What was found
FLIGHT 3676, LGA-BWI - AFTER TAKEOFF, THE CONTROLLER ISSUED A RIGHT TURN. THE CAPTAIN BEGAN THE TURN BUT IT TOOK THE FORCE OF BOTH THE CAPTAIN AND THE F/O TO TURN THE AIRCRAFT. AN EMERGENCY WAS DECLARED, CABIN WAS PREPPED, AND THE FLIGHT RETURNED TO THE FIELD, LANDING WITHOUTINCIDENT. NORMAL DEPLANING PROCEDURES WERE USED. MAINTENANCE INSPECTED THE FLIGHT CONTROL SYSTEM, FOUND THE LEFT AILERON SPRING TAB ATTACH FITTING CRACKED CAUSING RESISTANCE. THE LEFT AILERON SPRING TAB WAS REMOVED AND REPLACED. AIRCRAFT WAS RETURNED TO SERVICE.