Summary
We propose to supersede an existing airworthiness directive (AD) that applies to certain The Boeing Company Model DC-10-10, DC-10- 10F, DC-10-15, DC-10-30, DC-10-30F (KC-10A and KDC-10), DC-10-40, DC- 10-40F, MD-10-10F, and MD-10-30F airplanes. The existing AD currently requires installing or replacing with improved parts, as applicable, the bonding straps between the metallic frame of the fillet and the wing leading edge ribs, on both the left and right sides of the airplane. The existing AD also requires, for certain airplanes, repositioning or replacing two bonding straps, doing a bonding- resistance check and an inspection to determine correct installation of certain bonding straps, and applicable corrective actions. Since we issued that AD, we have determined that additional actions are necessary to address the identified unsafe condition. This proposed AD would add airplanes to the applicability and retain the requirements of the existing AD. This proposed AD would alsorequire, depending on the airplane configuration, installing new braided bonding straps, inspecting to determine if a certain strap is installed and replacing with or installing a braided bonding strap if necessary, measuring the electrical resistance of the bonding straps, verifying that brackets have an acceptable fillet seal, and corrective actions if necessary. We are proposing this AD to reduce the potential of ignition sources inside fuel tanks in the event of a severe lightning strike, which, in combination with flammable fuel vapors, could result in fuel tank explosions and consequent loss of the airplane.