GURPS 3e: Making a duct-rotor helicopter

[RyanW]

Originally Posted by thrash

That's not to say ducted fans don't involve a lot of additional weight and complexity, just that there are compensating gains.

On the other hand, helicopter rotors generate lift like a wing when the helicopter is moving, requiring much less down thrust (and thus power) than when hovering. A helicopter operating at the edge of its capacity can even stall (fully loaded Hinds in the high altitudes of Afghanistan had to make rolling takeoffs). If a ducted fan gains any lift that way, I'm sure it is greatly reduced.