What was found
AIR TURN BACK, RUDDER RATIO, AIRERON LOCKOUT & ALL THREE AUTOPILOTS WON'T ENGAGE. ACCOMPLISHED FIM TASK 73-21/892, 27-21-804 & 27-48-809 PROCEDURES. UNABLE TO DUPLICATE ON GROUND. PIMU BITE CHECKED, NO FAULTS FOUND. STAB TRIM AND RUDDER RATIO TRIM OPS CHECKED OK IAW AMM 73-00-00,73-21-00, 27-21-00, 27-41-00, & 27-48-00.