Airworthiness Directives; Boeing Model 727 Series Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to all Boeing Model 727 series airplanes, that requires repetitive inspections to detect cracks in the forward flange of the vertical beam of the aft pressure bulkhead at certain buttock lines, and installation of a splice repair, if necessary. The amendment also requires installation of a preventative modification on the vertical beam of the door frame in certain cases. This amendment is prompted by reports of fatigue cracks found in the vertical beam web and forward flange of the aft pressure bulkhead. The actions specified by this AD are intended to detect and correct such fatigue cracking, which could result in the inability of the subject vertical beam to withstand the fail-safe loads, and consequent loss of cabin pressurization.