What was found
AIR TURNBACK AFTER TAKE OFF ABOVE 2000 CAPTAINS AIRSPEED UNRELIABLE THEN BLANKED OUT. IT CAME BACK THEN WENT AWAY. AFTER 3 MINUTES IT CAME TO NORMAL. THESE WERE ACCOMPANIED WITH AILERON LOCKOUT AND RUDDER RATIO AIRDATA SWITCHING TEST PERFORMED IAW AMM 34-12-00-710-001 REV 142. TEST OK. LEFT ADC OPS TEST WITH RT ADC IN ALTN AND RT AD OPS TEST WITH LEFT ADC IN ALTN PERFORMED . ALL INDICATIONS NORMAL. NIL FAULTS. NIL MSG. AIRCRAFT RELEASED TO SERVICE IN CONSULTATION WITH AMC.