Multirotor

e-volo, the first manned electronic multirotor

A multirotor^[1] or multicopter is a rotorcraft with more than two rotors. An advantage of multirotor aircraft is the simpler rotor mechanics required for flight control. Unlike single- and double-rotor helicopters which use complex variable pitch rotors whose pitch varies as the blade rotates for flight stability and control, multirotors often use fixed-pitch blades; control of vehicle motion is achieved by varying the relative speed of each rotor to change the thrust and torque produced by each.

Due to their ease of both construction and control, multirotor aircraft are frequently used in radio control aircraft and UAV projects^{[2][3][4][5][6][7]} in which the names tricopter, quadcopter, hexacopter and octocopter are frequently used to refer to 3-, 4-, 6- and 8-rotor helicopters, respectively.^[8]

Hexacopter.^[9]

In order to allow more power and stability at reduced weight coaxial rotors can be employed, in which each arm has two motors, running in opposite directions (one facing up and one facing down).^[10]

Quadcopter coaxial - OnyxStar FOX-C8 XT Observer from AltiGator

Examples

• Cierva Air Horse - a British three-rotor "heavy lift" helicopter first flying in 1948. Three rotors were used to give a large lift without compromising rotor strength.^[11]
• e-volo - a German prototype electric multicopter with 16 rotors, the first electric multicopter in the world to achieve manned flight.^[12][13] The large number of low-cost motors make it economical, quiet and provide redundancy with ability to maintain control with up to four failed motors.^[14]

References

1. Early in helicopter development,"multi-rotor" was used to refer to helicopters with two rotor assemblies
2. "AeroQuad - The Open Source Quadcopter".
3. "Multicopter Table". multicopter.org. Retrieved 30 June 2015.
4. "FrontPage - UAVP-NG - The Open Source Next Generation Multicopter". uavp.ch. Retrieved 30 June 2015.
5. "FrontPage - UAVP-NG - The Open Source Next Generation Multicopter". uavp.ch. Retrieved 30 June 2015.
6. "DIY Drones". diydrones.com. Retrieved 30 June 2015.
7. OpenPilot Open source UAV autopilot for multirotors
8. "How to Pick The Best Multirotor Frame". My First Drone. Retrieved 30 June 2015.
9. "ALMA Filmed with Hexacopter". ESO Announcement. Retrieved 6 September 2013.
10. "Multirotor Frame Configurations". Coptercraft. Retrieved 23 December 2015.
11. Flight 14 April 1949 p427
12. "German multicopter makes first manned flight". sUAS news. 1 November 2011. Retrieved 3 Nov 2011.
13. "Volocopter: 18-propeller electric helicopter takes flight". CNN news. 27 November 2013. Retrieved 2 Dec 2013.
14. "New Aircraft Arises from Germany". Sport Aviation: 14. January 2012.