Airworthiness Directives; Boeing Model 747-100, -100B, -100B SUD, -200B, -200C, -200F, and -300 Series Airplanes; and Model 747SP and 747SR Series Airplanes; Equipped With Pratt and Whitney Model JT9D-3 or -7 (Except -70) Series Engines

The FAA is adopting a new airworthiness directive (AD) for certain Boeing transport category airplanes. This AD requires repetitive detailed inspections to detect cracking of the aft and forward surfaces of the bulkhead web at nacelle station 180, and repair if necessary. This AD is prompted by reports of cracking of the web bulkhead at nacelle station 180. We are issuing this AD to detect and correct fatigue cracking of the web bulkhead, and consequent loss of the load path of the bulkhead at nacelle station 180, which when combined with the loss of the midspar load path, could result in the in-flight separation of the engine and strut. Such separation may result in secondary damage to the airplane and consequent reduced controllability of the airplane.