Define V1 speed in takeoff performance.

V1 speed, often referred to as the takeoff decision speed, is a crucial parameter in aircraft takeoff performance. It represents the speed at which a pilot must make a decisive choice: whether to continue with the takeoff after an engine failure or to abort the takeoff and apply the brakes. If the aircraft reaches V1 and an engine fails, the pilot is committed to continuing the takeoff, as the required distance and performance to stop the aircraft safely would exceed the available runway.

Understanding V1 is essential for flight safety; it integrates various performance factors, such as aircraft weight, runway length, and environmental conditions. Pilots are trained to recognize true V1 speed in real-time conditions to mitigate risks associated with takeoff and ensure a safe operational environment.