Transport i infrastruktura · 28/10/1994

Airworthiness Directives; Boeing Model 747SP Series Airplanes

This document proposes the supersedure of an existing airworthiness directive (AD), applicable to certain Boeing Model 747SP series airplanes, that currently requires repetitive inspections for cracks in the web of the wing front spar over engine numbers 2 and 3, and repair, if necessary. This action would require additional inspections in an area beyond that specified in the existing AD. This action also would provide for a new, optional terminating modification, which, if accomplished, would constitute terminating action for the repetitive inspections. This proposal is prompted by a report of cracking in the web in an area outside the inspection zone specified in the existing AD. A crack in the web that is not detected before it extends outside the chord footprints can allow fuel leakage. The actions specified by the proposed AD are intended to prevent fuel leakage onto an engine and a resultant fire due to cracking in the web of the wing front spar.