What effect does a contaminated runway have on V1?

A contaminated runway, such as one covered with snow, ice, or water, can significantly impact an aircraft's takeoff performance. In particular, it affects the required takeoff speed—V1, which is the maximum speed during takeoff at which the pilot must decide whether to abort the takeoff or continue if an engine failure occurs.

When a runway is contaminated, it decreases the aircraft's acceleration due to reduced friction and increased drag. Consequently, the aircraft will not reach the required speed in the same distance it would on a clean runway. As a result, V1 is lowered, reflecting the need for the aircraft to reach a safe speed for aborting the takeoff earlier than it normally would under optimal conditions. Thus, in the context of flight operations, a contaminated runway directly leads to a decrease in V1 to ensure safe performance during takeoff.