Airworthiness Directives; Boeing Model 707 Airplanes and Model 720 and 720B Series Airplanes

The FAA is superseding an existing airworthiness directive (AD), which applies to certain Boeing Model 707 airplanes and Model 720 and 720B series airplanes. That AD currently requires a preventive modification of the front spar fitting on the outboard engine nacelle. This new AD removes the requirement to do this preventive modification, and requires repetitive inspections for cracking of the front spar fitting of the inboard and outboard nacelle struts, and replacement of any cracked fitting with a new fitting. This AD also applies to more airplanes. This AD is prompted by a report indicating that a crack was found in a front spar fitting that had been replaced as part of the modification required by the existing AD. We are issuing this AD to detect and correct this cracking, which could result in reduced structural integrity of the engine nacelle, and consequent separation of an engine from the airplane.