Which of the following is a function of the flight data recorder (FDR) green MAINT annunciator?

• A. Indicates IDARS memory is ~80% full
• B. Provides interface between IDARS and DTM
• C. Stores BIT data in system memory
• D. Provides for download of IDARS data

Answer: (A)

The thing being tested is how the flight data recorder signals when memory is getting full. The green MAINT annunciator on the FDR is a maintenance warning tied to the IDARS memory usage. When the IDARS memory reaches about 80% full, the indicator lights to alert crews that action is needed to offload or archive data to prevent overwriting important information. This makes it clear that the light is about memory capacity and the need for maintenance handling, not about interfacing with another system, storing built-in-test data, or enabling a data download process. So the best answer is that it indicates IDARS memory is around 80% full.