Flight of the Hawk — Gary Paulsen

When Andy Hawkes's parents are tragically killed by a hit-and-run driver, Andy is sent to live with his mysterious grandfather. Andy has only met Grandfather Hawkes once, at his parents' funeral. The old man seemed frail and sickly, and a little bit weird. But Andy soon finds out his grandfather isn't what he seems--he's an inventor, for one thing. Andy also discovers that his parents' deaths may not have been an accident. When Grandfather Hawkes's life is threatened, Andy decides he's not going to lose another person he loves. So Andy puts to use one of his grandfather's inventions and becomes...The Hawk!