Date: 201810
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: Turbulence; Windshear; 10
Light: Daylight
Aircraft: Gulfstream V / G500 / G550
Operator: Corporate
Operating under: Part 91
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class B ZZZ
ATC / advisory: TRACON ZZZ
Reporter organization: Corporate
Reporter function: Pilot Flying; First Officer
Reporter qualification: Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness; Troubleshooting; Distraction
Second reporter function: Captain; Pilot Not Flying
Anomaly: Aircraft Equipment Problem Less Severe; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Automation Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Overcame Equipment Problem; Flight Crew FLC Overrode Automation; Flight Crew Took Evasive Action
Contributing factors: ATC Equipment / Nav Facility / Buildings; Aircraft
Primary problem: Ambiguous

Narrative: On arrival into ZZZ cleared for the ILS circle to Runway X. Currently conditions; information Y; 34015G27; 10SM; CLR 16/07; A2958; ILS RWY CIR APH IN USE; RWY X/XY CLSD; LO LVL WND SHEAR ADZY IN EFCT. While descending from 3000 FT MSL to cross ZZZZZ at 1500 FT MSL; (mandatory crossing restriction); approximately 2;200 FT MSL transitioning from FMS data to ILS data in green needles the aircraft immediately rolled right into a 38 degree bank as the localizer went full deflection to the left. The Pilot Flying (PF) immediately clicked off the autopilot and made the comment 'What is this thing doing' the Pilot Monitoring (PM) immediately stated 'turn back to the left' and the PF was unable to get it to roll left due to excessive control yoke pressure. The PM made the statement 'I have the aircraft' and took over control of the aircraft. The PM was able to roll the wings level; but the aircraft was now into a nose down pitch attitude of approximately 11 degrees. The PM was successful in recovering the nose down attitude with nose up electric pitch trim and yoke back pressure. At no time during the event did the crew descend below the clearance altitude limit. The controller immediately commanded a left turn to 340 and climb to 3;000 FT MSL. The crew was able to accommodate the request by starting a climb. The controller then inquired if the crew had the ZZZ airport in sight and we replied with 'yes'. The controller then instructed the crew to start the circle approach and contact ZZZ Tower. The crew continued and landed without incident. Other aircraft and Approach Control communicated on Approach Control frequency that the ZZZ Localizer X was experiencing issues that morning due to maintenance being conducted at the airport; Runway X was closed due to scheduled maintenance. The PIC communicated the situation to include our flight conditions on final approach to the ZZZ Ground Controller once the crew cleared the runway and completed all checklists. The Ground Controller was aware of the localizer frequency in addition; the crew listened to other aircraft reporting the localizer situation. In addition; the crew asked if they infringed on ZZZ1 airspace and we were told that it was not an issue.


Second narrative: [Report narrative contained no additional information.]


Synopsis: Gulfstream G550 flight crew reported the aircraft rolled excessively into a bank while transitioning to the ILS. The pilot was later advised that other aircraft were reporting problems with the localizer.