B737-900
Situational Awareness
ATC Issue All Types; Aircraft Equipment Problem Less Severe; Deviation - Speed All Types; Inflight Event / Encounter Other / Unknown
Aircraft Equipment Problem Dissipated; Flight Crew Overcame Equipment Problem
ATC Equipment / Nav Facility / Buildings; Procedure; Environment - Non Weather Related; Airport; Aircraft
We believe the incident occurred at approximately 4;000 FT on the ILS to [Runway] 8R in IAH with ceilings of about 600 FT. The aircraft suddenly pitched up; climbing approximately 200 FT and lost about 12 KTS of airspeed. As I was reaching for the controls to take over manually; it then nosed over in excess of 1;000 FT per minute and accelerated past target; the nose then lifted again and the airspeed started dropping. I believe it was about the time it nosed over again that I decided that hand flying the aircraft was definitely a better option; clicked off the autopilot; lowered the nose and added some power to recover airspeed. I noted that the glideslope was settling down as was the command bars and hand flew the aircraft to follow the ILS signal once again. I figured something had driven in front of the ILS antenna; but I've never seen an aircraft respond so dramatically to that before. When we broke out of the clouds; an A380 was taxiing west on NA. It must have been that aircraft that caused such a large deviation in the ILS signal.
B737 Captain experienced autopilot anomalies at 4;000 FT on the ILS 8R approach to IAH; with the aircraft pitching up and down vigorously before the autopilot can be disconnected. After breaking out from the hand flown approach an A380 is seen taxiing on the parallel taxiway.