Airworthiness Directive · Amendment 39-12430 · Boeing Model 747-400 Series Airplanes
Boeing Model 747-400 Series Airplanes
Model 747-400 series airplanes, line numbers 1 through 1205 inclusive, certificated in any category, and equipped with dual crown skin heat exchangers.
This amendment supersedes an existing airworthiness directive (AD), applicable to certain Boeing Model 747-400 series airplanes, that currently requires repetitive inspections to detect damage or deflection of the crew rest heat exchanger, and follow-on actions, if necessary. This amendment adds a new requirement for a one-time inspection to determine the part number and shop code of the shell of the crew rest heat exchanger; and follow-on actions, if necessary; which terminate the currently required repetitive inspections. This action is necessary to prevent cracking and buckling of the front edge of the crew rest heat exchanger, which could result in a jam of the rudder or elevator control cables, and consequent reduced controllability of the airplane. This action is intended to address the identified unsafe condition.
