Action
Notice of proposed rulemaking (NPRM).
Summary
We propose to adopt a new airworthiness directive (AD) for certain Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747- 200C, 747-200F, 747-300, 747SR, and 747SP series airplanes. This proposed AD would require adding two new indicator lights on the P10 panel to inform the captain and first officer of a low pressure condition in the left and right override/jettison pumps of the center wing tanks. This proposed AD would also require replacing the left and right override/jettison switches on the M154 fuel control module on the P4 panel with improved switches and doing the associated wiring changes. This proposed AD would also require a revision to the FAA- approved maintenance program to incorporate airworthiness limitation No. 28-AWL-22. This proposed AD results from fuel system reviews conducted by the manufacturer. We are proposing this AD to prevent uncommanded operation of the override/jettison pumps of the center wing tanks, which could lead to an unwanted ignition source inside the center wing tank. This condition, in combination with flammable fuel vapors, could result in a center fuel tank explosion and consequent loss of the airplane.