What was found
AIRCRAFT WAS GROUNDED: DURING CRUISE AT 28,000' ,FLIGHT DECK DOOR WILL ONLY OPEN WHEN ROTATING HANDLE COUNTER CLOCKWISE, WILL NOT OPEN WHEN ROTATING CLOCKWISE. SAME PROBLEM ON GROUND. MAINTENANCE REPLACED FLIGHT DECK DOOR MECHANISM PER AMM 52-51-21 AND ACCOMPLISHED A SATISFACTORY OPERATIONAL CHHECK.