Final answer:
When the selected altitude is higher than the current altitude, pressing the EXPED pushbutton in a Flight Control Unit (FCU) will initiate a climb at the maximum safe rate of climb to reach the selected altitude quickly.
Step-by-step explanation:
When the selected altitude is higher than the current altitude and the EXPED pushbutton is pressed in a Flight Control Unit (FCU), the aircraft's autopilot will initiate a climb at the maximum safe rate of climb to reach the selected altitude quickly.
The EXPED pushbutton provides a way to expedite the climb or descent process in certain situations, such as when air traffic control requests the aircraft to deviate from its current altitude quickly.
For example, if the aircraft is currently flying at 30,000 feet and the pilot selects 40,000 feet using the FCU, pressing the EXPED pushbutton will command the autopilot to initiate a climb to reach 40,000 feet at the maximum safe rate of climb.