What does 'ground effect' refer to in aviation?

Ground effect in aviation refers to the phenomenon where an aircraft experiences increased lift and decreased drag when flying close to the ground. This effect occurs primarily during takeoff and landing phases, where the presence of the ground influences the airflow patterns around the aircraft. Specifically, as the aircraft approaches the ground, the air pressure under the wings increases, which leads to a reduction in the induced drag. This helps the aircraft to lift off at a lower speed and with less power required.

When an aircraft is within a certain distance from the ground – typically the wingspan distance – it benefits from ground effect, which is especially pronounced during low altitude operations. Pilots need to understand this effect to manage their takeoff and landing safely, and it's crucial because it can impact the aircraft's performance in those critical phases of flight.