As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FIRE RESISTANT SPACES AFT OF FIREWALL BETWEEN FIREWALL AND RUBBER FUEL BLADDER BURNED THROUGH. FIREWALL SHOWS NO SIGN OF OVERTEMP. FOUND DURING INSPECTION OF FUEL BLADDER AT ANNUAL INSPECTION. REPLACED SPACER ASSEMBLY. RECOMMEND INSPECTION MINIMUM 500 HOURS. LEFT ENGINE NACELLE. REF: AD 75-23-08R5.