If you push the "NAV" button on the FCU (Flight Control Unit) during a go-around, the A320 will attempt to fly the MCDU-stored missed approach, which is likely a runway centerline climb followed by a specific waypoint. The Sierra Pattern is a visual maneuver . You should remain in or TRK (Track) mode using the FCU heading knob.
If you push the "NAV" button on the FCU (Flight Control Unit) during a go-around, the A320 will attempt to fly the MCDU-stored missed approach, which is likely a runway centerline climb followed by a specific waypoint. The Sierra Pattern is a visual maneuver . You should remain in or TRK (Track) mode using the FCU heading knob.