Control cable failure and critical flutter speed margin?

  • Thread starter stevejeff
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Hi everyone here!

I'm a LSA and PPL pilot, working on my CPL, 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 problem. 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. lower than Vno or Va? Normally, assuming no malfunction, flutter speed is at least 10% above Vne or Vdf, which is dive test speed used during flight testing. How do you think 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!
 

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