In case of a failure of the primary navigation system, which system provides backup?

The inertial reference system serves as the backup in the event of a failure of the primary navigation system. This system relies on accelerometers and gyroscopes to calculate the aircraft's position, orientation, and velocity without the need for external reference. It independently calculates its trajectory based on initial conditions and the forces acting on the aircraft, providing a robust alternative to other navigation systems.

While radio navigation, GPS, and ground-based navigation aids are all important components of the overall navigation system, they typically rely on external signals or references. In contrast, the inertial reference system operates independently, allowing for continued navigation in scenarios where external signals may be compromised or unreliable. This self-contained capability makes the inertial reference system a vital asset in ensuring the continuity of navigation functions, especially in challenging environments where other systems might be affected.