Complex sentence: The RAAF handed over most of their UH-1s to the Australian Army in the late 1980s and all were eventually replaced by the Sikorsky UH-60 Black Hawk.
Split into simpler sentences: The RAAF handed over most of their UH-1s to the Australian Army in the late 1980s. And all aircraft were replaced by the Sikorsky UH-60 Black Hawk.