What does a change to mechanical backup indicate about the flight control system?

A change to mechanical backup in the flight control system indicates that severe system failures have occurred because it signifies a transition from a fully automated, fly-by-wire system to a more basic, manual control mechanism. This shift typically takes place when critical components of the primary flight control system malfunction, necessitating the use of mechanical controls that do not require hydraulic or electrical inputs.

In this scenario, the aircraft's ability to respond to inputs is compromised, which illustrates that the flight control system is no longer capable of operating under normal conditions. Mechanical backup allows for some degree of control, but it is an indication that the operational state of the aircraft has significantly degraded due to serious issues within the hydraulic and electronic components.