What is this small black rubber strip protruding out of the flap track fairing of the A320?
It appears to be one of the rubber seals that are on the moveable flap track fairing.



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Since the fairing moves away from the wing it has probably come loose and is caught between the fairing and the flap.

I can't find a good photo of a fairing from an A320, but here is a photo of the fixed fairing from an A350. It's hard to tell if they are exactly the same, but you can see that they look similar.



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