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sgrow787
Posts: 450
Joined: Fri May 16, 2014 8:12 pm

### Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

PixelFlight wrote:
XRAYretired wrote:
The writings you have attributed to me above are not mine, although I do not necessarily disagree with them.

Oops, very sorry for my confusion. Please forgive me,
sgrow787 wrote:
I recognise the statements regarding AOA analogue being separately routed to ADIRU and SYMD and it is likely that SYMD initiates the Stick Shaker.

The problem I still have in accepting 'not ADIRU' position is why is the affected side IAS is low, when I am being told that AOA high should result in AIS high as well?

Conversely, I have a problem accepting the 'it is AIDRU' position whist I do not have any information identifying what ADIRU problem or other source data used by ADIRU would result in AIS low, Altitude low and AOA high? I am conscious that all three begin at the same time stamp (but could just be related to WOW FALSE).
Ray.

Trying to learn about the AoA/IAS argument, I share my understanding from this document page 1 for the definition and page 7 for the Variation of Verror with AOA graph:
https://www.nal.res.in/FullPapers/P8-Po ... 0using.pdf
Verror = ((Vmeasured-Vfree)*100)/Vfree = 100*(Vmeasured/Vfree-1) => Vfree = Vmeasured/(Verror/100+1)
Assuming AoA indicate a +20° offset but that the Pitot tube angle of attack is still 0°, the Vmeasured will stay the same but the Verror used for the correction will increase from -3.5% to well over 3%. The Vfree computed with the wrong Verror caused by the +20° AoA offset will DECREASE.
For example:
Vmeasured = 300 and AoA = 0° => Verror = -3.5% => Vfree = 300/(-3.5/100+1) = 310.88
Vmeasured = 300 and AoA = 20° => Verror = 3% => Vfree = 300/(3/100+1) = 291.26

From that paper:

"At higher angle of attack, the probe measures a higher velocity as compared to the free stream due to local
flow acceleration around the boom."

That velocity is the velocity of the air moving through the pitot tube. It is not IAS, which is the velocity of air in the direction opposite of aircraft travel (which uses AOA and incident velocity (the velocity of the air moving through the pitot tube)).

IAS is the value computed by the ADIRU and recorded by the FDR.

So basically you have a paper of how aircraft angle of attack effects the measured incident velocity, specifically at certain angles of attack (I'm spelling it out here to emphasize the actual aircraft angle of attack vs getting confused with AOA sensor data) where the velocity of air at the static port (for a nose mounted probe) can increase higher (than the free velocity) due to "local flow acceleration around the boom".

The reason this doesn't apply to the 737 Max crashes, and my theory, is because I'm comparing two identical sensors, placed at identical positions on both sides of the airframe.
Just one sensor,
Oh just one se-en-sor,
Just one sensor,
Ooh ooh oo-ooh
Oo-oo-ooh.

sgrow787
Posts: 450
Joined: Fri May 16, 2014 8:12 pm

### Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

sgrow787 wrote:
PixelFlight wrote:
Trying to learn about the AoA/IAS argument, I share my understanding from this document page 1 for the definition and page 7 for the Variation of Verror with AOA graph:
https://www.nal.res.in/FullPapers/P8-Po ... 0using.pdf
Verror = ((Vmeasured-Vfree)*100)/Vfree = 100*(Vmeasured/Vfree-1) => Vfree = Vmeasured/(Verror/100+1)
Assuming AoA indicate a +20° offset but that the Pitot tube angle of attack is still 0°, the Vmeasured will stay the same but the Verror used for the correction will increase from -3.5% to well over 3%. The Vfree computed with the wrong Verror caused by the +20° AoA offset will DECREASE.
For example:
Vmeasured = 300 and AoA = 0° => Verror = -3.5% => Vfree = 300/(-3.5/100+1) = 310.88
Vmeasured = 300 and AoA = 20° => Verror = 3% => Vfree = 300/(3/100+1) = 291.26

From that paper:

"At higher angle of attack, the probe measures a higher velocity as compared to the free stream due to local
flow acceleration around the boom."

That velocity is the velocity of the air moving through the pitot tube. It is not IAS, which is the velocity of air in the direction opposite of aircraft travel (which uses AOA and incident velocity (the velocity of the air moving through the pitot tube)).

IAS is the value computed by the ADIRU and recorded by the FDR.

So basically you have a paper of how aircraft angle of attack effects the measured incident velocity, specifically at certain angles of attack (I'm spelling it out here to emphasize the actual aircraft angle of attack vs getting confused with AOA sensor data) where the velocity of air at the static port (for a nose mounted probe) can increase higher (than the free velocity) due to "local flow acceleration around the boom".

The reason this doesn't apply to the 737 Max crashes, and my theory, is because I'm comparing two identical sensors, placed at identical positions on both sides of the airframe.

Include the pitot port in the above w.r.t. increased velocity due to local flow acceleration, since that would be the main increase, the static port increase being minor.
Just one sensor,
Oh just one se-en-sor,
Just one sensor,
Ooh ooh oo-ooh
Oo-oo-ooh.

sgrow787
Posts: 450
Joined: Fri May 16, 2014 8:12 pm

### Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

It would be interesting to know if this "local flow acceleration" applies to a pitot tube mounted at the Cp = 0 position on the fuselage. Because if it does, then I would have to concede that could have an effect in lowering incident velocity for a false high AOA sensor value:
There would have to be tuning parameters to offset that "local flow acceleration", with the purpose of bringing the incident velocity DOWN from what the pitot tube is sensing. But if there is no real angle of attack (due to falsely high AOA sensor data) then the result would be the tuning parameters bring the true incident velocity DOWN. Then, the computation of IAS from that decreased incident velocity, with high AOA value, would bring it back UP (IAS = Vmeasured / cos(alpha)), but which would win out would be the question. So the question is, can you have "local flow acceleration" at high angle of attack at the Cp = 0 position.
Just one sensor,
Oh just one se-en-sor,
Just one sensor,
Ooh ooh oo-ooh
Oo-oo-ooh.

zeke
Posts: 14974
Joined: Thu Dec 14, 2006 1:42 pm

### Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

XRAYretired wrote:
Conversely, I have a problem accepting the 'it is AIDRU' position whist I do not have any information identifying what ADIRU problem or other source data used by ADIRU would result in AIS low, Altitude low and AOA high? I am conscious that all three begin at the same time stamp (but could just be related to WOW FALSE).

The preliminary factual report for the ET accident does not present information on prior maintenance status of the aircraft. Looking at the JT preliminary report the following were stated stated to have occurred

Speed Flag
Altitude Flag
Speed trim fail
Mach trim fail
Auto-throttle Arm disconnect
IAS and ALT disagree
feel diff press

Common causes for these

Speed flag
DEU
Pitot Air Data Module
Wiring from the ADIRU to the DEUs

Speed trim fail
Stab Trim Electric Motor
Stab Trim Relay
Column Switching Module
A/P Trim Cutout Switch
Flight Control Panel
Wiring
Flight Control Computer

Mach trim fail
Mach Trim Actuator
Integrated Flight System Accessory Unit
Flight Control Panel
Wiring
Flight Control Computer

Altitude flag
DEU
Static Air Data Module
Wiring from the ADIRU to the DEUs

Anyone suggesting the cause of these accidents is cut and dry is a fool, and anyone saying the only possible cause is AOA failure is a fool.

The ADIRU is still very much in the picture, both the ET and JT accidents had the ALT and SPD flags, a common element is the ADIRU. The feel diff press is an indication that the elevator feel shift has activated. Contrary what was reported, I was told the AOA that was removed from the JT aircraft was tested as being serviceable.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News

XRAYretired
Posts: 870
Joined: Fri Mar 15, 2019 11:21 am

### Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

zeke wrote:
XRAYretired wrote:
Conversely, I have a problem accepting the 'it is AIDRU' position whist I do not have any information identifying what ADIRU problem or other source data used by ADIRU would result in AIS low, Altitude low and AOA high? I am conscious that all three begin at the same time stamp (but could just be related to WOW FALSE).

The preliminary factual report for the ET accident does not present information on prior maintenance status of the aircraft. Looking at the JT preliminary report the following were stated stated to have occurred

Speed Flag
Altitude Flag
Speed trim fail
Mach trim fail
Auto-throttle Arm disconnect
IAS and ALT disagree
feel diff press

Common causes for these

Speed flag
DEU
Pitot Air Data Module
Wiring from the ADIRU to the DEUs

Speed trim fail
Stab Trim Electric Motor
Stab Trim Relay
Column Switching Module
A/P Trim Cutout Switch
Flight Control Panel
Wiring
Flight Control Computer

Mach trim fail
Mach Trim Actuator
Integrated Flight System Accessory Unit
Flight Control Panel
Wiring
Flight Control Computer

Altitude flag
DEU
Static Air Data Module
Wiring from the ADIRU to the DEUs

Anyone suggesting the cause of these accidents is cut and dry is a fool, and anyone saying the only possible cause is AOA failure is a fool.

The ADIRU is still very much in the picture, both the ET and JT accidents had the ALT and SPD flags, a common element is the ADIRU. The feel diff press is an indication that the elevator feel shift has activated. Contrary what was reported, I was told the AOA that was removed from the JT aircraft was tested as being serviceable.

Info on the removed sensor pre-JT043-

https://www.nytimes.com/2019/04/02/worl ... n-air.html

"Mr. Nurcahyo, the KNKT head of air accident investigations, said that before the second to last flight, engineers replaced the left angle of attack vane because the plane had suffered problems with data readings on three previous flights. Cold temperatures, he said, appeared to have caused the sensor to malfunction.
After the crash, the replaced angle of attack sensor was shipped to Minnesota, home of Rosemount Aerospace, the Boeing subcontractor that made it, Mr. Nurcahyo said. He and other Indonesian investigators went to Minneapolis in December. The sensor, he said, was deemed defective."

Ray

zeke
Posts: 14974
Joined: Thu Dec 14, 2006 1:42 pm

### Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

I had see that Ray, I was told different. That is why I stated despite what has been reported.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News

XRAYretired
Posts: 870
Joined: Fri Mar 15, 2019 11:21 am

### Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

zeke wrote:
I had see that Ray, I was told different. That is why I stated despite what has been reported.

OK. Can you divulge source?

Ray

zeke
Posts: 14974
Joined: Thu Dec 14, 2006 1:42 pm

### Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Just what I have been told by the avionics DERs, the cone heads have their own direct contacts with the component manufacturers as they are dealing with component repairs and modifications all the time. What I understand the AOA sensor model is common part used on many types, it has been around a long time before the MAX. The preliminary factual report does not actually indicate the AOA was faulty for the sectors mentioned in the article.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News

PixelFlight
Posts: 1018
Joined: Thu Nov 08, 2018 11:09 pm

### Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

sgrow787 wrote:
PixelFlight wrote:
XRAYretired wrote:
The writings you have attributed to me above are not mine, although I do not necessarily disagree with them.

Oops, very sorry for my confusion. Please forgive me,
sgrow787 wrote:
I recognise the statements regarding AOA analogue being separately routed to ADIRU and SYMD and it is likely that SYMD initiates the Stick Shaker.

The problem I still have in accepting 'not ADIRU' position is why is the affected side IAS is low, when I am being told that AOA high should result in AIS high as well?

Conversely, I have a problem accepting the 'it is AIDRU' position whist I do not have any information identifying what ADIRU problem or other source data used by ADIRU would result in AIS low, Altitude low and AOA high? I am conscious that all three begin at the same time stamp (but could just be related to WOW FALSE).
Ray.

Trying to learn about the AoA/IAS argument, I share my understanding from this document page 1 for the definition and page 7 for the Variation of Verror with AOA graph:
https://www.nal.res.in/FullPapers/P8-Po ... 0using.pdf
Verror = ((Vmeasured-Vfree)*100)/Vfree = 100*(Vmeasured/Vfree-1) => Vfree = Vmeasured/(Verror/100+1)
Assuming AoA indicate a +20° offset but that the Pitot tube angle of attack is still 0°, the Vmeasured will stay the same but the Verror used for the correction will increase from -3.5% to well over 3%. The Vfree computed with the wrong Verror caused by the +20° AoA offset will DECREASE.
For example:
Vmeasured = 300 and AoA = 0° => Verror = -3.5% => Vfree = 300/(-3.5/100+1) = 310.88
Vmeasured = 300 and AoA = 20° => Verror = 3% => Vfree = 300/(3/100+1) = 291.26

From that paper:

"At higher angle of attack, the probe measures a higher velocity as compared to the free stream due to local
flow acceleration around the boom."

That velocity is the velocity of the air moving through the pitot tube. It is not IAS, which is the velocity of air in the direction opposite of aircraft travel (which uses AOA and incident velocity (the velocity of the air moving through the pitot tube)).

IAS is the value computed by the ADIRU and recorded by the FDR.

So basically you have a paper of how aircraft angle of attack effects the measured incident velocity, specifically at certain angles of attack (I'm spelling it out here to emphasize the actual aircraft angle of attack vs getting confused with AOA sensor data) where the velocity of air at the static port (for a nose mounted probe) can increase higher (than the free velocity) due to "local flow acceleration around the boom".

The reason this doesn't apply to the 737 Max crashes, and my theory, is because I'm comparing two identical sensors, placed at identical positions on both sides of the airframe.

The paper statement is coherent with his Verror graph and the JT610 + ET302 FDR traces. As Vmeasured increase with high AoA, Verror increase too. In case Vmeasured stay the same but AoA is reading high due to AoA fault, the applied Verror will still increase on a system that is programmed to apply the correction in function of the AoA reading.. As the Verror/100+1 term is the divisor of Vmeasured, Vfree will DECREASE as Verror increase.
There are many documents about IAS->CAS->EAS->TAS the most easy to find: https://en.wikipedia.org/wiki/Airspeed
CAS (and not IAS) is the value computed by the ADIRU and recorded by the FDR.
The JT610 and ET302 officially published preliminary reports document FDR traces only show CAS.

I fail to understand why this will not apply to the 737. Each ADIRU compute a FDR recorded CAS from his side Pitot tube and his side AoA vane. On JT610 and ET302 all Pitot tube was most probably reading about the same value but the left side AoA was reading erratic high values that caused only the left ADIRU to compute a lower CAS by applying a too high correction. The right ADIRU was still reading a good right side AoA value and still applied the right correction to compute the CAS. That so perfectly fit the available data. Of course I can't exclude that I make an error and that an other scenario have occurred.
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)."

PixelFlight
Posts: 1018
Joined: Thu Nov 08, 2018 11:09 pm

### Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

zeke wrote:
XRAYretired wrote:
Conversely, I have a problem accepting the 'it is AIDRU' position whist I do not have any information identifying what ADIRU problem or other source data used by ADIRU would result in AIS low, Altitude low and AOA high? I am conscious that all three begin at the same time stamp (but could just be related to WOW FALSE).

The preliminary factual report for the ET accident does not present information on prior maintenance status of the aircraft. Looking at the JT preliminary report the following were stated stated to have occurred

Speed Flag
Altitude Flag
Speed trim fail
Mach trim fail
Auto-throttle Arm disconnect
IAS and ALT disagree
feel diff press

Common causes for these

Speed flag
DEU
Pitot Air Data Module
Wiring from the ADIRU to the DEUs

Speed trim fail
Stab Trim Electric Motor
Stab Trim Relay
Column Switching Module
A/P Trim Cutout Switch
Flight Control Panel
Wiring
Flight Control Computer

Mach trim fail
Mach Trim Actuator
Integrated Flight System Accessory Unit
Flight Control Panel
Wiring
Flight Control Computer

Altitude flag
DEU
Static Air Data Module
Wiring from the ADIRU to the DEUs

Anyone suggesting the cause of these accidents is cut and dry is a fool, and anyone saying the only possible cause is AOA failure is a fool.

The ADIRU is still very much in the picture, both the ET and JT accidents had the ALT and SPD flags, a common element is the ADIRU. The feel diff press is an indication that the elevator feel shift has activated. Contrary what was reported, I was told the AOA that was removed from the JT aircraft was tested as being serviceable.

Dear "zeke", no need to pretend that we all here have a "cut and dry" attitude and to merit rude words. It's constructive to inspect all possibles scenarios and for anyone to contribute to the knowledge about the implication of each scenario. It's also normal for anyone to share his thinking about the argument that make a scenario the most likely from his knowledge and understanding. We are all aware that nobody have all the definitive data yet and that any scenario is still speculative at this stage. This do not prevent anyone to share and learn.

The ADIRU is cited in the JT610 in the "abbreviations and definitions" and in the "resolution description" of the AFML for two main reasons:
1) There was error message, like: ADR Data invalid (34-21007), AOA SIGNAL FAIL (34-21023), 27-31-12 (AD data invalid), 27-31015 (ADIRU data invalid)
2) The device was reset and tested, like: Reset CB ADIRU L AC and DC and ADIRU L carried out. System test pass.
I don't see all the text you posted in the document https://reports.aviation-safety.net/201 ... MINARY.pdf
The understanding of the cause of each error message would be interesting.
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)."

PixelFlight
Posts: 1018
Joined: Thu Nov 08, 2018 11:09 pm

### Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

zeke wrote:
Just what I have been told by the avionics DERs, the cone heads have their own direct contacts with the component manufacturers as they are dealing with component repairs and modifications all the time. What I understand the AOA sensor model is common part used on many types, it has been around a long time before the MAX. The preliminary factual report does not actually indicate the AOA was faulty for the sectors mentioned in the article.

Please understand that at this stage your "what I have been told" is highly speculative compared to a KNKT public statement that have not be denied by any official source.
You still feel free to post your highly speculative view, so please let others do the same.
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)."

zeke
Posts: 14974
Joined: Thu Dec 14, 2006 1:42 pm

### Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

PixelFlight wrote:
Please understand that at this stage your "what I have been told" is highly speculative compared to a KNKT public statement that have not be denied by any official source.
You still feel free to post your highly speculative view, so please let others do the same.

A New York Times article is not a KNKT public statement. As I also said that article also says “left angle of attack vane because the plane had suffered problems with data readings on three previous flights” which is not in the preliminary factual report.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News

XRAYretired
Posts: 870
Joined: Fri Mar 15, 2019 11:21 am

### Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

zeke wrote:
PixelFlight wrote:
Please understand that at this stage your "what I have been told" is highly speculative compared to a KNKT public statement that have not be denied by any official source.
You still feel free to post your highly speculative view, so please let others do the same.

A New York Times article is not a KNKT public statement. As I also said that article also says “left angle of attack vane because the plane had suffered problems with data readings on three previous flights” which is not in the preliminary factual report.

I count 3 zeke? numbered 1, 2 and 3 in the Preliminary Report AFML section1.6.3:-

1 26 October 2018 Tianjin Binhai to Manado
2 27 October 2018 Denpasar to Manado
3 27 October 2018 Manado to Denpasar

Ray

zeke
Posts: 14974
Joined: Thu Dec 14, 2006 1:42 pm

### Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

XRAYretired wrote:

I count 3 zeke? numbered 1, 2 and 3 in the Preliminary Report AFML section1.6.3:-

1 26 October 2018 Tianjin Binhai to Manado
2 27 October 2018 Denpasar to Manado
3 27 October 2018 Manado to Denpasar

Ray

Those are the faults I mentioned above and listed the common causes for. They do not indicate the left AOA had failed on those 3 sectors. First two would indicate an air data issue or wiring.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News

XRAYretired
Posts: 870
Joined: Fri Mar 15, 2019 11:21 am

### Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

zeke wrote:
XRAYretired wrote:

I count 3 zeke? numbered 1, 2 and 3 in the Preliminary Report AFML section1.6.3:-

1 26 October 2018 Tianjin Binhai to Manado
2 27 October 2018 Denpasar to Manado
3 27 October 2018 Manado to Denpasar

Ray

Those are the faults I mentioned above and listed the common causes for. They do not indicate the left AOA had failed on those 3 sectors. First two would indicate an air data issue or wiring.

Lateral disection of rabbits zeke. Three flights with 'data reading' anomalies is entirely reaonable statement seems to me and the report says AOA removed due to 'repetitive problem'. The last two flights record AOA signal fail. Cant dismiss the whole quote on this basis of it isn't in the report in my view.

Ray
Ray

PixelFlight
Posts: 1018
Joined: Thu Nov 08, 2018 11:09 pm

### Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

zeke wrote:
Anyone suggesting the cause of these accidents is cut and dry is a fool, and anyone saying the only possible cause is AOA failure is a fool.

A am sure that you have read this post on the other thread:
viewtopic.php?f=3&t=1417545&start=6250#p21315565
The AoA is cited 13 times while the ADIRU in nowhere.
I hope that the Southwest "SENIOR DIRECTOR COMPLIANCE, OPERATIONS, & PROCEDURES" have the relevant information from Boeing to assert the safety of his PAX.
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)."

zeke
Posts: 14974
Joined: Thu Dec 14, 2006 1:42 pm

### Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

XRAYretired wrote:
Lateral disection of rabbits zeke. Three flights with 'data reading' anomalies is entirely reaonable statement seems to me and the report says AOA removed due to 'repetitive problem'. The last two flights record AOA signal fail. Cant dismiss the whole quote on this basis of it isn't in the report in my view.

Ray
Ray

Ray you cannot cherry pick parts of the faults. The first flight shows spd and alt flags on the CN PFD, that is not caused by AOA, second flight was again the same SPD and ALT flags with the addition of SPEED TRIM FAIL and MACH TRIM FAIL. I have given the causes for these above it is not AOA related.

The second flight shows when doing a bite test post flight they had invalid air data, the AOA fail can be a result of bad air data getting to the SYMD or a wiring issue.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News

zeke
Posts: 14974
Joined: Thu Dec 14, 2006 1:42 pm

### Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

PixelFlight wrote:
The AoA is cited 13 times while the ADIRU in nowhere.
I hope that the Southwest "SENIOR DIRECTOR COMPLIANCE, OPERATIONS, & PROCEDURES" have the relevant information from Boeing to assert the safety of his PAX.

That does not address either accident at all. Boeing and WN are not in a position to release any information relating to the accident investigations unless approved by the investigators.

That is a technical summary of why MCAS was installed and how it works.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News

PixelFlight
Posts: 1018
Joined: Thu Nov 08, 2018 11:09 pm

### Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

zeke wrote:
PixelFlight wrote:
The AoA is cited 13 times while the ADIRU in nowhere.
I hope that the Southwest "SENIOR DIRECTOR COMPLIANCE, OPERATIONS, & PROCEDURES" have the relevant information from Boeing to assert the safety of his PAX.

That does not address either accident at all. Boeing and WN are not in a position to release any information relating to the accident investigations unless approved by the investigators.

That is a technical summary of why MCAS was installed and how it works.

I disagree:this was all about the procedure to release the MAX from grounding.If the ADIRU was related to the death of >350 peoples that caused the MAX grounding, I can't see how a so detailed message from a so important position at Southwest to all the pilots could not event have any mention of it.
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)."

zeke
Posts: 14974
Joined: Thu Dec 14, 2006 1:42 pm

### Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

PixelFlight wrote:
I disagree:this was all about the procedure to release the MAX from grounding.If the ADIRU was related to the death of >350 peoples that caused the MAX grounding, I can't see how a so detailed message from a so important position at Southwest to all the pilots could not event have any mention of it.

Well let’s just stop the investigations then, you have all the answers.

You obviously can explain who they had alt, speed, speed trim fail , Mach Tim fail, diff prrsss, ias and alt disagree all at the same time without any professional aviation qualifications while others that have including the investigators cannot.

Well done.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News

XRAYretired
Posts: 870
Joined: Fri Mar 15, 2019 11:21 am

### Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

zeke wrote:
XRAYretired wrote:
Lateral disection of rabbits zeke. Three flights with 'data reading' anomalies is entirely reaonable statement seems to me and the report says AOA removed due to 'repetitive problem'. The last two flights record AOA signal fail. Cant dismiss the whole quote on this basis of it isn't in the report in my view.

Ray
Ray

Ray you cannot cherry pick parts of the faults. The first flight shows spd and alt flags on the CN PFD, that is not caused by AOA, second flight was again the same SPD and ALT flags with the addition of SPEED TRIM FAIL and MACH TRIM FAIL. I have given the causes for these above it is not AOA related.

The second flight shows when doing a bite test post flight they had invalid air data, the AOA fail can be a result of bad air data getting to the SYMD or a wiring issue.

Wasnt my intention. You were arguing to dismiss the Investigation chiefs quote relating to the investigation of the removed AOA on the basis of other aspects of the quote not being supported by the report. All I did was suggest how the quote was supported by the report. There are two sides to everything.

Ray

zeke
Posts: 14974
Joined: Thu Dec 14, 2006 1:42 pm

### Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

XRAYretired wrote:

Wasnt my intention. You were arguing to dismiss the Investigation chiefs quote relating to the investigation of the removed AOA on the basis of other aspects of the quote not being supported by the report. All I did was suggest how the quote was supported by the report. There are two sides to everything.

Ray

Ray, I am questioning the accuracy of what has been published by the NYT, it is not a written statement from the investigators. It would not be the first time that someone has taken what someone said out of context.

Their job is to sell advertising not to report facts.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News

XRAYretired
Posts: 870
Joined: Fri Mar 15, 2019 11:21 am

### Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

zeke wrote:
XRAYretired wrote:

Wasnt my intention. You were arguing to dismiss the Investigation chiefs quote relating to the investigation of the removed AOA on the basis of other aspects of the quote not being supported by the report. All I did was suggest how the quote was supported by the report. There are two sides to everything.

Ray

Ray, I am questioning the accuracy of what has been published by the NYT, it is not a written statement from the investigators. It would not be the first time that someone has taken what someone said out of context.

Their job is to sell advertising not to report facts.

OK.

PixelFlight
Posts: 1018
Joined: Thu Nov 08, 2018 11:09 pm

### Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

zeke wrote:
PixelFlight wrote:
I disagree:this was all about the procedure to release the MAX from grounding.If the ADIRU was related to the death of >350 peoples that caused the MAX grounding, I can't see how a so detailed message from a so important position at Southwest to all the pilots could not event have any mention of it.

Well let’s just stop the investigations then, you have all the answers.

You obviously can explain who they had alt, speed, speed trim fail , Mach Tim fail, diff prrsss, ias and alt disagree all at the same time without any professional aviation qualifications while others that have including the investigators cannot.

Well done.

I simply observe that Boeing, FAA, and at least Southwest have a procedure to release the 737 MAX before any of the JT610 or ET302 final report will be published. While I don't have all the information you attribute to me, that procedure indicate that Boeing, FAA and Southwest have that information. The fact is that none of them have communicate that the JT610 and/or ET302 final report need to be published before releasing the 737 MAX. This seem to indicate that there are very confident in what went wrong and how to avoid a future similar issue. Yet none of them was pointing at the ADIRU.

I agree that releasing the 737 MAX before the final reports are published look very strange. Definitively a trap in case the reports will unveil an unexpected important issue.
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)."

XRAYretired
Posts: 870
Joined: Fri Mar 15, 2019 11:21 am

### Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

PixelFlight wrote:
zeke wrote:
PixelFlight wrote:
I disagree:this was all about the procedure to release the MAX from grounding.If the ADIRU was related to the death of >350 peoples that caused the MAX grounding, I can't see how a so detailed message from a so important position at Southwest to all the pilots could not event have any mention of it.

Well let’s just stop the investigations then, you have all the answers.

You obviously can explain who they had alt, speed, speed trim fail , Mach Tim fail, diff prrsss, ias and alt disagree all at the same time without any professional aviation qualifications while others that have including the investigators cannot.

Well done.

I simply observe that Boeing, FAA, and at least Southwest have a procedure to release the 737 MAX before any of the JT610 or ET302 final report will be published. While I don't have all the information you attribute to me, that procedure indicate that Boeing, FAA and Southwest have that information. The fact is that none of them have communicate that the JT610 and/or ET302 final report need to be published before releasing the 737 MAX. This seem to indicate that there are very confident in what went wrong and how to avoid a future similar issue. Yet none of them was pointing at the ADIRU.

I agree that releasing the 737 MAX before the final reports are published look very strange. Definitively a trap in case the reports will unveil an unexpected important issue.

Perhaps overstating things a wee bit. The investigation team protocols allow them to issue an addendum to the Preliminary Report at any time should they find a significant issue that they deem requires urgent action. But, since the airframe is grounded anyway, they have until ~mid July to do so to enable any further action to be taken before the grounding is rescinded. I would expect that should a systemic or potentially widespread problem with ADIRU or wiring or something else is identified, this would fall into this category. However, the conclusion could be made that the modification being embodied is sufficiently robust not to require further action, particularly if there are two singular initiators of the errent AOA signal.

Ray

zeke
Posts: 14974
Joined: Thu Dec 14, 2006 1:42 pm

### Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

PixelFlight wrote:
I simply observe that Boeing, FAA, and at least Southwest have a procedure to release the 737 MAX before any of the JT610 or ET302 final report will be published. While I don't have all the information you attribute to me, that procedure indicate that Boeing, FAA and Southwest have that information. The fact is that none of them have communicate that the JT610 and/or ET302 final report need to be published before releasing the 737 MAX. This seem to indicate that there are very confident in what went wrong and how to avoid a future similar issue. Yet none of them was pointing at the ADIRU.

You are making things up again. The FAA don’t have a “procedure to release the 737 MAX” to service hence the reason the emergency order is in place. There is no FAA AD for the FCC software update, the only AD is the one for the runaway trim which was in place before the ET crash.

The FAA and WN do not participate in the JT and ET investigations (the NTSB participants as an observer), and Boeing’s role is one of the manufacturer (observer), not as the investigator.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News

par13del
Posts: 10262
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### Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

PixelFlight wrote:
I agree that releasing the 737 MAX before the final reports are published look very strange. Definitively a trap in case the reports will unveil an unexpected important issue.

The final reports will most likely not be made public until some time in 2020, it usually takes about a year.
So you expect the lawsuits, compensation to all and sundry to wait until 2020 or only Boeing should wait for the final report?

sgrow787
Posts: 450
Joined: Fri May 16, 2014 8:12 pm

### Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

PixelFlight wrote:
The paper statement is coherent with his Verror graph and the JT610 + ET302 FDR traces. As Vmeasured increase with high AoA, Verror increase too. In case Vmeasured stay the same but AoA is reading high due to AoA fault, the applied Verror will still increase on a system that is programmed to apply the correction in function of the AoA reading.. As the Verror/100+1 term is the divisor of Vmeasured, Vfree will DECREASE as Verror increase.
There are many documents about IAS->CAS->EAS->TAS the most easy to find: https://en.wikipedia.org/wiki/Airspeed
CAS (and not IAS) is the value computed by the ADIRU and recorded by the FDR.
The JT610 and ET302 officially published preliminary reports document FDR traces only show CAS.

I fail to understand why this will not apply to the 737. Each ADIRU compute a FDR recorded CAS from his side Pitot tube and his side AoA vane. On JT610 and ET302 all Pitot tube was most probably reading about the same value but the left side AoA was reading erratic high values that caused only the left ADIRU to compute a lower CAS by applying a too high correction. The right ADIRU was still reading a good right side AoA value and still applied the right correction to compute the CAS. That so perfectly fit the available data. Of course I can't exclude that I make an error and that an other scenario have occurred.

I believe the reports are referencing IAS - (a) I can only find Computed Airspeed in both crash report FDR traces, and (b) for the ET302 crash, the R-Comp Airspeed is a steady shoreline offset of 25 kts, and they state "indicated airspeed" in the report:
"The left indicated airspeed increased from approximately 305 kt to approximately 340 kt (VMO). The right indicated airspeed was approximately 20-25 kt higher than the left."

I don't see any reference to CAS, EAS, or TAS.
Just one sensor,
Oh just one se-en-sor,
Just one sensor,
Ooh ooh oo-ooh
Oo-oo-ooh.

XRAYretired
Posts: 870
Joined: Fri Mar 15, 2019 11:21 am

### Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

sgrow787 wrote:
PixelFlight wrote:
The paper statement is coherent with his Verror graph and the JT610 + ET302 FDR traces. As Vmeasured increase with high AoA, Verror increase too. In case Vmeasured stay the same but AoA is reading high due to AoA fault, the applied Verror will still increase on a system that is programmed to apply the correction in function of the AoA reading.. As the Verror/100+1 term is the divisor of Vmeasured, Vfree will DECREASE as Verror increase.
There are many documents about IAS->CAS->EAS->TAS the most easy to find: https://en.wikipedia.org/wiki/Airspeed
CAS (and not IAS) is the value computed by the ADIRU and recorded by the FDR.
The JT610 and ET302 officially published preliminary reports document FDR traces only show CAS.

I fail to understand why this will not apply to the 737. Each ADIRU compute a FDR recorded CAS from his side Pitot tube and his side AoA vane. On JT610 and ET302 all Pitot tube was most probably reading about the same value but the left side AoA was reading erratic high values that caused only the left ADIRU to compute a lower CAS by applying a too high correction. The right ADIRU was still reading a good right side AoA value and still applied the right correction to compute the CAS. That so perfectly fit the available data. Of course I can't exclude that I make an error and that an other scenario have occurred.

I believe the reports are referencing IAS - (a) I can only find Computed Airspeed in both crash report FDR traces, and (b) for the ET302 crash, the R-Comp Airspeed is a steady shoreline offset of 25 kts, and they state "indicated airspeed" in the report:
"The left indicated airspeed increased from approximately 305 kt to approximately 340 kt (VMO). The right indicated airspeed was approximately 20-25 kt higher than the left."

I don't see any reference to CAS, EAS, or TAS.

I guess it comes down to what you want to believe.

(Only!) all three FDR traces we have are marked as Computed Airspeed in two different formats.

IAS is mentioned twice in (only!) ET302 report in relationship to actual recorded values and are clearly in reference to the FDR trace that is actually marked as Computed Airspeed.

If the FDR trace is indeed Computerised Airspeed, then the data would appear to accord with the effects of AOA failed high (mostly?).

The alternative is an as yet, unknown failure mode, or several failures that would produce Airspeed low, Altitude low and AOA high coupled with an SYMD un-declared change to use the ADIRU AOA calculated value rather than direct AOA analogue signal per NG so as to activate the stick shaker (the Southwest write-up notice to pilots does not indicate SYMD as a modified flight controls system for the MAX).

At least, for now, I'll have to go with the former.

NB, the much vaunted AvH ET302 article actually says AIS-L was higher than AIS-R around take off by 12knots - error?

Ray

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### Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi Q1 2019

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