Takeoff decision speed (V1) defines a pilot’s go/no-go decision during takeoff, and it is a critical part of any discussion on takeoff safety. When compared to its more sedentary cousins—rotation speed (Vr) and takeoff safety speed (V2)—V1 is a bit fickle. Depending on conditions and other factors, its value can move up or down.
As a hypothetical example, at a given takeoff weight, configuration, runway condition (slope and wet or dry), and environment, an ATC-directed runway change to a shorter runway can result in a lower V1. Conversely, a longer runway using the same criteria may yield a higher V1 that may reduce the minimum runway required for takeoff. Likewise, a dry or wet runway condition will move the value of V1 to the right or left, respectively. But why?
Pilot, safety expert, consultant, and aviation journalist Stuart “Kipp” Lau writes about flight safety and airmanship for AIN.
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