Surprise surprise - now there are at least two of us concerned over the same problem. Thanks for your post RA.
A response has just been received from the airline as follows with a couple of changes to not yet reveal the identity of the airline and aircraft type.
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"Senior Fleet Engineer
At that time VH - XXX was inspected multiple times, and nil faults found, to indicate there was not an immediate airworthiness issue.
In this case Mr Cottee has reported what appears to be normal conditions of horizontal vibration at the upper end of the Flap moveable Fairing.
Aircraft Type Fleet Manager
When informed of this concern we initiated a detailed inspection of the inboard flap area L/H & R/H. No defects were found. This inspection was carried out by a highly experienced Licensed Aircraft Engineer cerified on type. The movement that Mr Cottee was concerned with is considered normal and comes from the armlink assembly moving on the bushing clamp. This is considered a normal movement, designed to do so. The Airline operates a rigid system of maintenance and on-goings to ensure the safety of our aircraft which involves inspections of the flight control system at scheduled intervals."
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My concerns over airworthiness remain. Had I been involved with the certification of the type I would not have accepted the fluttering for two reasons. Firstly anything fluttering the way this component does will inevitably lead to something failing. Secondly the effects on passengers is hardly conducive to them wanting to stay on board.
The flap fairings are immeditely behind the engines and my conclusion is that eddies from an engine's efflux set up the flutter conditions.
I guess it is now up to the manufacturer to address the problem. I do commend the airline for its reaction to yet another passenger suggestion even if it did come from a TP.
What would you experts do next?