MD-83
Aircraft Equipment Problem Less Severe; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Flight Crew Executed Go Around / Missed Approach; General Maintenance Action
Aircraft; ATC Equipment / Nav Facility / Buildings
During localizer capture and tracking the Captain and First Officer CDI needles fluctuated from 1/3 to one full dot on the CDI. Aircraft heading shifts went up to 20 degrees left and right of the inbound course. This was all done while the FMA showed TRK; TRK. Both localizer ID had been verified. A go-around was done due to the instability of the localizer indication resulting in large aircraft heading changes on the final approach course. An RNAV GPS to Runway 10 was accomplished and a logbook entry made at the gate.
MD83 Captain experiences localizer oscillations during an ILS approach to Runway 10 at MSY; resulting in as go-around. An RNAV approach is then accomplished successfully.