CJ!
Thank you for bringing up that Advisory Circular! Definition of an FAA Advisory Circular:

Advisory Circulars –

Advisory Circulars are publications issued by the FAA and international aviation authorities to provide guidance such as methods procedures and practices for complying with regulations and requirements. Advisory Circulars may also contain explanations of regulations and other guidance materials, best practices or information useful to the aviation community. Advisory circulars do not create or change a regulatory requirements.

That AC is there, kind of out dated. 1981?? And NOT a Law or FAA Reg by now?