What was found
AFTER TAKE-OFF, RT FLIGHT DIRECTOR DISAPPEARED TROUBLE SHOT IT AFTER 18K AND COULDN'T GET RESOLUTION SWITCHED RIGHT SIDE TO CENTER AND SGL SOURCE FD TCAS MSG APPEARED. MX MADE CALL TO RETURN TO AFW, (ATB) DEFERRED RT FLIGHT DIRECTOR SYSTEM IAW MEL C ABX-34-22-4A. RETURNED AIRCRAFT TO SERVICE.