AF 447 Thread No. 6
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Rudderrat
With an aircraft stalled the roll would lead to yaw in the direction of the roll. As the 330 is swept wing the wing on the downside would then be more directly into what airflow there was and generate slightly more lift and the aircraft would nod up and start rolling back the other way to repeat the yaw and roll on the other side. As I believe Dozy has said this is relatively standard swept wing behavior. Like a long period dutch-roll
However, into this action PF was putting in as much aileron as he could, often apparently full SS. The result of this would be to make the low wing AOA higher so less lift so a tendency for the aircraft to apparently do the opposite of what was wanted until the wing sweep effect was larger than the aileron AOA effect.
Perhaps someone with spare time could check - but if the total time with the SS held to the left is larger than to the right then that could explain the overall right turn in the descent track as the right wing was being held deeper in the stall by aileron AOA.
Speculation now - but for a pilot sitting in the right hand seat, just pulling the stick directly toward the pilot would be a Nose Up - Left Roll input. This would maintain the stall and result in a track that turned to the right.
Hi OK465, DW, henra,
Unless the aircraft was trimmed exactly to balance any asymmetric thrust (due TL moved in response to thrust lock), it would tend to roll one way and continue to roll, unless counteracted by pilot or Auto Pilot input.
Since it was in Alternate Law, there was no AP or FBW roll input - only pilot input.
At what attitude do you think it would stop rolling if left by itself?
Unless the aircraft was trimmed exactly to balance any asymmetric thrust (due TL moved in response to thrust lock), it would tend to roll one way and continue to roll, unless counteracted by pilot or Auto Pilot input.
Since it was in Alternate Law, there was no AP or FBW roll input - only pilot input.
At what attitude do you think it would stop rolling if left by itself?
However, into this action PF was putting in as much aileron as he could, often apparently full SS. The result of this would be to make the low wing AOA higher so less lift so a tendency for the aircraft to apparently do the opposite of what was wanted until the wing sweep effect was larger than the aileron AOA effect.
Perhaps someone with spare time could check - but if the total time with the SS held to the left is larger than to the right then that could explain the overall right turn in the descent track as the right wing was being held deeper in the stall by aileron AOA.
Speculation now - but for a pilot sitting in the right hand seat, just pulling the stick directly toward the pilot would be a Nose Up - Left Roll input. This would maintain the stall and result in a track that turned to the right.
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Hi Ian W
I don't know the physics of stalled aircraft behaviour, but I think the stability was a result of dihedral rather than sweep.
When stalled, if one wing is lower, it presents a greater plan surface area to the airflow than the higher wing, resulting in a levelling couple.
I think PF's roll input would help level the wings because the lowered aileron would present more drag. (edit in the same way that down elevator lowered the nose and reactivated the stall warning)
However, I will probably agree with Owain's analysis.
However, into this action PF was putting in as much aileron as he could, often apparently full SS. The result of this would be to make the low wing AOA higher so less lift so a tendency for the aircraft to apparently do the opposite of what was wanted until the wing sweep effect was larger than the aileron AOA effect.
When stalled, if one wing is lower, it presents a greater plan surface area to the airflow than the higher wing, resulting in a levelling couple.
I think PF's roll input would help level the wings because the lowered aileron would present more drag. (edit in the same way that down elevator lowered the nose and reactivated the stall warning)
However, I will probably agree with Owain's analysis.
Last edited by rudderrudderrat; 3rd Sep 2011 at 15:02.
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Quite a few folk here just a bit confused about aircraft, and in particular swept wing, stability, but I don't actually think any of this is relevant to this thread.
What is a fact relevant to this thread is that attempts to lift ANY stalled wing with aileron will result in the wing going further downwards. This can be seen on the PGF AB320 traces as well.
What is a fact relevant to this thread is that attempts to lift ANY stalled wing with aileron will result in the wing going further downwards. This can be seen on the PGF AB320 traces as well.
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:
Quote: Ian W
However, into this action PF was putting in as much aileron as he could, often apparently full SS. The result of this would be to make the low wing AOA higher so less lift so a tendency for the aircraft to apparently do the opposite of what was wanted until the wing sweep effect was larger than the aileron AOA effect.
However, into this action PF was putting in as much aileron as he could, often apparently full SS. The result of this would be to make the low wing AOA higher so less lift so a tendency for the aircraft to apparently do the opposite of what was wanted until the wing sweep effect was larger than the aileron AOA effect.
rudderrudderrat
i don't know the physics of stalled aircraft behaviour, but I think the stability was a result of dihedral rather than sweep.
When stalled, if one wing is lower, it presents a greater plan surface area to the airflow than the higher wing, resulting in a levelling couple.
i don't know the physics of stalled aircraft behaviour, but I think the stability was a result of dihedral rather than sweep.
When stalled, if one wing is lower, it presents a greater plan surface area to the airflow than the higher wing, resulting in a levelling couple.
I think PF's roll input would help level the wings because the lowered aileron would present more drag. (edit in the same way that down elevator lowered the nose and reactivated the stall warning)
From follow up post
Honestly i don´t know how this missing sideslip estimation influences the behaviour of the rudder in a stall, or how the functioning yaw damping influences it in a positive or negative way. But hopefully somebody can explain.
Honestly i don´t know how this missing sideslip estimation influences the behaviour of the rudder in a stall, or how the functioning yaw damping influences it in a positive or negative way. But hopefully somebody can explain.
BOAC
Quite a few folk here just a bit confused about aircraft, and in particular swept wing, stability, but I don't actually think any of this is relevant to this thread.
Quite a few folk here just a bit confused about aircraft, and in particular swept wing, stability, but I don't actually think any of this is relevant to this thread.
But i strongly disagree in general.
The aerodynamic behaviour of the aircraft seems to be a blanc card in nowadays training and knowledge base. We wonder, wy the pilot pulled the stick despite being in a stall. We might also wonder, why he applied full left aileron and not using rudder to level the wings. It might have the same reason: Not knowing, what the outcome in an aerodynamic point of view) theses actions would be. He wanted to stop the descent and climb up again, therefore pull back on the stick. That worked probably more than 99% of his flying career. Tell the aircraft what to do, point the nose up and apply sufficient power, and the aircraft will follow the orders. Same with bank. If right wing is down, put the SS to the left. When the wing is level, put the stick to neutral and it will stay there. That worked again more than 99% of his flying career.
Unfortunately there are situations, when you have to switch from normal behaviour to "trouble shooting mode", and for that you have to know the performance envelope of your aircraft and how it behaves, if you touch that envelope or go outside of it.
Military fast jet pilots do that on a day to day basis, therefore they know exactly how the aircraft will behave and and how to react by flight control input to get the desired result.
This crew had no clue what might have helped to get out of the situation they themselves flew (stalled) into. Agreed, they should not have gotten into this situation first hand, but that´s what ´s happening in our non perfect technical and human world.
Therefore again, i tend to say, that it is also very important to look into those issues after the stall happened instead of exchanging arguments about tactile feedback and yoke Vs.SS the 50th. time. We placed those statements and they stand from either side.
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Gentlemen,
I have read EVERY post here regarding AF 447. I remember June 2009 like it was yesterday. I am not a pilot. The intelligence and opinions here have been beyond enlightening. From takata believing the plane turned around (which it did but under different circumstances) to spot on weather examinations......all class work.
Unfortunately there are facts and the facts involved with AF 447 are disturbing. A STALL is a STALL. The plane was telling them that, the altitude was telling them that, buffeting was telling them that. OK... I get it...the pitots were clogged..there is confusion....the plane is confused....the pilots are confused. I hate to say it but the people on the flight deck were...morons. I know, it is terrible to say. How can a skilled aviator, make that 2, not know he is in a stalled position? We are talking about life and death and that is serious business. People are dead because 2 guys refused to acknowledge there was a problem.
What more is there to argue?
I have read EVERY post here regarding AF 447. I remember June 2009 like it was yesterday. I am not a pilot. The intelligence and opinions here have been beyond enlightening. From takata believing the plane turned around (which it did but under different circumstances) to spot on weather examinations......all class work.
Unfortunately there are facts and the facts involved with AF 447 are disturbing. A STALL is a STALL. The plane was telling them that, the altitude was telling them that, buffeting was telling them that. OK... I get it...the pitots were clogged..there is confusion....the plane is confused....the pilots are confused. I hate to say it but the people on the flight deck were...morons. I know, it is terrible to say. How can a skilled aviator, make that 2, not know he is in a stalled position? We are talking about life and death and that is serious business. People are dead because 2 guys refused to acknowledge there was a problem.
What more is there to argue?
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John3775: I've said it here before but no-one thinks it's shocking or surprising:
It's allowed (certified) for the AP to quit and make the pilots hand fly the plane at high altitude.
It's allowed for AF to use 'pilots' who have no training or experience in hand flying the plane at high altitude.
It's allowed (certified) for the AP to quit and make the pilots hand fly the plane at high altitude.
It's allowed for AF to use 'pilots' who have no training or experience in hand flying the plane at high altitude.
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It's allowed for AF to put guys on the FD who have no training or experience in hand flying the plane at high altitude.
It's ALLOWED for the whole industry.
Money counts!
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It's allowed (certified) for the (deleted) pilots hand fly the plane at high altitude.
Have fun...
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5. PF believed he was applying a correct procedure of stick back, apply TOGA and airbus protections especially alpha prot would prevent the bus from stalling with minimal height loss.
There also appears to be little reason for allowing the THS trim system to assist a pilot to trim right into and beyond the stall at altitude and cruise speed...
Yes, yes, i know... bad piloting, inexplicable piloting but that is why stick shakers and pushers have been around for years - because it is known that pilots stall aeroplanes and the consequences are often that with a large swept wing jet a/c (however tailed), recovery cannot always be guaranteed in a set height lossor limit 'g' once badly stalled (c.f. stall netry just averted).
What was the argument then for certifying in Alt2 without a stick shaker and pusher ?
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@VGCM66 Is there much more to say?
p.s. for all the A haters from B factoryland....B jets are not without faults; many deadly; and had it not been for government cash injection it would not be the mega company it is today (protectionism as much as the US would like it to be is not exclusive)...therefore I ask those of you with issues to do your homework and perhaps have a bit of understanding, acceptance and humility before passing judgement.
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QF72
Originally Posted by John3775
What more is there to argue?
The AF447 pilots probably had less than 60 seconds to get ahead of the aircraft that had run away from them. This was not an easy situation, totally untrained for. In this situation panic can occur quickly. You have to ask why did they behave the way they did. You need to dig deeper to find why they made the mistakes.
Originally Posted by atsb, QF72, Interim Factual #1, page 3,4
The crew were also receiving aural stall warning indications at this time, and the airspeed and altitude indications on the captain’s primary flight display (PFD) were also fluctuating.
Given the situation, the captain asked the second officer to call the first officer back
to the flight deck.
At 1242:27, while the second officer was using the cabin interphone to ask a flight
attendant to send the first officer back to the flight deck, the aircraft abruptly
pitched nose-down. The captain reported that he applied back pressure on his
sidestick to arrest the pitch-down movement. He said that initially this action
seemed to have no effect, but then the aircraft responded to his control input and he
commenced recovery to the assigned altitude. The aircraft reached a maximum
pitch angle of about 8.4 degrees nose-down during the event, and a maximum g
loading of -0.80g was recorded. The aircraft descended 650 ft during the event.
Given the situation, the captain asked the second officer to call the first officer back
to the flight deck.
At 1242:27, while the second officer was using the cabin interphone to ask a flight
attendant to send the first officer back to the flight deck, the aircraft abruptly
pitched nose-down. The captain reported that he applied back pressure on his
sidestick to arrest the pitch-down movement. He said that initially this action
seemed to have no effect, but then the aircraft responded to his control input and he
commenced recovery to the assigned altitude. The aircraft reached a maximum
pitch angle of about 8.4 degrees nose-down during the event, and a maximum g
loading of -0.80g was recorded. The aircraft descended 650 ft during the event.
Training, experience, design philosophy
A few good points recently.
I hitch hike on RF4's comments, if you will excuse me.
The military guys here flew jets with vastly different operational requirements, and some of our jets had vastly enhanced performance characteristics than the 'bus. So we flew the things to the edge of the envelope and maybe beyond during training. When we encountered a "bad" condition, we usually had seen it before and responded according to procedure and training. This was not the case with the AF447 crew.
There is no substitute for experience. You can fly a simulator all you want, but until you see and feel the real thing in the real situation, you are not fully prepared. Simply following a rote procedure will work 90% of the time, but that remaining 10% can be, and often is, fatal. It is very hard, very expensive, and maybe foolhardy, to experience stalls and high AoA flight conditions in a big commercial jet. Only way around this is to have a small fleet of planes to see and feel the flight characteristics of stall entry, and recovery. Sorta like the Shuttle folks used to practice their approaches.
Another thing I saw when checking out folks in the USAF Reserve and Guard was how commercial airline folks could go from flying the Viper or SLUF or Thud or Double Ugly on weekends to a 737 or 757 for their "day" job. i would take those guys and gals any time in a big jet that had entered unknown territory. So there IS A WAY.
The design philosophy that assumes engineers can build a jet that "protects" the crew and SLF's from all possible contingencies is failing us. As with your auto, you must be able to master the beast without a plethora of control laws and "back up" modes, and such. You must first of all, and lastly, be a pilot.
I'll go back to my cave now....
I hitch hike on RF4's comments, if you will excuse me.
The military guys here flew jets with vastly different operational requirements, and some of our jets had vastly enhanced performance characteristics than the 'bus. So we flew the things to the edge of the envelope and maybe beyond during training. When we encountered a "bad" condition, we usually had seen it before and responded according to procedure and training. This was not the case with the AF447 crew.
There is no substitute for experience. You can fly a simulator all you want, but until you see and feel the real thing in the real situation, you are not fully prepared. Simply following a rote procedure will work 90% of the time, but that remaining 10% can be, and often is, fatal. It is very hard, very expensive, and maybe foolhardy, to experience stalls and high AoA flight conditions in a big commercial jet. Only way around this is to have a small fleet of planes to see and feel the flight characteristics of stall entry, and recovery. Sorta like the Shuttle folks used to practice their approaches.
Another thing I saw when checking out folks in the USAF Reserve and Guard was how commercial airline folks could go from flying the Viper or SLUF or Thud or Double Ugly on weekends to a 737 or 757 for their "day" job. i would take those guys and gals any time in a big jet that had entered unknown territory. So there IS A WAY.
The design philosophy that assumes engineers can build a jet that "protects" the crew and SLF's from all possible contingencies is failing us. As with your auto, you must be able to master the beast without a plethora of control laws and "back up" modes, and such. You must first of all, and lastly, be a pilot.
I'll go back to my cave now....
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Hi,
DB64
And what is your advise for all the A haters from A factoryland ?
Xcitation
You give yourself the answer ....
totally untrained for
DB64
p.s. for all the A haters from B factoryland....B jets are not without faults; many deadly; and had it not been for government cash injection it would not be the mega company it is today (protectionism as much as the US would like it to be is not exclusive)...therefore I ask those of you with issues to do your homework and perhaps have a bit of understanding, acceptance and humility before passing judgement.
Xcitation
This was not an easy situation, totally untrained for. In this situation panic can occur quickly. You have to ask why did they behave the way they did. You need to dig deeper to find why they made the mistakes.
totally untrained for
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Full Back Stick
There are a several QRH procedures that call for Full Back Stick.
WIND SHEAR:
SRS ORDERS .... FOLLOW
This includes the use of full back stick if demanded.
If the FD Bars are not available , use an initial pitch attitude of 17.5 degs with full back stick, if necessary.
WINDSHEAR AHEAD:
Thrust Levers ….. TOGA
SRS ORDERS .... FOLLOW
This includes the use of full back stick, if required.
EGPWS ALERTS
PITCH ….. PULL UP
Pull to full back stick and maintain in that position
THRUST LEVERS …. TOGA
The pilots will have practised all of those procedures in the simulator, and will have gone away with the association of TOGA and Full back stick seems to work OK. Piloting skills don't seem to be required, simply pull back and let the computer fly the aircraft in pitch.
It is not mentioned anywhere that the "piloting technique" of respecting Alpha Max should be employed, and to relax the back pressure when very close.
Is it reasonable to ask a pilot to fly one particular way when in Normal Law, and a different way when in Alternate Law?
If AB had fitted a side stick buzzer, which was activated when approaching ALPHA MAX in NORMAL LAW, then he might have had the opportunity to practice flying the correct pitch attitude / angle of attack during the Wind Shear and EGPWS Alerts, on the edge of the Stick Buzzer / Shaker.
It may have reminded him to respect the stick shaker, when at FL 350, rather than go for TOGA & FULL Back stick again.
One solution is to simply change the crew - but if they failed to recognise their predicament due cockpit design, training, QRH procedures, etc. then you can bet there will be another crew able to do the same somewhere else.
@gums
I agree 100%. 
@ventus45
We had to do all our B707 emergency exercises in real life, Stalling, Emergency Descent, EFTO etc. Unfortunately we were writing off more aircraft during training than we did in normal passenger operations. There was no good reason to continue using the real thing once simulator fidelity came close. A crew learns far more by freezing the sim before impact than chatting to them in their hospital beds - or worse.
WIND SHEAR:
SRS ORDERS .... FOLLOW
This includes the use of full back stick if demanded.
If the FD Bars are not available , use an initial pitch attitude of 17.5 degs with full back stick, if necessary.
WINDSHEAR AHEAD:
Thrust Levers ….. TOGA
SRS ORDERS .... FOLLOW
This includes the use of full back stick, if required.
EGPWS ALERTS
PITCH ….. PULL UP
Pull to full back stick and maintain in that position
THRUST LEVERS …. TOGA
The pilots will have practised all of those procedures in the simulator, and will have gone away with the association of TOGA and Full back stick seems to work OK. Piloting skills don't seem to be required, simply pull back and let the computer fly the aircraft in pitch.
It is not mentioned anywhere that the "piloting technique" of respecting Alpha Max should be employed, and to relax the back pressure when very close.
Is it reasonable to ask a pilot to fly one particular way when in Normal Law, and a different way when in Alternate Law?
If AB had fitted a side stick buzzer, which was activated when approaching ALPHA MAX in NORMAL LAW, then he might have had the opportunity to practice flying the correct pitch attitude / angle of attack during the Wind Shear and EGPWS Alerts, on the edge of the Stick Buzzer / Shaker.
It may have reminded him to respect the stick shaker, when at FL 350, rather than go for TOGA & FULL Back stick again.
One solution is to simply change the crew - but if they failed to recognise their predicament due cockpit design, training, QRH procedures, etc. then you can bet there will be another crew able to do the same somewhere else.
@gums
You must first of all, and lastly, be a pilot.
@ventus45
It is way past high time that the "sim level D" mindset is smashed.
Last edited by rudderrudderrat; 5th Sep 2011 at 20:47.
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Reply to VGMC66 post #741 ... ref high altitude/weight buffet boundaries
VGCM66 - well said. And a fine Flight article too. AF447's initial altitude drift went virtually unchallenged
Please see post #1386 on 3 AUG 11 which seeks the figures for AR447 buffet boundary at the time of the accident. They were clearly exceeded and the inevitable aerodynamic upset resulted.
Has anyone listed these relevant AF447 Flight Manual figures yet?
http://www.pprune.org/tech-log/45687...no-5-a-70.html
Please see post #1386 on 3 AUG 11 which seeks the figures for AR447 buffet boundary at the time of the accident. They were clearly exceeded and the inevitable aerodynamic upset resulted.
Has anyone listed these relevant AF447 Flight Manual figures yet?
http://www.pprune.org/tech-log/45687...no-5-a-70.html
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John3775 #743
".. the people on the flight deck were morons.... 2 guys refused to acknowledge a problem... "
Whilst other modes of transport CAN stop and have time to think, this crew had just FOUR minutes...or less, and in Test Pilot country.
A test pilot might well have been flying by day, clear of cloud and anticipating the abnormal.
"Morons" is prehaps unreasonably harsh, especially as you have read all the other comments for two years.
".. the people on the flight deck were morons.... 2 guys refused to acknowledge a problem... "
Whilst other modes of transport CAN stop and have time to think, this crew had just FOUR minutes...or less, and in Test Pilot country.
A test pilot might well have been flying by day, clear of cloud and anticipating the abnormal.
"Morons" is prehaps unreasonably harsh, especially as you have read all the other comments for two years.