Comment by tshaddox

I’m not sure what reasons there would be for quadcopters not scaling up well. Bigger rotors should be more efficient like with any other aircraft. Perhaps there are scaling issues with quickly changing the speed of larger rotors to maintain flight control? That could be resolved by using variable-pitch rotors, although at that point you’ve lost the key advantage of multirotors (which is their mechanical simplicity) and you’re probably better off with just one even bigger rotor with cyclic pitch control (i.e. a helicopter).