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Aerodynamics: Flutter onset speed, control surface malfunction, how does it change?

• I'm a private pilot, and I have some questions to those who have knowledge of the aeroelastic effects and flutter phenomenon. I would like to talk a little about aerodynamic flutter onset speed and flight control malfunction. It is known that freeplay, worn-out control rods or slop in flight control cables might induce flutter. What I'm interested in is how critical flutter speed is affected by  those problems. I'm wondering especially about a cable control failure  where the surface would be disconnected and freefloating. There are  small light sport aircrafts and even some FAR 23 standard certified  aircrafts which don't have mass-balanced surfaces, especially ailerons  which I guess would be more prone to flutter. How critical flutter speed  lowers in a situation like that (and how prone to violently flutter are  these ailerons in an emergency disconnected sitation)? Is there a  linear drop in flutter speed? Can it reach even lower speeds in the  normal operating envelope e.g. below usual cruise speed? Normally, assuming  no malfunction, flutter speed is at least 10% above Vne (never exceed speed) or Vdf (max dive test speed used during certification flight test). How do you think these things  might change? The same about the others control surfaces e.g. a broken trim tab linkage. I really appreciate your help. Thank you very much!

• Answer:

  Sir, I am a phd student in high velocity re-entry regime and have little experience in the flight regimes of the lower atmosphere, but I will try to explain to the best my knowledge. Unfortunately, I cannot answer your question from the structural and aeroelastic pov but I will try to explain the physics behind it. The shape of the airfoil and the sweep of the wings are the primary factors that determine the transonic regime of an aircraft wing, thereby affecting the critical mach number. There is this old but pretty informative video The flutter is specifically discussed between 10:00 to 13:00 mark in the video but i would recommend watching the whole video. To give you a brief reply, I think the flutter is affected bu the airfoil shape, so loose cables, in my opinion, would not affect the onset of critical flutter speed. Please let me know if I answer made sense.