Lockheed Martin Corp’s (LMT.N) decision to buy helicopter maker Sikorsky Aircraft and sell $6 billion in lower-margin units marks a clear turning point for Lockheed CEO Marillyn Hewson, who is shaking up the world’s largest weapons maker. Thrust into the CEO job in January 2013 after retiring CEO Robert Stevens’ designated successor was fired for having an affair with a subordinate, Hewson spent her first year largely executing a strategy Stevens had mapped out and repairing tense ties with the Pentagon on the $391 billion F-35 fighter program.