Master Sergeant Kappelmann was the radar observer of a F7F-3N Tigercat fighter with the Marine Night Fighter Squadron 513, Marine Air Group 33, 1st Marine Air Wing. On July 15, 1952, while on a combat mission, his aircraft received a direct hit by anti-aircraft fire, exploded and crashed. He was listed as Missing in Action and He was presumed dead on December 17, 1953. His remains were not recovered. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.