There are two types of proficiency needed today for competent instrument flight. Of course, you must fly solely by reference to the instruments in highly variable weather ranging from low ceilings and visibility all the way up to a more active environment that might include precipitation, gusty winds, convection, and worse.
But system knowledge is critical. The best stick who doesn’t know the departure, arrival, and approach procedures can’t really master instrument flight. Now, break down that knowledge into two elements: simple rules and procedures, then the ability and judgment to apply those rules and procedures appropriately when needed.
