Airworthiness Directive · Amendment 39-18506 · Air conditioning
The Boeing Company Airplanes
This AD applies to The Boeing Company Model 747-8 series airplanes, certificated in any category, as identified in Boeing Alert Service Bulletin 747-21A2571, dated December 4, 2015.
We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 747-8 series airplanes. This AD requires a detailed inspection for correct installation of the flex hose clamp of the occupant backup air supply and a general visual inspection for damage of the flex hose, and related investigative and corrective actions if necessary. This AD was prompted by a report indicating that flex hoses of the occupant backup air supply were found disconnected from the adjacent fiberglass duct on two airplanes. We are issuing this AD to detect and correct an incorrect clamp installation on the inboard end of the flex hose, which allows the flex hose to slowly become disconnected from the adjacent fiberglass duct, and damage to the hose. This condition, in conjunction with a cargo fire event, can potentially lead to decreased airflow to the main deck, possibly resulting in smoke and/ or toxic fumes penetrating into the main deck passenger compartment, which could result in injury to the passengers or cabin crew.
Except as required by paragraph (h) of this AD, at the applicable time in paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 747-21A2571, dated December 4, 2015, do a detailed inspection for correct installation of the backup air supply clamp, and before further flight, do all applicable related investigative and corrective actions, in accordance with the Accomplishment Instructions of paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 747-21A2571, dated December 4, 2015.
Where paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 747-21A2571, dated December 4, 2015, specifies a compliance time “after the original issue date of this service bulletin,” this AD requires compliance within the specified compliance time after the effective date of this AD.
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.
Aircraft
