For what it is worth:
I have a small piece of tape to cover the hole of the rear wing pip
pins. Recently the aft end of this tape came loose and I had 1 inch of
tape end vibrating in the wind.
Unaware of this, I was strucked by a sudden buzzing vibration through
the ship. It behaved like described, with some speeds or prop settings
it was gone, to return at certain speeds, but a few times by temporarily
change a few parameters I could get it to stay away for a while.
I'm still surprised how difficult it was to determine what the source of
the vibration was, and how much vibration just 1 inch of tape can
create. The sound of it was much louder than the engine sound and it
appeared to come from everywhere.
I was worried enough to consider an immediate off field landing (it
could be flutter, or some critical part about to be teared off) but
decided to wait a little to see how it would develop. At least the
controls felt completely normal.
After the landing I discovered this small piece of tape, the end ragged
as a proof that it had been vibrating. After removing it the vibration
was gone and never returned.
Frans
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