Title of old sci-fi book about black girl protagonist and helicopter?

Circa 1972, I read a science fiction novel in my junior high school (personal choice from its library; not assigned reading) about a dystopian future Earth, where blacks become the majority populace following a post-nuclear world. The story is told from the viewpoint of a teenaged black girl, who, through her travels, meets a white boy, and, together, they find a wrecked helicopter that, miraculously, runs, and, even more miraculously, if not preposterously, she manages to fly it! I can't remember the title or anything else about it, but, I'd love to read it, again. Any ideas?