What is the Relationship Between Airworthiness Directives (AD,s) Service Bulletins (SB’s) & Alert Service Bulletins (ASB’s)

Airworthiness Directives

Airworthiness Directives (ADs) are legally enforceable rules issued by the Regulatory Authority of the Type Certificate Holder, (TCH) Supplemental Type Certificate Holder (STCH) or Original Equipment Manufacturer (OEM) (may also be issued by other Regulatory Authorities).

Now Consider the Following Statements :

       ⁰ Airworthiness Directives (AD,s) are Mandatory

       ⁰ If an Aircraft is not in compliance with AD requirements its Certificate of Airworthiness is not valid and the aircraft shall not fly legally.

       ⁰ AD,s are only issued by Regulatory Authorities – most usually the authority of the State of Design of the Aircraft or Product

Service Bulletins & Alert Service Bulletins

A Service Bulletin is a notice to an aircraft operator from the Aircraft Engine or component manufacturer informing of a product change or improvement.

An alert service bulletin is issued when an unsafe condition shows up that the manufacturer believes to be safety-related.

Now Consider the Following Statements

       ⁰ Service Bulletins are NOT Mandatory – The Organisation Responsible for Continuing Airworthiness (CAW Organisation or CAMO) is responsible to develop an assessment policy and determine the appropriate/necessary action or response.

       ⁰ Alert Service Bulletins are NOT Mandatory – The CAW Organisation is again responsible. However please consider the next bullet which is an important point!

                 ⁰ Because the issuer of Alert Service Bulletin has identified a Service Bulletin as Alert – Typically related to a Safety Issue it is expected that the CAW organization will fully comply with the objectives in the stated and required time frame. (Note - Not doing so would be seen as a serious breach of organizational responsibility without due & valid reason)

So Why Not Just Make Alert Service Bulletins Mandatory?

Quite Simply because the Manufacture does NOT have the authority to do so! (Only the Regulatory Authorities can “Mandate” such activity)

What does it mean when we talk about adopting a Service Bulletin?

It means that the Regulatory Authorities, who are in receipt of all Manufacturer's Bulletins which are related to a “Safety Concern” can decide to make a particular requirement “MANDATORY” in which case they issue an Airworthiness Directive requiring the actions referenced in the Service Bulletin to be accomplished with a time frame

       ⁰ Note the AD timeframe maybe be different from the SB timeframe (The AD Timeframe always takes precedence)

Summary

Compliance with an A.D. is exclusively mandatory; compliance with an S.B. is not mandatory unless the service bulletin references or is accompanied by an airworthiness directive