Krawchuk was a 23rd century member of Starfleet, who served as a security officer aboard the Federation starship USS Enterprise in the 2260s under the command of Captain James T. Kirk.
In 2270, while investigating a seemingly abandoned USS Yorktown, Spock assigned a security detail to cover various portions of that ship. Among the detail, Krawchuk covered engineering,while Chopra was assigned to sickbay, Murphy to deck nine, and Willis to deck twelve.
After Yorktown personnel were restored, Krawchuk reported that engineering was back to normal. (TOS - New Visions comic: "A Scent of Ghosts")