What was found
EZE - FLT 900 - ON T/O PFD CAPT BETWEEN 80 KTS AND V1, A/P BOX YELLOW, UNABLE T/O CLAMP. PFD CAPT 80 KT DIFF RAW DATA APPROX 400 FT AND 800 FT CAPT AIRSPEED 120KT WARN LOW SPEED FADEC 3 OFF LIGHTS. FLAP LIMIT OVERRIDE, AUTO SLAT FAIL AND ELEV FEEL MANUAL. ACCOMP ABNORMAL PROCEDURES. DUMPED FUEL AND RETURNED, LANDING W/O INCIDENT. REPLACED NR 1 FCC AND CLEANED CONNECTORS TO FCC NR 1 AND NR 2 SYS GROUND CHECKED NORM OP. A/C MX FERRY EZE/DFW, DURING WHICH CAPT AIRSPEED INDICATED 40 KTS LWR THAN F/O, NR 1 AND NR 2 WOULD DISENGAGE. AT CRUISE, A/P WOULD DISCONNECT. CADC NR 2 BOOT STRAPPED TO ALLOW CORRECTION OF CAPT AIRSPEED AND WARNINGS. A/C LANDED W/O INCIDENT. PURGED CAPT AND F/O PITOT STATIC LINES. ACC