Airworthiness Directives; The Boeing Company Model 747-100B, 747-200B, 747-200F, 747-300, 747-400, 747-400F, and 747SP Series Airplanes Equipped with Rolls-Royce RB211-524 Series Engines

We are adopting a new airworthiness directive (AD) for certain Model 747-100B, 747-200B, 747-200F, 747-300, 747-400, 747-400F, and 747SP series airplanes. This AD requires repetitive detailed and high frequency eddy current inspections of the forward and aft sides of the strut front spar chord for cracks and fractures at each strut location, and corrective actions if necessary. This AD results from reports of cracks and fractures in the nacelle strut front spar chord assembly. We are issuing this AD to detect and correct cracks and fractures of the nacelle strut front spar chord assembly. Fracture of the front spar chord assembly could lead to loss of the strut upper link load path and consequent fracture of the diagonal brace, which could result in in- flight separation of the strut and engine from the airplane.