Final answer:
Overspeed protection in PFD and ND becomes active when the aircraft exceeds its maximum operating speed and is indicated by warnings on the display.
Step-by-step explanation:
Overspeed protection in PFD (Primary Flight Display) and ND (Navigation Display) becomes active when the aircraft exceeds its maximum operating speed. This is typically indicated by an overspeed warning or caution message that appears on the display. The specific indication may vary depending on the aircraft and its avionics system.
One example of overspeed protection becoming active can be seen in modern aircraft with a digital display system. When the aircraft approaches or exceeds the maximum operating speed, the overspeed protection system may trigger an aural warning and display a visual warning message on the PFD or ND, such as 'OVERSPEED' or 'SPEED LIMIT EXCEEDED.'
It's crucial for pilots to pay attention to these warnings and take appropriate action to prevent the aircraft from exceeding its safe operating limits.