Constant Bearing Decreasing Range is indicated when which statement is true?

• A. A target's range is increasing and bearing is constant.
• B. A target's range is decreasing and bearing is changing.
• C. A target's range is increasing and bearing is changing.
• D. A target's range is decreasing and bearing is not changing.

Answer: (D)

Constant bearing decreasing range occurs when the other vessel stays on the same bearing from your viewpoint while the distance between you closes. That means you’re on a collision course unless someone alters course or speed, because the line of sight to the target remains fixed even as you get closer. The statement that the range is decreasing and the bearing is not changing exactly reflects that situation. If the bearing changes while range is decreasing, you’re not on a constant bearing line, so it’s not CBDR. If the range is increasing, or if both range and bearing change, you’re moving away or past the other vessel, not on a collision course. In practice, detect CBDR and take early action to break the constant bearing by changing course or speed to increase range or alter bearing.