Which action is NOT required for aircraft operating in Class B airspace?

In Class B airspace, aircraft are required to adhere to specific operational protocols to ensure safety and efficiency in what is typically busy airspace surrounding major airports. Among those protocols, having an operable transponder, maintaining radio communication, and following air traffic instructions are mandatory requirements.

The necessity for an operable transponder ensures that air traffic control can accurately track and manage aircraft within this space. Additionally, maintaining radio communication allows for real-time updates from air traffic controllers, which is crucial for managing traffic flow and providing safety instructions. Following air traffic instructions is essential for ensuring that all aircraft can operate without conflict, especially in an environment where numerous aircraft might be maneuvering simultaneously.

However, carrying a backup radar system is not a requirement for aircraft operating in Class B airspace. While a radar system is useful for situational awareness, it is not mandated as part of the operational requirements. Therefore, the correct option identifies an action that is not a regulatory necessity for aircraft operating in Class B airspace, distinguishing it from the other required actions.