Summary
This document revises an earlier supplemental notice of proposed rulemaking (NPRM), applicable to certain Boeing Model 737-300, -400, - 500, -600, -700, -700C, -800, and -900, and 747-400 series airplanes; and Model 757, 767, and 777 airplanes. The first supplemental NPRM would have required modifying the static inverter by replacing resistor R170 with a new resistor and relocating the new resistor. This new action revises the first supplemental NPRM by adding certain airplanes to the applicability, changing certain airplane groups, and adding certain part numbers. The actions specified by this second supplemental NPRM are intended to prevent a standby static inverter from overheating, which could result in smoke in the flight deck and cabin and loss of the electrical standby power system. This action is intended to address the identified unsafe condition.