Did Soviet pilots fly for the N Vietnamese air force and engage US in to combat?

Yes, Soviet pilots did fly for the North Vietnamese air force during the Vietnam War and engaged in combat with the United States. The Soviet Union provided significant military support to North Vietnam, including the deployment of fighter pilots and aircraft. Soviet pilots were known as "advisors" and flew MiG-17s and MiG-21s against American aircraft, including the F-4 Phantom and the F-105 Thunderchief. While the exact number of Soviet pilots who served in Vietnam is not known, estimates range from several dozen to several hundred. Soviet pilots were highly skilled and experienced, and they played a significant role in the air war over North Vietnam. They scored a number of air-to-air victories against American aircraft, and their presence helped to deter the United States from escalating the conflict.