MANUFACTURER: Boeing Model 747-400 and 747-400D
Series Airplanes SUBJECT: Airworthiness Directive 2009-10-06
SUMMARY: We are adopting a new airworthiness
directive (AD) for certain Boeing Model 747-400 and 747-400D series
airplanes. This AD requires repetitive inspections to detect cracks
in the floor panel attachment fastener holes of the Section 41
upper deck floor beam upper chords, and related investigative and
corrective actions if necessary. This AD results from reports of
cracks found in the Section 41 upper deck floor beam upper chords.
We are issuing this AD to detect and correct cracks in these
chords, which could become large and cause the floor beams to
become severed and result in rapid decompression or reduced
controllability of the airplane.