46-23-01 ERCO: (Was Mandatory Note 4 of AD-718-6.) Applies Only to 415-C, -CD and -D Aircraft Serial Numbers 113 to 362, Inclusive.
To be accomplished within next 50 hours of operation.
Trouble in service has indicated the necessity for replacing the original muffler on the serial numbers listed above with a new muffler, Erco P/N 145-40517.
(Erco Service Department Memorandum No. 7 dated February 1, 1946, covers this same subject.)