B757-200
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Aircraft Equipment Problem Less Severe; Deviation - Altitude Excursion From Assigned Altitude; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Flight Crew Overcame Equipment Problem
Aircraft
Descending to TUL. Heading to the marker for the approach to [Runway] 18L; approximately 2 miles before the localizer; the aircraft intercepted something like a false localizer and started turning to a heading parallel to the actual final course. We were caught by surprise. I kicked off the autopilot and turned back towards the marker as we were on the visual. But after all the turns; it took a bit to figure out again where we were. We may have gotten lower than normal during this time; but we reestablished a normal approach to landing.My question is; WHAT happened? Why did the aircraft turn. I've seen it before; but not often enough to expect it.
B757 Captain reported autopilot intercepted false localizer on approach.