High Speed Stall
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High Speed Stall
Hi All,
I was looking at some footage of some recent incidents and accidents at the Red Bull air race involving impacting the water. Thinking about the high speed stall I was wondering what the loading on the tail plane (and thus the control stick) would be like, at the time of the high-speed stall. I would have thought that the stick would feel unloaded, albeit momentarily, with a massive drop in the nose. With the aircraft such as these on the air race would there be some load given the lesser angle of attack and some prop wash?
Can anyone give me a description of what the loading and control is like of these aircraft in this phase of flight?
Have a look at what I've been looking at
Hall's amazing recovery :: Red Bull Air Race Videos
and...
For some reason I am getting a white box for the youtube link?
YouTube - Red Bull Air Race Crash, Perth, April 15, 2010 ? Adilson Kindlemann
Thanks!
I was looking at some footage of some recent incidents and accidents at the Red Bull air race involving impacting the water. Thinking about the high speed stall I was wondering what the loading on the tail plane (and thus the control stick) would be like, at the time of the high-speed stall. I would have thought that the stick would feel unloaded, albeit momentarily, with a massive drop in the nose. With the aircraft such as these on the air race would there be some load given the lesser angle of attack and some prop wash?
Can anyone give me a description of what the loading and control is like of these aircraft in this phase of flight?
Have a look at what I've been looking at
Hall's amazing recovery :: Red Bull Air Race Videos
and...
For some reason I am getting a white box for the youtube link?
YouTube - Red Bull Air Race Crash, Perth, April 15, 2010 ? Adilson Kindlemann
Thanks!
Last edited by SoundBarrier; 14th Jun 2010 at 16:41.
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SoundBarrier, can't help you with the question of what the flight controls might feel like but with the YouTube link the problem is that you posted the full link.
If you go to Jet Blast forum you will find a sticky at the top of the page that explains how to post the link thereby avoiding the dreaded white box.
If you go to Jet Blast forum you will find a sticky at the top of the page that explains how to post the link thereby avoiding the dreaded white box.
I'm guessing that after the stall break it would 'mush' in proportion to the amount of energy expended...like a snap roll....the control feel would be proportional to the dynamic pressure...and the loading at the stall depend at the exact speed the stall took place and increase in stall speed in a turn could be computed by
Vs[phi] =Vs*sqrt[n].... where Vs[phi] = the stall speed at bank angle 'phi' and n=1/cos[phi]
Vs[phi] =Vs*sqrt[n].... where Vs[phi] = the stall speed at bank angle 'phi' and n=1/cos[phi]
Last edited by Pugilistic Animus; 14th Jun 2010 at 07:58. Reason: I don't know
From my expierience in jet fighter aircraft:
There is no feel of unloading on the stick, in a highspeed stall you stall the main wings or one wing or parts of the wing, whereas the stabilator is still in the airstream. Therefore to break the stall you have to relax the stickforce to reduce the AOA and get the air flowing over the wings again.
franzl
There is no feel of unloading on the stick, in a highspeed stall you stall the main wings or one wing or parts of the wing, whereas the stabilator is still in the airstream. Therefore to break the stall you have to relax the stickforce to reduce the AOA and get the air flowing over the wings again.
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Confused...
This looked like a stall due to aoa and roll. The lift on the wing was transversing from positive to negative at a low altitude.
When you say high speed stall I think of "mach tuck" where the center of lift moves aft of the wing as the aircraft approaches trans mach instability, the tail foil may as well be a single airfoil at this point unable to controll the pitch of the aircraft w/o a pitch axis, the pitch axis is gone.
This looked like a stall due to aoa and roll. The lift on the wing was transversing from positive to negative at a low altitude.
When you say high speed stall I think of "mach tuck" where the center of lift moves aft of the wing as the aircraft approaches trans mach instability, the tail foil may as well be a single airfoil at this point unable to controll the pitch of the aircraft w/o a pitch axis, the pitch axis is gone.
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yeah muduckace, that's about right looking at the footage, however, I am wondering at the time of the stall, does the stick unload, even though the tailplane is at a lesser angle of attack? Furthermore is the roll to wings level a result of the stall or pilot input (or both).
I am just wondering away
I am just wondering away
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b4 i ask my question, i want to tell u i don't know much.
So, a high speed stall, is a stall which actually happens at a low speed, but since the fall of speed is so drastic, that the ASI is still showing a (rapidly falling)high speed. Is that an ASI lag? Is any of that right?
Or is it actually a high speed stall? Caused by sudden changes of airflow around the aerofoil, which is caused by some extreme maneuvers.
So, a high speed stall, is a stall which actually happens at a low speed, but since the fall of speed is so drastic, that the ASI is still showing a (rapidly falling)high speed. Is that an ASI lag? Is any of that right?
Or is it actually a high speed stall? Caused by sudden changes of airflow around the aerofoil, which is caused by some extreme maneuvers.
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I would call this a stall, a simple act of the air pressure below the wing equalizing with that above the wing (or neg) due to bank angle. This would be recoverable at a safe altitude. This aircraft is not capable of creating a "high speed stall" at this altitude.
It is simply a change in air loading due to bank angle for this aircraft. If it had more thust it could change the dynamics..
It is simply a change in air loading due to bank angle for this aircraft. If it had more thust it could change the dynamics..
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At the risk of making another stupid SLF posting, doesn't a wing (or part of a wing) stall when it's angle of attack exceeds a certain value? Regardless of how fast (or slow) you are going, it is the AOA that causes the stall, not the speed.
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Three flavours of stall to look at -
(a) 1g certification (AFM/POH data) stall. Probably not of all that much use operationally other than as the basic input to a number of other measurements. Characterised by a gentle approach to the stall and, usually, benign stall characteristics. Stall speed correlates with a repeatable angle of flow incidence to the wing.
(b) accelerated stall - ie not at 1g. Sometimes called a "g-stall". Typical problem with fixed wing real world stalling. Stall speed increases with the square root of the load factor. Similar to variation of stall speed with gross weight changes. Characterised by a more rapid approach to the stall and a higher stalling speed often with undesirable stall characteristics.
(c) accelerated stall - with very high pitch rate. If I recall correctly from a paper on the topic only a consideration with pitch rates in excess of around 70 deg/sec. Leads to the formation of a short lived spanwise vortex above the wing and can see a moderate overshoot of the normal stalling angle. Sometimes a problem with very high performance fixed wing but more a consideration in rotary wing flight. Generally can be ignored by fixed wing pilots.
(a) 1g certification (AFM/POH data) stall. Probably not of all that much use operationally other than as the basic input to a number of other measurements. Characterised by a gentle approach to the stall and, usually, benign stall characteristics. Stall speed correlates with a repeatable angle of flow incidence to the wing.
(b) accelerated stall - ie not at 1g. Sometimes called a "g-stall". Typical problem with fixed wing real world stalling. Stall speed increases with the square root of the load factor. Similar to variation of stall speed with gross weight changes. Characterised by a more rapid approach to the stall and a higher stalling speed often with undesirable stall characteristics.
(c) accelerated stall - with very high pitch rate. If I recall correctly from a paper on the topic only a consideration with pitch rates in excess of around 70 deg/sec. Leads to the formation of a short lived spanwise vortex above the wing and can see a moderate overshoot of the normal stalling angle. Sometimes a problem with very high performance fixed wing but more a consideration in rotary wing flight. Generally can be ignored by fixed wing pilots.
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it is the AOA that causes the stall, not the speed
My brain can't resist asking another question: Take any normal category aircraft, is it designed in such a way that the tail plane has a higher critical angle of attack than the wing?
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is it designed in such a way that the tail plane has a higher critical angle of attack than the wing?
