Which control system concept enables proportional corrections to the flight path based on line-of-sight angular rates to the target?

• A. Closed-loop control
• B. Proportional Navigation
• C. Feedforward Control
• D. Manual Control

Answer: (B)

The concept being tested is using the rate of change of the line of sight to the target as the feedback signal and applying corrections proportional to that rate to steer the flight path. In Proportional Navigation, the defender (or interceptor) continuously measures how fast the line of sight to the target is rotating. The control law then commands a turn (a normal acceleration) that is proportional to that line-of-sight angular rate, often also scaled by the closing speed. This causes the pursuer to turn in a way that reduces the LOS rate, guiding the flight path toward where the target will be—an intercept that is efficient and smooth. The proportional factor, the navigation constant, determines how aggressively the path is curved.

This approach stands out because it relies on the LOS rate as the primary error signal and creates automatic, curved pursuit toward interception rather than simply correcting for position error or following a preplanned path. It's distinct from generic closed-loop control, which could use other error signals; feedforward control, which uses only planned commands without feedback from the actual motion, and manual control, which depends on a human operator.