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Article #237: Coaxial RC Helicopters: How Do They Work?

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Coaxial helicopter is one of the more two rotors' lift complementing each other
popular images that come to mind when results in the extraordinary stability
people think about electric RC and hovering ability. Because hovering is
helicopters. And for good reasons too; one of the main components of a
these double-bladed helicopters is helicopter's flight, "easier to hover" is
accredited with bringing hordes of new almost synonymous to "easier to fly".
enthusiast into the world of RC aviation. Controlling the yaw in this setup becomes
Their popularity stems from their only a matter of slowing or speeding up
unequivocal stability in the air - which one of the two rotors. Another merit that
makes them relatively easier to master comes almost as a bonus is that
when compared to their single rotor theoretically, these helicopters do not
counter part. They are also predictable require a gyro - which means that much
enough to be flown within the compounds less tinkering and setting up is needed.
of one's home, securing its spot as one Although very widely praised, coaxial
of the most loved indoor fliers. Being helicopters are not without faults. The
able to fly right out of the box because first one stems from the fact that in
they are sold as RTF (Ready to Fly) kits order to fly, the speed of the two rotor
adds to their appeal. blades must be equal. In fact, these
So where did such stability come from? To helicopters are so dependent on the
answer that, the first step lies in synchronicity of its blades that even the
understanding how helicopters work. A slightest deviation is detrimental. So
single-rotor helicopter generates lift much so that these helicopters will just
when their rotor rotates. As the main spin wildly on the ground, never to lift
rotor turns, another force will also be off. Their two motors simply have to
generated - known as torque, which will always be in their most pristine state.
in turn cause the entire fuselage to turn Also, the stability of these helicopters
in the opposite direction. Since the days comes at the price of sacrificed
when helicopters were in their nascent maneuverability; they are notoriously
stage, their pioneers have learnt to slow and unresponsive. Nevertheless,
counter this effect by including another perhaps the utmost annoyance comes when
smaller perpendicular rotor in the tail. the two blades bite into each other in
This rotor counters the any rotation mid air when most extreme cyclic controls
generated by the torque as well as are applied.
provides pilots a mean to control the All in all, coaxial helicopters are here
direction in which the helicopter's nose to stay. They have become the favorite
is pointing at, more technically known as beginners' RC helicopter. At the same
the yaw. To control the yaw, the pilot time, many experienced pilot enjoy a
simply changes the pitch (or the angle) flight or two of easy indoor flying with
of the tail rotor. these helicopters once in a while.
Coaxial helicopters, on the other hand, Note: Although these coaxial helicopters
eliminate the need of a tail rotor are "relatively" easier to fly than their
completely. This is due to the fact that conventional counterparts, they still
these fliers have two rotors, one on top require hours of practice. Also, their
of the other, rotating in opposite fast rotating blade can cause just as
directions. In effect, the torque much injury as bigger model helicopters.
generated by each rotor cancels out one Therefore, never treat them like toys.
another. When such feat is coupled with






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