AD FAA-2014-0921

We are superseding Airworthiness Directive (AD) 2013-14-05 for certain The Boeing Company Model 747-400 and 747-400F series airplanes. AD 2013-14-05 required repetitive inspections of the longeron extension fittings for cracking, and related investigative and corrective actions if necessary. This new AD would continue to require the actions specified in AD 2013-14-05, and would add new repetitive high frequency eddy current (HFEC) inspections of any modified, repaired, or replaced longeron extension fitting for cracking, and applicable related investigative and corrective actions if necessary. This AD was prompted by reports of cracking in the outboard flange of the longeron extension fittings, and our determination that more work is necessary on airplanes on which a permanent repair, longeron extension fitting replacement, or modification was accomplished. We are issuing this AD to detect and correct cracks in the longeron extension fittings, which can become large and adversely affect the structural integrity of the airplane.