Before any person may be proceeded against on any complaint, such person or pilot must be notified in writing to appear before the commission. Such notice must specify the nature and substance of such complaint and be served personally or by certified mail addressed to such pilot at the pilot's last and usual place of abode at least 15 days before the time fixed in the notice for the pilot's appearance.   [RR 2021, c. 2, Pt. B, §228 (COR).]