cdr.rschultz
Member
Am having a mild aileron flutter during full deflection aileron rolls on an RV8? Has anyone enchanted similar airflow disruption and was there a solution?
Cheers, Bob
Cheers, Bob
Van's Air Force
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aileron flutter
- Thread starter cdr.rschultz
- Start date
jthocker
Well Known Member
Normal, solution is don't use full deflection or accept the buffeting!
Normal
The buffet is caused by flow seperation due to the angle of deflection.
For more details see;
http://www.vansairforce.com/community/showthread.php?t=21686
The buffet is caused by flow seperation due to the angle of deflection.
For more details see;
http://www.vansairforce.com/community/showthread.php?t=21686
DakotaHawk
Well Known Member
Yep, happens on my -7 too. It feels like a "tap... tap..." with the taps happeniing about three times per second. Like RV8Riveter says, its flow separation - you're just stalling your aileron. No big deal.
Flutter, on the other hand, will feel like a high frequency vibration and will result in rapid damage to the aileron.
Flutter, on the other hand, will feel like a high frequency vibration and will result in rapid damage to the aileron.
scsmith
Well Known Member
please don't call it flutter!
Flutter is something entirely different.
What you feel is a normal characteristic of Frise ailerons. At large deflection, the nose of the aileron is sticking down in the flow and it is too sharp a bend, so the flow separates, causing the buffet you feel.
You will learn to use just a bit less aileron, get more roll rate, and no buffet. But, it doesn't really hurt anything anyway.
Flutter is something entirely different.
What you feel is a normal characteristic of Frise ailerons. At large deflection, the nose of the aileron is sticking down in the flow and it is too sharp a bend, so the flow separates, causing the buffet you feel.
You will learn to use just a bit less aileron, get more roll rate, and no buffet. But, it doesn't really hurt anything anyway.
Kevin Horton
Well Known Member
This buffeting at full aileron deflection is quite normal for the short wing RVs and is nothing to be concerned about. It is not flutter.
Flutter has a very particular meaning in aviation and it refers to a very violent oscillation of a control surface, wing, tail surface, etc caused by an interaction of the aerodynamic forces, inertial forces and the structural stiffness. Flutter almost always ends with structural failure and a fatal accident. If you had experienced flutter you almost certainly wouldn't be here to talk about it.
You might be interested in these flutter videos.
Also see these old NACA Flutter Videos Reel 1 and Reel 2. Note that the time between the start of flutter and the destruction of the wind tunnel models was typically less than one-half second, which illustrates that there is often no chance to slow down and stop flutter once it starts. This
video of destructive flutter of an RC model is also instructive.
LAMPSguy
Well Known Member
agree to disagree
I agree with most comments regarding flutter. It is certainly bad and dangerous. My main complaint is the common disregard for the possibility of accidentally attaining it. So often when certain events are improbable, people assume that you are mistaken and couldn't have experienced it because "you would be dead if it had happened". This shortsighted thought eliminates any possibility of anyone learning from your mistakes and helping prevent them in the future. I had a similar issue about a year and a half ago called mast bumping in a helicopter and I made an emergency landing. I am convinced of what I heard. Our maintenance people and other "higher-up's" were so convinced that I would be dead if it happened that I could not have possibly had it. I agree the aileron deflection issue was very improbably flutter, and we need to be educated regarding the issue (especially with fast aircraft) but I just have a problem with a blanket assumption that its impossible if someone lived to tell about it.
Sorry fir the hijack
I agree with most comments regarding flutter. It is certainly bad and dangerous. My main complaint is the common disregard for the possibility of accidentally attaining it. So often when certain events are improbable, people assume that you are mistaken and couldn't have experienced it because "you would be dead if it had happened". This shortsighted thought eliminates any possibility of anyone learning from your mistakes and helping prevent them in the future. I had a similar issue about a year and a half ago called mast bumping in a helicopter and I made an emergency landing. I am convinced of what I heard. Our maintenance people and other "higher-up's" were so convinced that I would be dead if it happened that I could not have possibly had it. I agree the aileron deflection issue was very improbably flutter, and we need to be educated regarding the issue (especially with fast aircraft) but I just have a problem with a blanket assumption that its impossible if someone lived to tell about it.
Sorry fir the hijack
DakotaHawk
Well Known Member
Since cdr.rschulz stated that he got the "mild aileron flutter" during full aileron deflection, that leads me to believe that he's not flying anywhere near VNE. Full aileron deflection at those speeds would be exciting, to say the least, most likely resulting in flutter and probably catastrophic failure. Full control surface deflection above Va is not a good idea!
On the other hand, aileron bump is very common, but hard to describe if you don't really know what it is that you're feeling. It feels like someone is tapping on your aileron a couple times per second when it's at full deflection.
Having described what aileron bump is, and what the cause is (see scsmith's description), now it's up to cdr.rschulz to determine if he was getting aileron bump or some form of aileron flutter. I'd be interested to hear his response...
On the other hand, aileron bump is very common, but hard to describe if you don't really know what it is that you're feeling. It feels like someone is tapping on your aileron a couple times per second when it's at full deflection.
Having described what aileron bump is, and what the cause is (see scsmith's description), now it's up to cdr.rschulz to determine if he was getting aileron bump or some form of aileron flutter. I'd be interested to hear his response...
cdr.rschultz
Member
As most all of you have presumed correctly, this is in fact an "aileron bump" and the aircraft handles quite smoothly throughout this entire flight regime despite the momentary aileron stalls. Thanks to all for your thoughts and experiences. Cheers!
