What was found
COMBUSTION TUBE REMOVED FROM D83A28 JANITROL HEATER, MODEL NR S-50. OUTSIDE SKIN OF COMBUSTION TUBE BLOWN THROUGH AT CROSS-OVER PORT LOCATIONS. SUSPECT CAUSE IS DUE TO LACK OF MAINTENANCE AND NOT BEING OVERHAULED AT RECOMMENDED INTERVALS. THESE TUBES ARE INSTALLED IN BEECHCRAFT A55, B55, 56TC AIRCRAFT. SUBMITTER STATED TO PREVENT THESE OCCURRENCES, AN AD WOULD BE REQUIRED. THESE HEATERS ARE NOT BEING TAKEN CARE OF PER THE JANITROL AND BEECHCRAFT SM'S. PRESSURE DECAY TESTING WOULD FIND THE BAD TUBES.