When is the drag on an aircraft considered to be at maximum?

The drag on an aircraft is considered to be at maximum during landing due to several factors. When an aircraft is landing, it is typically configured for a slower speed, and the deployment of landing gear and flaps increases the surface area that opposes airflow, contributing to increased induced drag. Additionally, the aircraft operates at a lower Reynolds number during this phase, which further increases total drag.

During landing, the combination of the lower airspeed, increased lift demand due to the need to maintain control, and the additional aerodynamic surfaces deployed results in the maximum drag condition. This maximum drag is crucial for ensuring a stable descent and safe landing, allowing for controlled slowing down of the aircraft as it approaches the ground.

In contrast, other phases of flight such as climbing, cruising, or takeoff generally involve more optimized configurations and higher speeds where drag does not reach its peak levels as it does during the landing phase.