Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 747-100, - 200, -300, and 747SP series airplanes. This proposal would require certain inspections to find missing and alloy-steel taperlock fasteners (bolts) in the diagonal brace underwing fittings; and corrective actions, if necessary. For airplanes with missing or alloy-steel fasteners, this proposal also would mandate replacement of certain fasteners with new fasteners, which would constitute terminating action for the repetitive inspections. This action is necessary to prevent loss of the underwing fitting load path due to missing or damaged alloy-steel taperlock fasteners, which could result in separation of the engine and strut from the airplane. This action is intended to address the identified unsafe condition.