Final answer:
The green flashing SPEED message on the MSD indicates that the aircraft's approach speed is excessive when the Radio Altitude is below 100 feet, signaling the pilot to reduce speed for a safe landing.
Step-by-step explanation:
The green flashing SPEED message on the Multi-function Display (MSD) that appears when the Radio Altitude (RA) is less than 100 feet is used to inform the pilot of an excessive approach speed during the landing phase. This message is a part of the aircraft’s monitoring systems designed to enhance the safety and efficiency of the flight, particularly during critical phases such as landing. When the aircraft descends below 100 feet Radio Altitude and the system detects that the approach speed exceeds the recommended velocity, the green flashing message is displayed as a visual alert to prompt immediate pilot action to reduce speed and prevent a potential overshoot or other landing issues.