Final answer:
Refusal Speed (Vr) is the minimum speed at which an aircraft can safely stop or abort taking off without veering off the runway.
Step-by-step explanation:
Refusal Speed (Vr) refers to the minimum speed at which an aircraft can safely stop or abort taking off without veering off the runway. It is an important parameter in aviation for ensuring the safety of the aircraft and its passengers.
Refusal speed is influenced by factors such as the aircraft's weight, wind conditions, runway conditions, and aircraft configuration. Generally, it is calculated by taking into account the stall speed of the aircraft, the acceleration rate, and the distance required to come to a stop.
For example, if an aircraft has a refusal speed of 120 knots, it means that the pilot must decide to abort the takeoff before reaching that speed. If the aircraft hasn't reached Vr and has an issue, the pilot can safely stop at or below this speed.