AF447
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@Hyperveloce
The flight warning computer uses only AOA data and flap/slat position in normal law. In alternate law, the speed becomes part of the threshold calculation along with AOA information.
The flight warning computer uses only AOA data and flap/slat position in normal law. In alternate law, the speed becomes part of the threshold calculation along with AOA information.
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Stall warning
You mean airspeed becomes part of the calculation even if the alternate law has been triggered by an ADR disagreement ?! (corrupted airspeeds)
This would justify the ECAM status message "risks of undue stall warning" (that should be discarded according to certain SOPs, because the stall alarms are supposed to be based on the AoA and not the airspeeds)
Jeff
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Originally Posted by Hazelnuts39
Actually, these things are governed by airworthiness requirements, e.g.:
FAR/JAR 25.207 Stall warning (a)Stall warning with sufficient margin to prevent inadvertent stalling (...) must be clear and distinctive to the pilot in straight and turning flight.
FAR/JAR 25.207 Stall warning (a)Stall warning with sufficient margin to prevent inadvertent stalling (...) must be clear and distinctive to the pilot in straight and turning flight.
If these are found to be insufficient in any way, then discussion and resolution/agreement by both parties would be expected. But 'sufficient margin' indicates we are in an area of subjective judgement rather than predicated figures.
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Leading French daily Le Figaro says this morning a "Last Attempt" has been started to recover the flight recorders using sonar at the end of a 1,500m cable to "visually scan" for the wreckage down to 6,000 metres. The search will go back over the 16,000 sq.km. search zone and take four to weeks.
For the anecdotal laff, I have to add some source's complaint that pingers sounded like whales, or whales too much like pingers.
Source: Le Figaro - France : AF 447 : ultime tentative pour retrouver les boîtes noires
For the anecdotal laff, I have to add some source's complaint that pingers sounded like whales, or whales too much like pingers.
Source: Le Figaro - France : AF 447 : ultime tentative pour retrouver les boîtes noires
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vapilot2004
Do you notice something ironic about this considering it appears one of the ways you find yourself in alternate law conditions is loss of airspeed indication? 
JD-EE
The flight warning computer uses only AOA data and flap/slat position in normal law. In alternate law, the speed becomes part of the threshold calculation along with AOA information.
JD-EE
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Hi,
That's part of the great Airbus protection system ... never fail 
Bye.
The flight warning computer uses only AOA data and flap/slat position in normal law. In alternate law, the speed becomes part of the threshold calculation along with AOA information.
Do you notice something ironic about this considering it appears one of the ways you find yourself in alternate law conditions is loss of airspeed indication?
Bye.
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Stall warnings & corrupted airspeeds
From what was said, can we conclude that stall false alarms are a very natural outcome from an ADR disagree ? (and the subsequent alternate law 2). It may go hand in hand with overspeed alarms in certain cases.
If we assume there is a high probability that the AF 447 may have been subjected to false alarms, we could then try to figure out how a pilot could react to these stall alarms given the known contextual elements. Or try to find past cases of false alarms of stalling and the associated crew reaction. There are basically two main possibilities: either the crew discard the stall alarms and do not consider them as justified, or the crew makes the opposite choise ? The first possibility would lead to something similar to the Air Caraïbes scenario (not exactly the same though). Don't you think we should explore the second scenario ?
Jeff
PS) We could assess the aerodynamic margins as a function of time from this opposite crew decision & action (beyond whether a pilot could take this opposite decision or not given the context), to try to see how long could it take from the initiation of an overspeed situation to a loss of aerodynamical control, how much time the crew had to recognize and correct this situation gradually leading them out of the flight envelope, to get some timing references. We could try to see which were the clues or indicators that crew may have relied upon to make a correct assessment of the situation, even in the absence of airspeeds (taking in account past cases, we can also make hypothesis so as to the Pitot freezing event duration, or the time when the airspeeds may have recovered their normal values). We can compare this timeline to the ACARS sequence chronology (keeping in mind that the PRIM and SEC failure at 02:13Z may result from an intentional crew attempt to reset the faulty Master flight computer to regain the normal law for the rest of flight).
We would need inputs from experienced pilots for the crew reactions to the multiples signals given the context.
PPS) The Birgenair flight 301: Pitots problems due to maintenance, corrupted airspeeds, false overspeed alarm, and high altitude stall:
http://www.youtube.com/watch?v=vDd2fL5XYSA&feature=related
If we assume there is a high probability that the AF 447 may have been subjected to false alarms, we could then try to figure out how a pilot could react to these stall alarms given the known contextual elements. Or try to find past cases of false alarms of stalling and the associated crew reaction. There are basically two main possibilities: either the crew discard the stall alarms and do not consider them as justified, or the crew makes the opposite choise ? The first possibility would lead to something similar to the Air Caraïbes scenario (not exactly the same though). Don't you think we should explore the second scenario ?
Jeff
PS) We could assess the aerodynamic margins as a function of time from this opposite crew decision & action (beyond whether a pilot could take this opposite decision or not given the context), to try to see how long could it take from the initiation of an overspeed situation to a loss of aerodynamical control, how much time the crew had to recognize and correct this situation gradually leading them out of the flight envelope, to get some timing references. We could try to see which were the clues or indicators that crew may have relied upon to make a correct assessment of the situation, even in the absence of airspeeds (taking in account past cases, we can also make hypothesis so as to the Pitot freezing event duration, or the time when the airspeeds may have recovered their normal values). We can compare this timeline to the ACARS sequence chronology (keeping in mind that the PRIM and SEC failure at 02:13Z may result from an intentional crew attempt to reset the faulty Master flight computer to regain the normal law for the rest of flight).
We would need inputs from experienced pilots for the crew reactions to the multiples signals given the context.
PPS) The Birgenair flight 301: Pitots problems due to maintenance, corrupted airspeeds, false overspeed alarm, and high altitude stall:
http://www.youtube.com/watch?v=vDd2fL5XYSA&feature=related
Last edited by Hyperveloce; 21st Jul 2009 at 23:08. Reason: the post-post-scriptum with Birgenair flight 301 case
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voluntary PRIM reset ?
Has anyone ever had to reset his PRIM ?
How long does it take between the manual switching off/on and PRIM being back on line and operational ?
How long does it take for the related ECAM or ACARS (from the manual reset) to appear ?
If the crew was already hand flying, could the PRIM reset have interfered with the pilot's manual flight controls ?
Jeff
How long does it take between the manual switching off/on and PRIM being back on line and operational ?
How long does it take for the related ECAM or ACARS (from the manual reset) to appear ?
If the crew was already hand flying, could the PRIM reset have interfered with the pilot's manual flight controls ?
Jeff
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Autothrust OFF
Hi. the BEA report states that this ACARS alarm (AUTO FLT A/THR OFF) is the result of an unintentional disconnection (not the result of an "instinctive disconnect" buttons use, nor of a thrust lever put on idle).
In the case of Air Caraïbe it was already/intentionaly off (severe turbulence proc.) when the problems arised, same thing in the Paris-Antananarivo (AF A340), and in TOGA LK state after the sequence of problems. Jeff
AUTO FLT A/THR OFF (Single chime Master caution)
In the case of Air Caraïbe it was already/intentionaly off (severe turbulence proc.) when the problems arised, same thing in the Paris-Antananarivo (AF A340), and in TOGA LK state after the sequence of problems. Jeff
AUTO FLT A/THR OFF (Single chime Master caution)
Signification : ce message indique une déconnexion de l’auto-poussée autrement que par l’utilisation du bouton prévu à cet effet sur les manettes de commande de poussée (instinctive disconnect) ou par un déplacement de celles-ci sur le cran ralenti (idle). (BEA report page 52)
Last edited by Hyperveloce; 21st Jul 2009 at 18:33.
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Hi,
Why it's necessary to trow the dices in case of emergency 
Anyways it's 50/50 .. not bad for a game of chance
Bye.
There are basically two main possibilities: either the crew discard the stall alarms and do not consider them as justified, or the crew makes the opposite choise ?
Anyways it's 50/50 .. not bad for a game of chance
Bye.
Why it's necessary to trow the dices in case of emergency
Anyways it's 50/50 .. not bad for a game of chance
Anyways it's 50/50 .. not bad for a game of chance
But we haven't decided yet between man and machine in emergencies.
Man follows a thought process sometimes influence by softer things like from reading PPRune. The machine follows simple logic and rules which may not always consider the interface with man.
Thus the result is not anymore predictable than chance. (hopefully not nearly as bad as 50-50).
Right now the best the design of the product can do is to give you a chance that you can influence the outcome.
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Looking at two men walking a few steps on the surface of the moon on french TV, i wonder how much it would cost to send an instrumented business jet equipped with an assortment of pitot probes on a few flights across the upper layers of the ITCZ?
Last edited by HazelNuts39; 22nd Jul 2009 at 10:43. Reason: somewhat offtrack
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Looking at two men walking a few steps on the surface of the moon on french TV, i wonder how much it would cost to send an instrumented business jet equipped with an assortment of pitot probes on a few flights across the upper layers of the ITCZ?
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I hate to state the obvious, but that was just done and we are all pretty sure how it turned out.
I know that sounds flippant, but who would pay for it? Who would fly it? Who would do what the 300lb Gorilla in the room would say needs to be done (again).
I suspect the results would be the same.
Every night since this crash, 8 to 10 heavy transports procede along this route uneventfully and manage to avoid CNN.
5 did it the exact same night within +/- 6 hours. Along the same route. Same exact weather. They managed it without incident.
The answer to this crash is not in the DFDR. It probably has nothing to do with any design philosophy or defect. Have been through this area more times than I ever care to remember. In several different types of aircraft.
The answers are in the CVR.
I know that sounds flippant, but who would pay for it? Who would fly it? Who would do what the 300lb Gorilla in the room would say needs to be done (again).
I suspect the results would be the same.
Every night since this crash, 8 to 10 heavy transports procede along this route uneventfully and manage to avoid CNN.
5 did it the exact same night within +/- 6 hours. Along the same route. Same exact weather. They managed it without incident.
The answer to this crash is not in the DFDR. It probably has nothing to do with any design philosophy or defect. Have been through this area more times than I ever care to remember. In several different types of aircraft.
The answers are in the CVR.
Last edited by singpilot; 22nd Jul 2009 at 00:50. Reason: Clarity and Emphasis
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The post above by singpilot says it all, to all professional pilots the world over!
To all the armchair, fifth quarter, wise after the event, non pilots on Prune, please take note.
Your views are useless, ignored, disregarded and treated with patronising contempt by all professional pilots!!
Singpilots post should close this thread.
To all the armchair, fifth quarter, wise after the event, non pilots on Prune, please take note.
Your views are useless, ignored, disregarded and treated with patronising contempt by all professional pilots!!
Singpilots post should close this thread.
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A simple question.
Considering all the AB 330/340 pitot related incidents that have resulted in the AC control systems going to alternate law and throwing stall alarms at the flying crew - from the information discussed here and on Eurocockpit we seem to be looking at between 5 and 9 incidents.
Was AF447 the first such incident to happen in darkness when the flying crew will have had less visual feedback from their environment?
Considering all the AB 330/340 pitot related incidents that have resulted in the AC control systems going to alternate law and throwing stall alarms at the flying crew - from the information discussed here and on Eurocockpit we seem to be looking at between 5 and 9 incidents.
Was AF447 the first such incident to happen in darkness when the flying crew will have had less visual feedback from their environment?
Per Ardua ad Astraeus
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Indeed, singpilot's post is spot on, but do not forget we do not know if any other 330s had the same series of 'failures' that night on that route, nor does the fact that 1 Qantas 330 suffered a serious pitch excursion while others flew happily along mean there is not an underlying technical issue. Unfortunately the chances of the CVR being of use are practically nil, so we have to go on what is 'known'. You cannot just fold your arms and say "crew issue, full stop"
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"Indeed, singpilot's post is spot on, but do not forget we do not know if any other 330s had the same series of 'failures' that night on that route"
Well, that's an incorrect statement as you well know, BOAC!
If other operators had problems on that route we would know about it by now!
You know that!?
Well, that's an incorrect statement as you well know, BOAC!
If other operators had problems on that route we would know about it by now!
You know that!?
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Good - now that is clear, so that suggests that something 'unusual' happened with 447 which did not happen to the others. If others had had the same problems and 'survived', that would tend to point your way. Since they didn't it is not really relevant, I feel.
Can you put your cards on the table please. I believe you are endorsing sp's suggestion that it was a crew error? Is that your position?
Can you put your cards on the table please. I believe you are endorsing sp's suggestion that it was a crew error? Is that your position?