What was found
(AUS) TCAS ANTENNA MOUNTED ON THE TOP OF THE FUSELAGE LEAKING AIR THROUGH THE SEALANT. DURING REMOVAL OF THE ANTENNA IT WAS FOUND THAT THE TWO REAR SCREWS HAD LOOSE NUTS AND WASHERS INSTEAD OFANCHOR NUTS. THE RH FRONT SCREW WAS ALSO SPINNING IN THE ANCHOR NUT. ON REASSEMBLY OF THE ANTENNA IT WAS FOUND THAT THE REARSCREWS WERE TOO LONG AND BOTTOMED OUT LEAVING THE ANTENNA LOOSE ON THE MOUNT PLATE. PERSONNEL/MAINTENANCE ERROR. UNAPPROVED PART.