Summary
We propose to supersede an existing airworthiness directive (AD) that applies to certain The Boeing Company Model 737-200, -200C, - 300, -400 and -500 series airplanes. The existing AD currently requires a one-time mid-frequency eddy current (MFEC) inspection, a low frequency eddy current (LFEC) inspection, and a detailed inspection for damage or cracking of stringer S-4L and S-4R lap joints and stringer clips between body station (BS) 540 and BS 727, and follow-on inspections and repair if necessary. Since we issued that AD, we have received reports of cracking of the lap joint lower row. This proposed AD would instead require repetitive external eddy current inspections for cracking of certain fuselage crown lap joints and corrective actions; internal eddy current and detailed inspections for cracking of certain fuselage crown lap joints, and repair if necessary; and detailed inspections of certain stringer clips, and replacement with new stringer clips if necessary. This proposed AD would also add airplanes to the applicability. We are proposing this AD to detect and correct cracking of the fuselage lap joints, which could result in sudden decompression of the airplane.