Final answer:
The maximum flap extension speed is indicated using the Placard Speed and the Airspeed Indicator (ASI).
Step-by-step explanation:
The maximum flap extension speed is indicated using the Placard Speed and the Airspeed Indicator (ASI). The Placard Speed is a limit set by the manufacturer and is displayed on a placard inside the aircraft. It represents the maximum speed at which the flaps can safely be extended. The ASI is an instrument that displays the current airspeed of the aircraft and it may have different markings to indicate the maximum flap extension speed.