Whoa! Calling the Myth Busters!!

Non-sealed gaps are NOT the cause of flutter. Flutter is caused by aerodynamic forces surrounding the surface.

Sealing a gap can CHANGE these forces, BUT if you do not presently experience flutter, sealing the gap may make conditions right for you to START experiencing it.

Once I learned about gap sealing, I used to do it all the time. I no longer do.

Now, I seal a gap if - A) I think the plane needs more control and B) I think the gap is large enough that sealing it will increase control.

IF I were to experience flutter, I would definitely seal them, but I wouldn't think for a minute that that would completely eliminate the problem. More likely, the surface would just flutter at a different speed.

But to give you an idea of how uncommon it actually is, I have never (in over 40 years of flying) experienced flutter. I have, in fact seen (or rather "heard" ) it on several occaisions, but I could probably count them on one hand.

Now I will admit that newer planes with extremely large control surfaces are more suseptable to flutter, but good slop-free linkages and strong servos will do much more to avoid it than sealing the gap.