47-51-13 BELLANCA: Applies to Model 14-13 Serial Numbers 1060 Through 1513, 1545, 1548, 1551 Through 1560.
Compliance required not later than May 1, 1948.
To eliminate the possibility of an engine compartment fire entering the fuselage through the firewall cabin heater opening, remove the aluminum cabin heat control valve and replace with a steel valve of new design Bellanca Drawing No. 15067-40.
(Bellanca Service Bulletin No. 11 dated June 20, 1947, covers this same subject.)