Transport i lotnictwo · 6.09.2005

Airworthiness Directives; Boeing Model 747-400 Series Airplanes

The FAA proposes to adopt a new airworthiness directive (AD) for certain Boeing Model 747-400 series airplanes. This proposed AD would require doing a conductivity test of the upper deck floor beam at station 400 to identify the floor beam material. If the floor beam is manufactured from 7050 aluminum alloy, this proposed AD would also require inspecting the upper deck floor beam and certain fastener holes at the floor beam upper chord for cracking; repairing any cracking if necessary; and doing a preventative modification. This proposed AD results from several reports indicating that fatigue cracking was found in upper deck floor beams made from 7050 aluminum alloy. We are proposing this AD to find and fix cracking in the upper deck floor beam, which could extend and sever the floor beam. A severed floor beam could result in loss of controllability and rapid decompression of the airplane.