Summary
This document proposes the supersedure of an existing airworthiness directive (AD), applicable to certain Boeing Model 747- 100 series airplanes, that currently requires repetitive inspections to detect cracking of the wing front spar web above engine numbers 2 and 3, and to detect cracked or broken fasteners in the web; and repair, if necessary. That AD also provides an optional terminating action for the repetitive inspections. This proposal would require various improved inspections. This proposal is prompted by a report indicating that the existing inspections do not adequately detect vertical cracks. The actions specified by the proposed AD are intended to prevent fuel leakage onto an engine and a resultant fire due to cracked or broken fasteners in the wing front spar.