Can You Lead Something That You Haven't Mastered?

Jack Welch used to say that he would never fly in a plane with a jet engine that he built - a sensible enough statement considering that Welch was neither a mechanical engineer nor a physicist. Nevertheless, as CEO of General Electric, Welch led a company that manufactured jet engines, light bulbs, and medical equipment, and oversaw sundry other properties large and small, including NBC Universal. But how can one lead a team without any practical knowledge of how the end product is produced?