what works in 100g - 5kg drone does not work for much heavier machines.

- Small UAVs are mainly controlled by varying RPM of each rotor

- Full-scale machines keep ~constant RPM optimal for rotor aerodynamics and change angle of attack for each blade for control (collective and cyclic changes).

With big inertia and no alien materials technology, it isn't possible to apply 'quad' design for your average SAR helicopter.

Also, four points of failure isn't a particularly enticing feature for an already slightly terrifying aircraft if you're actually going to be in it.

There is quadcopter with variable pitch blade.