Summary
This document proposes the supersedure of an existing airworthiness directive (AD), applicable to certain Lockheed Model L- 1011-385 series airplanes, that currently requires repetitive inspections to detect cracking of the canted pressure bulkhead at fuselage station (FS) 1212, and repetitive inspections to detect cracking of the web at the fastener rows of the vertical stiffener-to- web; and repair or replacement of the web with a new web, if necessary. This action would require that the initial inspections be accomplished at a reduced threshold. This proposal is prompted by a report of fatigue cracking of the canted pressure bulkhead at FS 1212. The actions specified by the proposed AD are intended to detect and correct fatigue cracking of the canted pressure bulkhead at FS 1212, which could result in blowout of a panel between adjacent stiffeners and consequent cabin depressurization.