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dakota123
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Sun Nov 11, 2018 1:58 am

hivue wrote:
moa999 wrote:
And in my mind this comes back to the fact that this system seemingly can't be switched off, it will seemingly reactivate every 10secs if the data is still erroneous.


But it can be switched off -- with stabilizer trim cutoff switches located to hand on the pedestal. The fact that Boeing quickly issued a bulletin and the FAA issued an emergency AD reminding flight crews of that strongly suggests that they know that the accident crew failed, for whatever reason, to follow the procedure.


Indeed, according to the AD “all” one has to do is grab the trim wheel to stop the trimming in its tracks. (“All” in quotes, because we weren’t there.)
“And If I claim to be a wise man, well surely it means that I don’t know”
 
maint123
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Sun Nov 11, 2018 3:12 am

Most importantly -
Why replacing the AOA sensors did not cure the problem and led to a crash ?
Why Boeing put pilots in simulators after the crash and AOA issue emergence and then issued the advisory ?
Why have new systems in place where in a emergency situation , the pilots are still being second guessed by the automation in MANUAL mode and have to continuously monitor the automation ( Unable to switch on auto pilot , auto trimming ) ?
And why is Boeing supplying defective planes to its customers? Are the quality checks slipping ?
 
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Starlionblue
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Sun Nov 11, 2018 3:26 am

Nomadd wrote:
asdf wrote:
Redundancy was and is the credo of aviation.

The recent cases with the AOA -Sensors and the Pitot-Tubes show that the redundancy can also become a curse.

From a certain number of identical sensors, the reliability is no longer higher because the processing of the data of these many sensors is becoming increasingly complex.

In the case of sensors relevant to flight, in the case of unclear or deviating sensor values, attempts should not be made to provide the pilots with the best possible data and thus contribute to an accident in the worst case, but the automation should step back from the control of the machine in a graduated form at the request of a pilot.

For the further control of the aircraft, however, the pilot must then have alternative data on attitude, altitude and speed available.

A GPS-based emergency control unit could display the current altitude, the altitude change, the speed and the speed change as well as the direction of flight at a non-interfering position in front of each pilot independently of each other and independent of the actual flight sensors.

GPS is not 100% reliable and at least as far as the altitude is concerned, it is not accurate enough to fly with it. But it is by far enough as a handy tool for a pilot to stabilize a plane in unclear attitude and height and to start the troubleshooting of the actual problem.

GPS can do quite a bit better. Three antenna systems can give you very accurate point, yaw, pitch. roll, and rates of, and a much better altitude than given credit for with high quality units. The data errors from the sats that cause most of the inaccuracy re irrelevant because all three antennas are getting the same data, so errors cancel out. They don't need absolute accuracy. Only position relative to each other.



The laser gyros and accelerometers already on the aircraft already do a pretty flawless job at working out yaw, pitch, roll and acceleration. Much better than a GPS solution. And unlike pitot tubes, they're incredibly reliable, seeing as they are sealed, solid-state devices.

On the speed bit, again, GPS does not give you airspeed. Without some device to measure airflow, you cannot have an accurate airspeed indication. The wing does not care about ground speed.

We can already display the GPS information, by pressing pressing a couple of buttons on the FMS/MCDU. But it isn't very useful as a flying reference. Converting the data to some sort of pseudo-MFD has merit, but again, no airspeed...

To be clear, I'm all for innovations that could improve safety, but unless you can get a GPS unit to magically generate an airspeed figure, I don't see how a purely GPS based solution can be used for backup airspeed information.


LDRA wrote:
Sounds like 73m flight control design is an incoherent mess...

A single point of failure (one failed AOA probe out of two AOA probes) is allowed to propagate failure to system with pitch authority. There is no fault accommodation it seems.
There is AOA disagree warning, but it appears there is no actual proper safety rated correlation check between two AOA channels. In that case single AOA failure causing pitch issue is not even the biggest problem. The single AOA probe failure can become undetected and hence latent failure. When the second AOA probe fails, correlation check (if present) between AOA probes may not catch the second failure. Now you have an undetectable total AOA sensing system failure, no opportunity to accommodate fault!


My gut feel is that you can't keep adding stuff on to a 50 year old design without running into issues.

scbriml wrote:
ikramerica wrote:
In AF and this crash it seems as if the pilots are fighting against deeper level automation that they weren’t quite aware of.


While we don't yet know what happened with the Lion crash, let's be clear about AF447 - all those people died because the crew did not follow SOP, totally threw CRM out the window and displayed a shocking lack of basic airmanship . A situation that is commonplace around the World on an almost daily basis and is completely recoverable became a shocking disaster.


:checkmark: :checkmark: :checkmark:
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
airtechy
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Sun Nov 11, 2018 3:42 am

zeke wrote:
More the point how do you stop them if you see them moving ?


I would certainly hope that the motor driving the trim wheels could be over ridden by grabbing the wheels. Even if the motor could not be stopped, somewhere in the drive chain there should be a slip clutch to limit it's authority.

Jim
 
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DeltaMD90
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Sun Nov 11, 2018 4:23 am

airtechy wrote:
zeke wrote:
More the point how do you stop them if you see them moving ?


I would certainly hope that the motor driving the trim wheels could be over ridden by grabbing the wheels. Even if the motor could not be stopped, somewhere in the drive chain there should be a slip clutch to limit it's authority.

Jim

If the MAX trim wheels are anything like the 737-800s, then you can absolutely grab and stop them. They do spin super fast though, if the handles are out and it spins and hits a finger, it can draw blood (seen this happen lol.) I've messed with the handles once in a sim and the autopilot spun it suddenly and ouch that hurt (to be fair I was being an idiot)

So yes, they can be stopped, and yes they are super noticeable, but in an emergency situation who knows what they might've not noticed. There are switches that can easy disconnect the system too. The last step on our runway trim checklist was to just grasp and hold the wheel

And no, despite my screen name, I'm not a Delta pilot, I'm not quoting Delta 737 procedures in case anyone is wondering
 
spacecadet
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Sun Nov 11, 2018 5:12 am

moa999 wrote:
And in my mind this comes back to the fact that this system seemingly can't be switched off, it will seemingly reactivate every 10secs if the data is still erroneous.

Did the pilots think they had dealt with this issue and move onto other tasks/ alerts, only to get caught out again.


Well, I'm replying to you but this could actually apply to about half the responses since my last one. The thing is, the pilots were trained to fly this aircraft. If they thought they had dealt with the situation and moved on, that can only be pilot error, inadequate training and/or inadequate documentation on the part of Lion Air. It's not a problem with the aircraft in that case.

I recognize that there are man/machine interface issues that come up with any kind of automation in an airplane. But this particular issue is a pretty simple thing. Either the problem is fixed permanently by doing something in the cockpit or it's not and you need to keep compensating for it until you land. It's not normal or acceptable for the pilots to not know which type of problem it is (between those two options) and/or to not have documentation that properly explains what to do in this situation.

Given that the AOA protection is a pretty major difference from earlier models of the 737, this would be something the pilots should have been trained on specifically. Whether or not they were I'm sure will be part of the investigation, as will the Lion Air manuals and checklists.

Lots of people keep bringing up potential changes to the aircraft systems that should be made to avoid this type of accident; it's really not a question of that. Right now, at least, it seems to be about the crew doing what they're supposed to do. It's not necessarily their fault - like I said, it could be a training or documentation issue too - but there are two pilots sitting up there in the front of that airplane for a reason.
I'm tired of being a wanna-be league bowler. I wanna be a league bowler!
 
flightless
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Sun Nov 11, 2018 5:59 am

OK, I'm not a pilot, and I may be extremely off base here, but...

The automatic pitch trim is there for a reason. It does what it does to keep the plane from stalling. If it starts spinning the trim wheels to pitch the nose down, it's probably because the plane is getting into a stall condition, and it's going to help the pilots keep the plane out of a stall.

If the system was so bad that it was normally wrong, the default would be to turn it off. It's not normally wrong.

If it starts operating, and you KNOW DAMN WELL that it's wrong, then you immediately grab the wheel, pull back on the yoke, and flip the switch to disable the system.

If it's a confused situation, and the airplane is telling lies about airspeed, and the pilots aren't completely sure what part of the envelope they're operating in, and the auto pitch starts trimming down, I think it wouldn't be completely illogical for the pilots to at least initially believe it was operating correctly. I mean, aren't pilots drilled to "trust your instruments"?

If the pilots hesitated to override the system in this case, I don't think that would be unexpected. It may have taken some time before they got to the point of "hang on, that's not right" - and by that time, it may well have been too late.
 
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Finn350
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Sun Nov 11, 2018 7:18 am

spacecadet wrote:
Given that the AOA protection is a pretty major difference from earlier models of the 737, this would be something the pilots should have been trained on specifically. Whether or not they were I'm sure will be part of the investigation, as will the Lion Air manuals and checklists.

Lots of people keep bringing up potential changes to the aircraft systems that should be made to avoid this type of accident; it's really not a question of that. Right now, at least, it seems to be about the crew doing what they're supposed to do. It's not necessarily their fault - like I said, it could be a training or documentation issue too - but there are two pilots sitting up there in the front of that airplane for a reason.


Yes, the AOA protection is something the pilots should have been trained on. Based on the information we now have, it is likely that the pilots didn't recognize that they should have done Runaway Stabilizer Non-Normal Checklist (NNC).

Based on the fact that Boeing has now issued a Bulletin to amend Flight Crew Operations Manual (FCOM) for "Uncommanded Nose Down Stabilizer Trim Due to Erroneuous Angle of Attack (AOA) During Manual Flight Only", the FCOM or conversion training didn't adequately address this issue before the accident.

Most likely Boeing didn't even realize the dire consequences of the AOA failure effects during the 737MAX development, and I would be surprised if there were not aircraft system changes related to the issue.
 
packsonflight
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Sun Nov 11, 2018 10:35 am

It looks like Boeing is changing the system on the MAX, but not changing the training because the aircraft is sold on the merits it has the same the same pilot rating as the NG and both types can be flown by the same pilots with the same training
 
Dogbreath
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Sun Nov 11, 2018 10:41 am

maint123 wrote:
Most importantly -
Why replacing the AOA sensors did not cure the problem and led to a crash ?
Why Boeing put pilots in simulators after the crash and AOA issue emergence and then issued the advisory ?
Why have new systems in place where in a emergency situation , the pilots are still being second guessed by the automation in MANUAL mode and have to continuously monitor the automation ( Unable to switch on auto pilot , auto trimming ) ?
And why is Boeing supplying defective planes to its customers? Are the quality checks slipping ?


Why replacing the AOA sensors did not cure the problem and led to a crash?
Whaaaaat! We do not yet know the 'exact' circumstances and reasons for the crash. Last time I checked the investigation is still in progress and there has been no official report issued at this time to confirm ‘exactly’ what happened. The CVR is still yet to be found providing even more data for the investigation team. You’ll be pleased to know that A.net and the media are not a part of the official investigation team. A crash is usually the result of a series of events (not just one isolated event). We don’t yet know if the replacement of the Alpha Vane/s is relevant or not.

Why Boeing put pilots in simulators after the crash and AOA issue emergence and then issued the advisory?
Er why not! Surely as the manufacturer of the 737MAX, they will be continually testing and checking their product, especially in a time like this. Please correct me if I’m wrong but the Boeing Bulletin does not amend any procedures. It simply provides background information to certain systems and reminds flight crew to follow the QRH.

Why have new systems in place where in a emergency situation , the pilots are still being second guessed by the automation in MANUAL mode and have to continuously monitor the automation ( Unable to switch on auto pilot , auto trimming )?
Geez don’t get onboard any Airbus aircraft, or any new airplane designed in the past decade then! It may be that the requirements for airplane stability augmentation is a requirement to meet FAA Certification standards. For that reason STS is an augmentation system for the 737NG and 737MAX. The 737MAX also has MCAS. By the way STS and MCAS can always be disabled by selecting the STAB TRIM CUTOUT switches to OFF. STS and MCAS can also be overridden by manually controlling the trim wheel. Not an easy thing to do, but only used as a backup if the Cutout switches doesn’t stop the runaway trim.
Also, as an Airline Pilot you are continually monitoring the automation of the airplane. I was taught by a very wise Air Force Instructor that automation is great, but don’t trust it. Always know what the automation should be doing for you, and if the outcome is any different then do something about it. I’ve seen so many young pilots today that give 100% trust to automation, and it’s a hard sell to tell them otherwise.


And why is Boeing supplying defective planes to its customers? Are the quality checks slipping?
What proof are you offering to make this outrageous claim? Do you have the official Accident Report stating this as fact? I'm guessing not, so my advice (take it or leave it) is it might be worth waiting until then before making this silly accusation.
Truth, Honour, Loyalty
 
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PixelFlight
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Sun Nov 11, 2018 1:14 pm

asdf wrote:
raising the numbers of sensors is not the solution
if there is a reason why three sensors can fail at the same time, then theres is no reason why not even five sensors could fail
and it doesnt help if you have a failure in a common part of the datastream and there always is one where the redundanz ends

it needs to be a complete other system to keep the pilots shure to thrust on the data and GPS could be one


Exactly: redundancy and arbitration can't solve common mode failure. This is why aircraft will someday use different sensors and data merging/filtering with predictors.The Kalman filter is one of the well know simplest example of that kind of principle, but there is many others more appropriate for an aircraft. Ironically the Kalman filter was designed a half century ago to flight in space but is still not used to flight aircraft...
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
michi
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Sun Nov 11, 2018 1:33 pm

PixelFlight wrote:
... Ironically the Kalman filter was designed a half century ago to flight in space but is still not used to flight aircraft...


The Kalman filter is used for position computation. It is used to combine the IRS with the GPS position.

IRS position gives you a very accurate short term position. It also recognised small position changes. If I had an IRS unit on my desk and would move it an inch or a fraction of it, the IRS would notice the change.
On the long term, when I would leave the IRS on my desk for hours, the output position likely would have changed, as the IRS gyros will drift a bit.

GPS position gives you a very accurate long term position stability. If I leave a GPS receiver on my desk for hours, the output position will be the same. A GPS receiver however will not notice a small move. It still thinks that it is at the same position than before.

So you have 1 system which is very accurate for short term use and 1 system that gives you a good position on the long run. So you combine these 2 systems with a Kalman filter and voila, you have a position computation that is far better than the output of each system by itself. This position is called GPIRS position (there might be different names for this depending on the manufacturer).

So Kalman filters are used already in aviation.
 
kengo
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Sun Nov 11, 2018 1:39 pm

Dogbreath wrote:
maint123 wrote:
Most importantly -
Why replacing the AOA sensors did not cure the problem and led to a crash ?
Why Boeing put pilots in simulators after the crash and AOA issue emergence and then issued the advisory ?
Why have new systems in place where in a emergency situation , the pilots are still being second guessed by the automation in MANUAL mode and have to continuously monitor the automation ( Unable to switch on auto pilot , auto trimming ) ?
And why is Boeing supplying defective planes to its customers? Are the quality checks slipping ?


Why replacing the AOA sensors did not cure the problem and led to a crash?
Whaaaaat! We do not yet know the 'exact' circumstances and reasons for the crash. Last time I checked the investigation is still in progress and there has been no official report issued at this time to confirm ‘exactly’ what happened. The CVR is still yet to be found providing even more data for the investigation team. You’ll be pleased to know that A.net and the media are not a part of the official investigation team. A crash is usually the result of a series of events (not just one isolated event). We don’t yet know if the replacement of the Alpha Vane/s is relevant or not.

Why Boeing put pilots in simulators after the crash and AOA issue emergence and then issued the advisory?
Er why not! Surely as the manufacturer of the 737MAX, they will be continually testing and checking their product, especially in a time like this. Please correct me if I’m wrong but the Boeing Bulletin does not amend any procedures. It simply provides background information to certain systems and reminds flight crew to follow the QRH.

Why have new systems in place where in a emergency situation , the pilots are still being second guessed by the automation in MANUAL mode and have to continuously monitor the automation ( Unable to switch on auto pilot , auto trimming )?
Geez don’t get onboard any Airbus aircraft, or any new airplane designed in the past decade then! It may be that the requirements for airplane stability augmentation is a requirement to meet FAA Certification standards. For that reason STS is an augmentation system for the 737NG and 737MAX. The 737MAX also has MCAS. By the way STS and MCAS can always be disabled by selecting the STAB TRIM CUTOUT switches to OFF. STS and MCAS can also be overridden by manually controlling the trim wheel. Not an easy thing to do, but only used as a backup if the Cutout switches doesn’t stop the runaway trim.
Also, as an Airline Pilot you are continually monitoring the automation of the airplane. I was taught by a very wise Air Force Instructor that automation is great, but don’t trust it. Always know what the automation should be doing for you, and if the outcome is any different then do something about it. I’ve seen so many young pilots today that give 100% trust to automation, and it’s a hard sell to tell them otherwise.


And why is Boeing supplying defective planes to its customers? Are the quality checks slipping?
What proof are you offering to make this outrageous claim? Do you have the official Accident Report stating this as fact? I'm guessing not, so my advice (take it or leave it) is it might be worth waiting until then before making this silly accusation.


Well said.
 
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PixelFlight
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Sun Nov 11, 2018 2:46 pm

asdf wrote:
Redundancy was and is the credo of aviation.

The recent cases with the AOA -Sensors and the Pitot-Tubes show that the redundancy can also become a curse.

From a certain number of identical sensors, the reliability is no longer higher because the processing of the data of these many sensors is becoming increasingly complex.

In the case of sensors relevant to flight, in the case of unclear or deviating sensor values, attempts should not be made to provide the pilots with the best possible data and thus contribute to an accident in the worst case, but the automation should step back from the control of the machine in a graduated form at the request of a pilot.


I highly disagree. Redundancy and arbitration must be avoided and replaced by data merging/filtering, predictors and probability. The automation vs pilot is an other debate: the data reliability is the key.

asdf wrote:
For the further control of the aircraft, however, the pilot must then have alternative data on attitude, altitude and speed available.

A GPS-based emergency control unit could display the current altitude, the altitude change, the speed and the speed change as well as the direction of flight at a non-interfering position in front of each pilot independently of each other and independent of the actual flight sensors.

GPS is not 100% reliable and at least as far as the altitude is concerned, it is not accurate enough to fly with it. But it is by far enough as a handy tool for a pilot to stabilize a plane in unclear attitude and height and to start the troubleshooting of the actual problem.


GPS sensor is just a simple antenna. The GPS computer make all the work and highly rely on data merging/filtering, predictor and probability. In fact the readout of a GPS is just the highest probability of position computed from a variable number of unreliable signals. This is exactly how the futures aircraft computers must be designed to overcome the actual limitations. No human brain can do in real time what a GPS computer do . Give up to the pilot is not an option.
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
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PixelFlight
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Sun Nov 11, 2018 2:54 pm

michi wrote:
PixelFlight wrote:
... Ironically the Kalman filter was designed a half century ago to flight in space but is still not used to flight aircraft...


The Kalman filter is used for position computation. It is used to combine the IRS with the GPS position.


You are right, I was writing my post too quickly. I wanted to say that Kalman filter is not used at the system level, and this is the problem. Multiple sources of data must be merger with a predictor to get higher reliability of the essentials variable required to flight. Simple arbitration as done yet must die.
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
LDRA
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Sun Nov 11, 2018 3:55 pm

PixelFlight wrote:
asdf wrote:
raising the numbers of sensors is not the solution
if there is a reason why three sensors can fail at the same time, then theres is no reason why not even five sensors could fail
and it doesnt help if you have a failure in a common part of the datastream and there always is one where the redundanz ends

it needs to be a complete other system to keep the pilots shure to thrust on the data and GPS could be one


Exactly: redundancy and arbitration can't solve common mode failure. This is why aircraft will someday use different sensors and data merging/filtering with predictors.The Kalman filter is one of the well know simplest example of that kind of principle, but there is many others more appropriate for an aircraft. Ironically the Kalman filter was designed a half century ago to flight in space but is still not used to flight aircraft...


Kalman filter and observer are widely used in flight control software, especially in range plausibility diagnostic of inputs
 
N212R
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Sun Nov 11, 2018 4:30 pm

Finn350 wrote:
spacecadet wrote:
Most likely Boeing didn't even realize the dire consequences of the AOA failure effects during the 737MAX development, and I would be surprised if there were not aircraft system changes related to the issue.


I'm not buying that supposition for a Renton minute. They understood the potential (knock-on) issues related to moving the CofG aft.
 
ikramerica
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Sun Nov 11, 2018 5:10 pm

packsonflight wrote:
It looks like Boeing is changing the system on the MAX, but not changing the training because the aircraft is sold on the merits it has the same the same pilot rating as the NG and both types can be flown by the same pilots with the same training

Not true.
Of all the things to worry about... the Wookie has no pants.
 
dragon6172
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Sun Nov 11, 2018 5:49 pm

From some other forums, a more detailed description of the system that is installed on the MAX that is probably the culprit
MCAS (Maneuvering Characteristics Augmentation System) is implemented on the 737 MAX to enhance pitch characteristics with flaps UP and at elevated angles of attack. The MCAS function commands nose down stabilizer to enhance pitch characteristics during steep turns with elevated load factors and during flaps up flight at airspeeds approaching stall. MCAS is activated without pilot input and only operates in manual, flaps up flight. The system is designed to allow the flight crew to use column trim switch or stabilizer aislestand cutout switches to override MCAS input. The function is commanded by the Flight Control computer using input data from sensors and other airplane systems.

The MCAS function becomes active when the airplane Angle of Attack exceeds a threshold based on airspeed and altitude. Stabilizer incremental commands are limited to 2.5 degrees and are provided at a rate of 0.27 degrees per second. The magnitude of the stabilizer input is lower at high Mach number and greater at low Mach numbers. The function is reset once angle of attack falls below the Angle of Attack threshold or if manual stabilizer commands are provided by the flight crew. If the original elevated AOA condition persists, the MCAS function commands another incremental stabilizer nose down command according to current aircraft Mach number at actuation.


Note in the description that the system can be overridden with control column trim switches or turned off with the cutout switches.

Also should be noted that the other forums I have seen this posted say that this system info was not included in FCOM or AFM
Phrogs Phorever
 
LDRA
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Sun Nov 11, 2018 6:48 pm

dragon6172 wrote:
From some other forums, a more detailed description of the system that is installed on the MAX that is probably the culprit
MCAS (Maneuvering Characteristics Augmentation System) is implemented on the 737 MAX to enhance pitch characteristics with flaps UP and at elevated angles of attack. The MCAS function commands nose down stabilizer to enhance pitch characteristics during steep turns with elevated load factors and during flaps up flight at airspeeds approaching stall. MCAS is activated without pilot input and only operates in manual, flaps up flight. The system is designed to allow the flight crew to use column trim switch or stabilizer aislestand cutout switches to override MCAS input. The function is commanded by the Flight Control computer using input data from sensors and other airplane systems.

The MCAS function becomes active when the airplane Angle of Attack exceeds a threshold based on airspeed and altitude. Stabilizer incremental commands are limited to 2.5 degrees and are provided at a rate of 0.27 degrees per second. The magnitude of the stabilizer input is lower at high Mach number and greater at low Mach numbers. The function is reset once angle of attack falls below the Angle of Attack threshold or if manual stabilizer commands are provided by the flight crew. If the original elevated AOA condition persists, the MCAS function commands another incremental stabilizer nose down command according to current aircraft Mach number at actuation.


Note in the description that the system can be overridden with control column trim switches or turned off with the cutout switches.

Also should be noted that the other forums I have seen this posted say that this system info was not included in FCOM or AFM


Good info!

Is there explicit indication in cockpit that MCAS is active or not. Based on description, MCAS can kick in and out, in and out...
 
dragon6172
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Sun Nov 11, 2018 6:53 pm

LDRA wrote:

Is there explicit indication in cockpit that MCAS is active or not. Based on description, MCAS can kick in and out, in and out...

It moves the horizontal stab trim, which means the trim wheels will be turning when MCAS commands changes.
Phrogs Phorever
 
LDRA
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Sun Nov 11, 2018 6:58 pm

dragon6172 wrote:
LDRA wrote:

Is there explicit indication in cockpit that MCAS is active or not. Based on description, MCAS can kick in and out, in and out...

It moves the horizontal stab trim, which means the trim wheels will be turning when MCAS commands changes.


Does trim wheel normally move around much when MCAS not active?
 
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PixelFlight
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Sun Nov 11, 2018 7:00 pm

LDRA wrote:
Kalman filter and observer are widely used in flight control software, especially in range plausibility diagnostic of inputs


Right. In fact there is probably a lot of subsystems inside an aircraft that use it internally. View that way, it's strange that the most critical data path at the system level don't use this design too.
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
o0OOO0oChris
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Sun Nov 11, 2018 7:47 pm

That leaked AA eMail to their 737 pilots on page 49 of the other forum is really interesting. A completely new max system designed to operate the trim uncommanded when it thinks the aircraft is approaching a stall is pretty significant. Not publishing any info of it anywhere is a very astonishing move by boeing.

Also it seems to be hard to diagnose this AOA error condition as the previous crew didn`t get it too, as they have only written up an UAS issue ad STS misbehaviour. So it looks like at least two crews where not able to detect the true cause of this upset.

So it may be that this new system pitched the trim down while the crew was busy dealing with the UAS-issue, stall warnings, stick shakers. As the plane was traveling at the upper end of the speed envelop, when the dive started the downtrim became even more of an issue with increasing airspeed giving the trim an even more pronounced pitchdown effect.

Due to their speed, it was probably to late to trim back. Looks like this jackscrew moves pretty slow:
https://www.youtube.com/watch?v=rxPa9A-k2xY
With the increasing speed in the dive, the rising pitchdown trim effect was probably larger than the slow uptrim-counteraction effect of the pilots?
 
dakota123
Posts: 241
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Sun Nov 11, 2018 8:11 pm

o0OOO0oChris wrote:
That leaked AA eMail to their 737 pilots on page 49 of the other forum is really interesting. A completely new max system designed to operate the trim uncommanded when it thinks the aircraft is approaching a stall is pretty significant. Not publishing any info of it anywhere is a very astonishing move by boeing.

Also it seems to be hard to diagnose this AOA error condition as the previous crew didn`t get it too, as they have only written up an UAS issue ad STS misbehaviour. So it looks like at least two crews where not able to detect the true cause of this upset.

So it may be that this new system pitched the trim down while the crew was busy dealing with the UAS-issue, stall warnings, stick shakers. As the plane was traveling at the upper end of the speed envelop, when the dive started the downtrim became even more of an issue with increasing airspeed giving the trim an even more pronounced pitchdown effect.

Due to their speed, it was probably to late to trim back. Looks like this jackscrew moves pretty slow:
https://www.youtube.com/watch?v=rxPa9A-k2xY
With the increasing speed in the dive, the rising pitchdown trim effect was probably larger than the slow uptrim-counteraction effect of the pilots?


There’s no way that is true. Either pilots go through differences training, or they are trained from scratch.

This looked very much like STS misbehavior (which was noted, if the squawk sheet making the rounds is correct), or was easily confused as such. In any case, it was “runaway trim”, whatever the cause. When you have runaway trim, you stop the behavior first and ask questions second.

Somebody had an idea it was an AOA system error; a sensor is reported to have been replaced two? flights prior.

What seems certain is that they were dealing with a challenging situation.
“And If I claim to be a wise man, well surely it means that I don’t know”
 
ikramerica
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Sun Nov 11, 2018 9:01 pm

PixelFlight wrote:
LDRA wrote:
Kalman filter and observer are widely used in flight control software, especially in range plausibility diagnostic of inputs


Right. In fact there is probably a lot of subsystems inside an aircraft that use it internally. View that way, it's strange that the most critical data path at the system level don't use this design too.

It’s because they aren’t approaching the control system from a clean sheet perspective.

Failed thinking leading to crashes: how do I adapt this 50/100 year old paradigm to automation

Proper design path: we have smart phones with 1 billion times the processing power and 2000 times the memory compared to the Apollo moon missions. How can we design a fool proof aircraft control system that makes flying easier and safer without confusing pilots into crashing their aircraft. What old paradigms must we THROW OUT to make it so?

Airbus threw out the yoke. Everyone replaced the flight engineer and navigator with computers that communicate with external sources. But what seems to be a weak link is the way flight control data is collected and processed.

As for using error correcting algorithms to make up for faulty sensors, I think that misses the point. All that is really necessary is to express confidence that one set of readings is correct. If that set is correct, the systems will use that set and notify the pilots that the other set is faulty. If no sets can be verified correct (complete failure due to flying through ash or something like that) then the systems would know that too, alert the pilots and allow them to disable the system and fly manually and declare an emergency. Further, the system could continually monitor the sets of data and if the issue clears itself or is cleared through checklists, it could regain confidence in a data set and resume an emergency level of function.

If it’s true that Lion wasn’t aware that the aircraft systems had lost situational awareness on the previous flight because the flight systems never alerted anyone who could investigate it, that’s a problem that Boeing is directly responsible for. What’s the point of redundancy if A: it doesn’t work and B: no one is made aware that it didn’t work?
Of all the things to worry about... the Wookie has no pants.
 
maint123
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Sun Nov 11, 2018 11:11 pm

Dogbreath wrote:
maint123 wrote:
Most importantly -
Why replacing the AOA sensors did not cure the problem and led to a crash ?
Why Boeing put pilots in simulators after the crash and AOA issue emergence and then issued the advisory ?
Why have new systems in place where in a emergency situation , the pilots are still being second guessed by the automation in MANUAL mode and have to continuously monitor the automation ( Unable to switch on auto pilot , auto trimming ) ?
And why is Boeing supplying defective planes to its customers? Are the quality checks slipping ?


Why replacing the AOA sensors did not cure the problem and led to a crash?
Whaaaaat! We do not yet know the 'exact' circumstances and reasons for the crash. Last time I checked the investigation is still in progress and there has been no official report issued at this time to confirm ‘exactly’ what happened. The CVR is still yet to be found providing even more data for the investigation team. You’ll be pleased to know that A.net and the media are not a part of the official investigation team. A crash is usually the result of a series of events (not just one isolated event). We don’t yet know if the replacement of the Alpha Vane/s is relevant or not.

Why Boeing put pilots in simulators after the crash and AOA issue emergence and then issued the advisory?
Er why not! Surely as the manufacturer of the 737MAX, they will be continually testing and checking their product, especially in a time like this. Please correct me if I’m wrong but the Boeing Bulletin does not amend any procedures. It simply provides background information to certain systems and reminds flight crew to follow the QRH.

Why have new systems in place where in a emergency situation , the pilots are still being second guessed by the automation in MANUAL mode and have to continuously monitor the automation ( Unable to switch on auto pilot , auto trimming )?
Geez don’t get onboard any Airbus aircraft, or any new airplane designed in the past decade then! It may be that the requirements for airplane stability augmentation is a requirement to meet FAA Certification standards. For that reason STS is an augmentation system for the 737NG and 737MAX. The 737MAX also has MCAS. By the way STS and MCAS can always be disabled by selecting the STAB TRIM CUTOUT switches to OFF. STS and MCAS can also be overridden by manually controlling the trim wheel. Not an easy thing to do, but only used as a backup if the Cutout switches doesn’t stop the runaway trim.
Also, as an Airline Pilot you are continually monitoring the automation of the airplane. I was taught by a very wise Air Force Instructor that automation is great, but don’t trust it. Always know what the automation should be doing for you, and if the outcome is any different then do something about it. I’ve seen so many young pilots today that give 100% trust to automation, and it’s a hard sell to tell them otherwise.


And why is Boeing supplying defective planes to its customers? Are the quality checks slipping?
What proof are you offering to make this outrageous claim? Do you have the official Accident Report stating this as fact? I'm guessing not, so my advice (take it or leave it) is it might be worth waiting until then before making this silly accusation.

Agreed that ultimately a official report will give us the reason for the crash but quite a few people here are happily blaming the pilots for not responding properly , in absence of your aforementioned evidence. I am similarly blaming the plane. My AOA point was that if the AOA was a contributory factor, mainly 3 areas have to be checked. The sensor, cabling or software logic. If AOA sensor was replaced and still the problem continued, then the cabling or software gave the erroneous inputs to auto trim. Which is a total blunder on Boeing's part. Can't blame the crew or maint team on a brand new plane.
Boeing has amended , and asked that their advisory be made part of airlines documentation within 3 days. Again a blatant oversight on Boeing's part.
Your 3rd reply is meaningless as this advisory applies ONLY to MAX planes not NG. Points to changes made in MAX flying procedures which were not incorporated in the training.
Lastly the lack of properly documented changes in flying procedures and introducing unproven changes in automation during manual flight, all point towards carelessness on Boeing's part. And no amount of white washing will hide that.
And if my comments upset you , just go through the complete thread where people here are gladly blaming the lion air maintenance crew and/or pilots from page 1 , in absence of any official evidence.
 
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PixelFlight
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Sun Nov 11, 2018 11:35 pm

ikramerica wrote:
Proper design path: we have smart phones with 1 billion times the processing power and 2000 times the memory compared to the Apollo moon missions. How can we design a fool proof aircraft control system that makes flying easier and safer without confusing pilots into crashing their aircraft. What old paradigms must we THROW OUT to make it so?

Arbitration (between a redundancy set of sensors).

ikramerica wrote:
But what seems to be a weak link is the way flight control data is collected and processed.

Agree.

ikramerica wrote:
As for using error correcting algorithms to make up for faulty sensors, I think that misses the point. All that is really necessary is to express confidence that one set of readings is correct. If that set is correct, the systems will use that set and notify the pilots that the other set is faulty. If no sets can be verified correct (complete failure due to flying through ash or something like that) then the systems would know that too, alert the pilots and allow them to disable the system and fly manually and declare an emergency. Further, the system could continually monitor the sets of data and if the issue clears itself or is cleared through checklists, it could regain confidence in a data set and resume an emergency level of function.

This how this work now and this is based on the arbitration principle: elect the sensors that seem to work well. This is obsolete and this is a weak point that make aircraft dangerous. Unreliable sensors must use the appropriate algorithm to produce the best possible result and this is only possible by processing all of them together with a predictor.

The values produced by the sensors are not just for automation as pilot need them in many cases to flight safely.
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
benjjk
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Mon Nov 12, 2018 1:19 am

wingman wrote:
I want to ask this question again and sorry for dumbing down the conversation..but whatever the technical errors in the pitot tubes or trim system, it seems like the pilots should've been able to hand fly the plane back to the field if they had gone full manual. Without understanding much of what most posts are saying, isn't this what the prior pilot did, and possibly the three before him? A lot of that is unknown right now but it feels like in the final flight the pilots may have been trying to figure out a technical problem and they ran out of room to save themselves by just going manual. I keep thinking that with a recurring problem in prior flights noted in the logs and maintenance documents they should have been anticipating (to some degree) that a similar problem would come up again. I'm not casting blame on the pilots and clearly something was wrong with the instruments or software, but it'll be very interesting, and terrible of course, to listen to the CVR matched against the technical parameters.

All of this made me go back and watch some really great You Tube videos and this is one of my favorites..visually and with very simple explanations how one hand flies a modern jetliner out of very bad stall or AoA situations. I think this is from the SIA Training Center. Not sure if it has any relevance whatsoever to Lion Air but still incredible to see how counter intuitive the solution is to a nose down stall or inverting corkscrew. At one point the Captain makes the comment about glider flying and how that gives pilots valuable experience in recovery situations. It reminded me of Sully's comments of course.
http://www.youtube.com/watch?v=OasrxfOvPr8


Boeing said that this problem only occurs in manual flight, indicating that the pilots were flying manually. So it is possible that the accident flight crew were already dealing with one mechanical issue, preventing them from using the autopilot, and then this second issue doomed it. Alternatively the trim issue may have appeared almost immediately after takeoff. In any case, automation is supposed to be used to relieve workload, and when troubleshooting a problem you need that relief as much as possible.

Interesting video too, but yes it's too early to assume this crew has a similar situation. Soon, no airline will be allowed to fly to the USA unless they have completed UPRT training which I think is a good move. EASA have not mandated the same, but I guess on an Airbus it is a lot harder to get into that situation in the first place...
 
7673mech
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Mon Nov 12, 2018 2:35 am

maint123 wrote:
Dogbreath wrote:
maint123 wrote:
Most importantly -
Why replacing the AOA sensors did not cure the problem and led to a crash ?
Why Boeing put pilots in simulators after the crash and AOA issue emergence and then issued the advisory ?
Why have new systems in place where in a emergency situation , the pilots are still being second guessed by the automation in MANUAL mode and have to continuously monitor the automation ( Unable to switch on auto pilot , auto trimming ) ?
And why is Boeing supplying defective planes to its customers? Are the quality checks slipping ?


Why replacing the AOA sensors did not cure the problem and led to a crash?
Whaaaaat! We do not yet know the 'exact' circumstances and reasons for the crash. Last time I checked the investigation is still in progress and there has been no official report issued at this time to confirm ‘exactly’ what happened. The CVR is still yet to be found providing even more data for the investigation team. You’ll be pleased to know that A.net and the media are not a part of the official investigation team. A crash is usually the result of a series of events (not just one isolated event). We don’t yet know if the replacement of the Alpha Vane/s is relevant or not.

Why Boeing put pilots in simulators after the crash and AOA issue emergence and then issued the advisory?
Er why not! Surely as the manufacturer of the 737MAX, they will be continually testing and checking their product, especially in a time like this. Please correct me if I’m wrong but the Boeing Bulletin does not amend any procedures. It simply provides background information to certain systems and reminds flight crew to follow the QRH.

Why have new systems in place where in a emergency situation , the pilots are still being second guessed by the automation in MANUAL mode and have to continuously monitor the automation ( Unable to switch on auto pilot , auto trimming )?
Geez don’t get onboard any Airbus aircraft, or any new airplane designed in the past decade then! It may be that the requirements for airplane stability augmentation is a requirement to meet FAA Certification standards. For that reason STS is an augmentation system for the 737NG and 737MAX. The 737MAX also has MCAS. By the way STS and MCAS can always be disabled by selecting the STAB TRIM CUTOUT switches to OFF. STS and MCAS can also be overridden by manually controlling the trim wheel. Not an easy thing to do, but only used as a backup if the Cutout switches doesn’t stop the runaway trim.
Also, as an Airline Pilot you are continually monitoring the automation of the airplane. I was taught by a very wise Air Force Instructor that automation is great, but don’t trust it. Always know what the automation should be doing for you, and if the outcome is any different then do something about it. I’ve seen so many young pilots today that give 100% trust to automation, and it’s a hard sell to tell them otherwise.


And why is Boeing supplying defective planes to its customers? Are the quality checks slipping?
What proof are you offering to make this outrageous claim? Do you have the official Accident Report stating this as fact? I'm guessing not, so my advice (take it or leave it) is it might be worth waiting until then before making this silly accusation.

Agreed that ultimately a official report will give us the reason for the crash but quite a few people here are happily blaming the pilots for not responding properly , in absence of your aforementioned evidence. I am similarly blaming the plane. My AOA point was that if the AOA was a contributory factor, mainly 3 areas have to be checked. The sensor, cabling or software logic. If AOA sensor was replaced and still the problem continued, then the cabling or software gave the erroneous inputs to auto trim. Which is a total blunder on Boeing's part. Can't blame the crew or maint team on a brand new plane.
Boeing has amended , and asked that their advisory be made part of airlines documentation within 3 days. Again a blatant oversight on Boeing's part.
Your 3rd reply is meaningless as this advisory applies ONLY to MAX planes not NG. Points to changes made in MAX flying procedures which were not incorporated in the training.
Lastly the lack of properly documented changes in flying procedures and introducing unproven changes in automation during manual flight, all point towards carelessness on Boeing's part. And no amount of white washing will hide that.
And if my comments upset you , just go through the complete thread where people here are gladly blaming the lion air maintenance crew and/or pilots from page 1 , in absence of any official evidence.


Let me start by saying I think there is too much speculation in this thread.

That said - was the AOA replaced correctly?
We don't know that.
So let's go after Boeing since they have the most $$$?
 
7673mech
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Mon Nov 12, 2018 2:37 am

Dogbreath wrote:
maint123 wrote:
Most importantly -
Why replacing the AOA sensors did not cure the problem and led to a crash ?
Why Boeing put pilots in simulators after the crash and AOA issue emergence and then issued the advisory ?
Why have new systems in place where in a emergency situation , the pilots are still being second guessed by the automation in MANUAL mode and have to continuously monitor the automation ( Unable to switch on auto pilot , auto trimming ) ?
And why is Boeing supplying defective planes to its customers? Are the quality checks slipping ?


Why replacing the AOA sensors did not cure the problem and led to a crash?
Whaaaaat! We do not yet know the 'exact' circumstances and reasons for the crash. Last time I checked the investigation is still in progress and there has been no official report issued at this time to confirm ‘exactly’ what happened. The CVR is still yet to be found providing even more data for the investigation team. You’ll be pleased to know that A.net and the media are not a part of the official investigation team. A crash is usually the result of a series of events (not just one isolated event). We don’t yet know if the replacement of the Alpha Vane/s is relevant or not.

Why Boeing put pilots in simulators after the crash and AOA issue emergence and then issued the advisory?
Er why not! Surely as the manufacturer of the 737MAX, they will be continually testing and checking their product, especially in a time like this. Please correct me if I’m wrong but the Boeing Bulletin does not amend any procedures. It simply provides background information to certain systems and reminds flight crew to follow the QRH.

Why have new systems in place where in a emergency situation , the pilots are still being second guessed by the automation in MANUAL mode and have to continuously monitor the automation ( Unable to switch on auto pilot , auto trimming )?
Geez don’t get onboard any Airbus aircraft, or any new airplane designed in the past decade then! It may be that the requirements for airplane stability augmentation is a requirement to meet FAA Certification standards. For that reason STS is an augmentation system for the 737NG and 737MAX. The 737MAX also has MCAS. By the way STS and MCAS can always be disabled by selecting the STAB TRIM CUTOUT switches to OFF. STS and MCAS can also be overridden by manually controlling the trim wheel. Not an easy thing to do, but only used as a backup if the Cutout switches doesn’t stop the runaway trim.
Also, as an Airline Pilot you are continually monitoring the automation of the airplane. I was taught by a very wise Air Force Instructor that automation is great, but don’t trust it. Always know what the automation should be doing for you, and if the outcome is any different then do something about it. I’ve seen so many young pilots today that give 100% trust to automation, and it’s a hard sell to tell them otherwise.


And why is Boeing supplying defective planes to its customers? Are the quality checks slipping?
What proof are you offering to make this outrageous claim? Do you have the official Accident Report stating this as fact? I'm guessing not, so my advice (take it or leave it) is it might be worth waiting until then before making this silly accusation.


Spot on.
 
747megatop
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Mon Nov 12, 2018 6:19 am

Is this the 1st incident where a brand new commercial jet crashed within a few weeks of entering service?
 
mandala499
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Mon Nov 12, 2018 6:55 am

Something we need to have a look at here:
https://leehamnews.com/2018/11/07/boein ... -accident/

Any such Automatic trim action which doesn’t makes sense has the feel of a runaway pitch trim which is a very common emergency simulator training scenario. In isolation, this should be easy to spot and the correct action (Cut out the trim as described below) could be taken in relative calmness. I’m inclined to think the JT610 crew had to handle a more difficult and stressing false Stall warning and recovery situation, which is the same between the 737NG and the 737 MAX.

The Stall warning and recovery functions are:

Above a preset AOA, a stall warning audio voice says: “Stall, Stall, Stall” and the Pilots control yoke on the side with the high AOA start shaking as an additional physical warning
If the AOA does not decrease after the triggered Stick Shaker but stays at a high angle, the system then creates a stronger control Yoke force through the Elevator Feel & Centering unit by applying a nose down stick force for the present Yoke position.
As an additional measure, the Flight Control Computer starts a stabilizer trim nose down movement using the Autopilot trim channel. The trim action lasts 10 seconds. The Pilot’s can counteract the trim by using their trim buttons, it overrides the Stall system trim.
If the AOA persists, the Pitch trim nose down will trigger again after a certain time lapse. If the PIlots have counter trimmed, the system waits 5 seconds until it repeats the trim nose down for 10 seconds


I tend to agree that they've got their hands full... If false AOA reading can trigger the STS nose down trim, wouldn't it also trigger the stick shaker, and the stick pusher function too? And to do that in unreliable airspeed (pitch n power)?

That said - was the AOA replaced correctly?

I wonder if the replaced AOA vane was broken at all... if it turns out that it was not broken, this accident investigation will become very very interesting...
When losing situational awareness, pray Cumulus Granitus isn't nearby !
 
zippy
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Mon Nov 12, 2018 6:55 am

747megatop wrote:
Is this the 1st incident where a brand new commercial jet crashed within a few weeks of entering service?


Nope, United wrecked a 727 about ten weeks after taking delivery.
 
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seahawk
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Mon Nov 12, 2018 7:16 am

The really strange thing is that MCAS does not turn off, when detecting sensor problems.
 
PlanesNTrains
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Mon Nov 12, 2018 7:17 am

747megatop wrote:
Is this the 1st incident where a brand new commercial jet crashed within a few weeks of entering service?


This question was asked earlier in the thread and multiple examples were shared of younger frames crashing. The GOL midair 737-800 was only 3 weeks old when it was lost.
-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.
 
MatthewDB
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Mon Nov 12, 2018 7:43 am

michi wrote:
PixelFlight wrote:
... Ironically the Kalman filter was designed a half century ago to flight in space but is still not used to flight aircraft...


The Kalman filter is used for position computation. It is used to combine the IRS with the GPS position.

IRS position gives you a very accurate short term position. It also recognised small position changes. If I had an IRS unit on my desk and would move it an inch or a fraction of it, the IRS would notice the change.
On the long term, when I would leave the IRS on my desk for hours, the output position likely would have changed, as the IRS gyros will drift a bit.

GPS position gives you a very accurate long term position stability. If I leave a GPS receiver on my desk for hours, the output position will be the same. A GPS receiver however will not notice a small move. It still thinks that it is at the same position than before.

So you have 1 system which is very accurate for short term use and 1 system that gives you a good position on the long run. So you combine these 2 systems with a Kalman filter and voila, you have a position computation that is far better than the output of each system by itself. This position is called GPIRS position (there might be different names for this depending on the manufacturer).

So Kalman filters are used already in aviation.


Even straight GPS uses Kalman filters. Any time there are more than 4 satellites visible, there are multiple solutions for position. Kalman filters are used to assign weighting to each satellite's input to the solution and arrive at the most accurate positioning for the available satellites.
 
patplan
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Mon Nov 12, 2018 8:43 am

7673mech wrote:
---snipped---
That said - was the AOA replaced correctly?
We don't know that.
So let's go after Boeing since they have the most $$$?


My question is re: the AOA sensor replacement. The Lion Air Management claimed that the AOA sensor was replace at DPS. So, I looked at the Lion Air PK-LQP flight history:

Denpasar International (DPS) - Soekarno Hatta Intl (CGK) JT43 2018-10-28 15:50:00
Sam Ratulangi (MDC) - Denpasar International (DPS) JT775 2018-10-28 02:01:00

The flight from MDC to DPS takes about 02h20m. Taking that into account, the maintenance crews would've had about 9 hours top to replace the AOA sensor and to calibrate/test it. Is that considered enough time to accomplish those procedures??
 
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PixelFlight
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Mon Nov 12, 2018 12:27 pm

MatthewDB wrote:
Even straight GPS uses Kalman filters. Any time there are more than 4 satellites visible, there are multiple solutions for position. Kalman filters are used to assign weighting to each satellite's input to the solution and arrive at the most accurate positioning for the available satellites.


Unfortunately this kind of filter is actually not used in civil aviation to produce a better air speed and AoA signals to flight either by automation or by pilot. Searching on the web it's easy to find publications about filters with predictor used on military and/or unmanned aircraft. Not surprising as this is two applications where there is no time or possibility to manually switch off subsystems because of a unreliable sensor. I bet that someday the civil aviation will switch to this design too.

Just a single example: https://www.iosrjen.org/Papers/ICEMS-20 ... 021-25.pdf
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
N212R
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Mon Nov 12, 2018 6:03 pm

One of the most important aviation threads of the year has fallen off the front page here at Airliners.

The powers that be are circling the wagons. The proverbial shite must be ready to hit the fan.
 
F9Animal
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Mon Nov 12, 2018 6:26 pm

I find it rather disturbing that technology to prevent an accident, hinders a crew ability to save a plane when that technology fails. Can you imagine what those pilots faced in the final moments? At such a low altitude, troubleshooting is not much of an option, especially when they couldn't maintain level flight.

As my uncle once said.... We have become too reliant on technology, and stick and rudder days are pretty much gone. A "WTF" situation on takeoff has to be pretty horrifying.
I Am A Different Animal!!
 
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PixelFlight
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Mon Nov 12, 2018 6:33 pm

F9Animal wrote:
We have become too reliant on technology


To reliant on obsolete arbitration technology. A appropriate filter with predictor from multiple different sources would have saved hundreds of lives already.
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
WIederling
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Mon Nov 12, 2018 6:38 pm

maint123 wrote:
Most importantly -
Why replacing the AOA sensors did not cure the problem and led to a crash ?

follow the signal path.

Wiring defect, computer defect, software bug. ....
Murphy is an optimist
 
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exFWAOONW
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Mon Nov 12, 2018 7:07 pm

F9Animal wrote:
....As my uncle once said.... We have become too reliant on technology, and stick and rudder days are pretty much gone. A "WTF" situation on takeoff has to be pretty horrifying.
Are the guys in the pointy end joystick jockeys or pilots? I hope the latter, we need them more.
Is just me, or is flying not as much fun anymore?
 
OLDCROW77
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Mon Nov 12, 2018 10:46 pm

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

Mon Nov 12, 2018 11:35 pm

WIederling wrote:
maint123 wrote:
Most importantly -
Why replacing the AOA sensors did not cure the problem and led to a crash ?

follow the signal path.

Wiring defect, computer defect, software bug. ....


Maybe. But since you've got manufacturing/design defect covered, in the interest of being thorough, I would amend your list to include improper installation of the sensor, failure to properly calibrate, and any of a number of other possible issues that may have arisen during the maintenance and/or troubleshooting of the aircraft.

In other words, notwithstanding the certainty of some on this thread that fault lies with one party or another, I am unaware of any report wherein such fault has been established and, thus, will keep an open mind about what could have caused the apparent erratic behaviour in the first place.
 
maint123
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Tue Nov 13, 2018 12:29 am

7673mech wrote:
maint123 wrote:
Dogbreath wrote:

Why replacing the AOA sensors did not cure the problem and led to a crash?
Whaaaaat! We do not yet know the 'exact' circumstances and reasons for the crash. Last time I checked the investigation is still in progress and there has been no official report issued at this time to confirm ‘exactly’ what happened. The CVR is still yet to be found providing even more data for the investigation team. You’ll be pleased to know that A.net and the media are not a part of the official investigation team. A crash is usually the result of a series of events (not just one isolated event). We don’t yet know if the replacement of the Alpha Vane/s is relevant or not.

Why Boeing put pilots in simulators after the crash and AOA issue emergence and then issued the advisory?
Er why not! Surely as the manufacturer of the 737MAX, they will be continually testing and checking their product, especially in a time like this. Please correct me if I’m wrong but the Boeing Bulletin does not amend any procedures. It simply provides background information to certain systems and reminds flight crew to follow the QRH.

Why have new systems in place where in a emergency situation , the pilots are still being second guessed by the automation in MANUAL mode and have to continuously monitor the automation ( Unable to switch on auto pilot , auto trimming )?
Geez don’t get onboard any Airbus aircraft, or any new airplane designed in the past decade then! It may be that the requirements for airplane stability augmentation is a requirement to meet FAA Certification standards. For that reason STS is an augmentation system for the 737NG and 737MAX. The 737MAX also has MCAS. By the way STS and MCAS can always be disabled by selecting the STAB TRIM CUTOUT switches to OFF. STS and MCAS can also be overridden by manually controlling the trim wheel. Not an easy thing to do, but only used as a backup if the Cutout switches doesn’t stop the runaway trim.
Also, as an Airline Pilot you are continually monitoring the automation of the airplane. I was taught by a very wise Air Force Instructor that automation is great, but don’t trust it. Always know what the automation should be doing for you, and if the outcome is any different then do something about it. I’ve seen so many young pilots today that give 100% trust to automation, and it’s a hard sell to tell them otherwise.


And why is Boeing supplying defective planes to its customers? Are the quality checks slipping?
What proof are you offering to make this outrageous claim? Do you have the official Accident Report stating this as fact? I'm guessing not, so my advice (take it or leave it) is it might be worth waiting until then before making this silly accusation.

Agreed that ultimately a official report will give us the reason for the crash but quite a few people here are happily blaming the pilots for not responding properly , in absence of your aforementioned evidence. I am similarly blaming the plane. My AOA point was that if the AOA was a contributory factor, mainly 3 areas have to be checked. The sensor, cabling or software logic. If AOA sensor was replaced and still the problem continued, then the cabling or software gave the erroneous inputs to auto trim. Which is a total blunder on Boeing's part. Can't blame the crew or maint team on a brand new plane.
Boeing has amended , and asked that their advisory be made part of airlines documentation within 3 days. Again a blatant oversight on Boeing's part.
Your 3rd reply is meaningless as this advisory applies ONLY to MAX planes not NG. Points to changes made in MAX flying procedures which were not incorporated in the training.
Lastly the lack of properly documented changes in flying procedures and introducing unproven changes in automation during manual flight, all point towards carelessness on Boeing's part. And no amount of white washing will hide that.
And if my comments upset you , just go through the complete thread where people here are gladly blaming the lion air maintenance crew and/or pilots from page 1 , in absence of any official evidence.


Let me start by saying I think there is too much speculation in this thread.

That said - was the AOA replaced correctly?
We don't know that.
So let's go after Boeing since they have the most $$$?

Unfortunately your saving $$ for Boeing has been the overriding sentiment in this thread, with most of your countrymen not even questioning why a brand new plane required major hardware maintenance ? Or why have a manual mode only in MAX, where the pilots will still be overridden by automation ?
 
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7BOEING7
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Tue Nov 13, 2018 1:21 am

maint123 wrote:
Or why have a manual mode only in MAX, where the pilots will still be overridden by automation ?


The only time the pilot can be overridden with this system is if he has his hands off the controls or is pushing the nose over (then he's getting help) -- if he has his hands on the controls and has some back force (which he would if the airplane was trying to nose over) the automatic nose down trim is overridden.
 
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SuseJ772
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Tue Nov 13, 2018 1:55 am

F9Animal wrote:
I find it rather disturbing that technology to prevent an accident, hinders a crew ability to save a plane when that technology fails. Can you imagine what those pilots faced in the final moments? At such a low altitude, troubleshooting is not much of an option, especially when they couldn't maintain level flight.

As my uncle once said.... We have become too reliant on technology, and stick and rudder days are pretty much gone. A "WTF" situation on takeoff has to be pretty horrifying.
This is statistically wrong. We are at the safest time in aviation history by far. While at the same time the highest amount of automation. Yes automation can be over relied on. But is has also saved untold thousands of lives. Which we will never know that number so a comparison is useless with the data we have.
Currently at PIE, requesting FWA >> >>
 
VS11
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Re: Lion Air 737MAX8 Crashed Jakarta to Pangal Pinang

Tue Nov 13, 2018 1:56 am

"Southwest, American pilots unions question 737 Max documentation after Indonesia crash"

"Two U.S. pilots' unions say the potential risks of a safety feature on Boeing Co.'s 737 Max aircraft that has been linked to a deadly crash in Indonesia weren't sufficiently spelled out in their manuals or training.

Boeing and the Federal Aviation Administration issued directives last week telling flight crews about the system, which is designed to provide extra protection against pilots losing control. That prompted aviators, unions and training departments to realize that none of the documentation for the Max aircraft included an explanation of the system, the union leaders said."

https://www.dallasnews.com/business/air ... esia-crash

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