Airworthiness Directive · Amendment 39-16344 · Air conditioning
The Boeing Company Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747-400, 747-400F, 747SR, and 747SP Series Airplanes
This AD applies to the airplanes specified in paragraphs (c)(1) and (c)(2) of this AD, certificated in any category.
(1) The Boeing Company Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747-400, 747SR, and 747SP series airplanes identified in Boeing Service Bulletin 747-21A2421, Revision 2, dated December 19, 2006.
(2) The Boeing Company Model 747-100, 747-100B, 747-200B, 747-200C, 747-200F, 747-300, 747-400F, 747SR, and 747SP series airplanes identified in Boeing Service Bulletin 747-21A2422, Revision 2, dated November 16, 2006.
We are adopting a new airworthiness directive (AD) for certain Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747-400, 747-400F, 747SR, and 747SP series airplanes. This AD requires reworking or replacing certain duct assemblies in the environmental control system (ECS). This AD results from reports of duct assemblies in the ECS with burned Boeing Material Specification (BMS) 8-39 polyurethane foam insulation. This proposed AD also results from a report from the airplane manufacturer that airplanes were assembled with duct assemblies in the ECS wrapped with BMS 8-39 polyurethane foam insulation, a material of which the fire retardant properties deteriorate with age. We are issuing this AD to prevent a potential electrical arc from igniting the BMS 8-39 polyurethane foam insulation on the duct assemblies of the ECS, which could propagate a small fire and lead to a larger fire that might spread throughout the airplane through the ECS.
You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done.
Within 72 months after the effective date of this AD, rework or replace the applicable duct assemblies in the ECS specified in and in accordance with the Accomplishment Instructions and Appendices A through F of Boeing Service Bulletin 747-21A2421, Revision 2, dated December 19, 2006 (for Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747-400, 747SR, and 747SP series airplanes); and the Accomplishment Instructions and Appendices A through C of Boeing Service Bulletin 747-21A2422, Revision 2, dated November 16, 2006 (for Model 747-100, 747-100B, 747-200B, 747-200C, 747-200F, 747-300, 747-400F, 747SR, and 747SP series airplanes).
As of the effective date of this AD, no person may install an ECS duct assembly with BMS 8-39 polyurethane foam insulation on any airplane.
