At what minimum altitude must the autopilot be engaged for takeoff or go-around?

For the Dassault Falcon 7X, the autopilot must be engaged at a minimum altitude of 400 feet for takeoff or go-around. This requirement is based on ensuring that the aircraft has reached a safe and stable flight envelope, where the autopilot can effectively maintain control and assist the pilot in safely climbing away from the runway. Engaging the autopilot at or above this altitude allows for proper system integration and function, thereby enhancing safety and operational efficiency during critical phases of flight.

The specific altitude of 400 feet is established to account for the varying performance and handling characteristics of the aircraft at lower altitudes, where conditions may be less stable. This altitude allows pilots enough time to monitor flight conditions and engage the autopilot only after the aircraft has transitioned to more stable flight conditions.