What occurs when IDARS reaches approximately 80% fullness?

When IDARS (Integrated Data Acquisition and Reporting System) reaches approximately 80% fullness, a green MAINT annunciator illuminates. This signal indicates that the system is approaching its capacity for data collection and storage but is still operational. The green MAINT light serves as an early warning to the pilot or crew that attention may be needed to manage the data output or to prepare for maintenance, ensuring that the system continues to function effectively without risk of data loss. It's essential for operational readiness and data integrity in flight operations.

The other answer choices relate to warning and caution systems that typically indicate immediate action is required, unlike the MAINT annunciator, which suggests monitoring without imminent risk.