory authorities thought, too,” said an FAA engineer. “It makes a difference in your assessment of the hazard involved.”


This real 2.5 degree versus 0.6 degree in the certification could be part of the explanation why Boeing didn't document the MCAS before.
 
frmrCapCadet
Posts: 5413
Joined: Thu May 29, 2008 8:24 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Sun Mar 17, 2019 3:43 pm

The Dominic Gates long story in today's Seattle Times is a must read. link in post just above this #2917. I posted it in another thread.
 
VS11
Posts: 1821
Joined: Mon Jul 02, 2001 6:34 am

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Sun Mar 17, 2019 3:58 pm

PixelFlight wrote:
https://www.seattletimes.com/business/boeing-aerospace/failed-certification-faa-missed-safety-issues-in-the-737-max-system-implicated-in-the-lion-air-crash/

Aside of the FAA safety assessment activity delegation to Boeing scandal, I found this regarding MCAS:

The original Boeing document provided to the FAA included a description specifying a limit to how much the system could move the horizontal tail — a limit of 0.6 degrees, out of a physical maximum of just less than 5 degrees of nose-down movement. That limit was later increased after flight tests showed that a more powerful movement of the tail was required to avert a high-speed stall, when the plane is in danger of losing lift and spiraling down. After the Lion Air Flight 610 crash, Boeing for the first time provided to airlines details about MCAS. Boeing’s bulletin to the airlines stated that the limit of MCAS’s command was 2.5 degrees.

That number was new to FAA engineers who had seen 0.6 degrees in the safety assessment. “The FAA believed the airplane was designed to the 0.6 limit, and that’s what the foreign regulatory authorities thought, too,” said an FAA engineer. “It makes a difference in your assessment of the hazard involved.”


This real 2.5 degree versus 0.6 degree in the certification could be part of the explanation why Boeing didn't document the MCAS before.


In addition, MCAS engaged on both sides even though the AOA was faulty on the left side. From the Seattle Times article:

"The black box data released in the preliminary investigation report shows that after this cycle repeated 21 times, the plane’s captain ceded control to the first officer. As MCAS pushed the nose down two or three times more, the first officer responded with only two short flicks of the thumb switches."

Why did MCAS engage while the FO was flying the plane? If his AOA indicator was functioning properly, MCAS should not have engaged. People expressing concern with the air data computers may have a point. It could be more than just MCAS.
 
User avatar
Finn350
Posts: 1601
Joined: Tue Jul 09, 2013 4:57 am

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Sun Mar 17, 2019 4:30 pm

VS11 wrote:
PixelFlight wrote:
https://www.seattletimes.com/business/boeing-aerospace/failed-certification-faa-missed-safety-issues-in-the-737-max-system-implicated-in-the-lion-air-crash/

Aside of the FAA safety assessment activity delegation to Boeing scandal, I found this regarding MCAS:

The original Boeing document provided to the FAA included a description specifying a limit to how much the system could move the horizontal tail — a limit of 0.6 degrees, out of a physical maximum of just less than 5 degrees of nose-down movement. That limit was later increased after flight tests showed that a more powerful movement of the tail was required to avert a high-speed stall, when the plane is in danger of losing lift and spiraling down. After the Lion Air Flight 610 crash, Boeing for the first time provided to airlines details about MCAS. Boeing’s bulletin to the airlines stated that the limit of MCAS’s command was 2.5 degrees.

That number was new to FAA engineers who had seen 0.6 degrees in the safety assessment. “The FAA believed the airplane was designed to the 0.6 limit, and that’s what the foreign regulatory authorities thought, too,” said an FAA engineer. “It makes a difference in your assessment of the hazard involved.”


This real 2.5 degree versus 0.6 degree in the certification could be part of the explanation why Boeing didn't document the MCAS before.


In addition, MCAS engaged on both sides even though the AOA was faulty on the left side. From the Seattle Times article:

"The black box data released in the preliminary investigation report shows that after this cycle repeated 21 times, the plane’s captain ceded control to the first officer. As MCAS pushed the nose down two or three times more, the first officer responded with only two short flicks of the thumb switches."

Why did MCAS engage while the FO was flying the plane? If his AOA indicator was functioning properly, MCAS should not have engaged. People expressing concern with the air data computers may have a point. It could be more than just MCAS.


There is a single MCAS implementation, not separate for the Captain and the FO. It doesn't matter who flies the plane, during any single flight the MCAS used only one of the two AoA sensors as input.
 
VS11
Posts: 1821
Joined: Mon Jul 02, 2001 6:34 am

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Sun Mar 17, 2019 4:47 pm

Finn350 wrote:
VS11 wrote:
PixelFlight wrote:
https://www.seattletimes.com/business/boeing-aerospace/failed-certification-faa-missed-safety-issues-in-the-737-max-system-implicated-in-the-lion-air-crash/

Aside of the FAA safety assessment activity delegation to Boeing scandal, I found this regarding MCAS:



This real 2.5 degree versus 0.6 degree in the certification could be part of the explanation why Boeing didn't document the MCAS before.


In addition, MCAS engaged on both sides even though the AOA was faulty on the left side. From the Seattle Times article:

"The black box data released in the preliminary investigation report shows that after this cycle repeated 21 times, the plane’s captain ceded control to the first officer. As MCAS pushed the nose down two or three times more, the first officer responded with only two short flicks of the thumb switches."

Why did MCAS engage while the FO was flying the plane? If his AOA indicator was functioning properly, MCAS should not have engaged. People expressing concern with the air data computers may have a point. It could be more than just MCAS.


There is a single MCAS implementation, not separate for the Captain and the FO. It doesn't matter who flies the plane, during any single flight the MCAS used only one of the two AoA sensors as input.


In previous articles it was explained that M.C.A.S. was using the AOA from the side that is flying the aircraft. So when FO took over, M.C.A.S. would have used the right side AOA.
 
User avatar
Finn350
Posts: 1601
Joined: Tue Jul 09, 2013 4:57 am

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Sun Mar 17, 2019 4:48 pm

VS11 wrote:
Finn350 wrote:
VS11 wrote:

In addition, MCAS engaged on both sides even though the AOA was faulty on the left side. From the Seattle Times article:

"The black box data released in the preliminary investigation report shows that after this cycle repeated 21 times, the plane’s captain ceded control to the first officer. As MCAS pushed the nose down two or three times more, the first officer responded with only two short flicks of the thumb switches."

Why did MCAS engage while the FO was flying the plane? If his AOA indicator was functioning properly, MCAS should not have engaged. People expressing concern with the air data computers may have a point. It could be more than just MCAS.


There is a single MCAS implementation, not separate for the Captain and the FO. It doesn't matter who flies the plane, during any single flight the MCAS used only one of the two AoA sensors as input.


In previous articles it was explained that M.C.A.S. was using the AOA from the side that is flying the aircraft. So when FO took over, M.C.A.S. would have used the right side AOA.


You have misunderstood it.
 
User avatar
SheikhDjibouti
Posts: 2348
Joined: Sat Sep 30, 2017 4:59 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Sun Mar 17, 2019 5:01 pm

Finn350 wrote:
VS11 wrote:
Finn350 wrote:

There is a single MCAS implementation, not separate for the Captain and the FO. It doesn't matter who flies the plane, during any single flight the MCAS used only one of the two AoA sensors as input.


In previous articles it was explained that M.C.A.S. was using the AOA from the side that is flying the aircraft. So when FO took over, M.C.A.S. would have used the right side AOA.


You have misunderstood it.

In that case you can add me to the list; I must have "misunderstood" it too. :o

I just wish I could find the relevant posts upthread; I'm not certain what search criteria is needed to narrow it down from over 6000 posts
 
VS11
Posts: 1821
Joined: Mon Jul 02, 2001 6:34 am

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Sun Mar 17, 2019 5:13 pm

SheikhDjibouti wrote:
Finn350 wrote:
VS11 wrote:

In previous articles it was explained that M.C.A.S. was using the AOA from the side that is flying the aircraft. So when FO took over, M.C.A.S. would have used the right side AOA.


You have misunderstood it.

In that case you can add me to the list; I must have "misunderstood" it too. :o

I just wish I could find the relevant posts upthread; I'm not certain what search criteria is needed to narrow it down from over 6000 posts


It was in the thread about the NYT article (https://www.nytimes.com/2019/02/03/worl ... ilots.html) :
viewtopic.php?f=3&t=1414709&p=21067105#p21067105

Here is the passage:
"In designing the 737 Max, Boeing decided to feed M.C.A.S. with data from only one of the two angle of attack sensors at a time, depending on which of two, redundant flight control computers — one on the captain’s side, one on the first officer’s side — happened to be active on that flight."

Can the active side switch mid-flight? If yes, then I most certainly did not misunderstand. If no, then I sure did and thanks for clarifying. It does make a difference.
 
mandala499
Posts: 6600
Joined: Wed Aug 29, 2001 8:47 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Sun Mar 17, 2019 5:43 pm

VS11 wrote:
Here is the passage:
"In designing the 737 Max, Boeing decided to feed M.C.A.S. with data from only one of the two angle of attack sensors at a time, depending on which of two, redundant flight control computers — one on the captain’s side, one on the first officer’s side — happened to be active on that flight."

Can the active side switch mid-flight? If yes, then I most certainly did not misunderstand. If no, then I sure did and thanks for clarifying. It does make a difference.

Just a guess, but... maybe MCAS selection of side depends on which flight director is Master at the time... Left or Right... and if none selected, MCAS either remains latched on to the last one until landing, or, if no Flight Director as master, then default to the left side.

Just a guess...
 
User avatar
Finn350
Posts: 1601
Joined: Tue Jul 09, 2013 4:57 am

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Sun Mar 17, 2019 6:57 pm

VS11 wrote:
SheikhDjibouti wrote:
Finn350 wrote:

You have misunderstood it.

In that case you can add me to the list; I must have "misunderstood" it too. :o

I just wish I could find the relevant posts upthread; I'm not certain what search criteria is needed to narrow it down from over 6000 posts


It was in the thread about the NYT article (https://www.nytimes.com/2019/02/03/worl ... ilots.html) :
https://www.airliners.net/forum/viewtop ... #p21067105

Here is the passage:
"In designing the 737 Max, Boeing decided to feed M.C.A.S. with data from only one of the two angle of attack sensors at a time, depending on which of two, redundant flight control computers — one on the captain’s side, one on the first officer’s side — happened to be active on that flight."

Can the active side switch mid-flight? If yes, then I most certainly did not misunderstand. If no, then I sure did and thanks for clarifying. It does make a difference.


This is the best quote I could find: MCAS is implemented within the two Flight Control Computers (FCCs). The Left FCC uses the Left AOA sensor for MCAS and the Right FCC uses the Right AOA sensor for MCAS. Only one FCC operates at a time to provide MCAS commands. With electrical power to the FCCs maintained, the unit that provides MCAS changes between flights. In this manner, the AOA sensor that is used for MCAS changes with each flight.

http://www.b737.org.uk/mcas.htm
 
WIederling
Posts: 10041
Joined: Sun Sep 13, 2015 2:15 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Sun Mar 17, 2019 6:58 pm

mandala499 wrote:
Just a guess...


in the software world that is tagged as "spaghetti code".
So convoluted and badly arranged that it is unreadable and uncheckable for errors.
 
User avatar
AirlineCritic
Posts: 1789
Joined: Sat Mar 14, 2009 1:07 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Sun Mar 17, 2019 7:13 pm

The Seattle Times article is shocking. Or perhaps more than shocking. To begin with, even if the initial miss in the certification was perhaps a mistake, both FAA and Boeing knew *before* the ET crash that certification had missed a significant change, because Seattle Times told them. It seems to me that ET and the relatives of the passengers have a clear case against Boeing *and* FAA for, basically, wilful hiding of a significant failure in both the aircraft and the certification process. What other outcome should there have been even before the ET crash than to withdraw the certification temporarily and work to fix the system and/or redo the certification? But instead, they chose to sit on this information, and now 170 more people are dead.

I'd say the high standing of FAA in the world is now gone, and quite appropriately so. No sane regulator in the rest of the world should follow their advice.
 
VS11
Posts: 1821
Joined: Mon Jul 02, 2001 6:34 am

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Sun Mar 17, 2019 7:59 pm

Finn350 wrote:
VS11 wrote:
SheikhDjibouti wrote:
In that case you can add me to the list; I must have "misunderstood" it too. :o

I just wish I could find the relevant posts upthread; I'm not certain what search criteria is needed to narrow it down from over 6000 posts


It was in the thread about the NYT article (https://www.nytimes.com/2019/02/03/worl ... ilots.html) :
viewtopic.php?f=3&t=1414709&p=21067105#p21067105

Here is the passage:
"In designing the 737 Max, Boeing decided to feed M.C.A.S. with data from only one of the two angle of attack sensors at a time, depending on which of two, redundant flight control computers — one on the captain’s side, one on the first officer’s side — happened to be active on that flight."

Can the active side switch mid-flight? If yes, then I most certainly did not misunderstand. If no, then I sure did and thanks for clarifying. It does make a difference.


This is the best quote I could find: MCAS is implemented within the two Flight Control Computers (FCCs). The Left FCC uses the Left AOA sensor for MCAS and the Right FCC uses the Right AOA sensor for MCAS. Only one FCC operates at a time to provide MCAS commands. With electrical power to the FCCs maintained, the unit that provides MCAS changes between flights. In this manner, the AOA sensor that is used for MCAS changes with each flight.

http://www.b737.org.uk/mcas.htm


Thank you. That's very helpful. I did misunderstand how the input worked. ;)
 
User avatar
zeke
Posts: 17261
Joined: Thu Dec 14, 2006 1:42 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Sun Mar 17, 2019 9:34 pm

WIederling wrote:

is that two independent resolvers working on the same vane or just a twinned output driver?

( how do they accomodate the left right swap? swap resolvers too, with one resolver handing out the complement of the other ersolver?)


My understanding it is a single AOA probe has two resolvers on the one vane. A resolver is a form of sensor that relies on inductive coupling to two orthogonal pickups (SIN and COS). The outputs of the resolver are modulated by a reference carrier. Their output amplitudes relate to the shaft angle. The aircraft also has two Stall Management Yaw Dampers (SMYD), and two Flight Control Computers (FCC).

I understand the one of the outputs of the resolver go to same side SYMD, and the other to the opposite side FCC.
 
User avatar
PixelFlight
Posts: 1033
Joined: Thu Nov 08, 2018 11:09 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Sun Mar 17, 2019 10:44 pm

zeke wrote:
WIederling wrote:

is that two independent resolvers working on the same vane or just a twinned output driver?

( how do they accomodate the left right swap? swap resolvers too, with one resolver handing out the complement of the other ersolver?)


My understanding it is a single AOA probe has two resolvers on the one vane. A resolver is a form of sensor that relies on inductive coupling to two orthogonal pickups (SIN and COS). The outputs of the resolver are modulated by a reference carrier. Their output amplitudes relate to the shaft angle. The aircraft also has two Stall Management Yaw Dampers (SMYD), and two Flight Control Computers (FCC).

I understand the one of the outputs of the resolver go to same side SYMD, and the other to the opposite side FCC.


https://www.satcom.guru/2018/11/737-fcc ... mmand.html

It look like none of the FCC has AoA input. Instead each ADIRU have an AoA input. Each FCC use both ADIRU. So the FCC can use both AoA values (from the two ADIRUs).
What's strange is that both SYMDs are feed by the two ADIRUs too, but for some unexplained reason, without the AoA values. Each SYMD use a dedicated SIN/COS link from a single sensor to get that AoA value. That part puzzle me...
 
klkla
Posts: 852
Joined: Fri Jul 16, 2004 8:51 am

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Sun Mar 17, 2019 11:31 pm

DDR wrote:
RickNRoll wrote:
There is a warning system on the 737Max that warns if the AoA sensors disagree. It's an Optional Extra.


For the love of God, why would it be optional?


Also, for the love of god, why would any airline NOT order it?
 
impilot
Posts: 232
Joined: Mon Jul 30, 2018 1:38 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Sun Mar 17, 2019 11:34 pm

klkla wrote:
DDR wrote:
RickNRoll wrote:
There is a warning system on the 737Max that warns if the AoA sensors disagree. It's an Optional Extra.


For the love of God, why would it be optional?


Also, for the love of god, why would any airline NOT order it?


If Boeing and the FAA tell me it's plenty safe without it, why would I need it? I read somewhere it's part of a specific HUD/CATIII package...not sure if that is true or not. But if so, if they have no need for CATIII, they may not see it as a safety thing but a capability they don't need to pay for, not knowing at the time they ordered it that the second AOA had a safety value associated with it.
 
User avatar
zeke
Posts: 17261
Joined: Thu Dec 14, 2006 1:42 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Mon Mar 18, 2019 1:05 am

PixelFlight wrote:

It look like none of the FCC has AoA input. Instead each ADIRU have an AoA input. Each FCC use both ADIRU. So the FCC can use both AoA values (from the two ADIRUs).
What's strange is that both SYMDs are feed by the two ADIRUs too, but for some unexplained reason, without the AoA values. Each SYMD use a dedicated SIN/COS link from a single sensor to get that AoA value. That part puzzle me...


This was posted earlier in this thread by fadecfault, it shows an AOA input to the FCC.

Image
 
SuperEighty
Posts: 9
Joined: Mon Mar 11, 2019 11:19 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Mon Mar 18, 2019 1:26 am

Irreparable damage to both Boeing and the FAA if the Seattle Times story is accurate. And deservedly so.

“If it’s Boeing, I ain’t going”
 
User avatar
PixelFlight
Posts: 1033
Joined: Thu Nov 08, 2018 11:09 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Mon Mar 18, 2019 5:40 pm

zeke wrote:
PixelFlight wrote:

It look like none of the FCC has AoA input. Instead each ADIRU have an AoA input. Each FCC use both ADIRU. So the FCC can use both AoA values (from the two ADIRUs).
What's strange is that both SYMDs are feed by the two ADIRUs too, but for some unexplained reason, without the AoA values. Each SYMD use a dedicated SIN/COS link from a single sensor to get that AoA value. That part puzzle me...


This was posted earlier in this thread by fadecfault, it shows an AOA input to the FCC.

Image


This schematic in your message is a software algorithm, not real wires between the AoA sensor and the FCC. The AoA values are provided from the ADIRUs to the FCC. See this schematic where you can see the AoA values into the data streams from the L/R ADIRU to the FCC A/B.
Image
This part of the design looks ok, with a least a minimum of redundancy. The SMYD don't match that minimum level...
 
mxaxai
Posts: 3136
Joined: Sat Jun 18, 2016 7:29 am

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Mon Mar 18, 2019 5:54 pm

klkla wrote:
DDR wrote:
RickNRoll wrote:
There is a warning system on the 737Max that warns if the AoA sensors disagree. It's an Optional Extra.


For the love of God, why would it be optional?


Also, for the love of god, why would any airline NOT order it?

Because it's declared optional, hence obviously not safety critical, and costs money?

An airline has to rely on the manufacturer and the certifying agency that the aircraft is, in principle, safe as sold.
 
smartplane
Posts: 1914
Joined: Fri Aug 03, 2018 9:23 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Mon Mar 18, 2019 7:35 pm

mxaxai wrote:
klkla wrote:
DDR wrote:

For the love of God, why would it be optional?


Also, for the love of god, why would any airline NOT order it?

Because it's declared optional, hence obviously not safety critical, and costs money?

An airline has to rely on the manufacturer and the certifying agency that the aircraft is, in principle, safe as sold.

And optional extras are excluded from the grandfathering formula. If standard fit, they are included, which should then trigger an FAA please explain, becomes a 'change' in the grandfathering formula, and FAA apply an importance weighting.
 
dakota123
Posts: 245
Joined: Wed Aug 30, 2006 11:03 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Mon Mar 18, 2019 8:00 pm

mxaxai wrote:
klkla wrote:
DDR wrote:

For the love of God, why would it be optional?


Also, for the love of god, why would any airline NOT order it?

Because it's declared optional, hence obviously not safety critical, and costs money?

An airline has to rely on the manufacturer and the certifying agency that the aircraft is, in principle, safe as sold.


Also because chief pilots to some degree get to impart their view of the world on fleet purchase decisions, and there are plenty of folks out there that don't believe that having AOA data available is worthwhile.
 
DDR
Posts: 1767
Joined: Sat Sep 28, 2013 11:09 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Mon Mar 18, 2019 11:31 pm

klkla wrote:
DDR wrote:
RickNRoll wrote:
There is a warning system on the 737Max that warns if the AoA sensors disagree. It's an Optional Extra.


For the love of God, why would it be optional?


Also, for the love of god, why would any airline NOT order it?


Amen! Great post!!
 
moa999
Posts: 1207
Joined: Tue Mar 13, 2018 6:37 am

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Mon Mar 18, 2019 11:59 pm

Same as why MH didn't select the full Inmarsat tracking subscription.
 
frmrCapCadet
Posts: 5413
Joined: Thu May 29, 2008 8:24 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Tue Mar 19, 2019 1:28 am

DDR wrote:
klkla wrote:
DDR wrote:

For the love of God, why would it be optional?


Also, for the love of god, why would any airline NOT order it?


Amen! Great post!!


So far as I know there are no statements by Boeing that MAXs will fall out of the sky if you don't buy one. Or even statements close to that. If you know otherwise please post the statements.
 
edu2703
Posts: 186
Joined: Sun Oct 25, 2015 12:50 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Wed Mar 20, 2019 12:26 am

From Bloomberg:

BREAKING: An off-duty pilot who happened to be riding in the cockpit saved a diving Boeing 737 Max 8. The next day, the same Lion Air jet crashed into the Java Sea, killing all 189 aboard

https://www.bloomberg.com/news/articles ... er-crashed
 
downdata
Posts: 590
Joined: Wed Feb 17, 2016 2:38 am

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Wed Mar 20, 2019 12:48 am

Does this mean we are going to see SOs in narrowbody cockpits again :)
 
RogerMurdock
Posts: 187
Joined: Sat Aug 23, 2014 9:01 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Wed Mar 20, 2019 6:36 am

edu2703 wrote:
From Bloomberg:

BREAKING: An off-duty pilot who happened to be riding in the cockpit saved a diving Boeing 737 Max 8. The next day, the same Lion Air jet crashed into the Java Sea, killing all 189 aboard

https://www.bloomberg.com/news/articles ... er-crashed


So this effectively means that of the 3 known likely MCAS activations in commercial flight of the MAX, none of them were successfully counteracted by the regular flight crew running the runaway stabilizer NNC. It took the increased resources of a jumpseater to troubleshoot. So much for Boeing’s human factors evaluation of MCAS (see Seattle Times article linked above).
Last edited by RogerMurdock on Wed Mar 20, 2019 7:05 am, edited 2 times in total.
 
RogerMurdock
Posts: 187
Joined: Sat Aug 23, 2014 9:01 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Wed Mar 20, 2019 6:37 am

Sorry, multipost due to website error.
Last edited by RogerMurdock on Wed Mar 20, 2019 6:40 am, edited 1 time in total.
 
RogerMurdock
Posts: 187
Joined: Sat Aug 23, 2014 9:01 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Wed Mar 20, 2019 6:39 am

Sorry, multipost due to website error.
 
User avatar
Jouhou
Posts: 2541
Joined: Tue May 24, 2016 4:16 am

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Wed Mar 20, 2019 8:16 am

https://www.reuters.com/article/us-indo ... SKCN1R10FB

More details on front page of Reuters right now

“They didn’t seem to know the trim was moving down,” the third source said. “They thought only about airspeed and altitude. That was the only thing they talked about.”


Might be why they didn't find a solution like the previous crew did.
 
User avatar
PW100
Posts: 4126
Joined: Mon Jan 28, 2002 9:17 pm

Re: Lion Air 737MAX8 Crashed Jakarta to Pangkal Pinang

Wed Mar 20, 2019 12:17 pm

DDR wrote:
klkla wrote:
DDR wrote:

For the love of God, why would it be optional?


Also, for the love of god, why would any airline NOT order it?


Amen! Great post!!


Great post??? Do you realize the contents of the message?

* Why would an airline order such optional system?
* Because the aircraft may not be safely operated without.
* But that means that Boeing is willingly and knowingly selling an unsafe basic plane.
* And FAA allowed Boeing doing that.

Popular Searches On Airliners.net

Top Photos of Last:   24 Hours  •  48 Hours  •  7 Days  •  30 Days  •  180 Days  •  365 Days  •  All Time

Military Aircraft Every type from fighters to helicopters from air forces around the globe

Classic Airliners Props and jets from the good old days

Flight Decks Views from inside the cockpit

Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior

Cargo Aircraft Pictures of great freighter aircraft

Government Aircraft Aircraft flying government officials

Helicopters Our large helicopter section. Both military and civil versions

Blimps / Airships Everything from the Goodyear blimp to the Zeppelin

Night Photos Beautiful shots taken while the sun is below the horizon

Accidents Accident, incident and crash related photos

Air to Air Photos taken by airborne photographers of airborne aircraft

Special Paint Schemes Aircraft painted in beautiful and original liveries

Airport Overviews Airport overviews from the air or ground

Tails and Winglets Tail and Winglet closeups with beautiful airline logos