Air Plains STC is not required. The installation of the 3 Point Primer is covered in the (IPC) parts catalog as an optional item.
If you have an Air Plains 172-180hp that was done prior to 2021 it is very likely the original primer system (either a single point or existing 3 point) was reinstalled with the new engine. While the previous process works just fine, Air Plains has added an option to the upgrade kit now offering a new three point primer kit.
