Flight Crew Air Transport Pilot (ATP)
Situational Awareness; Distraction; Human-Machine Interface
ATC Issue All Types; Aircraft Equipment Problem Less Severe; Inflight Event / Encounter CFTT / CFIT; Inflight Event / Encounter Unstabilized Approach
Air Traffic Control Issued Advisory / Alert; Flight Crew FLC Overrode Automation; Flight Crew Returned To Clearance
Airport; ATC Equipment / Nav Facility / Buildings; Environment - Non Weather Related
During our approach to runway CLT 36R; [a flight] (#unknown) informed the tower that they would need to return to the gate. For whatever reason (taxiway construction? and aircraft awaiting takeoff on the east side of the runway); the tower chose to taxi the aircraft from the approach end of 36R to an exit taxiway farther down the runway to rejoin C taxiway.By doing this; our glideslope signal was disturbed causing the Avionic Flight Control System (AFCS) to pitch up to follow the distorted glideslope signal causing a sudden upset during final flap extension. The aircraft was stable; configured properly and the AFCS was engaged and properly tracking the localizer and glideslope prior to this disturbance. Noticing the rapid decrease in airspeed; the AFCS was disengaged; pitch reduced and thrust increased to stabilize the aircraft. Because of the rapid change in pitch attitude; the aircraft descended below the glideslope while regaining airspeed.  This resulted in a low altitude warning from the tower. By this time; the aircraft was in visual conditions; the runway and the Vertical Glideslope Indicator (VGSI) were in sight and we were in a position to continue a stable visual approach to landing.The aircraft behind us on the approach also complained of ILS disturbance during this same event.
The flight crew reported that; during a critical phase of their approach; the ILS glideslope signal was disturbed by an aircraft taxiing down the runway. The autopilot was quickly disengaged; however the aircraft momentarily descended below the glidescope; generating a terrain proximity warning from the control Tower. A timely correction was made and the approach and landing were completed successfully.