BTW Irish Steve forgive the pedantry but flutter is (basically) defined as vibration of increasing amplitude, leading to failure, so what you witnessed is not flutter.
Irish Steve, perhaps I should have been a little more specific, flutter is (basically) defined as vibration of
rapidly increasing amplitude, leading to
certain failure
in a short period of time, so what you witnessed is not flutter.
Is that a bit better?
Now, I'm not criticising you for doing what you did, you felt it was right to do so, but don't belittle my input. Having spent over 10 years in stress and vibration engineering, and in particular relating to engine and airframe design and structural integrity, I do know what I'm talking about.
Very briefly to try to explain, have you heard of an S-N curve. S = Stress, N=Number of cycles (of vibration) before failure.
If the stress induced in the structure is high, then the number of cycles the structure will endure is low, and vice versa. There comes a point where the induced stress is so low that the structure will endure an infinite number of cycles, and hence never fail.
I suspect that the induced stress in this structure is pretty low (but I haven't done and FE Analysis on it, so what do I know?)
Now that I'm flying these things I'm as worried as the next guy that things will unexpectedly fail, but I know that these things have been designed with high margins of safety, and are tested thoroughly. So, generally I'm happy with life!