AF447 wreckage found
In Alternate and Direct Law the stall warning is now based on AOA only as the computers recognize the IAS may be wrong ( amongst other things) .
Seems like a good fall back thing to me.
Seems like a good fall back thing to me.
yeah Bloggs I agree with you. I guess Airbus thought an A330 wouldn't get that slow in the air!!
A simple thing to re program I would think.
It's still complicated though because as they fell toward the sea at <60 KIAS with a very high AOA they were in Alternate law and the speed should have had nothing to do with the stall warning activation. So it should still have sounded. Maybe the Flight Controls reverted to normal law after the probes thawed????
The more you read FCOM 1 the more you get confused!!
Time to close the book....
A simple thing to re program I would think.
It's still complicated though because as they fell toward the sea at <60 KIAS with a very high AOA they were in Alternate law and the speed should have had nothing to do with the stall warning activation. So it should still have sounded. Maybe the Flight Controls reverted to normal law after the probes thawed????
The more you read FCOM 1 the more you get confused!!
Time to close the book....
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Stall warning fix
yeah Bloggs I agree with you. I guess Airbus thought an A330 wouldn't get that slow in the air!!
A simple thing to re program I would think.
It's still complicated though because as they fell toward the sea at <60 KIAS with a very high AOA they were in Alternate law and the speed should have had nothing to do with the stall warning activation. So it should still have sounded. Maybe the Flight Controls reverted to normal law after the probes thawed????
A simple thing to re program I would think.
It's still complicated though because as they fell toward the sea at <60 KIAS with a very high AOA they were in Alternate law and the speed should have had nothing to do with the stall warning activation. So it should still have sounded. Maybe the Flight Controls reverted to normal law after the probes thawed????
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Turkish Crash at Amsterdam was ex military, this other incident where a 737 crashed during the night in a turn where the cpat was pilot flying was ex mil.
Ex mil is not safer, or less safe.
Ex mil is not safer, or less safe.
Bloggs:--
I've had another read of your post.
If all the Pitot tubes iced up evenly together and there was no immediate discrepancy between the 3 ADR's then the Flight controls may well stay in Normal Law and all protections would still work including Stall Warnings. Therefore if the speed is iced up slow you will get incorrect Stall warnings. Hence the warning in the QRH.
If however if there is a discrepancy between the ADR's the Flight controls will revert to Alternate Law and then the stall warning will only be based on AOA directly from the vanes. Hence the warning in the QRH to respect Stall warnings while in Alternate or Direct Law.
THE TRICK FOR THE PILOT IS TO KNOW WHICH LAW YOU ARE IN
I've had another read of your post.
If all the Pitot tubes iced up evenly together and there was no immediate discrepancy between the 3 ADR's then the Flight controls may well stay in Normal Law and all protections would still work including Stall Warnings. Therefore if the speed is iced up slow you will get incorrect Stall warnings. Hence the warning in the QRH.
If however if there is a discrepancy between the ADR's the Flight controls will revert to Alternate Law and then the stall warning will only be based on AOA directly from the vanes. Hence the warning in the QRH to respect Stall warnings while in Alternate or Direct Law.
THE TRICK FOR THE PILOT IS TO KNOW WHICH LAW YOU ARE IN
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Am I right in thinking that -10,000 ft/min is around 100kts down? In which case if their airspeed was <60kts a normal attitude would produce a very high AoA.
If so they may have a normal attitude displayed, unknown airspeed indication, and no stall warning. Perhaps only clue was high rate of descent which they might not have believed given normal attitude?
If so they may have a normal attitude displayed, unknown airspeed indication, and no stall warning. Perhaps only clue was high rate of descent which they might not have believed given normal attitude?
The last recorded information was that they were moving at 107 kts ground speed, so depending on what direction the wind was blowing, they might have had sufficient forward speed for the stall warning to continue sounding for the entire descent.
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The trick for the pilot is to know which law you are in
Nitpicker330: THE TRICK FOR THE PILOT IS TO KNOW WHICH LAW YOU ARE IN
Tell me this could be averted or is everyone screwed in similar circumstances?
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"Blame the Pilots of Air France 447? Not So Fast"
It's happened before and they survived.
We don't yet know all the details of this accident, what the Pilots were thinking
or exactly what Law this Aircraft was in.
Indeed the whole Flight Control Law system is complicated and I'm not an expert in it..
I would expect that following this accident Pilots are even more aware of the problem.
We don't yet know all the details of this accident, what the Pilots were thinking
or exactly what Law this Aircraft was in.
Indeed the whole Flight Control Law system is complicated and I'm not an expert in it..
I would expect that following this accident Pilots are even more aware of the problem.
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Indeed the whole Flight Control Law system is complicated.....
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Is there some problem in displaying AOA prominantly? Does this lead to some other disasterous scenario ?
If your first action in an emergency is AVIATE. If AOA is the single most important indicator of this...why bury it on page 7 of some subsiduary display ???
Yes good crew should be able to interpret the conflicting information presented to them as possibly occured in this accident. But why make it difficult ?
We all have our "Off-Days". Two days ago I put petrol in my diesel car...for the second time!?! I was distracted at the time by some idiot trying to park nearby. I was mortified. Not because of diesle in my car but because of such a stupid mistake which in a less forgiving enviroment (aviation) could have been disasterous.
If your first action in an emergency is AVIATE. If AOA is the single most important indicator of this...why bury it on page 7 of some subsiduary display ???
Yes good crew should be able to interpret the conflicting information presented to them as possibly occured in this accident. But why make it difficult ?
We all have our "Off-Days". Two days ago I put petrol in my diesel car...for the second time!?! I was distracted at the time by some idiot trying to park nearby. I was mortified. Not because of diesle in my car but because of such a stupid mistake which in a less forgiving enviroment (aviation) could have been disasterous.
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Here's an observation which may or may not be relevant. The plane decelerated from horizontal Mach 0.82 to 107 knots over a period of 3 min 30s. By my estimate that is an average horizontal deceleration of around 0.1g.
It seems to me that, given no visual cues nor instrument readings, a pilot flying by the seat of his pants may interprete a pitch up attitude coupled with such a horizontal deceleration as level flight. Furthermore, lowering the nose would immediately decrease the horizontal component of deceleration, which the pilot may perceive confusingly as his nose pitching up (which is what it has been all along). Pulling back on the stick would return to the illusion of level flight, albeit with a stick operating "in reverse". (This is assuming the control sufaces are still capable of controlling the a/c.)
Note the report states "inputs made by the PF were mainly nose-up", (my italics) and in its 3D diagram the descent appears to consist of straight lines.
It seems to me that, given no visual cues nor instrument readings, a pilot flying by the seat of his pants may interprete a pitch up attitude coupled with such a horizontal deceleration as level flight. Furthermore, lowering the nose would immediately decrease the horizontal component of deceleration, which the pilot may perceive confusingly as his nose pitching up (which is what it has been all along). Pulling back on the stick would return to the illusion of level flight, albeit with a stick operating "in reverse". (This is assuming the control sufaces are still capable of controlling the a/c.)
Note the report states "inputs made by the PF were mainly nose-up", (my italics) and in its 3D diagram the descent appears to consist of straight lines.
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Quote: According to the BEA report, the AOA was indicated at 4 degrees as they went over the top. Since this is the primary driver of the stall warning, the warning would likely have shut off, no matter what the speed was, and even if they didn't disable it a low speed.
This is interesting. In researching FBW accidents for a presentation to ISASI, there was an A-340 (with similiar control laws) that triggered Angle-of-attack protection during cruise at FL360 over the north Atlantic. Once AoA protection is invoked, zero stick input will cause the airplane to maintain alpha-prot (about 4 something AoA). Since AoA at cruise is about 1 degree, this will result in a zoom. In the A-340 case, it zoomed over 2000 ft before the pilot could recover.
Now I know the airplane was reported to be in alternate law (AoA protection not available), but I would still wonder. I think we need to let BEA figure all this stuff out.
One more thing. There have been references to the NWA B-727 which departed KJFK with the pitot heat off. This was a colleague of mine and, at the time, I wondered "how could he be so dumb?" Well a year or so later, I found out just how dumb on can be. When all sorts of contradictory information is present from various failures, it is very easy to latch onto one conclusion and only see those facts that support that conclusion and ignore those that don't.
This is interesting. In researching FBW accidents for a presentation to ISASI, there was an A-340 (with similiar control laws) that triggered Angle-of-attack protection during cruise at FL360 over the north Atlantic. Once AoA protection is invoked, zero stick input will cause the airplane to maintain alpha-prot (about 4 something AoA). Since AoA at cruise is about 1 degree, this will result in a zoom. In the A-340 case, it zoomed over 2000 ft before the pilot could recover.
Now I know the airplane was reported to be in alternate law (AoA protection not available), but I would still wonder. I think we need to let BEA figure all this stuff out.
One more thing. There have been references to the NWA B-727 which departed KJFK with the pitot heat off. This was a colleague of mine and, at the time, I wondered "how could he be so dumb?" Well a year or so later, I found out just how dumb on can be. When all sorts of contradictory information is present from various failures, it is very easy to latch onto one conclusion and only see those facts that support that conclusion and ignore those that don't.
Also don't blame the THS trimming up to 13 deg nose up. It was a result of the Pilots demanding back stick pitch up ( to counter what they thought was an overspeed ) the speed obviously decayed during the manoeuvre requiring more and more trim to help it satisfy the Pilots demand.
In this case, the system trimmed full nose up and stayed there. That doesn't sound like a good idea to me and wouldn't have helped any nose down recovery effort by the crew, at least in the initial bit at the top of the zoom. They wouldn't have had to hold in a shedload of forward stick to get the thing to start trimming nose down.
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30+ years ago I read an announcement of the Rosemount company developing a self-actuated Pitot heat system; it consisted of a vibrating reed in the airflow. If ice builds on the reed, it changes the natural frequency of vibration, and this frequency shift activates the ice protection.
Does anyone know what became of this system?
Does anyone know what became of this system?
Bloggs......Hang on a sec, on a normal aircraft if you thought you had an overspeed and pulled back on the stick you would most likely also trim back to assist as well.
In this case as the Pilot demanded nose up as the speed decayed it trimmed full up and stayed there most likely because the Pilots never pushed the stick forward during the stalled free fall from 38,000 feet so the Flight Control computers didn't see the need to trim forward either......
If they had applied full forward Sidestick in an attempt to un stall the wing then the stab would have moved forward to assist. It seems they not only didn't push forward they pulled back.
In this case as the Pilot demanded nose up as the speed decayed it trimmed full up and stayed there most likely because the Pilots never pushed the stick forward during the stalled free fall from 38,000 feet so the Flight Control computers didn't see the need to trim forward either......
If they had applied full forward Sidestick in an attempt to un stall the wing then the stab would have moved forward to assist. It seems they not only didn't push forward they pulled back.
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@barit1
Todays pitot heat are usually auto/on by default. Airbus have the pitots heated low on ground as long as one engine is running and normal in flight mode. There's a switch to go from AUTO to ON for PROBE/WINDOW HEAT.
Todays pitot heat are usually auto/on by default. Airbus have the pitots heated low on ground as long as one engine is running and normal in flight mode. There's a switch to go from AUTO to ON for PROBE/WINDOW HEAT.
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If I remember correctly those Air Caraibes guys who managed their loss of speed indication, also had the good idea to throw that switch from AUTO to ON and that probably helped to regain correct speed indications