Some may have already seen this video.
During an civilian airshow in 1997, a F-117 Stealth fighter experienced catastrophic wing-aileron flutter. The airplane was lost but the pilot successfully ejected.
The aileron is not mass balanced, but depends on actuator load loop stiffness to preclude flutter instead. The Military accident investigation determined that it was caused by an improper repair to the rear spar backup structure where the aileron actuator attaches to the wing. This resulted in a reduction in the stiffness of the backup structure, causing a reduction in the actuator load loop stiffness. This reduced the aileron rotation frequency to a point where the aileron rotation mode coupled with the wing bending & torsion modes, causing flutter to occur within the operating envelope of the airplane.
The event happens at about 1:02 minutes into the video, with a slow motion version at 1:38. In the slow motion version you can see aileron rotation coupling with wing bending & torsion leading to the structural failure of the outboard wing. Notice how quickly it happens.
http://www.youtube.com/watch?v=X2wYvr20nAg
The RV point here is that when repairs are made, not only does the original
strength have to be restored, but also the original
stiffness.