Air Asia Indonesia Lost Contact from Surabaya to Singapore
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OEB49
AirLive.net: BREAKING Pilots of AirAsia #QZ8501 Disabled Critical Computers Moments Before AirAsia Crash
Indication that they turned 2 ADRs off and the plane was in ALT LAW?
Indication that they turned 2 ADRs off and the plane was in ALT LAW?
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Wow.
And of course when you only partially release information, you leave a number of interpretations of it:
1. They were screwing around with something to troubleshoot something that might not be consistent with published procedures. And this lead to the upset.
2. They shut down something after something had gone wrong in an effort to
recover from a problem.
I would sure like to more fully understand what is being said only in whispers and not from the authorities (as of yet) .
And of course when you only partially release information, you leave a number of interpretations of it:
1. They were screwing around with something to troubleshoot something that might not be consistent with published procedures. And this lead to the upset.
2. They shut down something after something had gone wrong in an effort to
recover from a problem.
I would sure like to more fully understand what is being said only in whispers and not from the authorities (as of yet) .
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FCOM ON FACs
For non-Airbus readers, the following may be useful regarding just what functions the FAC computers perform. Bolded sentences are by my action.
AUTO FLIGHT
FLIGHT AUGMENTATION
1.22 40 P 1
SEQ 001 REV 25
GENERAL
The aircraft has two flight augmentation computers (FACs) that perform four main
functions:
• Yaw function
— Yaw damping and turn coordination
— Rudder trim
— Rudder travel limitation
• Flight envelope function
— PFD speed scale management
* Minimum/maximum speed computation
Maneuvering speed computation
— Alpha-floor protection
• Low-Energy Warning function <I
• Windshear detection function <
In performing these functions the FAC uses independent channels :
Yaw damper
Rudder trim
Rudder travel limit
Flight envelope
Each FAC interfaces with the elevator aileron computers (ELACs) when the APs are
disengaged, or with the FMGS when at least one AP is engaged.
Both FACs engage automatically at power-up.
The pilot can disengage or reset each FAC (in case of failure) by means of a
pushbutton on the flight control overhead panel.
When a FAC is disengaged (FAC pushbutton set off) but still valid, the flight envelope
function of the FAC remains active.
If both FACs are valid, FAC1 controls the yaw damper, turn coordination, rudder trim,
and rudder travel limit, and FAC2 is in standby.
FAC1 keeps the aircraft within the flight envelope through F171 ; FAC2 performs this
function through FD2.
If a failure is detected on any channel of FAC1 ,
FAC2 takes over the corresponding
channel.
Note that the FACs also control the rudder operation in certain important ways. For that reason, it may be more than coincidental that the following comment by 747SP5 reported repeated problems with that aircraft's rudder system, the same computer system that the crew was attempting to shut down during their departure from controlled flight.
http://www.pprune.org/rumours-news/5...ml#post8841170
Did they use the switches on the overhead panels? That would not work too well if the flight envelope protection part of the FAC system was malfunctioning without failing its self test.
AUTO FLIGHT
FLIGHT AUGMENTATION
1.22 40 P 1
SEQ 001 REV 25
GENERAL
The aircraft has two flight augmentation computers (FACs) that perform four main
functions:
• Yaw function
— Yaw damping and turn coordination
— Rudder trim
— Rudder travel limitation
• Flight envelope function
— PFD speed scale management
* Minimum/maximum speed computation
Maneuvering speed computation
— Alpha-floor protection
• Low-Energy Warning function <I
• Windshear detection function <
In performing these functions the FAC uses independent channels :
Yaw damper
Rudder trim
Rudder travel limit
Flight envelope
Each FAC interfaces with the elevator aileron computers (ELACs) when the APs are
disengaged, or with the FMGS when at least one AP is engaged.
Both FACs engage automatically at power-up.
The pilot can disengage or reset each FAC (in case of failure) by means of a
pushbutton on the flight control overhead panel.
When a FAC is disengaged (FAC pushbutton set off) but still valid, the flight envelope
function of the FAC remains active.
If both FACs are valid, FAC1 controls the yaw damper, turn coordination, rudder trim,
and rudder travel limit, and FAC2 is in standby.
FAC1 keeps the aircraft within the flight envelope through F171 ; FAC2 performs this
function through FD2.
If a failure is detected on any channel of FAC1 ,
FAC2 takes over the corresponding
channel.
http://www.pprune.org/rumours-news/5...ml#post8841170
Did they use the switches on the overhead panels? That would not work too well if the flight envelope protection part of the FAC system was malfunctioning without failing its self test.
Last edited by Machinbird; 29th Jan 2015 at 23:41. Reason: remove redundant word
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This preliminary report that was not meant to be made public has more leaks than a sieve.
JAKARTA (BLOOMBERG) - The pilots of AirAsia flight QZ8501 cut power to a critical computer system that normally prevents planes from going out of control shortly before it plunged into the Java Sea, two people with knowledge of the investigation said.
The action appears to have helped trigger the events of Dec 28, when the Airbus A320 climbed so abruptly that it lost lift and began falling with warnings blaring in the cockpit, the people said. All 162 aboard were killed.
The pilots had been attempting to deal with alerts about the flight augmentation computers, which control the A320's rudder and also automatically prevent it from going too slow. After initial attempts to address the alerts, the flight crew cut power to the entire system, which is comprised of two separate computers that back up each other, the people said.
- See more at: AirAsia flight QZ8501: Pilots disabled critical computers just before crash, say sources - South-east Asia News & Top Stories - The Straits Times
The action appears to have helped trigger the events of Dec 28, when the Airbus A320 climbed so abruptly that it lost lift and began falling with warnings blaring in the cockpit, the people said. All 162 aboard were killed.
The pilots had been attempting to deal with alerts about the flight augmentation computers, which control the A320's rudder and also automatically prevent it from going too slow. After initial attempts to address the alerts, the flight crew cut power to the entire system, which is comprised of two separate computers that back up each other, the people said.
- See more at: AirAsia flight QZ8501: Pilots disabled critical computers just before crash, say sources - South-east Asia News & Top Stories - The Straits Times
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Machinbird, re your post 2748.
<quote>
When a FAC is disengaged (FAC pushbutton set off) but still valid, the flight envelope function of the FAC remains active.
</quote>
<quote>
Did they use the switches on the overhead panels?
</quote>
<quote>
That would not work too well if the flight envelope protection part of the FAC system was malfunctioning without failing its self test.
</quote>
If the FAC is "disengaged" by pushing the FAC set off button on the overhead panel, why does the FAC remain active in any way at all ?
Off is Off in my book.
This reads like "Off is only half off".
What is the point in having an off button for one part of the FAC's funtionality, but not the other part (the flight envelope functions).
Perhaps there should be two buttons, the second one for "flight envelope functions off".
Since there is none, the only option left is the circuit breaker ?
How many times would a FAC be turned off in normal ops, do you think ?
How many times, in what circumstances, and for what reasons, would turning off a FAC by done in the sim ?
Is it implicit in those sim exercises that the the flight envelope functions remain engaged, always, or not ?
If not, is it implicit in ANY sim exercise that total FAC shutdown, by pulling circuit breaker is required, and what the specific circumstances are, and what the consequent implications then are for continued safe flight ?
Do any of those sim'd circumstances and exercises "gell" in any way with any credible circumstance that may have occured on 8501 ?
In other words, could they have identifed (or thought they had identified) a circumstance that they had trained for, and were just working the list, or is it more likely they were in a whole "new world" situation, not trained for, no list printed, and trying to work it out themselves from square one ?
The whole idea of an off button that is not actually an off button at all bugs me.
Talk about "man - machine interface" - jesus - what are the engineers thinking when they design these things ?
It sounds more like a case of - "I can't let you do that Dave" - as in - a "prime directive" - sort of thing.
Machinbird, I do not understand the rationalle of the logic in play here.
"Please Explain".
(It is lunchtime. Perhaps I should go and have some fish and chips).
<quote>
When a FAC is disengaged (FAC pushbutton set off) but still valid, the flight envelope function of the FAC remains active.
</quote>
<quote>
Did they use the switches on the overhead panels?
</quote>
<quote>
That would not work too well if the flight envelope protection part of the FAC system was malfunctioning without failing its self test.
</quote>
If the FAC is "disengaged" by pushing the FAC set off button on the overhead panel, why does the FAC remain active in any way at all ?
Off is Off in my book.
This reads like "Off is only half off".
What is the point in having an off button for one part of the FAC's funtionality, but not the other part (the flight envelope functions).
Perhaps there should be two buttons, the second one for "flight envelope functions off".
Since there is none, the only option left is the circuit breaker ?
How many times would a FAC be turned off in normal ops, do you think ?
How many times, in what circumstances, and for what reasons, would turning off a FAC by done in the sim ?
Is it implicit in those sim exercises that the the flight envelope functions remain engaged, always, or not ?
If not, is it implicit in ANY sim exercise that total FAC shutdown, by pulling circuit breaker is required, and what the specific circumstances are, and what the consequent implications then are for continued safe flight ?
Do any of those sim'd circumstances and exercises "gell" in any way with any credible circumstance that may have occured on 8501 ?
In other words, could they have identifed (or thought they had identified) a circumstance that they had trained for, and were just working the list, or is it more likely they were in a whole "new world" situation, not trained for, no list printed, and trying to work it out themselves from square one ?
The whole idea of an off button that is not actually an off button at all bugs me.
Talk about "man - machine interface" - jesus - what are the engineers thinking when they design these things ?
It sounds more like a case of - "I can't let you do that Dave" - as in - a "prime directive" - sort of thing.
Machinbird, I do not understand the rationalle of the logic in play here.
"Please Explain".
(It is lunchtime. Perhaps I should go and have some fish and chips).
Last edited by ventus45; 30th Jan 2015 at 02:04.
While not on the 320, I do fly airbus and maybe its worth putting some points out regarding the last bit of leaked info. My interpretation may not be perfect and may even be incorrect for the 320 however...
The airbus does not have Circuit Breakers (except for a number in the Electrical Control Area beneath the cockpit). The airbus has Reset buttons. Wether you want to argue that its the same thing but that's what they are called. It allows the many multitude of computers that run the different systems to be disconnected, then after resetting allow a boot up of the system. My interpretation is that a CB wont necessarily reboot a system but rather just cut the power to it.
Airbus designed these reset buttons too not just cut the power but also enable the system once reset to "start again". Many issues found on the ground are fixed by just resetting the system. Not always the case but a "get out of jail card" in some respects.
The important thing to remember with reset buttons is that they may be restrictions on when they can be used and a reset performed. Some systems can be rebooted on the ground or also in the air, some may even need the engines off. Airbus provides a Quick Reference Handbook which has a section on computer resets, it will tell you of any restrictions imposed on resetting a certain system.
Wether or not some frantic button pushing of the Flight Control Computers were going to save the day it would be interesting to know wether correct interpretation of these resets and its consequences may off set off a chain reaction.
The airbus does not have Circuit Breakers (except for a number in the Electrical Control Area beneath the cockpit). The airbus has Reset buttons. Wether you want to argue that its the same thing but that's what they are called. It allows the many multitude of computers that run the different systems to be disconnected, then after resetting allow a boot up of the system. My interpretation is that a CB wont necessarily reboot a system but rather just cut the power to it.
Airbus designed these reset buttons too not just cut the power but also enable the system once reset to "start again". Many issues found on the ground are fixed by just resetting the system. Not always the case but a "get out of jail card" in some respects.
The important thing to remember with reset buttons is that they may be restrictions on when they can be used and a reset performed. Some systems can be rebooted on the ground or also in the air, some may even need the engines off. Airbus provides a Quick Reference Handbook which has a section on computer resets, it will tell you of any restrictions imposed on resetting a certain system.
Wether or not some frantic button pushing of the Flight Control Computers were going to save the day it would be interesting to know wether correct interpretation of these resets and its consequences may off set off a chain reaction.
The A320 is presumably always under computer control, just the extent of it modulated in case of glitches to alternate or direct. That the FAC would likewise have residual action seems unsurprising. How those specific demarcation lines are laid out or understood by the crew is less clear.
It does seem that a very experienced Captain and a mature and dedicated FO felt they were at the controls of an unresponsive or defective aircraft.
They may have been mistaken, but how that mistake came about needs to be made clear, if only to prevent recurrences.
It does seem that a very experienced Captain and a mature and dedicated FO felt they were at the controls of an unresponsive or defective aircraft.
They may have been mistaken, but how that mistake came about needs to be made clear, if only to prevent recurrences.
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How many times, in what circumstances, and for what reasons, would turning off a FAC by done in the sim ?
Is it implicit in those sim exercises that the the flight envelope functions remain engaged, always, or not ?
Is it implicit in those sim exercises that the the flight envelope functions remain engaged, always, or not ?
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Originally Posted by Ventus45
Machinbird, I do not understand the rationalle of the logic in play here.
"Please Explain".
"Please Explain".
Take HEALY's points on Airbus computer re-set philosophy and consider that Airbus engineers gave the computers dominance over the pilots in their operational concept. That you and I think this is foolish has no bearing on what has transpired already. We may only be able to influence what direction future aircraft designs take.
I suspected early on that QZ8501 was going to be a man/machine authority horror story and so far, I am not dissuaded from that viewpoint.
I'd like to point out that without the FDR data, we readers do not know when the FAC shutdown attempt occurred relative to the flight control problems. The sooner they can publish the FDR readouts, the sooner we can begin to properly wrap our minds around what caused this accident.
If the pilots felt that the active law was blocking their recovery effort, they might decide to turn off some boxes in a last ditch effort.
When software goes bad, it takes considerable time just to identify exactly what the misbehavior constitutes. And it might not be the result of a miscalculation, but an unanticipated set of conditions that has the software running off in the wrong direction.
I like the philosophy in the Embraer Legacy 500 as described in the current issue of Flying.
There's just two laws: Normal and Direct.
Much less potential for confusion when things start going wrong
When software goes bad, it takes considerable time just to identify exactly what the misbehavior constitutes. And it might not be the result of a miscalculation, but an unanticipated set of conditions that has the software running off in the wrong direction.
I like the philosophy in the Embraer Legacy 500 as described in the current issue of Flying.
There's just two laws: Normal and Direct.
Much less potential for confusion when things start going wrong
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Not bashing Airbus here........ It bashes its ownself quite well enough.
Reading the accident reports and explanations from "experienced" pilots, sounds like the old "Who's on first, what's on second" comedy routine of Abbott & Costello. This newer version is, unfortunately such a tragic one and seeming to repeat itself.
Cool sidestick controller whose position is hidden from other pilots, and if being manually manipulated by both pilots for whatever reason simultaneously, the A320 flight computers ADD the 2 control inputs together. Combined with thrust levers that don't move when FADEC makes thrust changes, major or minor.
Also it is alleged the 320 family will sometimes fully move the THS to full or nearly so, nose up, causing big difficulty,in getting the nose down - particularly when high thrust is occurring in low speed flight.
They said Titanic was unsinkable.
The 320, cant be stalled.
Reading the accident reports and explanations from "experienced" pilots, sounds like the old "Who's on first, what's on second" comedy routine of Abbott & Costello. This newer version is, unfortunately such a tragic one and seeming to repeat itself.
Cool sidestick controller whose position is hidden from other pilots, and if being manually manipulated by both pilots for whatever reason simultaneously, the A320 flight computers ADD the 2 control inputs together. Combined with thrust levers that don't move when FADEC makes thrust changes, major or minor.
Also it is alleged the 320 family will sometimes fully move the THS to full or nearly so, nose up, causing big difficulty,in getting the nose down - particularly when high thrust is occurring in low speed flight.
They said Titanic was unsinkable.
The 320, cant be stalled.
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Hi Healy
I presume you are 330 or 340?
340 IIRC just had the small panel above/behind the overhead panel, and were mostly/only "resets". A320 series has this, but also has the whole rear wall of the cockpit as CB panels - and most of these I think are normal CBs? Often have to reset "CBs", iaw FCOM, and FCOM is clear some are CBs (wiring protection) and some are reset buttons. FCOM also clear as to what / where you can reset.
A quick look does not reveal FACs as items to be reset, especially airborne. ELACs and SECs can be reset, albeit only one at a time. In my Airbus time, the emphasis has shifted from "keep resetting" things to rest only when specifically required by that table. I am very clear with my colleague as to what is being done, why and by whom - and if in doubt do not rest / play.
While not on the 320, I do fly airbus and maybe its worth putting some points out regarding the last bit of leaked info. My interpretation may not be perfect and may even be incorrect for the 320 however...
The airbus does not have Circuit Breakers (except for a number in the Electrical Control Area beneath the cockpit). The airbus has Reset buttons. Wether you want to argue that its the same thing but that's what they are called. It allows the many multitude of computers that run the different systems to be disconnected, then after resetting allow a boot up of the system.
The airbus does not have Circuit Breakers (except for a number in the Electrical Control Area beneath the cockpit). The airbus has Reset buttons. Wether you want to argue that its the same thing but that's what they are called. It allows the many multitude of computers that run the different systems to be disconnected, then after resetting allow a boot up of the system.
340 IIRC just had the small panel above/behind the overhead panel, and were mostly/only "resets". A320 series has this, but also has the whole rear wall of the cockpit as CB panels - and most of these I think are normal CBs? Often have to reset "CBs", iaw FCOM, and FCOM is clear some are CBs (wiring protection) and some are reset buttons. FCOM also clear as to what / where you can reset.
A quick look does not reveal FACs as items to be reset, especially airborne. ELACs and SECs can be reset, albeit only one at a time. In my Airbus time, the emphasis has shifted from "keep resetting" things to rest only when specifically required by that table. I am very clear with my colleague as to what is being done, why and by whom - and if in doubt do not rest / play.
Last edited by NigelOnDraft; 30th Jan 2015 at 09:16. Reason: Corrections (thanks Roo!)
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Link
Usually yes. But there are FAC CBs (proper ones!) - see link above B3 & B4.
The press article earlier might be implying these were pulled, rather than the pbs?
It may be a small point in the end, but the FACs are controlled by switches, not by CBs.
The press article earlier might be implying these were pulled, rather than the pbs?
An engineer explained to me that green simply means the circuit is monitored and will display on the ECAM CB page when tripped. Nothing to do with it being reset vs cb. Black CBs are un monitored by ECAM and important ones would logically need to be where pilots could check them. Hence 330 EEC being full of green CBs while 320 has wall of black ones in the cockpit. In the 330 in our outfit the reset switches are black btw.
Abnormal Attitude Law..
The A320 will switch to this mode whenever the normal envelope is exceded in pitch, roll or speed.
The aircraft will revert to alt/direct law and stay there even after recovery.
My guess is that this has occurred and the crew have tried a FAC reset to try and recover normal law..
The A320 will switch to this mode whenever the normal envelope is exceded in pitch, roll or speed.
The aircraft will revert to alt/direct law and stay there even after recovery.
My guess is that this has occurred and the crew have tried a FAC reset to try and recover normal law..
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In time all the info will be released due to the lawsuits. It may take a while.
So far Airbus has not issued any AD's regarding the FAC's or anything else regarding this crash. Is this telling in any way or just too early????
So far Airbus has not issued any AD's regarding the FAC's or anything else regarding this crash. Is this telling in any way or just too early????
