Definition
A takeoff decision speed (V1) deliberately set lower than the maximum allowable value, used on contaminated, slippery, or shorter runways to ensure the airplane can be safely stopped on the remaining runway if the takeoff is rejected. Lowering V1 shortens the accelerate-stop distance required, at the cost of a longer accelerate-go distance if an engine fails after V1.
Plain English
It's a lower-than-normal go/no-go speed chosen so that, if something goes wrong during the takeoff roll, the airplane has enough runway left to stop. The trade-off is that if a problem happens after that lower speed, the crew is committed to continuing the takeoff with less performance margin.
Context Anchor
Seen in takeoff performance planning and rejected takeoff discussions, especially when pilots are reviewing the speed at which they must decide to stop or continue.
Derivation
Reduced comes from a Latin root meaning “to lead back” or “bring down.” In this term, it means the V1 speed has been brought down from the usual calculated value. The “V” in V1 stands for speed or velocity, and the “1” marks this as the first major takeoff decision speed.
Why Pilots Care
Choosing a reduced V1 increases the likelihood of stopping the airplane on the remaining runway if an engine failure or other problem occurs before rotation.
Grounding Statement
A reduced V1 moves the takeoff decision point to a lower speed, so the crew must make the stop-or-go decision earlier in the takeoff roll.
Intuition Check
Reduced does not automatically mean safer here. It means the decision speed is lower, which helps stopping distance but must still leave enough performance to continue the takeoff if stopping is no longer the correct choice.
Example Sentence 1
Because the runway was wet and shorter than usual, the crew calculated a reduced V1 to make sure they could stop the airplane if they had to reject the takeoff.
Example Sentence 2
On the short wet runway the captain chose a reduced V1 to ensure adequate accelerate-stop distance remained available.