Serge Serfaty wrote:
It looks to me that it could be a Prandlt tube.

My ventus B had a combination pitot/static probe at that location. It
is likely plugged by an insect that uses mud to build a nest. I've
cleared similar fittings by disconnecting the instruments, and using a
compressed air bottle to blow out the debris. Don't seal the compressed
air nozzle against the fitting, or you may blow the tubing off inside
the fin.

Marc