Airworthiness Directives; Boeing Model 747-100, -200, 747SP, and 747SR Series Airplanes Equipped With Pratt & Whitney JT9D-7, -7A, -7F, and -7J Series Engines

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 747-100, -200, 747SP, and 747SR series airplanes, that requires one-time detailed visual and eddy current inspections to detect cracking of the nose cowl mounting flange; rework of the nose cowl mounting flange; eddy current inspection to detect cracking of the reworked nose cowl mounting flange; and corrective action, if necessary. This amendment is prompted by reports of the nose cowl separating from the engine and departing the airplane following severe engine vibration. The actions specified by this AD are intended to prevent separation of the nose cowl from the engine, which could cause collateral damage to the airplane, and, possibly, reduced controllability of the airplane.