Explain the function of supplemental type certificates (STC), service bulletins (SB), and airworthiness directives (AD).

Explanation should include 

• researching STCs through the FAA website Links to an external site. 
• identifying the reason STCs are issued 
• identifying information presented on the STC 
• identifying reasons for an AD being issued. 

Process/Skill Questions:

• What is the function of ADs?  
• Why would an AD be issued? 
• Why would an STC be issued?