Airworthiness Directive · Amendment 39-12055 · Boeing Model 737, 747, 757, and 767 Series Airplanes
Boeing Model 737, 747, 757, and 767 Series Airplanes
Model 737-300, 737-400, 737-500, 747, 757-200, 757-300, 767-200, 767-300, and 767-300F sries airplanes, certificated in any category, having the line numbers listed in the following table:
| Model | Affected line numbers (L/N) | Except L/N |
|---|---|---|
| 737-300, -400, -500, | 2591, 2601, 2720, 2723, 2730, 2733, 2734, 2736 through 2850 inclusive, 2852 through 3126 inclusive | N/A |
| 747 | 1011 through 1233 inclusive | 1012, 1174, 1216 |
| 757-200, -300 | 580 through 895 inclusive | 581, 583 through 586 inclusive, 589, 595, 609, 613, 615, 622, 624, 626, 669, 674 |
| 767-200, -300, -300F | 521 through 767 inclusive, | 522, 525, 718, 758 770 |
Note 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (b) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.
This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 737, 747, 757, and 767 series airplanes, that requires rework of certain duct assemblies of the environmental control system (ECS) or replacement of the duct assemblies with new or reworked duct assemblies. This action is necessary to prevent potential ignition of fiberglass insulation material installed on the outside of the ECS ducts, which could propagate a small fire and lead to a larger fire. This action is intended to address the identified unsafe condition.
To prevent potential ignition of fiberglass insulation in the environmental control system (ECS) ducts, which could propagate a small fire and lead to a larger fire, accomplish the following:
(a) Within 6 years after the effective date of this AD, rework ECS duct assemblies or replace existing duct assemblies with new or reworked duct assemblies, in accordance with Boeing Alert Service Bulletins 737-21A1129, 747-21A2416, 757-21A0084, 757-21A0085, or 767-21A0158; all including Appendices A and B; all dated June 29, 2000; as applicable.
The aircraft, engines and makers this AD names, by the model designations in its text. A model listed here may still be outside the AD's serial ranges.
