Coaxial-rotor aircraft

He had developed a small helicopter model with coaxial rotors in July 1754 and demonstrated it to the Russian Academy of Sciences.

[2][3] Two pioneering helicopters, the Corradino D'Ascanio-built "D'AT3" of 1930, and the generally more successful French mid-1930s Gyroplane Laboratoire, both used coaxial rotor systems for flight.

Having two coaxial sets of rotors provides symmetry of forces around the central axis for lifting the vehicle and laterally when flying in any direction.

Also, helicopters using coaxial rotors tend to be more compact (with a smaller footprint on the ground), though at the price of increased height, and consequently have uses in areas where space is at a premium; several Kamov designs are used in naval roles, being capable of operating from confined spaces on the decks of ships, including ships other than aircraft carriers (an example being the Kara-class cruisers of the Russian navy, which carry a Ka-25 'Hormone' helicopter as part of their standard equipment).

Because of the greater number of moving parts and complexity, the coaxial rotor system is more prone to mechanical faults and possible failure.

[4] The system's inherent stability and quick control response make it suitable for use in small radio-controlled helicopters.

Compensating for even the slightest breeze causes the model to climb rather than to fly forward even with full application of cyclic.

Multirotor type unmanned aerial vehicles exist in numerous configurations including duocopter,[5] tricopter, quadcopter, hexacopter and octocopter.

All of them can be upgraded to coaxial configuration in order to bring more stability and flight time while allowing carrying much more payload without gaining too much weight.

Having more lifting power for a greater payload explains why coaxial multirotors are preferred for nearly all large-payload commercial applications of UAS.