Action
Supplemental notice of proposed rulemaking (NPRM); reopening of comment period.
Summary
We are revising an earlier proposed airworthiness directive (AD) for the products listed above. That NPRM proposed replacing the power control relays for the fuel boost pumps and override pumps with new relays having a ground fault interrupt (GFI) feature. That NPRM was prompted by results from fuel system reviews conducted by the manufacturer. This action revises that NPRM for all airplanes by proposing to require an electrical bonding resistance measurement for certain GFI relays to verify that certain bonding requirements are met. This action also revises that NPRM by proposing to require, for certain airplanes, an inspection to ensure that certain screws are properly installed, and re-installing longer screws if necessary. We are proposing this supplemental NPRM to prevent damage to the fuel pumps caused by electrical arcing that could introduce an ignition source in the fuel tank, which, in combination with flammable fuel vapors, could result in a fuel tank explosion and consequent loss of the airplane. Since these actions impose an additional burden over that proposed in the NPRM, we are reopening the comment period to allow the public the chance to comment on these proposed changes.