As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AT FL310 AND .74 MACH, EXPERIENCED RUDDER FLUTTER. ADDED RIGHT RUDDER TRIM, AIRCRAFT WAS THEN OUT OF TRIM BUT FLUTTER WENT AWAY. REPLACED BOTH LIGHTNING WIRE PROTECTION MODULES IAW 22-12-0B. OPS CHECK GOOD. P/N 2: 822-0332-401, S/N OFF: 216.