What happens if the primary radar is temporarily out of service?

When primary radar is temporarily out of service, secondary radar systems can often continue to function independently. Secondary radar operates on a different principle, relying on transponders in aircraft that respond to interrogation signals from the ground. This means that even if the primary radar fails, the secondary radar can still provide valuable data about aircraft position, speed, and identification.

Because secondary radar does not depend on the primary radar's functionality, it can effectively serve as the sole display source during outages, allowing for continued air traffic management. This capability ensures that air traffic controllers can still maintain oversight and safety despite the primary radar being unavailable.

The other options indicate conditions that are not necessarily true when primary radar is out of service. For instance, secondary radar can indeed be used regardless of the primary system’s status, so it does not become completely unavailable. Furthermore, it is not accurate to say that radar services are entirely unavailable; rather, they are partially operational through secondary radar. Lastly, alignment checks are routine procedures that do not specifically apply to the situation of the primary radar being out of service, as the maintenance processes for radar systems involve regular checks regardless of operational status.