Airworthiness Directive · Amendment 39-16932 · Air conditioning
The Boeing Company Airplanes
This AD applies to The Boeing Company Model 737-100, -200, -200C, and -300 series airplanes, certificated in any category; as identified in Boeing Service Bulletin 737-21A1132, Revision 3, dated February 16, 2011.
We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-100, -200, -200C, and -300 series airplanes. This AD was prompted by a report from the airplane manufacturer that airplanes were assembled with air distribution ducts in the environmental control system (ECS) wrapped with Boeing Material Specification (BMS) 8-39 or Aeronautical Materials Specifications (AMS) 3570 polyurethane foam insulation, a material with fire-retardant properties that deteriorate with age. This AD requires reworking certain air distribution ducts in the ECS. We are issuing this AD to prevent ignition of the BMS 8-39 or AMS 3570 polyurethane foam insulation on the duct assemblies of the ECS due to a potential electrical arc, which could start a small fire and lead to a larger fire that may spread throughout the airplane through the ECS.
Within 72 months after the effective date of this AD, rework the applicable duct assemblies in the ECS specified in and in accordance with the Accomplishment Instructions and Appendix A of Boeing Service Bulletin 737-21A1132, Revision 3, dated February 16, 2011.
Reworking the applicable duct assemblies in the ECS in accordance with the Accomplishment Instructions and Appendix A of Boeing Service Bulletin 737-21A1132, Revision 2, dated June 13, 2007, before the effective date of this AD is acceptable for compliance with the corresponding actions required by paragraph (g) of this AD.
As of the effective date of this AD, no person may install an ECS duct assembly with BMS 8-39 or AMS 3570 polyurethane foam insulation on any airplane.
