Assuming constant IAS, when an aeroplane leaves ground effect, what happens to the effective angle of attack?

When an aeroplane leaves ground effect, the effective angle of attack decreases due to the reduction in lift generated by the proximity of the ground. In ground effect, the aircraft benefits from an increased lift-to-drag ratio because the ground disrupts the airflow around the wings, allowing the aircraft to experience increased lift and reduced induced drag. However, once the aircraft descends out of ground effect, the airflow becomes more turbulent without the influence of the ground, leading to a reduction in lift at the same indicated airspeed.

As the aircraft transitions into free air, the effective angle of attack—defined as the angle between the chord line of the wing and the relative wind—reduces. This is because, while maintaining constant indicated airspeed, the actual airspeed may not produce enough lift to compensate for the higher induced drag experienced when not in ground effect. Thus, to maintain level flight or a climb after leaving ground effect, the pilot may need to increase the angle of attack to sustain sufficient lift, but initially, there's a decrease as the aircraft transitions out of the beneficial ground effect conditions.

Understanding the aerodynamics involved during this transition helps demonstrate why the effective angle of attack indeed decreases when the aircraft leaves ground effect.