SwissCanuck
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 18, 2019 9:11 am

zeke wrote:
SwissCanuck wrote:
Simon has weighed in on this crash, very out of character for him. He seems to put the fact that the ET pilots were informed about MCAS/details of LionAir into doubt. An interesting read:

http://avherald.com/h?article=4c534c4a/0045&opt=0


In an airline environment something like an emergency AD is not distributed with a new issue of the FCOM.

They would have a formal process either via paper and/or electronically to distribute timely operational information to all crew and aircraft.

Airlines are very fluid environments with lots of changes on a daily basis. There is a formal process on how this is distributed.


I agree Zeke, but I just re-read the AD. Unless I'm missing something, the AD's only directive was to update the flight manual in a very specific way. Within 3 days the manuals needed to be updated and redistributed. Simon is implying that that didn't happen, and thus Ethiopian didn't comply with the AD.

Please let me know if I've missed a bit.
 
XRAYretired
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 18, 2019 11:14 am

SwissCanuck wrote:
zeke wrote:
SwissCanuck wrote:
Simon has weighed in on this crash, very out of character for him. He seems to put the fact that the ET pilots were informed about MCAS/details of LionAir into doubt. An interesting read:

http://avherald.com/h?article=4c534c4a/0045&opt=0


In an airline environment something like an emergency AD is not distributed with a new issue of the FCOM.

They would have a formal process either via paper and/or electronically to distribute timely operational information to all crew and aircraft.

Airlines are very fluid environments with lots of changes on a daily basis. There is a formal process on how this is distributed.


I agree Zeke, but I just re-read the AD. Unless I'm missing something, the AD's only directive was to update the flight manual in a very specific way. Within 3 days the manuals needed to be updated and redistributed. Simon is implying that that didn't happen, and thus Ethiopian didn't comply with the AD.

Please let me know if I've missed a bit.

Having had a deeper look at Simons narrative compared to what is in the ET302 Preliminary Report, it would seem there is some discrepancy.

Simons assertion is the FCOM dated 30th Nov 18 was the current version as of 10th Mar 19 and did not include the EAD/TBC-19 insertion, and further more, that this is supportive of the hypothesis that pilots not having been adequately advised of the instructions in case of MCAS activation under fault condition.

This is in direct conflict with Preliminary report statement viz:-
1.16.2 OPERATION MANUAL EXTRACTS
1.16.2.1 ETHIOPIAN AIRLINES AIRCRAFT FLIGHT MANUAL (AFM)
A check of the AFM provided by Ethiopian Airlines showed that the airline had incorporated the revisions A180625 on November, 11 2018 required by Airworthiness Directive 2018-23-51. The two pages from the AFM are in Appendix .
1.16.2.2 FCOM BULLETIN ISSUED BY BOEING TO ETHIOPIAN AIRLINES An FCOM bulletin issued by Boeing to Ethiopian Airlines (ETH-12) regarding uncommanded nosedown stabilizer trim required Ethiopian Airlines to insert the bulletin in their B737MAX FCOM. The US Ops/hp technical advisors were provided an electronic copy of the Airline’s B737MAX FCOM, and the bulletin was found to be incorporated per Boeing directions.
The bulletin is shown in Appendix 4

Further 'Appendix 4' holds the following footer information 'February 21, 2019 D6-27370-MAX-ETH' implying inclusion of the relevant instructions in a formal issue of the ETH FCOM 21 February 19. Is this the actual latest version?

Whilst Simon does not directly say so, his implication is the Preliminary report is 'incorrect' although he does, at least partially, relay on the veracity of other parts of the Preliminary Report. Well, there is something smelling fishy somewhere?

I don't think the veracity of either or other statements actually proves or disproves the pilots being adequately informed or not but is does seem to illustrate the miss-trust surrounding this investigation.

NB. If the Preliminary Report is indeed incorrect, has the NTSB been hoodwinked?

Ray
 
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zeke
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 18, 2019 11:29 am

SwissCanuck wrote:
I agree Zeke, but I just re-read the AD. Unless I'm missing something, the AD's only directive was to update the flight manual in a very specific way. Within 3 days the manuals needed to be updated and redistributed. Simon is implying that that didn't happen, and thus Ethiopian didn't comply with the AD.

Please let me know if I've missed a bit.


Generally speaking no pilot or aircraft of an airliner would have a flight manual. The flight manual is a very skinny document with some very limited information in it. Almost every pilot and aircraft would have a flight crew operation manual (FCOM). The FCOM has expanded and airline specific information in it.

Where I work if such an AD would come out, an internal notice to pilots would be raised and distributed electronically. The notice would indicate that it would be later incorporated into the electronic manuals which could take 6 months.

We electronically sign for the receipt of the notices on our iPads to shows we have read, understand, and will comply with the contents as directed.

I think Simon is chasing parked cars with this angle.
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morrisond
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 18, 2019 12:12 pm

XRAYretired wrote:
SwissCanuck wrote:
zeke wrote:

In an airline environment something like an emergency AD is not distributed with a new issue of the FCOM.

They would have a formal process either via paper and/or electronically to distribute timely operational information to all crew and aircraft.

Airlines are very fluid environments with lots of changes on a daily basis. There is a formal process on how this is distributed.


I agree Zeke, but I just re-read the AD. Unless I'm missing something, the AD's only directive was to update the flight manual in a very specific way. Within 3 days the manuals needed to be updated and redistributed. Simon is implying that that didn't happen, and thus Ethiopian didn't comply with the AD.

Please let me know if I've missed a bit.

Having had a deeper look at Simons narrative compared to what is in the ET302 Preliminary Report, it would seem there is some discrepancy.

Simons assertion is the FCOM dated 30th Nov 18 was the current version as of 10th Mar 19 and did not include the EAD/TBC-19 insertion, and further more, that this is supportive of the hypothesis that pilots not having been adequately advised of the instructions in case of MCAS activation under fault condition.

This is in direct conflict with Preliminary report statement viz:-
1.16.2 OPERATION MANUAL EXTRACTS
1.16.2.1 ETHIOPIAN AIRLINES AIRCRAFT FLIGHT MANUAL (AFM)
A check of the AFM provided by Ethiopian Airlines showed that the airline had incorporated the revisions A180625 on November, 11 2018 required by Airworthiness Directive 2018-23-51. The two pages from the AFM are in Appendix .
1.16.2.2 FCOM BULLETIN ISSUED BY BOEING TO ETHIOPIAN AIRLINES An FCOM bulletin issued by Boeing to Ethiopian Airlines (ETH-12) regarding uncommanded nosedown stabilizer trim required Ethiopian Airlines to insert the bulletin in their B737MAX FCOM. The US Ops/hp technical advisors were provided an electronic copy of the Airline’s B737MAX FCOM, and the bulletin was found to be incorporated per Boeing directions.
The bulletin is shown in Appendix 4

Further 'Appendix 4' holds the following footer information 'February 21, 2019 D6-27370-MAX-ETH' implying inclusion of the relevant instructions in a formal issue of the ETH FCOM 21 February 19. Is this the actual latest version?

Whilst Simon does not directly say so, his implication is the Preliminary report is 'incorrect' although he does, at least partially, relay on the veracity of other parts of the Preliminary Report. Well, there is something smelling fishy somewhere?

I don't think the veracity of either or other statements actually proves or disproves the pilots being adequately informed or not but is does seem to illustrate the miss-trust surrounding this investigation.

NB. If the Preliminary Report is indeed incorrect, has the NTSB been hoodwinked?

Ray


The whole report seems quite fishy for what it doesn't include. You would think if the pilots were intimately familiar with MCAS that would have somehow been noted in the cockpit conversations.

Given all the great points that we all have made on many sides of the issues it's becoming increasingly clear that we don't know the whole story on what went on at Ethiopian and ET302. We need to hear the CVR's.

Until then we are just going around and around in circles.
 
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scbriml
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 18, 2019 1:08 pm

XRAYretired wrote:
NB. If the Preliminary Report is indeed incorrect, has the NTSB been hoodwinked?


The NTSB have been fully involved. How would they be 'hoodwinked'?

Didn't they say they were in agreement with the Preliminary Report?
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OldAeroGuy
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 18, 2019 1:10 pm

sgrow787 wrote:
OldAeroGuy wrote:
The AVHerald editorial is incorrect to say that the NG does not correct air data for AoA. Here's what an online 737-800 QRH says:

AOA DISAGREE Message
Condition: The AOA DISAGREE alert indicates the left and right angle of attack vanes disagree.
1 Airspeed errors and the IAS DISAGREE alert may occur.
2 Altimeter errors and the ALT DISAGREE alert may occur.


Those are symptoms for triage while in flight, not for troubleshooting. As such, one would expect to include airspeed and altitude disagree (by using the word 'may'), since a faulty ADIRU could be the cause. And we know what a faulty ADIRU means.


I'm not sure what point you're trying to make here.

I agree that the word "may" is used because the amount of Airspeed and Altitude Disagree will vary with the amount of AoA Disagree.

AVHerald said the 737 NG did not use AoA values to correct Airspeed and Altitude and the 737 MAX did. This is incorrect.

Both the 737 NG and the 737 MAX correct Airspeed and Altitude for AoA.
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XRAYretired
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 18, 2019 1:36 pm

scbriml wrote:
XRAYretired wrote:
NB. If the Preliminary Report is indeed incorrect, has the NTSB been hoodwinked?


The NTSB have been fully involved. How would they be 'hoodwinked'?

Didn't they say they were in agreement with the Preliminary Report?


Just pointing out the conflicts and asking the questions. Personnally, I think NTSB would have objected if they were aware of any shenanigans, so do we assume the report is correct and Simons narrative mistaken? Perhaps AvH has been sold a pup?

Ray
 
RedBob
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 18, 2019 3:05 pm

zeke wrote:
RedBob wrote:
Second is more complicated: why did the system activate in a situation which didn't look like stall in every single aspect other than one AoA value?


An aircraft can be stalled in any attitude and at any airspeed. A stall occurs when the critical angle of attack is exceeded.


Point is, based on observed thrust, air speed, vertical speed and input aircraft weight you can roughly approximate AoA over that period; if your true AoA is as high as it was in Ethiopian Air crash, your plane can't gain altitude, with low trim and pilots trying to counter it. It's not that stall can't occur at high speed; it's that everything else is inconsistent with stall occurring.

This is even more true if we keep in mind if we remember that MCAS is not stall prevention system; it's a system that is supposed to make MAX behave more in line with NG, even in close to stall situations.
 
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zeke
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 18, 2019 7:46 pm

RedBob wrote:
Point is, based on observed thrust, air speed, vertical speed and input aircraft weight you can roughly approximate AoA over that period; if your true AoA is as high as it was in Ethiopian Air crash, your plane can't gain altitude, with low trim and pilots trying to counter it. It's not that stall can't occur at high speed; it's that everything else is inconsistent with stall occurring.

This is even more true if we keep in mind if we remember that MCAS is not stall prevention system; it's a system that is supposed to make MAX behave more in line with NG, even in close to stall situations.


MCAS from what I understand is designed to operate at high angles of bank and high air speeds. I would not be confident in guessing my AOA in such an attitude. This is common to both JT and ET crashes, both were in high angle of bank turns just prior to crashing.
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fadecfault
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 18, 2019 10:04 pm

zeke wrote:
fadecfault wrote:
How does mcas increase stick force?


Stab position is an input to the elevator feel computer, by MCAS driving a change in stab, via the elevator feel computer stick forces change.

OldAeroGuy wrote:
By override cutoff switches on the column, are you referring to the electric trim switches?


I think they are referring to the switches under the floor mechanically attached to the column which cutout with the electric trim movement based upon the control column position. If the control column is moved in opposition to the direction of stabilizer trim. eg pull back on the column to oppose a runaway nose-down trim, and the stabilizer trim logic would disengage in response. However not for MCAS.

This is for the NG.

Image

RedBob wrote:
Second is more complicated: why did the system activate in a situation which didn't look like stall in every single aspect other than one AoA value?


An aircraft can be stalled in any attitude and at any airspeed. A stall occurs when the critical angle of attack is exceeded.


I questioned it because during an EFC ops check the MM directs you to leave the stab at 4 units and only measure column force with changes to airspeed. But now I see the diagram in the SDS showing airspeed input and stab position operating two cams to change hydraulic pressure. Interestingly I tested column force with the stab at 0 and at 17 and I could not feel an appreciable difference . I have to assume it only makes a difference at higher airspeeds.
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kalvado
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Thu Apr 18, 2019 10:14 pm

zeke wrote:
RedBob wrote:
Point is, based on observed thrust, air speed, vertical speed and input aircraft weight you can roughly approximate AoA over that period; if your true AoA is as high as it was in Ethiopian Air crash, your plane can't gain altitude, with low trim and pilots trying to counter it. It's not that stall can't occur at high speed; it's that everything else is inconsistent with stall occurring.

This is even more true if we keep in mind if we remember that MCAS is not stall prevention system; it's a system that is supposed to make MAX behave more in line with NG, even in close to stall situations.


MCAS from what I understand is designed to operate at high angles of bank and high air speeds. I would not be confident in guessing my AOA in such an attitude. This is common to both JT and ET crashes, both were in high angle of bank turns just prior to crashing.

Do you imply that both flights got problems because of aerodynamic conditions in the bank, or its just a pure coincidence that both flights were in a bank while trying to turn around and return to takeoff airport?
Or just saying that it may be difficult to estimate one variable (AoA) from the set of other (bank, airspeed, etc)? If the last one - I bet it is a more involved calculation with more variables, but definitely doable by proper software. Pilot guessing real time in cockpit? Maybe not.
 
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PixelFlight
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 12:07 am

zeke wrote:
MCAS from what I understand is designed to operate at high angles of bank and high air speeds. I would not be confident in guessing my AOA in such an attitude. This is common to both JT and ET crashes, both were in high angle of bank turns just prior to crashing.

The high bank angle is probably a consequence of the final lost of control. I doubt that the JT and ET pilots that was on high workload fighting to save the aircraft would voluntary command a such attitude.
 
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zeke
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 2:18 am

fadecfault wrote:
I have to assume it only makes a difference at higher airspeeds.


The force should increase with airspeed, the baseline starting force should change with stab position. The stab position is indirectly saying where the CG is, hence the moment arm for the elevator.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
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zeke
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 2:24 am

kalvado wrote:
Do you imply that both flights got problems because of aerodynamic conditions in the bank, or its just a pure coincidence that both flights were in a bank while trying to turn around and return to takeoff airport?
Or just saying that it may be difficult to estimate one variable (AoA) from the set of other (bank, airspeed, etc)? If the last one - I bet it is a more involved calculation with more variables, but definitely doable by proper software. Pilot guessing real time in cockpit? Maybe not.


It was an observation, both were in high speed high angle of bank turns.

Pilots cannot estimate AOA in such situations hence the reason AOA sensors are installed.

Not sure why you need software to estimate it, when it can easily be measured.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
kalvado
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 2:51 am

zeke wrote:
Not sure why you need software to estimate it, when it can easily be measured.

Just reading too much into your comments, sorry.
I am talking about some sort of a sanity check. Cross-reference of AoA, airspeed, pressure, thrust, etc. Since parameters depend on each other, data errors (sensor malfunction etc) can be detected as data mismatch. Possibly for verification of black boxes data as well: I was under the impression you implied wrong data or aerodynamic issues in a steep turn, hence commented that it may make sense to verify if recorded data is valid and adds up, or there was really something abnormal in those turns.
 
smartplane
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 4:42 am

PixelFlight wrote:
zeke wrote:
MCAS from what I understand is designed to operate at high angles of bank and high air speeds. I would not be confident in guessing my AOA in such an attitude. This is common to both JT and ET crashes, both were in high angle of bank turns just prior to crashing.

The high bank angle is probably a consequence of the final lost of control. I doubt that the JT and ET pilots that was on high workload fighting to save the aircraft would voluntary command a such attitude.

Or like in many vehicle stability control systems, even when supposedly powered off, in certain 'threatening' situations, can re-start for the duration of the threat? In high angles of bank, does MCAS re-start, even if the switches say no?
 
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zeke
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 5:16 am

kalvado wrote:
I am talking about some sort of a sanity check. Cross-reference of AoA, airspeed, pressure, thrust, etc. Since parameters depend on each other, data errors (sensor malfunction etc) can be detected as data mismatch.


That is already available, Boeing have a synthetic AOA on its newer aircraft models.

smartplane wrote:
In high angles of bank, does MCAS re-start, even if the switches say no?


Not that I am aware of.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
asdf
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 9:48 am

zeke wrote:
kalvado wrote:
I am talking about some sort of a sanity check. Cross-reference of AoA, airspeed, pressure, thrust, etc. Since parameters depend on each other, data errors (sensor malfunction etc) can be detected as data mismatch.


That is already available, Boeing have a synthetic AOA on its newer aircraft models.


add GPS to it
make it a unit completely separated from the normal aviation tools
give it a intuitiv clear output interface
maybe even a simple graphic attitude display with speed, flight level, AOA etc etc etc so that it can be understood immediately
make it upgradeable on any actual aircraft
and make it mandatory for aircrafts with non aviation standard technology
I would suspect that to be a fool proof emergency hand to hold an for crews in problems in aircrafts without up to date technology

or
the better way

throw away that unbelievable process of grandfathering 50 years old technology


the MAX is going to be sold the next 10 years I guess
and it has a life span of 35 years at least, maybe more

that means in 2065 the grandfathered technology is based on a more than 100 year old development
how far will this go?

will we go back to the wright brothers to gain a few bucks more for the investors?
 
Some1Somewhere
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 10:58 am

The Russians (and people with a GPS logger on their truck's dashboard) really like messing with GPS signals.

That said, actual exact position isn't really necessary. Gyroscopic measurements are more than accurate enough - which is called an ADIRU.

The issue with both of these is they aren't affected by actual air conditions, so don't show headwinds/tailwinds/crosswinds/updrafts/downdrafts.
 
asdf
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 11:50 am

Some1Somewhere wrote:
The Russians (and people with a GPS logger on their truck's dashboard) really like messing with GPS signals.
That said, actual exact position isn't really necessary. Gyroscopic measurements are more than accurate enough - which is called an ADIRU.


the ADIRU is probably the part that was faulty and crashed the two planes

i see a use for a unit like this if something doesn't add up at all
if you do your checklists and you have no result
if you are in low level and you know that you will not have time to go through the checklists
this will usually not happen to modern aircrafts
but as long as we have to handle that 1960 rubbish ...


GPS is poor on showing altitude but it shows if you are in climb or in sink
what would maybe have saved the AF flight

the ET guys probably knew their position well but struggled with the trust in their AOA and their speed
if they would have known the speed and the attitude they maybe would have been able to fly a safe thrust&pitch profile
 
kalvado
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 12:02 pm

asdf wrote:
Some1Somewhere wrote:
The Russians (and people with a GPS logger on their truck's dashboard) really like messing with GPS signals.
That said, actual exact position isn't really necessary. Gyroscopic measurements are more than accurate enough - which is called an ADIRU.


the ADIRU is probably the part that was faulty and crashed the two planes

i see a use for a unit like this if something doesn't add up at all
if you do your checklists and you have no result
if you are in low level and you know that you will not have time to go through the checklists
this will usually not happen to modern aircrafts
but as long as we have to handle that 1960 rubbish ...


GPS is poor on showing altitude but it shows if you are in climb or in sink
what would maybe have saved the AF flight

the ET guys probably knew their position well but struggled with the trust in their AOA and their speed
if they would have known the speed and the attitude they maybe would have been able to fly a safe thrust&pitch profile

It is fairly obvious from FDR traces that plainly keeping pitch stable was a big issue.
 
kalvado
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 12:05 pm

zeke wrote:
kalvado wrote:
I am talking about some sort of a sanity check. Cross-reference of AoA, airspeed, pressure, thrust, etc. Since parameters depend on each other, data errors (sensor malfunction etc) can be detected as data mismatch.


That is already available, Boeing have a synthetic AOA on its newer aircraft models.

Of course, this is a low hanging fruit these days. There is definitely a lot to be gained with newer control systems...
 
morrisond
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 12:21 pm

asdf wrote:
Some1Somewhere wrote:
The Russians (and people with a GPS logger on their truck's dashboard) really like messing with GPS signals.
That said, actual exact position isn't really necessary. Gyroscopic measurements are more than accurate enough - which is called an ADIRU.


the ADIRU is probably the part that was faulty and crashed the two planes

i see a use for a unit like this if something doesn't add up at all
if you do your checklists and you have no result
if you are in low level and you know that you will not have time to go through the checklists
this will usually not happen to modern aircrafts
but as long as we have to handle that 1960 rubbish ...


GPS is poor on showing altitude but it shows if you are in climb or in sink
what would maybe have saved the AF flight

the ET guys probably knew their position well but struggled with the trust in their AOA and their speed
if they would have known the speed and the attitude they maybe would have been able to fly a safe thrust&pitch profile


Isn't that why they have the Standby Instrument with Airspeed/Altitude and Pitch on a separate Pitot and Static source so they can cross check there main displays - or am I missing something?
 
asdf
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 12:31 pm

morrisond wrote:
Isn't that why they have the Standby Instrument with Airspeed/Altitude and Pitch on a separate Pitot and Static source so they can cross check there main displays - or am I missing something?


yes they have them
besides a few dozens other informations via displays, switches and else

there are checklists to go through
and routines to check them
and this has proven to be sufficient through decades

but now we obviously start to build and fly planes with center of drag not at the center of gravity
we start to hook electronic aids on a fifty year old aviation technolgy

this opens new cans of worms
it brings in a new dynamic in crew procedures

at some point it could be a last resort to have one single point to look at
a resource if the plane needs to be handflown and you need to hold a pitch&speed profile to get the altitude and the time to figure out what has gone wrong
 
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SomebodyInTLS
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 12:36 pm

kalvado wrote:
zeke wrote:
kalvado wrote:
I am talking about some sort of a sanity check. Cross-reference of AoA, airspeed, pressure, thrust, etc. Since parameters depend on each other, data errors (sensor malfunction etc) can be detected as data mismatch.


That is already available, Boeing have a synthetic AOA on its newer aircraft models.

Of course, this is a low hanging fruit these days. There is definitely a lot to be gained with newer control systems...


AoA is a physical measure of air molecules passing the aircraft... that can NOT be determined from GPS etc.!

It's like how people on this forum constantly confuse airspeed and ground speed. One is about your position in space and navigation... and the other is about how the aircraft is flying through the air.

I don't doubt that you can estimate AoA through synthesis of a lot of other data - but unless you can measure the local windflow everywhere in the atmosphere at all times it will never be accurate enough to do the job of the AoA vanes.
"As with most things related to aircraft design, it's all about the trade-offs and much more nuanced than A.net likes to make out."
 
morrisond
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 12:42 pm

asdf wrote:
morrisond wrote:
Isn't that why they have the Standby Instrument with Airspeed/Altitude and Pitch on a separate Pitot and Static source so they can cross check there main displays - or am I missing something?


yes they have them
besides a few dozens other informations via displays, switches and else

there are checklists to go through
and routines to check them
and this has proven to be sufficient through decades

but now we obviously start to build and fly planes with center of drag not at the center of gravity
we start to hook electronic aids on a fifty year old aviation technolgy

this opens new cans of worms
it brings in a new dynamic in crew procedures

at some point it could be a last resort to have one single point to look at
a resource if the plane needs to be handflown and you need to hold a pitch&speed profile to get the altitude and the time to figure out what has gone wrong


You make it sound like it would take exceptional pilot skills to hold a pitch and speed profile hand flying an aircraft using the standby instrument?

That really should not be considered a difficult task. Quite frankly it should be the default action to go to manual and rely on that backup instrument when the nannies (A/P, Auto trim. Auto Throttle, etc..) and displays start doing unexpected things.

IMO from what I have read Pilots are rarely shown this in real life or in the SIM's once they graduate to the big iron.

Are you implying that the MAX is aerodynamically unstable or are you talking about future designs?
 
asdf
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 1:04 pm

SomebodyInTLS wrote:
I don't doubt that you can estimate AoA through synthesis of a lot of other data - but unless you can measure the local windflow everywhere in the atmosphere at all times it will never be accurate enough to do the job of the AoA vanes.


this is not on routine piloting a aircraft
this is meant as a last resource to hold a plane safe in the air when you have a speed and AOA disagree or other effects you can not determine in short order

of course you can raise the general credibility in adding a forth or fifth AOA vane (or use a second one in case of the MAX ....) but if the procession of the data is faulty you get only thrash as result

I have the impression that the addition of GPS data (height change & speed) should be significant enough to set a plane on a safe speed&pitch profile in a situation without proper AoA data
 
asdf
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 1:10 pm

morrisond wrote:
You make it sound like it would take exceptional pilot skills to hold a pitch and speed profile hand flying an aircraft using the standby instrument?
That really should not be considered a difficult task. Quite frankly it should be the default action to go to manual and rely on that backup instrument when the nannies (A/P, Auto trim. Auto Throttle, etc..) and displays start doing unexpected things.


if you have a AoA disagree and a speed disagree (what seems to have happened)
on what would you relate your actions?


morrisond wrote:
Are you implying that the MAX is aerodynamically unstable ......

from my point of view this question is answered pretty clear
 
morrisond
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 1:33 pm

asdf wrote:
morrisond wrote:
You make it sound like it would take exceptional pilot skills to hold a pitch and speed profile hand flying an aircraft using the standby instrument?
That really should not be considered a difficult task. Quite frankly it should be the default action to go to manual and rely on that backup instrument when the nannies (A/P, Auto trim. Auto Throttle, etc..) and displays start doing unexpected things.


if you have a AoA disagree and a speed disagree (what seems to have happened)
on what would you relate your actions?


morrisond wrote:
Are you implying that the MAX is aerodynamically unstable ......

from my point of view this question is answered pretty clear


The standby instrument which provides all the information you need to fly safely....

If you think the MAX is aerodynamically unstable please provide evidence.

If it's the old moving the engines up and forward a little puts it out of balance and it's dangerous - you do realize that it is probably less of an effect than having the first 5 rows empty or half full?

Flight test showed the MAX is stable - it's only that the controls get a little light at very light TOW and full aft COG - having the engines further forward would actually lessen this as from a loading standpoint it would be more difficult to get to full rear COG assuming MAX and NG have the same COG limits.

That brings up a good point - Does anyone know if the MAX has the same COG range and rear limit as the NG? If they are the same - it might have just been easier to limit the aft COG range then no MCAS needed - which effectively would mean you could still load at least the same weight in the back of the MAX as the NG - just not more like you can in the MAX if if has the same rear COG limit as the NG.

Or maybe they didn't mount the Engines far enough forward...
 
kalvado
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 2:02 pm

SomebodyInTLS wrote:
kalvado wrote:
zeke wrote:

That is already available, Boeing have a synthetic AOA on its newer aircraft models.

Of course, this is a low hanging fruit these days. There is definitely a lot to be gained with newer control systems...


AoA is a physical measure of air molecules passing the aircraft... that can NOT be determined from GPS etc.!

It's like how people on this forum constantly confuse airspeed and ground speed. One is about your position in space and navigation... and the other is about how the aircraft is flying through the air.

I don't doubt that you can estimate AoA through synthesis of a lot of other data - but unless you can measure the local windflow everywhere in the atmosphere at all times it will never be accurate enough to do the job of the AoA vanes.

GPS - no. from 3 components of airspeed and acceleration, thrust, weight, CoG and static pressure and controls position - probably yes (for a given configuration, of course)
While AoA is a purely frame-to-air interaction parameter, it is not a random one, it is part of motion dynamics, and parameters should be linked. Not saying that AoA is the best one to compute; but parameter space definitely has expected regions, desired and undesired; and regions where the plane cannot really be found.
 
asdf
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 2:22 pm

morrisond wrote:
If you think the MAX is aerodynamically unstable please provide evidence.
If it's the old moving the engines up and forward a little puts it out of balance and it's dangerous - you do realize that it is probably less of an effect than having the first 5 rows empty or half full?


the calculated weight difference of 2500 pounds (1200kg?) at the front of a plane should be the reason that a plane can not certified?
I doubt that

morrisond wrote:
Flight test showed the MAX is stable

evidence?
the open public knows about a correction value which has to be increased to a multiple from its initial number because of test flight results
this does not sound like a strength of colum case at all
Last edited by asdf on Fri Apr 19, 2019 2:23 pm, edited 1 time in total.
 
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zeke
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 2:23 pm

asdf wrote:
add GPS to it


I have done this before on a microprocessor level for small UAVs, however the output AOA is nowhere near the accuracy of a conventional AOA probe. The two ways I have done this is by using GPS and acceleration to come up with AOA, the other way I have done it is to use multiple GPS antennas placed on the wingtips and fore and aft on the fuselage.

No one cares if a hobby UAV crashes.

That is nowhere near what they have been able to do on the 787.

asdf wrote:
throw away that unbelievable process of grandfathering 50 years old technology


There is nothing wrong with grandfathering, it is the normal engineering process to improve on existing design. Whenever you start from scratch you will have new unknown issues develop despite the engineers best efforts.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
asdf
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 2:34 pm

zeke wrote:
asdf wrote:
There is nothing wrong with grandfathering, it is the normal engineering process to improve on existing design. Whenever you start from scratch you will have new unknown issues develop despite the engineers best efforts.


grandfathering how it is applied by Boeing in case of the MAX can not be the intention of a normal engineering process
obviously they simple used grandfathering rules to avoid the observance of modern aviation conditions

different centers of drag and centers of gravity would not be certifiably in an actual certification as far as I know

at the time the 737 was certified in the 1960 this condition was not part of the rulebook
so it was possible to move the engines in front of the wing now

this has nothing to do with a " ....normal engineering process to improve on existing design ..."

rather the opposite
 
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Polot
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 2:39 pm

asdf wrote:
zeke wrote:
asdf wrote:
There is nothing wrong with grandfathering, it is the normal engineering process to improve on existing design. Whenever you start from scratch you will have new unknown issues develop despite the engineers best efforts.


grandfathering how it is applied by Boeing in case of the MAX can not be the intention of a normal engineering process
obviously they simple used grandfathering rules to avoid the observance of modern aviation conditions

different centers of drag and centers of gravity would not be certifiably in an actual certification as far as I know

at the time the 737 was certified in the 1960 this condition was not part of the rulebook
so it was possible to move the engines in front of the wing now

this has nothing to do with a " ....normal engineering process to improve on existing design ..."

rather the opposite

That is not how grandfathering works.

Grandfathering means you don’t have to update old aspects that no longer meet current regulations if you are not changing them. Any changes to the aircraft you do make still have to meet current standards. Grandfathering is not some blank check where Boeing (or Airbus) can do whatever they want to their aircraft as long as it meets the regulations in place when the aircraft was first certified.
 
morrisond
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 2:59 pm

asdf wrote:
morrisond wrote:
If you think the MAX is aerodynamically unstable please provide evidence.
If it's the old moving the engines up and forward a little puts it out of balance and it's dangerous - you do realize that it is probably less of an effect than having the first 5 rows empty or half full?


the calculated weight difference of 2500 pounds (1200kg?) at the front of a plane should be the reason that a plane can not certified?
I doubt that

morrisond wrote:
Flight test showed the MAX is stable

evidence?
the open public knows about a correction value which has to be increased to a multiple from its initial number because of test flight results
this does not sound like a strength of colum case at all


I'm not even sure what you are trying to prove or what you mean by your statements.

You are not adding the weight of new engines to the front of the plane - you are moving an exisiting mass slightly heavier further forward.

Please read through the threads to understand the real reason MCAS was needed.

It went through 300 flights with the FAA and there are pilots reports all over the web - it would not have been certified if it was not stable or unsafe - they just missed the fact that MCAS was a really bad design if the AOA vanes failed.
 
Interested
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 3:07 pm

morrisond wrote:
asdf wrote:
morrisond wrote:
If you think the MAX is aerodynamically unstable please provide evidence.
If it's the old moving the engines up and forward a little puts it out of balance and it's dangerous - you do realize that it is probably less of an effect than having the first 5 rows empty or half full?


the calculated weight difference of 2500 pounds (1200kg?) at the front of a plane should be the reason that a plane can not certified?
I doubt that

morrisond wrote:
Flight test showed the MAX is stable

evidence?
the open public knows about a correction value which has to be increased to a multiple from its initial number because of test flight results
this does not sound like a strength of colum case at all


I'm not even sure what you are trying to prove or what you mean by your statements.

You are not adding the weight of new engines to the front of the plane - you are moving an exisiting mass slightly heavier further forward.

Please read through the threads to understand the real reason MCAS was needed.

It went through 300 flights with the FAA and there are pilots reports all over the web - it would not have been certified if it was not stable or unsafe - they just missed the fact that MCAS was a really bad design if the AOA vanes failed.


You've not answered his question. Why did they change nose down from 0.6 to 2.5?

If all was good with initial design?
 
asdf
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 3:15 pm

Polot wrote:
That is not how grandfathering works.
Grandfathering means you don’t have to update old aspects that no longer meet current regulations if you are not changing them. Any changes to the aircraft you do make still have to meet current standards. Grandfathering is not some blank check where Boeing (or Airbus) can do whatever they want to their aircraft as long as it meets the regulations in place when the aircraft was first certified.



the 737 MAX does not meet stability requirements by FAR
those requirements have been posted a few times in this thread and obviously the MAX don't meet them

the MAX could be certified because those requirements in 1965 didn't exist in FAR those days
so they do not apply on the 737 today

thats how grandfathering works
 
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zeke
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 3:19 pm

asdf wrote:
the 737 MAX does not meet stability requirements by FAR those requirements have been posted a few times in this thread and obviously the MAX don't meet them

the MAX could be certified because those requirements in 1965 didn't exist in FAR those days
so they do not apply on the 737 today

thats how grandfathering works


What you are posting simply is not true. Any changes to the MAX from the NG is certified to FAR standards at the date when the FAA accepted their application.

It would meet the current stability requirements.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
asdf
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 4:55 pm

zeke wrote:
asdf wrote:
the 737 MAX does not meet stability requirements by FAR those requirements have been posted a few times in this thread and obviously the MAX don't meet them

the MAX could be certified because those requirements in 1965 didn't exist in FAR those days
so they do not apply on the 737 today

thats how grandfathering works


What you are posting simply is not true. Any changes to the MAX from the NG is certified to FAR standards at the date when the FAA accepted their application.

It would meet the current stability requirements.


Well
You are a lot more experienced in that things than me

I Will Go find and Check back that Regulations and try to Unterstand Why it Sounds like that but doesnt mean it
 
Interested
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 5:12 pm

Interested wrote:
morrisond wrote:
asdf wrote:

the calculated weight difference of 2500 pounds (1200kg?) at the front of a plane should be the reason that a plane can not certified?
I doubt that


evidence?
the open public knows about a correction value which has to be increased to a multiple from its initial number because of test flight results
this does not sound like a strength of colum case at all


I'm not even sure what you are trying to prove or what you mean by your statements.

You are not adding the weight of new engines to the front of the plane - you are moving an exisiting mass slightly heavier further forward.

Please read through the threads to understand the real reason MCAS was needed.

It went through 300 flights with the FAA and there are pilots reports all over the web - it would not have been certified if it was not stable or unsafe - they just missed the fact that MCAS was a really bad design if the AOA vanes failed.


You've not answered his question. Why did they change nose down from 0.6 to 2.5?

If all was good with initial design?


It's amazing the amount of time you ask questions on here and don't get replies.

It's like posters have to go and get the official reply from someone at Boeing?
 
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zeke
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 5:27 pm

asdf wrote:
Well
You are a lot more experienced in that things than me

I Will Go find and Check back that Regulations and try to Unterstand Why it Sounds like that but doesnt mean it


The information is available for anyone to see in the 737 TCDS

https://rgl.faa.gov/Regulatory_and_Guid ... enDocument

“CERTIFICATION BASIS:
Date of application: June 30, 2012 (737-8), and June 12, 2013 (737-9)
The certification basis for the 737-8 and 737-9 airplanes is Title 14, Code of Federal Regulations (14 CFR) part 25 as amended by Amendments 25-0 through 25-137, plus amendment 25-141 with exceptions permitted by 14 CFR 21.101.

Now if you look here https://www.faa.gov/aircraft/air_cert/d ... nssd_list/

You will see 25-137 is dated 7/2/2013, and 25-141 is dated 3/13/2015.

That means the changes to 737-8/9 is certified against the FAR 25 amendments up to 7/2/2013 with the addition of the 3/13/2015 changes.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
PlanesNTrains
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 6:17 pm

asdf wrote:
zeke wrote:
asdf wrote:
the 737 MAX does not meet stability requirements by FAR those requirements have been posted a few times in this thread and obviously the MAX don't meet them

the MAX could be certified because those requirements in 1965 didn't exist in FAR those days
so they do not apply on the 737 today

thats how grandfathering works


What you are posting simply is not true. Any changes to the MAX from the NG is certified to FAR standards at the date when the FAA accepted their application.

It would meet the current stability requirements.


Well
You are a lot more experienced in that things than me

I Will Go find and Check back that Regulations and try to Unterstand Why it Sounds like that but doesnt mean it


You’ve already stated it as fact. What’s to check?
-Dave


MAX’d out on MAX threads. If you are starting a thread, and it’s about the MAX - stop. There’s already a thread that covers it.
 
WPIAeroGuy
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 6:31 pm

PlanesNTrains wrote:
asdf wrote:
zeke wrote:

What you are posting simply is not true. Any changes to the MAX from the NG is certified to FAR standards at the date when the FAA accepted their application.

It would meet the current stability requirements.


Well
You are a lot more experienced in that things than me

I Will Go find and Check back that Regulations and try to Unterstand Why it Sounds like that but doesnt mean it


You’ve already stated it as fact. What’s to check?


:thumbsup:
-WPIAeroGuy
 
smartplane
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 8:42 pm

zeke wrote:
asdf wrote:
the 737 MAX does not meet stability requirements by FAR those requirements have been posted a few times in this thread and obviously the MAX don't meet them

the MAX could be certified because those requirements in 1965 didn't exist in FAR those days
so they do not apply on the 737 today

thats how grandfathering works


Any changes to the MAX from the NG is certified to FAR standards at the date when the FAA accepted their application.

But the loophole is in the definition of 'change'. As a result of precedent and/or grandfathering, there is provision to accept structural scaling, and material substitution within agreed parameters. And like all precedents, it's been pushed to include flight characteristics, and systems, and............... This is one of the first discussions OEM's have with the authorities when contemplating new models.

Was MCAS a change, or sold as STS enhanced?

Were some changes deemed not to be, on the basis the 737 story would cease with the MAX?
 
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zeke
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 8:55 pm

smartplane wrote:
But the loophole is in the definition of 'change'. As a result of precedent and/or grandfathering, there is provision to accept structural scaling, and material substitution within agreed parameters. And like all precedents, it's been pushed to include flight characteristics, and systems, and............... This is one of the first discussions OEM's have with the authorities when contemplating new models.

Was MCAS a change, or sold as STS enhanced?

Were some changes deemed not to be, on the basis the 737 story would cease with the MAX?


You need to go away and read FAR 21.101. The term change is not a loophole.

MCAS was a change.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
PStechPaul
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 9:21 pm

Since the AoA sensors are so important, and also vulnerable to bird strike, why not...

1. Add a means (camera?) for visual inspection of the vanes (and other external surfaces) by the pilots

2. Add FOD sensors (microphones?) to determine if there has been a bird strike or similar occurrence

3. Install some sort of protective cage forward of the sensor to deflect or minimize damage from foreign object collisions
 
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zeke
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 9:26 pm

Because if you have heard that thud of a bird strike on an AOA probe just outside the cockpit, you won’t have time to look at a camera. As for putting a cage around it. A similar suggestion came from the Irish CAA, they suggested to install the probe inside the cabin where it would be even more protected. :roll:
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
OldAeroGuy
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 9:34 pm

zeke wrote:
smartplane wrote:
But the loophole is in the definition of 'change'. As a result of precedent and/or grandfathering, there is provision to accept structural scaling, and material substitution within agreed parameters. And like all precedents, it's been pushed to include flight characteristics, and systems, and............... This is one of the first discussions OEM's have with the authorities when contemplating new models.

Was MCAS a change, or sold as STS enhanced?

Were some changes deemed not to be, on the basis the 737 story would cease with the MAX?


You need to go away and read FAR 21.101. The term change is not a loophole.

MCAS was a change.


:thumbsup: :thumbsup: :thumbsup:

As was the Leap engine installation. Its incorporation opened up the whole flight test process with an attendant step up to the new amendment level.

Compliance with stall handling characteristic requirements led to MCAS.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
OldAeroGuy
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 9:38 pm

zeke wrote:
Because if you have heard that thud of a bird strike on an AOA probe just outside the cockpit, you won’t have time to look at a camera. As for putting a cage around it. A similar suggestion came from the Irish CAA, they suggested to install the probe inside the cabin where it would be even more protected. :roll:


Careful. ;)
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
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zeke
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Re: Ethiopian Airlines 737MAX crashes enroute to Nairobi

Fri Apr 19, 2019 9:48 pm

OldAeroGuy wrote:

Careful. ;)


They also suggested to install the camera on a selfie stick as the bird might hit the cage, probe, and skin mounted camera. ;)

They all agreed the last thing that would go through the birds mind was a 737.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News

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