Which feature is specifically designed to limit overspeed in the autothrottle system?

The feature that is specifically designed to limit overspeed in the autothrottle system is the autothrottle guard. This component serves as a safety mechanism in the autothrottle system, preventing the engines from exceeding their maximum permissible speed during operation. By doing so, it helps to maintain optimal performance and protects the engines from potential damage that can occur due to overspeed conditions.

In essence, the autothrottle guard works by monitoring the engine speed and, if it detects that the throttle position may lead to an overspeed situation, it intervenes by limiting the thrust. This ensures that the engine operates within safe parameters, ultimately contributing to both efficiency and safety during flight operations.

The other options, while related to aircraft systems, do not specifically focus on limiting overspeed. Thrust reversers aid in slowing down the aircraft during landing, warning alarms provide audible and visual signals for various system statuses, and engine monitoring systems track performance metrics but do not actively limit throttle movements. Therefore, the autothrottle guard is the dedicated feature that directly addresses overspeed concerns within the autothrottle system.