What is a critical speed to avoid during landing after a controllability check?

The critical speed to avoid during landing after a controllability check is identified as 90 KIAS because it is typically the speed at which aircraft may experience control difficulties if configuration changes occur or if an unexpected situation arises. Maintaining speeds above this threshold provides a margin that helps ensure adequate control and response, particularly as the aircraft approaches landing, where lower speeds could lead to a stall condition or reduced control authority.

The selection of 90 KIAS as a critical marker is based on operational safety considerations specific to aircraft handling characteristics during the landing phase. This speed allows pilots to manage the aircraft's descent and approach, enabling them to perform necessary adjustments without risking loss of control.

The other speed options may not provide the adequate buffer required during landings, as they either fall below or above the typical thresholds that are set for safe aircraft operation during critical phases.