Paul Baumgartl designed helicopters in Vienna during the Second World War. In 1941, he premiered the Heliofly I:
The Heliofly I is exactly what it appears to be. It is a back-pack mounted auto-gyro "for sporting use." Leaving aside the burning question of which sports require the use of a back-pack auto-gyro, the Heliofly I was less than successful, commercially. Ignoring the whole, "There's a war on," thing for a moment, this made sense. For one, the craft handled...well, it handled as well as a back-pack auto-gyro could be asked to handle: poorly. Also, landing was difficult on smooth and solid surfaces, and virtually impossible on anything else.
And a lousy landing in the Heliofly I was not an enjoyable experience.
Imagine flubbing the landing on an immensely complicated gymnastic routine...
And then having a riding mower land directly on top of your head.
Undeterred, Baumgartl proceeded to design the Heliofly III-57 in 1943. The III-57 is basically the I model, with the addition of an Argus 8 engine. This would give the III-57 the ability to take flight at any time, from anywhere. Baumgartl's "revolutionary" (get it!?) craft was never adopted by the German military for a couple of reasons. 1. The damn thing was still nigh on impossible to control or land, and the results of a botched landing get far worse with the III-57's extra weight and on board gasoline supply thrown into the mix. 2. There is simply no real tactical situation that could be improved by men in back-pack helicopters. They're unarmed, as it required both hands to operate. They're unarmored, because it's a Goddamned back-pack. And, to add insult to injury (or, in all likelihood fatality), the blasted thing didn't really fly. It just...hopped. It hopped a long way, sure. And was rather frightening looking, to be sure. But at the end of the day, what possible purpose is there to having a group of hopping, unarmed troops with a good chance of being minced by their own back-packs on the battlefield?