What does ESIS stand for?

The term ESIS stands for Electronic Standby Instrument System. This system is crucial in aviation as it provides a backup set of instruments that are vital for flight when primary instruments fail. The Electronic Standby Instrument System typically includes information on critical flight parameters such as altitude, airspeed, and heading, ensuring that pilots maintain situational awareness and control of the aircraft in the event of an instrument failure.

The choice that refers to Emergency Standby Instrument System is not the correct description; while both serve as backup systems, the terminology specifically defines the electronic aspect of the standby instruments. The other options, such as Electronic System Integrity Safety and Essential Safety Instrumentation System, do not accurately portray the established terminology recognized in aviation for backup instrumentation. Thus, the correct choice reflects the specific electronic nature and role of the standby instrument system in maintaining flight safety and control.