Summary
The FAA proposes to supersede an existing airworthiness directive (AD) that applies to certain Boeing Model 707 airplanes and Model 720 and 720B series airplanes. The existing AD currently requires a preventive modification of the front spar fitting on the outboard engine nacelle. This proposed AD would remove the requirement to do this preventive modification, and would require 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. The proposed AD would also apply to more airplanes. This proposed 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 proposing 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.