44-52-01\tBOEING: (Was Service Note 1 of AD-558-1 and Service Note 1 of AD-524-1.) Applies to 247-D Aircraft. \n\tInspect immediately and every 250 hours thereafter the outer wing panel 17SRT aluminum alloy spar chord members for cracks. Unless special openings are installed, the outer panels may have to be removed to permit thorough inspection. If cracks are found, the members should be repaired or replaced in a manner satisfactory to the FAA. If replacement 24ST tubing is installed no further inspection will be necessary. Boeing Service Bulletin No. 1 of D-6134 describes a satisfactory method of installation of inspection openings in the lower surface of the outer wing. Boeing Service Bulletin No. 2 of D-6134 covers replacement of 17SRT spar chords with 24ST spar chords.