Summary
The FAA proposes to adopt a new airworthiness directive (AD) for all Boeing Model 707 Airplanes, and Model 720 and 720B series airplanes. This proposed AD would require revising the FAA-approved maintenance program by incorporating new airworthiness limitations (AWLs) for fuel tank systems to satisfy Special Federal Aviation Regulation No. 88 requirements. This proposed AD would also require the initial performance of certain repetitive AWL inspections to phase in those inspection, and repair if necessary. This proposed AD results from a design review of the fuel tank systems. We are proposing this AD to prevent the potential for ignition sources inside fuel tanks caused by latent failures, alterations, repairs, or maintenance actions, which, in combination with flammable fuel vapors, could result in fuel tank explosions and consequent loss of the airplane.