What does S1 represent?

In aviation, S1 is a critical speed that represents the go/no go decision point during the takeoff roll. Specifically, it is the speed at which the pilot must determine whether to continue the takeoff or abort it in case of an emergency, such as an engine failure. If the aircraft reaches S1 and an issue arises, the pilot has committed to taking off, as it is generally unsafe to stop the aircraft once it has surpassed this speed.

Understanding the concept of S1 is crucial for pilots, as it affects decision-making during the high-speed phase of takeoff. This speed is usually established through performance calculations based on aircraft weight, airport elevation, and environmental conditions, ensuring that pilots can operate safely within the aircraft's performance limits.