AD 56-01-02

56-01-02 BOEING: Applies to All model 377 Aircraft. Compliance required as indicated. As a result of cracks discovered at wing spar splice bolt holes the following inspection and possible rework is required. At the next basic check period and subsequent thereto, at each basic check period but not to exceed an interval of 2,500 hours flight time, the No. 1 bolt hole in each rear spar Station 246 joint and Nos. 1 and 6 bolt holes in each front and rear spar Station 510 joints shall be carefully inspected by use of borescope or equivalent method. If cracks are found, the splice should be reworked in accordance with instructions contained in Boeing Service Letter No. 289. Within the next 500 flight hours, unless recently accomplished, the outboard bolt holes in each front and rear spar Station 47.75 joints shall be inspected for cracks by use of borescope or equivalent method. If cracks are found, they shall be repaired in accordance with Boeing Instructions. This supersedes AD 55-23-01.