Action
Notice of proposed rulemaking (NPRM).
Summary
We propose to supersede airworthiness directive (AD) 2006- 0707, for certain A300 B4-600, B4-600R, and F4-600R series airplanes, and Model C4-605R variant F airplanes (collectively called A300-600 series airplanes). AD 2006-0707 requires modifying nine bolt holes in the vertical flange of the center spar sealing angles. Since we issued AD 2006-0707, we have received reports that fatigue and damage tolerance analyses show that the inspection threshold and interval must be reduced to allow timely detection of cracks. This proposed AD would continue to require modification of bolt holes in the vertical flange of the center spar sealing angles, and any applicable related investigative and corrective actions. This proposed AD would also require inspections for cracks, a modification by cold expansion of the center spar sealing angles, replacement of both sealing angles and cold expansion of the attachment holes if necessary, and post-repair repetitive inspections and corrective actions if necessary. We are proposing this AD to prevent crack formation in the sealing angles, which could rupture the sealing angle and lead to subsequent crack formation in the bottom skin of the wing, and result in reduced structural integrity of the center spar section of the wing.