AF 447 Thread No. 8
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The successful recoveries that pre-dated AF447 prove that this was not the case.
In the case of the Concorde .. predated problems with tires happened and none produced a fire ..
And one day .. same problem .. and fire .. and end of flight at Gonesse (it's not a airport ... unfortunately)
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@jcj:
What you think is not the issue here. I repeat - an AD is only necessary when a fault is severe enough to be likely to cause the loss of the aircraft every time it occurs - for example, the DC-10 cargo door failure leading to hydraulic failure.
If ADs were required in every case where a fault made it possible to lose the aircraft then a lot of the world's fleets would spend a lot of the time grounded.
For example, if you go back to the late 1990s, the 737 fleet was flying around with a known problem in the rudder PCU, they just did not know what that fault was at that stage. The NTSB were considering pushing the FAA and international authorities AD to ground the 737, but it was considered impractical (not to mention the fact that Boeing was fighting tooth-and-nail to get UA535 and US427 classified as pilot error - note that Airbus is *not* doing this in the case of AF447). The NTSB investigator in charge of the 737 issues literally had nightmares about another crash occurring - specifically nightmares in which he was called before Congress and asked why the type was not grounded after two fatal incidents.
Compare that situation - where you have two fatal incidents and an isolated issue, but not enough information to confirm it - with the situation around the Thales pitot tubes, where the issue was successfully solved in 12 incidents out of 13.
Boeing published a workaround which involved maintaining a higher approach speed in the 737 while the issue was being solved. I boarded a few 737s during that period, and I must confess I didn't feel 100% safe, but trusted the pilots enough to get us out of any difficulties.
Likewise, Airbus published a procedure to deal with UAS while the Service Bulletin was taking effect. Unlike with the 737 PCU, the pitot tube fix was known and was being implemented, and with the UAS procedure in place, theoretically things were safe. Unfortunately in the case of AF447 the procedure was not followed.
[NB : The Concorde accident was down to a failure mode which was not considered at the time the aircraft was designed, and no procedure could have saved the aircraft. With AF447, the failure mode was known and workarounds put in place (which, sadly, were not followed) - it's a completely different scenario. ]
What you think is not the issue here. I repeat - an AD is only necessary when a fault is severe enough to be likely to cause the loss of the aircraft every time it occurs - for example, the DC-10 cargo door failure leading to hydraulic failure.
If ADs were required in every case where a fault made it possible to lose the aircraft then a lot of the world's fleets would spend a lot of the time grounded.
For example, if you go back to the late 1990s, the 737 fleet was flying around with a known problem in the rudder PCU, they just did not know what that fault was at that stage. The NTSB were considering pushing the FAA and international authorities AD to ground the 737, but it was considered impractical (not to mention the fact that Boeing was fighting tooth-and-nail to get UA535 and US427 classified as pilot error - note that Airbus is *not* doing this in the case of AF447). The NTSB investigator in charge of the 737 issues literally had nightmares about another crash occurring - specifically nightmares in which he was called before Congress and asked why the type was not grounded after two fatal incidents.
Compare that situation - where you have two fatal incidents and an isolated issue, but not enough information to confirm it - with the situation around the Thales pitot tubes, where the issue was successfully solved in 12 incidents out of 13.
Boeing published a workaround which involved maintaining a higher approach speed in the 737 while the issue was being solved. I boarded a few 737s during that period, and I must confess I didn't feel 100% safe, but trusted the pilots enough to get us out of any difficulties.
Likewise, Airbus published a procedure to deal with UAS while the Service Bulletin was taking effect. Unlike with the 737 PCU, the pitot tube fix was known and was being implemented, and with the UAS procedure in place, theoretically things were safe. Unfortunately in the case of AF447 the procedure was not followed.
[NB : The Concorde accident was down to a failure mode which was not considered at the time the aircraft was designed, and no procedure could have saved the aircraft. With AF447, the failure mode was known and workarounds put in place (which, sadly, were not followed) - it's a completely different scenario. ]
Last edited by DozyWannabe; 8th May 2012 at 15:23.
RetiredF4;
Further research on the AoA issues raised has yielded some interesting results.
Boeing has produced a document entitled, "Operational Use of Angle of Attack". In the introduction, Boeing states:
The document answers my question:
I haven't seen a similar document from Airbus yet but will continue research. Essentially however, this is how an AoA indication should function for an airline crew and I think may address Owain Glyndwr's points as well.
Further research on the AoA issues raised has yielded some interesting results.
Boeing has produced a document entitled, "Operational Use of Angle of Attack". In the introduction, Boeing states:
A dedicated AOA indicator shown on the primary flight display (PFD) recently has been developed in cooperation with airline customers. The new indicator is offered as an option on the 737-600/-700/-800/ -900, 767-400, and 777 at this time.
During the development of the new indicator, discussions with airlines, the NTSB, and U.S. Federal Aviation Administration (FAA) pilots and engineers provided a unique opportunity to examine potential uses of AOA and the many existing uses that have evolved in recent decades along with advances in display and indication technology.
This article discusses the following:
1. Basic principles of AOA.
2. Airplane performance and AOA.
3. AOA measurement.
4. AOA indications and flight crew procedures in current Boeing production models.
5. Design and uses of a separate AOA indicator.
During the development of the new indicator, discussions with airlines, the NTSB, and U.S. Federal Aviation Administration (FAA) pilots and engineers provided a unique opportunity to examine potential uses of AOA and the many existing uses that have evolved in recent decades along with advances in display and indication technology.
This article discusses the following:
1. Basic principles of AOA.
2. Airplane performance and AOA.
3. AOA measurement.
4. AOA indications and flight crew procedures in current Boeing production models.
5. Design and uses of a separate AOA indicator.
Boeing and several operators worked together to develop the display format for an optional AOA indicator (fig. 12). The upper right location was chosen as one that can be accomplished without significant rearrangement of the existing PFD or electronic flight display formats. The indicator itself consists of an analog scale and pointer, and digital representation similar to displays of many other parameters throughout the flight deck.
Stall warning AOA is shown with a red tick mark, which will change position as a function of Mach number for those airplanes with Mach dependent stall warning schedules.
A green approach reference band is shown whenever landing flaps are selected. The range of the approach reference band accounts for normally expected variations in CG, thrust, sideslip, and other considerations.
Many AOA indicators used in the past have been of the “normalized” type, where AOA is shown in arbitrary units and scaled so that zero load factor is shown as an AOA of zero and stall is shown as an AOA of one. Normalized AOA on a commercial jetliner would require that Mach number be introduced into the calculation of AOA because stall AOA and buffet margins are a function of Mach number.
The indicator developed shows body AOA in degrees and is not normalized, which is related to the second objective above, that the indicator be useful when pitot or static data, and therefore Mach calculations, are unreliable because of blockage or a fault in the system. The pointer of a normalized indicator in this condition would behave erratically, making the indicator unusable.
With the non-normalized design, the position of the needle is a function only of sensed AOA. The red tick mark for stall warning may behave erratically in a pitot or static failure state, as may stick shaker, PLI, and speed tape amber and red bands. However, the AOA needle and digits will remain stable, and the indicator itself still will be useful as a backup for unreliable airspeed, provided the AOA vanes are undamaged.
Stall warning AOA is shown with a red tick mark, which will change position as a function of Mach number for those airplanes with Mach dependent stall warning schedules.
A green approach reference band is shown whenever landing flaps are selected. The range of the approach reference band accounts for normally expected variations in CG, thrust, sideslip, and other considerations.
Many AOA indicators used in the past have been of the “normalized” type, where AOA is shown in arbitrary units and scaled so that zero load factor is shown as an AOA of zero and stall is shown as an AOA of one. Normalized AOA on a commercial jetliner would require that Mach number be introduced into the calculation of AOA because stall AOA and buffet margins are a function of Mach number.
The indicator developed shows body AOA in degrees and is not normalized, which is related to the second objective above, that the indicator be useful when pitot or static data, and therefore Mach calculations, are unreliable because of blockage or a fault in the system. The pointer of a normalized indicator in this condition would behave erratically, making the indicator unusable.
With the non-normalized design, the position of the needle is a function only of sensed AOA. The red tick mark for stall warning may behave erratically in a pitot or static failure state, as may stick shaker, PLI, and speed tape amber and red bands. However, the AOA needle and digits will remain stable, and the indicator itself still will be useful as a backup for unreliable airspeed, provided the AOA vanes are undamaged.
AOA
Well, would be too easy to just switch gauges from an fighter into an Airliner, didnt believe either that it would be possible.
So the AOA signal from the vane is available, the logic is there as well, it´s the engineers task to create a gadget which gives the necessary information for the required task. Use units or degrees, digits or a round gauge. the point i tried to make, its easy to use and doesn´t need sophisticated training.
The rhinos had different wings, stabilizers, Leading edge flaps, slats, BLC or no BLC, and therefore different onspeed values, different stall speeds and different wing rock behaviour. Therefore the numbers are only valid for one specific type, i estimate it´s the F4B. But that is no important point, as you tried to show how simple the system was built and that the indications lacked the accuracy necessary for air transport flying. I didn´t expect anything else and as mentioned before, i didn´t care. Despite that inaccuracy the phantom and other second generation fighters flew worldwide some millions flight hours with such a system and it kept thousands of pilots out of trouble.
Therefore the system might be inaccurate in todays standards, but it did its job well and never ever did i hear of an accident being caused by the inaccuracy of the AOA gauge.
Modern fighters still retain the indication of AOA in a modernized version, and those systems should somehow work in a air transport aircraft as well.
It´s not a question of technical feasability or of the necessary understanding and training, it´s a question of money and will.
@ PJ2 saw your post after i finished mine.
PJ2
Here is the ECAM logic which triggers the stall warning from AoA in Alternate Law - this was posted earlier, (can't recall who to credit), but it may illustrate what is meant by the question:
Here is the ECAM logic which triggers the stall warning from AoA in Alternate Law - this was posted earlier, (can't recall who to credit), but it may illustrate what is meant by the question:
@ Owain Glyndwr
Therefore the system might be inaccurate in todays standards, but it did its job well and never ever did i hear of an accident being caused by the inaccuracy of the AOA gauge.
Modern fighters still retain the indication of AOA in a modernized version, and those systems should somehow work in a air transport aircraft as well.
It´s not a question of technical feasability or of the necessary understanding and training, it´s a question of money and will.
@ PJ2 saw your post after i finished mine.
Last edited by RetiredF4; 8th May 2012 at 15:54.
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Airline pilots who've forgotten how to fly - Learmount
Relevant snippet (in the comments) :
Originally Posted by David Learmount
Airbus, and others, will be reviewing the aoa indicator option when all the wisdom is assembled in the BEA's final report. But that will not be for a while yet.
RetiredF4, thanks for a good discussion on this important item. Perhaps we'll see some authentic change in these areas which should be relatively straightforward to implement. I also look forward to how the BEA Final Report's recommendations on this and other issues raised. The installation of an AoA indication was also an NTSB recommendation made in the Airborne Express DC8 accident in 1996.
Re your comment, "...it´s a question of money and will.", Yes sir, it most certainly is, especially in these times, or as someone put it so well here, "It's an indication of the value placed by a carrier on human life", or some such similar pithy statement.
Dozy, thanks for the link. The comment makes sense, given that Airbus is "in process" regarding all outcomes of the BEA work.
Re your comment, "...it´s a question of money and will.", Yes sir, it most certainly is, especially in these times, or as someone put it so well here, "It's an indication of the value placed by a carrier on human life", or some such similar pithy statement.
Dozy, thanks for the link. The comment makes sense, given that Airbus is "in process" regarding all outcomes of the BEA work.
DW
He did try to correct the PF verbally, so it's reasonable to assume he realised, or at least felt that something was wrong. I'm not an expert, but his speech pattern seems to indicate indecision. The captain has put the PF in charge - if the PNF takes over before the captain arrives, will it reflect badly on him if it turns out to be unnecessary? Perhaps he felt that correcting the PF verbally until the captain arrived would be the safest path to take
Retired F4
But he didn´t get the clue, otherwise he would have asked or even he would have taken over the aircraft like you mentioned, correct?
But he didn´t get the clue, otherwise he would have asked or even he would have taken over the aircraft like you mentioned, correct?
2 h 10 min 11 What is that?
2 h 10 min 17 We’ve lost the the the speeds so… engine thrust ATHR engine lever thrust
2 h 10 min 22 Alternate law protections (law/low/lo)
2 h 10 min 24 Wait we’re losing…
2 h 10 min 25 Wing anti-ice
2 h 10 min 27 Watch your speed Watch your speed
2 h 10 min 31 Stabilise Go back down
2 h 10 min 33 You’re at Go back down
2 h 10 min 39 I’ll put you in in ATT (*)…
2 h 10 min 49 (…) where is he er?
2 h 11 min 00 Above all try to touch the lateral controls as little as possible eh
2 h 11 min 06 (…) is he coming or not?
2 h 11 min 21 But we’ve got the engines what’s happening (…)?
2 h 11 min 38 Controls to the left (and puts the SS to the full left stop)
(2 h 11 min 43 Captain on the deck: Er what are you doing?)
2 h 11 min 43 What’s happening? I don’t know I don’t know what’s happening
2 h 12 min 07 No above all don’t extend (the)
2 h 12 min 13 What do you think about it what do you think what do we need to do?
2 h 10 min 17 We’ve lost the the the speeds so… engine thrust ATHR engine lever thrust
2 h 10 min 22 Alternate law protections (law/low/lo)
2 h 10 min 24 Wait we’re losing…
2 h 10 min 25 Wing anti-ice
2 h 10 min 27 Watch your speed Watch your speed
2 h 10 min 31 Stabilise Go back down
2 h 10 min 33 You’re at Go back down
2 h 10 min 39 I’ll put you in in ATT (*)…
2 h 10 min 49 (…) where is he er?
2 h 11 min 00 Above all try to touch the lateral controls as little as possible eh
2 h 11 min 06 (…) is he coming or not?
2 h 11 min 21 But we’ve got the engines what’s happening (…)?
2 h 11 min 38 Controls to the left (and puts the SS to the full left stop)
(2 h 11 min 43 Captain on the deck: Er what are you doing?)
2 h 11 min 43 What’s happening? I don’t know I don’t know what’s happening
2 h 12 min 07 No above all don’t extend (the)
2 h 12 min 13 What do you think about it what do you think what do we need to do?
Is that really a pilot monitoring in the loop?
2 h 10 min 11 What is that?
2 h 10 min 27 Watch your speed Watch your speed
2 h 10 min 31 Stabilise Go back down
2 h 10 min 33 You’re at Go back down
2 h 11 min 00 Above all try to touch the lateral controls as little as possible eh
2 h 11 min 21 But we’ve got the engines what’s happening (…)?
2 h 11 min 38 Controls to the left (and puts the SS to the full left stop)
2 h 11 min 43 What’s happening? I don’t know I don’t know what’s happening
2 h 12 min 07 No above all don’t extend (the)
2 h 12 min 13 What do you think about it what do you think what do we need to do?
Tell me again, he had any plan on what was happening, why it was happening, and what could have been done about it. He was pilot monitoring, he could have used his whole concentration into that matter, but he didn´t get the picture.
Last edited by RetiredF4; 8th May 2012 at 17:16.
Airliner HUD
Thanks for the super link to Boeing, PJ.
@ other.....
You don't need to know the exact AoA you are at or the exact degrees that will get you into trouble. You just need relative values to be displayed. The Boeing link discusses the mach correction and configuration effects.
I once bumped the flap switch in my SLUF on approach and had only leading edge flaps ( they really smoothed out the buffet). So a poor cross check with speed had me maybe 10 or 15 knots faster than I should have been although I had the AoA bracket nailed in the HUD. No problem with stall, but a rain-soaked runway and long landing created a serious problem. Had to take the departure end barrier with my trusty hook and all was well ( except for meeting the boss and taking the heat for being stupid).
Although a decent AoA display could allow an optimum cruise, my personal thoughts are it should primarily help the crew prevent a stall and have an optimum approach AoA.
Seems the commercial airline folks do not want to implement a wide field-of-view HUD, but I can tell you that the sucker is invaluable in bad weather. Apparently the 737 fleet had the option a few years back, but I don't know if there are many being used. Some of the commercial pilots here could comment.
The HUD's I used were a lot easier to interpret than some of the panel displays I have seen here. Sure, they can be cluttered, but the ones I used had de-clutter options to help out.
Secondly, with the increasing deployment of FBW systems, HAL should use all available inputs to make the flight safer and easier than the old days. Why the AoA is ignored below 60 knots befuddles me. There are too many other sensor inputs to use than the airspeed or the AoA by themselves. So it comes down to the reversion laws and such, huh?
Lastly, and @ several here, the zero gee trajectory vastly reduces the chance of a stall. The 'bus keeps trying for the one gee Nz, and the trim system doesn't allow a trim otherwise. Compared with the Viper, we could trim the basic system for any gee from minus whatever to zero or about 3.5 positive gees. So a neat demo for the nugget was to run the trim all the way back and watch the jet do a hands-off perfect loop. As speed got low and we reached the AoA limit we stayed at the AoA limit until flying back down, when the gee limit came into play.
@ other.....
You don't need to know the exact AoA you are at or the exact degrees that will get you into trouble. You just need relative values to be displayed. The Boeing link discusses the mach correction and configuration effects.
I once bumped the flap switch in my SLUF on approach and had only leading edge flaps ( they really smoothed out the buffet). So a poor cross check with speed had me maybe 10 or 15 knots faster than I should have been although I had the AoA bracket nailed in the HUD. No problem with stall, but a rain-soaked runway and long landing created a serious problem. Had to take the departure end barrier with my trusty hook and all was well ( except for meeting the boss and taking the heat for being stupid).
Although a decent AoA display could allow an optimum cruise, my personal thoughts are it should primarily help the crew prevent a stall and have an optimum approach AoA.
Seems the commercial airline folks do not want to implement a wide field-of-view HUD, but I can tell you that the sucker is invaluable in bad weather. Apparently the 737 fleet had the option a few years back, but I don't know if there are many being used. Some of the commercial pilots here could comment.
The HUD's I used were a lot easier to interpret than some of the panel displays I have seen here. Sure, they can be cluttered, but the ones I used had de-clutter options to help out.
Secondly, with the increasing deployment of FBW systems, HAL should use all available inputs to make the flight safer and easier than the old days. Why the AoA is ignored below 60 knots befuddles me. There are too many other sensor inputs to use than the airspeed or the AoA by themselves. So it comes down to the reversion laws and such, huh?
Lastly, and @ several here, the zero gee trajectory vastly reduces the chance of a stall. The 'bus keeps trying for the one gee Nz, and the trim system doesn't allow a trim otherwise. Compared with the Viper, we could trim the basic system for any gee from minus whatever to zero or about 3.5 positive gees. So a neat demo for the nugget was to run the trim all the way back and watch the jet do a hands-off perfect loop. As speed got low and we reached the AoA limit we stayed at the AoA limit until flying back down, when the gee limit came into play.
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Originally Posted by DozyWannabe
"Are you pulling up?"
"Yes. Shouldn't I be?"
"No - we're approaching stall - I have control."
"You have control."
"Yes. Shouldn't I be?"
"No - we're approaching stall - I have control."
"You have control."
RF4, I do salute your patience. Your explanations are clear.
I find amusing how DW, who sat down twice in a A320 simulator (but I don’t know about the experience of OC ?) is teaching you what flying is and more specifically instruments flying :
Even if you've got a yoke in front of you, unless you're in a life-and-death situation (which this wasn't at that point), you should take it gently, follow through and verbally confirm what you're feeling before you try to take over. I've never heard of a successful recovery requiring handing over of control where one pilot simply grabbed the controls from the other.
Originally Posted by DozyWannabe
The Airbus Service Bulletin was binding in terms of the work being *required*, not recommended - and the work having to be done by a given date. An Airworthiness Directive is the next level up where the type is effectively grounded until the work is done, and that wasn't really necessary in this case. ADs are only used when a fault is so severe that it is likely to result in the loss of the aircraft every time it occurs.
My personal view on the AoA gauge on an airliner is that it has to be very simple and the training must suggest that anything approaching 5 degrees in cruise, or 15 deg at low level is inapropriate.
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@RF4/franzl :
There's a missing piece of info that renders this statement interesting (my bold)
What this means is that his words could be referring to either of his actions, or indeed both. I've not had any definite confirrmation as to what he was likely to be implying here.
In any case, this doesn't seem to be perceived by the PF as a definite assertion of control, as 2 seconds later he's back on his own sidestick.
We're losing a lot of context in transcript and translation, so it's difficult to read too much certainty into what he was saying. Your point of view is that he was almost as at sea as the PF, which may be valid. But I see another way of reading it - which is that he was aware he might have had a better handle on things but wasn't sure, hence the nervousness about the arrival of the Captain, and his automatic delegation and deference to the same as soon as he arrived.
Was it a "pilot monitoring, [fully] in the loop"? Probably not.
But - prior to the Captain's arrival - he definitely seems to be more savvy than his colleague when he does open his mouth. His calls are correct (if non-standard) and his inputs more measured (although the latter takes some extrapolation). He puts all his faith in the Captain, even when the captain is not on the flight deck, and his confidence seems to wane when it seems that the captain (who has been called back from rest) seems none the wiser.
Either of us could be right or both of us could be completely wrong. I doubt we'll ever know for sure because the guys we're talking about are all dead. What we have to contemplate is the possibility that the Captain's decision to delegate the relief role to the junior F/O might have made the PNF reticent to act decisively.
We know that a steep command gradient can cause a PNF to not correct a senior PF (e.g. Birgenair, KLM4805) and we know that a more competent PNF will defer to his commander if they have been conditioned to defer to authority (e.g. Palm 90). What we have here is a scenario where a commander has made a decision on command gradient which runs contrary to that which might be expected, which is new to the study of HF.
I've said before that it's a drawback to the sidestick concept, but there are benefits in some scenarios which outweigh it.
Not in the least. I'll happily defer to Franzl on flight and aerodynamics factors, but HF is an area in which we're both on fairly similar ground. Given that you (CONF) have repeatedly misrepresented the importance of airspeed to the alpha (AoA) max calculation, I guess we're even.
Nor do you hear about successful sidestick handovers. Let me get this straight - are you saying that it *is* the norm on a scheduled flight for one pilot to take control from another without saying a word?
OK - so the grounding date may be set in the future, but it doesn't change the fact that an AD would have been overkill in this case.
There's a missing piece of info that renders this statement interesting (my bold)
2 h 11 min 38 Controls to the left (Selects LHS sidestick priority and puts the [LHS] SS to the full left stop)
In any case, this doesn't seem to be perceived by the PF as a definite assertion of control, as 2 seconds later he's back on his own sidestick.
We're losing a lot of context in transcript and translation, so it's difficult to read too much certainty into what he was saying. Your point of view is that he was almost as at sea as the PF, which may be valid. But I see another way of reading it - which is that he was aware he might have had a better handle on things but wasn't sure, hence the nervousness about the arrival of the Captain, and his automatic delegation and deference to the same as soon as he arrived.
Was it a "pilot monitoring, [fully] in the loop"? Probably not.
But - prior to the Captain's arrival - he definitely seems to be more savvy than his colleague when he does open his mouth. His calls are correct (if non-standard) and his inputs more measured (although the latter takes some extrapolation). He puts all his faith in the Captain, even when the captain is not on the flight deck, and his confidence seems to wane when it seems that the captain (who has been called back from rest) seems none the wiser.
Either of us could be right or both of us could be completely wrong. I doubt we'll ever know for sure because the guys we're talking about are all dead. What we have to contemplate is the possibility that the Captain's decision to delegate the relief role to the junior F/O might have made the PNF reticent to act decisively.
We know that a steep command gradient can cause a PNF to not correct a senior PF (e.g. Birgenair, KLM4805) and we know that a more competent PNF will defer to his commander if they have been conditioned to defer to authority (e.g. Palm 90). What we have here is a scenario where a commander has made a decision on command gradient which runs contrary to that which might be expected, which is new to the study of HF.
I find amusing how DW ... is teaching you what flying is and more specifically instruments flying :
BTW Dozy, it is taking place everyday in the world, and not only in flying school. You don’t hear about it everytime it is successful.
You have been answered on this point already, so would you stop making the same erroneous comment.
Last edited by DozyWannabe; 8th May 2012 at 17:46.
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Retired F4
I was not unaware that the numbers were type specific. My point was simply that an AoA instrument for airline use would have to be more sophisticated than that on your F4 and that it might not give entirely reliable advice in a UAS situation. The Boeing explanation posted by PJ2 seems to bear this out.
I'm happy with that statement. And as I said I was not trying to argue against installation of AoA instruments, just to be clear on what they can or cannot give.
I was not unaware that the numbers were type specific. My point was simply that an AoA instrument for airline use would have to be more sophisticated than that on your F4 and that it might not give entirely reliable advice in a UAS situation. The Boeing explanation posted by PJ2 seems to bear this out.
With the non-normalized design, the position of the needle is a function only of sensed AOA. The red tick mark for stall warning may behave erratically in a pitot or static failure state, as may stick shaker, PLI, and speed tape amber and red bands. However, the AOA needle and digits will remain stable, and the indicator itself still will be useful as a backup for unreliable airspeed, provided the AOA vanes are undamaged.
DW
There's a missing piece of info that renders this statement interesting (my bold)
Quote:
2 h 11 min 38 Controls to the left (Selects LHS sidestick priority and puts the [LHS] SS to the full left stop)
What this means is that his words could be referring to either of his actions, or indeed both. I've not had any definite confirrmation as to what he was likely to be implying here.
There's a missing piece of info that renders this statement interesting (my bold)
Quote:
2 h 11 min 38 Controls to the left (Selects LHS sidestick priority and puts the [LHS] SS to the full left stop)
What this means is that his words could be referring to either of his actions, or indeed both. I've not had any definite confirrmation as to what he was likely to be implying here.
Here is the original one and it is without doubt,
2 h 11 min 38 Controls to the left
And explanatory text in IR 3:
The pilot in the captain’s seat takes over the controls. The Captain sidestick is positioned left in stop position.
Last edited by RetiredF4; 8th May 2012 at 19:07.
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@franzl - Exactly. Where I'm at a loss as to decide what he meant by that statement is that he uses the words "Commande ŕ gauche", which is ambiguous as to whether he is referring to putting in full left aileron, transferring control authority to the left-hand (Captain's) seat, or both - bearing in mind my understanding of French is limited to a translation dictionary.
The English translation is similarly ambiguous. I'm sure that if the BEA were certain as to what he was attempting to convey, they'd have translated it accordingly.
The English translation is similarly ambiguous. I'm sure that if the BEA were certain as to what he was attempting to convey, they'd have translated it accordingly.
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@PJ2..."If the AoA indication adjusts for high Mach Number, (as the ECAM stall warning does when the Airbus is in Alternate Law), then the indication is useful."......
To be brief, does the ECAM (FCM) have time after a/p loss and Alternate 2 to recalc the STALLWARN AoA? As near as I can tell that would be 4 degrees at M.80? IOW, you are satisfied the "STALLSTALL" is legit?(the first one). Also, what does Bank Angle play in the ECAM's (display, via FCM logic?)
@DOZY.....
"Well, for a start I don't think there's an updraft in existence that could cause a heavy widebody to climb like that, plus an updraft wouldn't necessarily cause the pitch to increase."
All aircraft are susceptible to updraft, size and mass are not irrelevant, but by itself, the size and mass of 447 doesn't innoculate it from the effects of UPDRAFT. Yes, the PITCH may remain constant, but the AoA will not, it will INCREASE......Dozy, is it possible the presence of updraft may have caused the initial divergence in PITCH/AoA?
To be brief, does the ECAM (FCM) have time after a/p loss and Alternate 2 to recalc the STALLWARN AoA? As near as I can tell that would be 4 degrees at M.80? IOW, you are satisfied the "STALLSTALL" is legit?(the first one). Also, what does Bank Angle play in the ECAM's (display, via FCM logic?)
@DOZY.....
"Well, for a start I don't think there's an updraft in existence that could cause a heavy widebody to climb like that, plus an updraft wouldn't necessarily cause the pitch to increase."
All aircraft are susceptible to updraft, size and mass are not irrelevant, but by itself, the size and mass of 447 doesn't innoculate it from the effects of UPDRAFT. Yes, the PITCH may remain constant, but the AoA will not, it will INCREASE......Dozy, is it possible the presence of updraft may have caused the initial divergence in PITCH/AoA?
Last edited by Lyman; 8th May 2012 at 18:41.
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Lyman, all values are recalculated in real time - don't think of it as a home computer where tasks are prioritised differently and the machine will slow down as it has to process more. These computers are designed to process all the streams of information without missing a beat.
In answer to your question, the STALLSTALL at 02:10:10 was "G" induced and was silenced almost as quickly as it appeared. The *next* STALLSTALL was the real deal, however - and stayed on until the aircraft was well outside the designed operating envelope.
An updraft may mess with the AoA, but crucially the flight path does not indicate a climb of this nature, and nor does the DFDR data. This was a commanded climb.
In answer to your question, the STALLSTALL at 02:10:10 was "G" induced and was silenced almost as quickly as it appeared. The *next* STALLSTALL was the real deal, however - and stayed on until the aircraft was well outside the designed operating envelope.
An updraft may mess with the AoA, but crucially the flight path does not indicate a climb of this nature, and nor does the DFDR data. This was a commanded climb.
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Doze....
"Lyman, all values are recalculated in real time - don't think of it as a home computer where tasks are prioritised differently and the machine will slow down as it has to process more. These computers are designed to process all the streams of information without missing a beat."
Yes, I know, it was a bit of a trick question, but not meant in any sinister way. What was the calculated AoA for STALLWARN at the instant of STALLSTALL? Via that data, you might guess what I am after.....
"In answer to your question, the STALLSTALL at 02:10:10 was "G" induced and was silenced almost as quickly as it appeared. The *next* STALLSTALL was the real deal, however - and stayed on until the aircraft was well outside the designed operating envelope."
Yes, but to acquire "G" what needs to happen? What silenced the WARN? G is a symptom.....
"An updraft may mess with the AoA, but crucially the flight path does not indicate a climb of this nature, and nor does the DFDR data. This was a commanded climb."
Yes, a commanded climb, no argument. Any other possibilities? Assistances?
The STALLWARN happened after loss of Autopilot, and the machine will not WARN in Normal Law, and we know (?) the aircraft was in ALTERNATE LAW, is it possible the a/c degraded merely (only) to acommodate the WARNING?
Lyman
"Lyman, all values are recalculated in real time - don't think of it as a home computer where tasks are prioritised differently and the machine will slow down as it has to process more. These computers are designed to process all the streams of information without missing a beat."
Yes, I know, it was a bit of a trick question, but not meant in any sinister way. What was the calculated AoA for STALLWARN at the instant of STALLSTALL? Via that data, you might guess what I am after.....
"In answer to your question, the STALLSTALL at 02:10:10 was "G" induced and was silenced almost as quickly as it appeared. The *next* STALLSTALL was the real deal, however - and stayed on until the aircraft was well outside the designed operating envelope."
Yes, but to acquire "G" what needs to happen? What silenced the WARN? G is a symptom.....
"An updraft may mess with the AoA, but crucially the flight path does not indicate a climb of this nature, and nor does the DFDR data. This was a commanded climb."
Yes, a commanded climb, no argument. Any other possibilities? Assistances?
The STALLWARN happened after loss of Autopilot, and the machine will not WARN in Normal Law, and we know (?) the aircraft was in ALTERNATE LAW, is it possible the a/c degraded merely (only) to acommodate the WARNING?
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I'm not in a position to do the maths right now, Lyman - but what I can tell you is that we got the same "G"-induced STALLSTALL in the sim at the moment I commanded pitch to 15 degrees - it was not caused by the updraft (the effects of which were simulated by the TRE using asymmetric thrust).
The "G"-induced STALLSTALL was caused by the sudden change in AoA caused by the pitch input, and was silenced because the airspeed was sufficient to climb and the values settled within limits. The behaviour would be the same with an electro-mechanical stall warning system, as far as I know.
The "G"-induced STALLSTALL was caused by the sudden change in AoA caused by the pitch input, and was silenced because the airspeed was sufficient to climb and the values settled within limits. The behaviour would be the same with an electro-mechanical stall warning system, as far as I know.
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DozyWannabe I'm not in a position to do the maths right now, Lyman - but what I can tell you is that we got the same "G"-induced STALLSTALL in the sim at the moment I commanded pitch to 15 degrees - it was not caused by the updraft (the effects of which were simulated by the TRE using asymmetric thrust).
Yes, but in Which LAW was the SIM when you got STALLWARN...... And had you programmed "UAS" prior to unlatch?
In NORMAL LAW, the a/c will respond to a/p within certain limits of rate and deflection. It will also respond to rate ONLY..... So if G loaded beyond the limit of a/p, it will unlatch the a/p, by definition. So how are we to know what caused the a/p to unlatch? Speeds, or G, or "Rate". Or TREND? Inability to arrest TREND inside limits? This is an old question, but I thought I'd bring it up now that we're there, again.
Yes, but in Which LAW was the SIM when you got STALLWARN...... And had you programmed "UAS" prior to unlatch?
In NORMAL LAW, the a/c will respond to a/p within certain limits of rate and deflection. It will also respond to rate ONLY..... So if G loaded beyond the limit of a/p, it will unlatch the a/p, by definition. So how are we to know what caused the a/p to unlatch? Speeds, or G, or "Rate". Or TREND? Inability to arrest TREND inside limits? This is an old question, but I thought I'd bring it up now that we're there, again.
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All evidence suggests that the autopilot disconnected because of UAS itself, as it was designed to do - not because of any external factors. Modern autopilots are designed to cope with moderate turbulence of the kind encountered by AF447, but you should know this because we've discussed that very subject before.
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jcjeant,
Here is an interesting Powerpoint presentation that gives you the timeline and information on the pitot tubes. Slide #37 is a discussion between AF and Airbus, in French that perhaps you can translate the gist of for me. Hope you can open it...
http://henrimarnetcornus.20minutes-b.../151647242.ppt
TD
Here is an interesting Powerpoint presentation that gives you the timeline and information on the pitot tubes. Slide #37 is a discussion between AF and Airbus, in French that perhaps you can translate the gist of for me. Hope you can open it...
http://henrimarnetcornus.20minutes-b.../151647242.ppt
TD