47-10-39 LOCKHEED: (Was Service Note 10 of AD-763-3.) Applies to All Model 49 Serials Up to and Including 2046 on Which All Metal Ailerons Are Not Installed.
At periods not to exceed 250 hours, inspect the aileron inboard of the trim tab for evidence of cracks in the trailing edge and in the aft portions of the ribs. When cracks are found, parts of heavier gage should be installed and the aileron rebalanced. The periodic inspection may be discontinued when this modification has been made.
(LAC Service Bulletin 49/SB-52 covers this same subject.)