AD FAA-2012-1161

We are superseding an existing airworthiness directive (AD) for certain The Boeing Company Model 737-200, -200C, -300, -400, and - 500 series airplanes. That 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. This new AD instead requires repetitive external eddy current inspections for cracking of certain fuselage crown lap joints, and corrective actions if necessary; 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 AD also adds airplanes to the applicability. This AD was prompted by reports of cracking of the lap joint lower row. We are issuing this AD to detect and correct cracking of the fuselage lap joints, which could result in sudden decompression of the airplane.