Summary
We propose to adopt a new airworthiness directive (AD) for certain Boeing Model 727-100 and 727-200 series airplanes. This proposed AD would require repetitive internal and external high frequency eddy current, mid frequency eddy current, low frequency eddy current, and magneto optic imaging inspections to detect cracks, corrosion, delamination, and materials loss in the lower fastener row of the lower skin and the upper fastener row of the upper skin, and corrective actions if necessary. This proposed AD results from a report of decompression in a Boeing Model 737 airplane at flight level 290. We are proposing this AD to detect and correct scratches and excessive reduction in material thickness from excessive blend-out or corrosion, which could lead to premature cracking in the lap joint. Such cracking could adversely affect the structural integrity of the airplane.