Under what circumstances would the emergency hydraulic system be utilized?

The emergency hydraulic system is designed as a backup to maintain essential flight control and system functions in critical situations. Its primary purpose comes into play when there is a simultaneous failure of both the primary hydraulic system and the engines. This ensures that the aircraft can still be controlled and operated safely even during severe failure scenarios.

In cases of engine failure, the emergency hydraulic system may not necessarily need to be activated if the primary hydraulic system is functioning properly. Similarly, a battery bus failure does not automatically require the use of the emergency hydraulic system, as it is intended more for hydraulic system failures. Routine maintenance does not typically involve utilizing the emergency hydraulic system, as it is reserved for emergency situations.

Thus, the conditions where both engine failure and primary hydraulic system failure occur present the most critical need for the emergency hydraulic system, making it essential for safeguarding the aircraft and its occupants during dire circumstances.