Why the quad-rotor configuration has not been adopted as an actual aircraft?

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Quadrotor configuration I think is the most common configuration for drones. Why has it not been made into a full-size production aircraft? I think that it could be better than helicopters as it does not need a tail.

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Anonymous 0 Comments

The drone quad rotor configuration hits a bit of a mechanical design sweet spot. Each rotor is fixed pitch (simple), and driven by a directly connected electric motor (no mechanical transmission). Changing the lift generated by each rotor is achieved by changing the RPM of the electric motor. Everything is small enough that these changes in RPM can happen sufficiently quickly to maintain control and manoeuvre.

The trouble with trying to scale this stuff up is that some things don’t scale in the same way. As the rotors and motors get bigger (larger diameter) proportionally to account for the heavier vehicle, the moment of inertia of these things increases faster than the resulting increase in rotor area and motor torque. The end result is a system that can’t respond sufficiently quickly (ie change motor/rotor rpm) to maintain control or manoeuvre safely.

Solutions can include variable pitch control on the rotors (but then you’re back to half the complexity of a conventional helicopter), or using lots and lots of small motor/rotors to carry the required payload (but you’re moving away from the elegance of a simple quad rotor).

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