NATION

John O’Brien, president and chief operating officer, was named chief executive of Grumman Corp. O’Brien succeeds John C. Bierwirth. O’Brien also will succeed Bierwirth as chairman on Aug. 1, when Bierwirth will retire. O’Brien will retain his title as president, but a chief operating officer will not be named. Grumman, headquartered in Bethpage, N.Y., is best known as a maker of military aircraft and aerospace systems.