Final answer:
Concentric rings on an instrument procedure indicate a DME arc, a navigational procedure for maintaining a constant distance from a navigational aid.
Step-by-step explanation:
If an instrument procedure is depicted with concentric rings, it typically indicates the presence of a DME arc. A DME arc is a navigational procedure that pilots use to transition between different segments of an instrument approach or to intercept a final approach course.
It involves flying a constant distance from a navigational aid by tuning into the DME (Distance Measuring Equipment) frequency, which provides the distance information to the airplane. As the aircraft flies this arc, it's maintaining a constant distance, depicted by the rings, from the navigational aid.