Sexual act with the female on top. The female does a split and inserts lubed penis into vagina. The male then grabs hold of the female's legs and spins her around rapidly, similar to that of a helicopter's blades.
Has a high failure rate, roughly 100%. Failure results in Female either falling over or vomiting, and Male losing penis.
Theoretically, a successful helicopter, if done fast enough, could generate lift for the female for about 2 seconds. There have been 3 reported cases of success, but they were all in Japan so you never know.
Dude 1: Yo d00d my girlfriend and I totally did the helicopter last night!