What was found
AIRCRAFT WAS GROUNDED: AN EMERGENCY WAS DECLARED AND THE AIRCRAFT RETURNED TO CLT DUE TO THE FLIGHT CREW REPORTING THAT THE AUTO THRUST WOULD NOT OPERATE IN MANAGED SPEED. THE AIRCRAFT LANDED SAFELY AT CLT WITHOUT FURTHER INCIDENT. MAINTENANCE ACCOMPLISHED THE FOLLOWING OPERATIONAL TESTS: FWC 1+2 PER AMM 31-50-00, ENGINE/AUTOTHRUST SYSTEM CHECK PER AMM 22-30-00. AFS TEST PER AMM 22-96-00 AND CAT III CAPABILITY TEST PER AMM 22-97-00 WITH NO DEFECTS NOTED. MAINTENANCE WAS UNABLE TO IDENTIFY A SPECIFIC PART THAT WOULD HAVE CAUSED THE ISSUE REPORTED BY THE FLIGHT CREW.