I ride in helicopters fairly regularly and as impressive as they are, they scare the chit out of me. Don't get me wrong, I LOVE flying in helicopters but when one reflects on the stupidly large forces at work in a very light weight vehicle, it boggles the mind that helicopters don't tear themselves apart upon spool up. The volocopter looks interesting to me because it spreads those forces around a bit and appears to place less stress on any one piece. On the other hand, the same basic physics applies. Karlsruhe, Germany is at 400 feet above sea level. The flights I take routinely land at 7000-9000 feet msl. That's a work out for most light to medium helicopters. The power requirements to fly at elevation are significantly higher than for sea level flight.