Summary
We propose to adopt a new airworthiness directive (AD) for certain The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This proposed AD was prompted by a report of an approximate 8-inch crack found in the fuselage skin under the aft drain mast. This proposed AD would require a detailed inspection for cracking and corrosion of the channel and fillers adjacent to the drain mast bolts, an inspection to determine the location of the bonding strap, a measurement of the washers under the drain mast bolts, and related investigative actions and repair if necessary. We are proposing this AD to detect and correct cracking in the fuselage skin and internal support structure, which could result in uncontrolled decompression of the airplane.