In what situation should the speed to rotate (Vrot) not be less than S1?

The situation where the speed to rotate (Vrot) should not be less than S1 relates to the critical decision speed during takeoff. S1 is defined as the speed beyond which the takeoff should not be aborted; it is the minimum speed at which an aircraft can safely transition from the ground to airborne flight.

In the context of using split markers, this indicates a scenario where the pilot can identify different segments of the runway and their respective performance metrics. Maintaining Vrot equal to or above S1 in this context ensures that the aircraft has adequate speed and performance capability to handle unexpected situations that may arise during takeoff, such as takeoff roll continuation or safe climb performance if an engine failure occurs.

In retained decision-making on Vrot and S1, particularly when using split markers, the pilot is reinforced by the understanding of the necessity for each speed’s role in ensuring safety and performance control during takeoff, thus emphasizing the importance of adhering to these critical metrics.