How is Vr defined in aviation?

The definition of Vr, or "rotation speed," is critically important for pilots during takeoff. It is the speed at which the pilot initiates the rotation of the aircraft's nose to achieve takeoff. This speed is typically reached shortly before the aircraft becomes airborne, allowing it to safely transition from ground to flight.

Understanding rotation speed is essential because it helps ensure that the aircraft has enough lift to take off safely. If the aircraft is rotated too early, it may not have enough airspeed to generate adequate lift, leading to a risk of stalling. Conversely, if the rotation occurs too late, it could result in longer takeoff distances and impaired performance.

The other provided options address different aspects of flight but do not accurately describe Vr. The speed at which ascent begins refers more to the climb speed after takeoff, while the speeds required for landing and cruising altitude indicate different phases of flight, not the crucial moment of rotation during takeoff.