During which phase of flight should ground spoilers not be extended above 25 knots?

Ground spoilers are designed to help reduce lift on landing and improve braking effectiveness by increasing the weight of the aircraft on the wheels. During the landing phase, extending ground spoilers at speeds above 25 knots is generally not advised because it can disrupt airflow over the wings and potentially lead to a reduction in controllability. High speeds with extended spoilers can also increase drag significantly and may affect the aircraft’s handling characteristics adversely.

In contrast, during takeoff, cruise, and taxiing, the aircraft dynamics and operational procedures differ. During takeoff, spoilers are usually not engaged until after the aircraft is airborne. In cruise, spoilers are not typically used at all, as their purpose is not relevant in that phase of flight when the aircraft is stable and gaining altitude. During taxiing, the use of ground spoilers is often limited as well, but they may not pose the same risk factors as they would during landing when the aircraft is transitioning from flight to ground operation. Thus, the focus should remain on maintaining control and not inducing negative aerodynamic effects that ground spoilers could cause at higher speeds during landing.