When following the one-engine inoperative climb profile, what configuration change is allowed below 400 feet?

During a one-engine inoperative climb profile, the main goal is to maintain a safe and effective climb while managing the aircraft's configuration appropriately. Below 400 feet, the retraction of landing gear is typically allowed because it is an essential step in transitioning the aircraft from takeoff to climb configuration. Once the aircraft has safely lifted off and established a climb, retracting the landing gear reduces drag, which is crucial for maximizing climb performance.

The other configuration changes, such as retracting flaps or slats, and reducing power to maximum continuous, are generally not permitted below this altitude, as they could significantly impact the aircraft's lift and overall performance in a critical phase of flight. Maintaining adequate climb performance and safety is paramount, making the retraction of landing gear a standard and necessary action in this specific situation.