Summary
We propose to adopt a new airworthiness directive (AD) for certain McDonnell Douglas Model MD-90-30 airplanes. This proposed AD would require installing fuses and wire protection in certain wing and fuel tank spars. This proposed AD results from fuel system reviews conducted by the manufacturer. We are proposing this AD to prevent possible damage to the fuel level float or pressure switch wires. Such damage could become a potential ignition source inside the fuel tank, and, combined with flammable fuel vapors, could result in a fuel tank explosion and consequent loss of the airplane.