Why are we not seeing more variable-pitch quadcopters?

[Jarfi]

Been doing some research on propeller-pitch. And it seems that a variable-pitch-propeller seems superior, with a constant-speed-propeller(adjusting pitch for constant RPM) seems the most efficient of all.

A quadcopter with a low RPM will generally spend less energy on air-drag so we have more efficiency. The problem is once you accelerate the RPM increases and efficiency is lost due to airdrag, similar to a car in a low gear driving fast, causing a too high RPM of the engine itself, which wastes energy.

I've seen a few variable pitch-quads, most seem to be in the development stage, there are even petrolium variable-quads being researched.

My question is, are there(other than added weight) some big mechanical drawbacks to having a variable-pitch propellers over a conventional propeller?

Also will all the professional high-speed quads be using variable-pitch like helicopters in the future?

 

[russ_watters]

Cost and complexity.

 

[Jarfi]

Cost and complexity.

Already got answers on another forum, cost and complexity is an extra factor but this one seemed convincing:

the big issue is slow response time to change, The ESC can change at 400Hz, and go from 0 to 100% in close to the same time,I don't see a mechanical system or servo system getting close to 20Hz and staying in one piece long enough to fly.