Turning our attention to the diagram above, we see that the two wings
are arranged so that the leading edges face in the same rotational
direction. Combining this information with the lift priciple, it is reasonable
to assume that a boomerang would simply fly off in one direction as it spun.
If you held it horizontally when you threw it, like you do with a Frisbee
(a flying disc toy), the motion arising from lift should be upward. The boomerang
would fly up into the sky like a helicopter taking off, until it stopped spinning
and gravity pulled it down again.
And, if you threw it end over end, which is the proper way to throw a
boomerang, it seems that it should simply fly off to the right or left. Why
doesn't this happen?