Published date: 9 August 2022


This AC provides a means acceptable to the Director for showing compliance with Part 21 in order to gain a supplemental type certificate (STC).

The guidelines provided in this AC are general in nature and intended to help applicants and design organisations gain a better understanding of the STC process including their respective roles and responsibilities.

Related rules

This AC relates specifically to Civil Aviation Rule Part 21 Subpart E – 'Supplemental Type Certificates'.

Change notice

Revision 3:

  • Updates the Baseline Acceptable means of Compliance (MOC) ASTM F44 standards in the compliance matrix in Appendix B1
  • Updates link to Federal Aviation Administration (FAA) document
  • Adds a note directing participants using the compliance matrix template not to alter the format of the matrix, and 
  • Makes minor punctuation and stylistic updates.

Note: as the excel tables in the two Appendices may be difficult to cut and paste from a PDF document, they are available here:

AC21-8, Design Changes - Supplemental Type Certificate, Appendix A, Revision 3 [XLSX 12 KB]

AC21-8, Design Changes - Supplemental Type Certificate, Appendix B, Revision 3 [XLSX 28 KB]

Please note, if you use the template matrix in Appendix B, it is important that you do not alter the format of the matrix, as it allows for clear identification of acceptable MOCs compared to selected MOCs for the project.

A version of this AC [XLSX 27 KB] and Appendix B [DOCX 307 KB] with insertions in yellow highlight and deletions in strikethrough are also available.