No torque and fast

Not electric but interesting nevertheless. French Alps. Custom designed reinforced ITV “Awak” wing to fly a very special PPG - YouTube

Makes me wonder about using a pair of the same sort of shrouded electric fans as used by the Lilium “jet”.

The hard part is that you would still need a 130cm ducted fan(or maybe dual 90cm fans) to come close to the efficiency that we need. By that point you might as well just use aerodynamic torque compensation like scout, nirvana, flattop, pap, etc, or lamels to get the same effect so you don’t need entirely redesigning the paramotor in a way that adds significant weight and likely reduces efficiency.

Well, the Lilium jet actually lifts 600 kg vertically with 36 of these fans, which means that each one is producing just under 17 kg of thrust. If we were trying to produce 150 lbs forward thrust to compare with the OpenPPG SP140, we would need four of these – [600 / 36 x 4 = 66.67 kg (146.67 lbs)] – perhaps two mounted on each side of the pilot’s “seat”. No need for torque compensation, especially if these could be rotating in opposite directions. That is no problem for the motors, but it demands different rotor blades just as with any counter-rotating scheme, However, with four separate centers of torque and limited rotor mass, even all rotating the same direction shouldn’t produce serious yaw or roll to be compensated.

Now, I don’t have the data on the individual weight of these motors, their ducts and their fans, nor for their power consumption, so I can’t compare their efficiency to that of the SP140 130 cm unducted fan or the four fans of the X4. But I imagine that their weight and that of a simplified frame to mount them ought to be comparable to the X4 and its frame.

Its not to say you couldn’t do it, but four lilium jet ducted fans will never come even close to the efficiency of even the relatively inefficient X4 power system. So with a ducted fan, no mater what you do, flight time will suffer.

The only real advantages of a ducted fan is that they are more efficient at higher speeds(albeit less efficient at lower speeds), their propeller is shielded, and they are very power dense.

I have wanted to take something like a 390mm ducted fan to mount to the back of a paraglider harness coupled with some small super high current LiPo batteries. The idea is that you could get a small boost for paragliding with almost no drag penalty and a relativelys small weight penalty. On the flip side, you would be lucky to gain 100 feet of elevation from such system or get more than a 2 minutes of flight time from it.