Airworthiness Directives; Boeing Model 747-200C and -200F Series Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 747-200C and -200F series airplanes, that requires repetitive inspections to find fatigue cracking in the upper chord of the upper deck floor beams, and repair if necessary. For certain airplanes, this amendment also provides an optional repair/ modification, which extends certain repetitive inspection intervals. This action is necessary to find and fix cracking in certain upper deck floor beams. Such cracking could extend and sever floor beams at a floor panel attachment hole location and could result in rapid decompression and consequent loss of controllability of the airplane. This action is intended to address the identified unsafe condition.