What was found
DURING TAKEOFF ROLL F/O AIRSPEED INDICATOR FROZEN AT ZERO WITH NO WARNING FLAGS OR EICAS LIGHTS. ONCE AIRBORNE A/S INDICATOR BEGAN TO MOVE AND PEGGED HIGH AT 400KTS. WITH ASSOCIATED IAS DISAGREE. RUDDER RATIO-AIL LOCKOUT AND L/R EEC MODE EICAS ILLUM. F/O SELECTED ALT AIR DATA AND A/S AND ALTIMETER RETURNED TO NORMAL. EICAS WARNS THE SAME EXCEPT FOR TAS DISAGREE OUT. REMOVED AND REPLACED RT ADC. PERFORMED TEST 30 CHKS OK. PERFORMED ADC TEST CHKS NORMAL. OK FOR SERVICE.