47-49-08 LOCKHEED: (Was Service Note 8 of AD-763-3.) Applies to All Model 49 Serials Up to and Including 2046.
At periods not to exceed 250 hours, inspect the aileron leading edge ribs at Stations 571 and 577, the adjacent leading edge skin and the counterbalance supports for signs of cracks. When cracks are found, install heavier supports, new rib elements, new leading edge skin, and rib reinforcements, as required. When both ribs have been reinforced and heavier supports installed, this periodic inspection may be discontinued.
(LAC Service Bulletin 49/SB-162 covers this same subject.)