What was found
AIRCRAFT WAS GROUNDED: SPEED TRIM FAIL INDICATION AFTER TAKE OFF. FIRST OFFICERS PFD SPEED LIMIT FLAG IN VIEW MMO TAPE DISAPPEARS AND REAPPEARS. IN ADDITION, AUTO PILOT A OR B COULD NOT BE ENGAGED AND DUE TO THE SPEED FAIL INDICATION THE AIRCRAFT COULD NOT ENTER RVSM AIR SPACE. THE AIRCRAFT RETURNED TO DFW, NO EMERGENCY WAS DECLARED AND THE AIRCRAFT LANDED SAFELY. REPLACED FLIGHT CONTROL COMPUTER (FCC) CHANNEL A AND ACCOMPLISHED A SATISFACTORY OPERATIONAL CHECK PER AMM 22-11-33.