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20-176 - Design Approval Holder Best Practices for Service Bulletins Related to Airworthiness Directives

Date Issued
December 19, 2011
Responsible Office

 This advisory circular (AC) presents various best practices for design approval holders (DAHs) of aircraft, aircraft engines, propellers, and appliances when drafting service bulletins (SBs) related to an airworthiness directive (AD). This AC also provides information and guidance on avoiding overlapping and conflicting actions in SBs, ex parté communication, alternative methods of compliance (AMOCs), and maintaining airworthiness of AD-mandated design changes.