A320 unreliable speed . . . only if you are a nerd like me
Any aircraft can stall but the bus tries very hard not to. If you are back somewhere beween alpha prot and alpha max and you encounter a windshear it could stall, that is why the fctm encourages you not to hang around in this corner of the envelope.
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Josua - but see C-Star and CONF's posts earlier - AoA protection takes priority over overspeed protection and AoA prot is controlled by AoA vanes, not pitot static system, so it is unaffected by blockage. System should not let you stall (though TL is right in that this is not a nice part of the envelope to hang about in).
the scenario under discussion is why the full sentence from the QRH reads:
i.e. DON'T DELAY troubleshooting by climbing higher than absolutely necessary.
I love the QRH statement "level off for troubleshooting".
when at, or above MSA or circuit altitude level off for troubleshooting
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RHS
The only way to get out of this was to switch off two ADRs thus forcing alternate law where manual control of pitch could be reestablished?
Example: Theoretically you can switch Off both FAC and you have Alternate Law but you cannot find it as a procedure.
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"Flight control protections kicked in and tried to force the nose of the aircraft upward as designed to exit the overspeed condition, but in this unique set of circumstances led toward a stall condition. The only way to get out of this was to switch off two ADRs thus forcing alternate law where manual control of pitch could be reestablished?"
Better summing up than I could do.
From Stall Recovery A320 QRH. " In case of lack of pitch down authority, reducing thrust may be necessary"
So are we going to be really concerned which protection takes priority in Airbus logic or will I just think " Fn"3k it this is not doing what I want it to do" 2 times ADR OFF!
As I said scary...
Better summing up than I could do.
From Stall Recovery A320 QRH. " In case of lack of pitch down authority, reducing thrust may be necessary"
So are we going to be really concerned which protection takes priority in Airbus logic or will I just think " Fn"3k it this is not doing what I want it to do" 2 times ADR OFF!
As I said scary...
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Originally Posted by tubby linton
Any aircraft can stall but the bus tries very hard not to. If you are back somewhere beween alpha prot and alpha max and you encounter a windshear it could stall, that is why the fctm encourages you not to hang around in this corner of the envelope.
"If FD bars are unavailable, use an initial pitch attitude up to 17.5 ° with full backstick, if necessary. If needed, to minimize the loss of height, increase this pitch attitude."
Airbus wants you to rely faithfully on their protections and their management of alpha.
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i'm not sure if your scenario is possible in real a/c. However, two things should be noted here:
- Hi AoA protection has priority over high speed protection, so you shouldn't stall as long as you stay in Normal Law.
- switching off 2 ADR's is sufficient to force Alternate Law. While it's is not the procedure for UAS (it is for the spurious AoA port), I think it's quite justified in your scenario- after all, you have to stabilize the path first, then troubleshoot...
- Hi AoA protection has priority over high speed protection, so you shouldn't stall as long as you stay in Normal Law.
- switching off 2 ADR's is sufficient to force Alternate Law. While it's is not the procedure for UAS (it is for the spurious AoA port), I think it's quite justified in your scenario- after all, you have to stabilize the path first, then troubleshoot...
Airbus also state the following CONF-
The PF must not deliberately fly the aircraft in alpha protection, except for brief periods, when maximum maneuvering speed is required.
If alpha protection is inadvertently entered, the PF must exit it as quickly as possible, by easing the sidestick forward to reduce the angle-of-attack, while simultaneously adding power (if alpha floor has not yet been activated, or has been cancelled). If alpha floor has been triggered, it must be cancelled with the instinctive disconnect pushbutton (on either thrust lever), as soon as a safe speed is resumed.
The PF must not deliberately fly the aircraft in alpha protection, except for brief periods, when maximum maneuvering speed is required.
If alpha protection is inadvertently entered, the PF must exit it as quickly as possible, by easing the sidestick forward to reduce the angle-of-attack, while simultaneously adding power (if alpha floor has not yet been activated, or has been cancelled). If alpha floor has been triggered, it must be cancelled with the instinctive disconnect pushbutton (on either thrust lever), as soon as a safe speed is resumed.
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The PF must not deliberately fly the aircraft in alpha protection
Don't go there just for the fun of it.
If alpha protection is inadvertently entered
If entered by accident, don't stay there.
But never you'll see Airbus doubting their capacity to keep you out of a stall by applying their full back stick procedure. When requested, they just want you to go there without thinking.
Don't go there just for the fun of it.
If alpha protection is inadvertently entered
If entered by accident, don't stay there.
But never you'll see Airbus doubting their capacity to keep you out of a stall by applying their full back stick procedure. When requested, they just want you to go there without thinking.
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Because it is not desirable to apply a procedure longer than necessary but not because "If you are back somewhere beween alpha prot and alpha max and you encounter a windshear it could stall"
You imply doubt where Airbus has shown none.
You imply doubt where Airbus has shown none.
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Alpha MAX is not a fixed quantity. It is being adjusted to changing parameters. So even if a stall occurs or is occurring because of quick changing environmental factors FCC is taking action to reduce the AOA. In other words recovery is already in progress, so you are not likely to exceed approach to stall phase which is much more benign than full stall that can occur in alternate and direct law. Imagine being in wind shear in a non protected aircraft where you are pushing and pulling against the stick shaker without any assistance from the aircraft and you can easily pull the aircraft in a full blown stall. Basically the protections are for inadvertent pilot excursions. Can there be any protection when going down the Niagara?
Last edited by vilas; 14th Dec 2015 at 16:35.
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Valpha prot shown on the PFD is actually AOA displayed as speed. What is not understood by many is that it is a latching conditions. The aircraft will maintain that speed/AOA and will not exit the regime unless the stick is pushed forward. This was the cause of the air proximity incident between A340 and A330 across the Atlantic.
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vilas,
Er... you would be pulling against the natural speed stability of the aircraft as it wanted to return to its trimmed AoA. Since the stab trim remains where you left it, you would relax the back pressure when the stall warning activated.
Pilots call it flying.
Imagine being in wind shear in a non protected aircraft where you are pushing and pulling against the stick shaker without any assistance from the aircraft and you can easily pull the aircraft in a full blown stall.
Pilots call it flying.
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Surely it is called flying and all those who do it are called pilots then why all these discussions? If stability was all that required then nobody would have thought of envelope protection Boeing included.
Last edited by vilas; 15th Dec 2015 at 02:02.
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Golden
If you loose A/Skid it is not the end of the world if you use proper braking technique but would you rather not have A/Skid because you have the skill? Aren't lesser mortals better of in an aircraft that tries to unstall itself? We discuss events where stable attitude was badly pitched up without any environmental provocation and then somebody comes around banging his chest about piloting skills in a wind shear. I won't bet on it.
If you loose A/Skid it is not the end of the world if you use proper braking technique but would you rather not have A/Skid because you have the skill? Aren't lesser mortals better of in an aircraft that tries to unstall itself? We discuss events where stable attitude was badly pitched up without any environmental provocation and then somebody comes around banging his chest about piloting skills in a wind shear. I won't bet on it.
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vilas,
My comment to you about your statement
was to reassure all those pilots (and passengers) on conventional Boeings that a "full blown stall" is not inevitable. The aircraft will assist you with it's natural speed stability, provided the stab trim stays where you left it. You seem to suggest that unprotected aircraft are more at risk.
Crew responses to Alternate Law in AF447 and QZ8501 seem to suggest crews find the aircraft particularly difficult to control (due FCC & auto stab trim?) or they are out of practice at piloting skills or both.
See Aerodynamic Principles of Large-Airplane Upsets
"An important concept for pilots to understand is that if the airplane is at a balanced, "in-trim" angle of attack in flight, it will generally seek to return to the trimmed angle of attack if upset by external forces or momentary pilot input. This is due to the longitudinal stability designed into that airplane."
Better tell Boeing, Lockheed & Douglas Flight training departments to stop banging their chests and that their comments are "arrogant"
My comment to you about your statement
Imagine being in wind shear in a non protected aircraft where you are pushing and pulling against the stick shaker without any assistance from the aircraft and you can easily pull the aircraft in a full blown stall
We discuss events where stable attitude was badly pitched up without any environmental provocation and then somebody comes around banging his chest about piloting skills in a wind shear.
See Aerodynamic Principles of Large-Airplane Upsets
"An important concept for pilots to understand is that if the airplane is at a balanced, "in-trim" angle of attack in flight, it will generally seek to return to the trimmed angle of attack if upset by external forces or momentary pilot input. This is due to the longitudinal stability designed into that airplane."
Better tell Boeing, Lockheed & Douglas Flight training departments to stop banging their chests and that their comments are "arrogant"
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Golden
I am not denying anything you are saying. I am comparing the two concepts. And Boeing also has switched to protected airplanes because it is definitely a help. Life of 737 you may be aware was prolonged to MAX only because of Southwest airlines ultimatum to switch to AB unless Boeing immediately provided an answer to neo.
I am not denying anything you are saying. I am comparing the two concepts. And Boeing also has switched to protected airplanes because it is definitely a help. Life of 737 you may be aware was prolonged to MAX only because of Southwest airlines ultimatum to switch to AB unless Boeing immediately provided an answer to neo.