Summary
The FAA proposes to supersede an existing airworthiness directive (AD) that applies to all Boeing Model 747-100, 747-100B, 747- 100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747-400, 747-400D, 747-400F, and 747SR series airplanes. The existing AD currently requires repetitive inspections to find cracking of the web, strap, inner chords, and inner chord angle of the forward edge frame of the number 5 main entry door cutouts, and repair, if necessary. This proposed AD would expand the inspection areas to include the frame segment between stringers 16 and 23. This proposed AD would reinstate the repetitive inspections specified above for certain airplanes. This proposed AD would also require repetitive inspections for cracking of repairs. This proposed AD results from additional reports of cracks that have been found in the strap and inner chord of the forward edge frame of the number 5 main entry door cutouts, between stringers 16 and 23. We are proposing this AD to detect and correct such cracks. This condition, if not corrected, could cause damage to the adjacent body structure, which could result in depressurization of the airplane in flight.