What condition requires notifying maintenance according to FDR lights?

The requirement to notify maintenance when over-G may have occurred is based on the importance of assessing the airframe's structural integrity after it has been subjected to forces beyond typical operating limits. An excessive load factor, often indicated by G-forces exceeding specified limits, can lead to undetected damage. Maintenance personnel need to evaluate any potential impacts on the aircraft's structure and systems to ensure continued safety and airworthiness.

The other options may indicate issues that, while serious, do not specifically require immediate notification of maintenance based on FDR (Flight Data Recorder) lights. For instance, systems like navigation errors or power failures may be addressed through standard operational procedures, but they do not necessarily indicate a concern with the aircraft's integrity that would warrant maintenance intervention. Similarly, exceeding weight limits might raise operational concerns but does not intrinsically call for maintenance oversight unless it results in extreme operational states like over-G.