Summary
We propose to adopt a new airworthiness directive (AD) for all The Boeing Company Model 707 series airplanes and Model 720 and 720B series airplanes. This proposed AD was prompted by a report indicating that a fracture of the midspar fitting resulted in the separation of the inboard strut and engine from the airplane, and a determination that existing inspections are not sufficient for timely detection of cracking. This proposed AD would require repetitive inspections of certain nacelle strut spar and overwing fittings, and diagonal braces and associated fittings; replacement of the diagonal brace assembly on certain airplanes; and applicable related investigative and corrective actions. We are proposing this AD to address the unsafe condition on these products.