What is the primary function of flight data recorders?

The primary function of flight data recorders is to capture flight parameters for accident investigation. These devices, commonly referred to as "black boxes," are designed to store crucial data regarding the aircraft's performance and operational state during flight. This includes information such as altitude, speed, heading, and other critical flight parameters that can be vital in understanding the sequence of events leading up to an aviation incident or accident.

By analyzing the data collected by flight data recorders, investigators can reconstruct the circumstances surrounding an accident, identify any anomalies, and assess human factors and mechanical issues that may have contributed to the event. This in-depth analysis helps improve safety measures, inform future training protocols, and lead to enhancements in aircraft design and technology.

The other options, while they relate to various functions within aviation, do not accurately represent the primary role of flight data recorders. For instance, real-time performance data is valuable to pilots but is typically provided by other onboard systems, and monitoring passenger behavior or logging pilot communications serves different purposes that are not the central focus of flight data recorders.