What must be operational for navigation using GPS?

• A. Rear unit
• B. Backup navigation systems
• C. Front unit
• D. Auxiliary control panel

Answer: (C)

For navigation using GPS, the front unit must be operational, as it is typically the primary interface for the GPS system in most aircraft. The front unit is responsible for receiving the satellite signals, processing the data, and displaying the navigation information to the pilot. It allows for input and interaction with the data being processed, crucial for effective navigation.

Having a fully functional front unit enables accurate position tracking, route plotting, and waypoint navigation. If the front unit is not operational, the primary functions of GPS navigation will be compromised, resulting in an inability to effectively receive and interpret navigation data.

The other components mentioned, while they may serve important roles in the overall navigation system, do not directly influence GPS functionality in the same immediate way that the front unit does. Backup navigation systems and auxiliary control panels may be used for contingencies or additional support, but they do not replace the necessity of a working front unit for GPS navigation.