Airworthiness Directive · Amendment 39-19916 · Nacelles/pylons
The Boeing Company Airplanes
This AD applies to The Boeing Company Model 737-8 and 737-9 airplanes, certificated in any category, as identified in Boeing Special Attention Service Bulletin 737-54-1056, dated December 11, 2019.
The FAA is adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-8 and 737-9 airplanes. This AD was prompted by a report that certain exterior fairing panels on the top of the engine nacelle and strut (the thumbnail fairing and mid strut fairing panels) may not have the quality of electrical bonding necessary to ensure adequate shielding of the underlying wiring from the electromagnetic effects of high intensity radiated fields (HIRF), which could potentially lead to a dual-engine power loss event and/or display of hazardously misleading primary propulsion parameters. This AD requires a detailed inspection of the thumbnail fairing panels and mid strut fairing panels for excessive rework of the metallic (aluminum foil) inner surface layer, replacement of any excessively reworked panels, and modification of the thumbnail fairing assembly to ensure adequate bonding. The FAA is issuing this AD to address the unsafe condition on these products.
Before further flight, do a detailed inspection of the thumbnail fairing panels and mid strut fairing panels for excessive rework of the metallic (aluminum foil) inner surface layer, and, before further flight, do the modification as applicable in accordance with Steps 4., 6. through 8. inclusive, and 11. of the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-54-1056, dated December 11, 2019.
(1) Where Boeing Special Attention Service Bulletin 737-54-1056, dated December 11, 2019, specifies thumbnail fairings having part number “311A6111-5 or 311A6111-7 or 311A6111-9,” for this AD use part number “313A6110-5 or 313A6110-7 or 313A6110-9.”
(2) Where note (d) to Figure 4 of Boeing Special Attention Service Bulletin 737-54-1056, dated December 11, 2019, specifies to drill a hole with a diameter of “0.192-0.196,” for this AD the hole diameter must be “0.097-0.101.”
(3) For inspections of critical bonding areas, as specified in Step 4.a. of the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-54-1056, dated December 11, 2019, any panel with cumulative foil cut lengths greater than 4.0 inches within any 12.0 inches in length must be replaced; any panel with a foil cut gap greater than 0.25 inch also must be replaced.
(4) For inspections of non-critical bonding areas, as specified in Step 4.b. of the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-54-1056, dated December 11, 2019, any panel with cumulative foil cut lengths greater than 12.0 inches within a 12.0-inch by 12.0-inch area must be replaced; any panel with a foil cut gap greater than 0.25 inch also must be replaced.
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
