Summary
We propose to supersede Airworthiness Directive (AD) 2007-16- 08, which applies to all The Boeing Company Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-300, 747-400, 747-400D, and 747SR series airplanes. AD 2007-16-08 currently requires repetitive inspections for cracking of the station 800 frame assembly, and repair if necessary. Since we issued AD 2007-16-08, we have received additional reports of cracks found at the forward and aft inner chord strap and angles on the station 800 frame on the left-side and right- side main entry doors. This proposed AD would expand the inspection area. We are proposing this AD to detect and correct fatigue cracks that could extend and fully sever the frame, which could result in development of skin cracks that could lead to rapid depressurization of the airplane.