EASA AD US-2020-11-12
Nacelles / Pylons - Thumbnail Fairing and Mid Strut Fairing Panels - Inspection / Replacement / Modification
Summary
Federal Aviation Administration Airworthiness Directive 2020-11-12 is a final rule addressing certain Boeing 737-8 and 737-9 airplanes. It focuses on inspection, replacement, and modification of the thumbnail fairing and mid strut fairing panels on the engine nacelle and strut to ensure proper electrical bonding and shielding against high intensity radiated fields (HIRF). This directive aims to prevent potential dual-engine power loss and misleading propulsion parameter displays.
What Changed
This new airworthiness directive requires a detailed inspection of the thumbnail and mid strut fairing panels for excessive rework of the metallic inner surface layer, replacement of any panels that are excessively reworked, and modification of the thumbnail fairing assembly to ensure adequate electrical bonding. It also updates part number references and clarifies inspection criteria and rivet hole sizes based on public comments and Boeing's input.
Why It Matters
This directive is critical for operators and maintenance organizations to prevent electrical bonding deficiencies that could lead to dual-engine power loss or misleading flight deck information. Compliance ensures continued airworthiness and safety by protecting wiring from electromagnetic interference caused by HIRF. It also reduces the risk of forced off-airport landings and excessive pilot workload.
What To Do
Operators of affected Boeing 737-8 and 737-9 airplanes must perform detailed inspections of the thumbnail and mid strut fairing panels, replace any panels with excessive rework, and modify the thumbnail fairing assembly as specified. They must comply with the directive by July 30, 2020, and use the corrected part numbers and installation instructions provided. Service information from Boeing should be consulted for detailed procedures.
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