Action
Supplemental notice of proposed rulemaking (NPRM); reopening of comment period.
Summary
We are revising an earlier proposed airworthiness directive (AD) for certain The Boeing Company Model 757 airplanes. The NPRM proposed to require modifying the fuel quantity indication system (FQIS) wiring or fuel tank systems to prevent development of an ignition source inside the center fuel tank. The NPRM was prompted by fuel system reviews conducted by the manufacturer. This action revises the NPRM by revising the applicability, including optional actions for cargo airplanes, and extending the compliance time. We are proposing this supplemental NPRM (SNPRM) to prevent ignition sources inside the center fuel tank, which, in combination with flammable fuel vapors, could result in fuel tank explosions and consequent loss of the airplane. Since these actions significantly change the corrective action options for cargo airplanes relative to the proposal in the NPRM, and because the cost estimate is significantly revised, we are reopening the comment period to allow the public the chance to comment on these proposed changes.