Facts about Dual-Rotor RC Helicopters
Dual-rotor also known as coaxial rotors helicopters consist of a pair of rotors rotating in opposite directions. One rotor
is positioned above the other. Coaxial helicopters are popular because of its clear stability while in flight making it
easier to learn. It is also considered to be a favorite indoor activity compare to the single rotor model. Its
maneuverability makes it ideal and safe even within one’s home.
Underlying Theory
When a helicopter is not in motion its angular momentum is zero. Once the engine is started, it produces a significant
amount of angular momentum that can cause the body of the helicopter to spin around in opposite direction of the rotors.
To maintain flight stability, coaxial rotors are used by turning each rotor in opposite directions. This allows the
fuselage to sustain a zero angular momentum.
How does it work?
Coaxial helicopters do not necessarily need a tail rotor. The torque created by the 2 rotors spinning in opposite
directions cancels each other. This results to a more stable flight and hovering capabilities. Hovering is one of the main
elements in flying a helicopter. When the pilot slows down or speeds up one of the 2 rotors, he can control the hover or
direction of the helicopter.
Why go for a dual-rotor helicopter?
Coaxial designs are remarkable because of its ability to maximize every available engine power. A tail rotor naturally
throws away some of the power would have been used in lifting and thrusting. It also observed that most dual-rotor R/C
helicopters have less noise. Conventional R/C helicopters generate a loud “blowing” noise because of the interaction
involving the flow of air between main and tail rotors. More and more coaxial helicopters available in the market these
days consume less space making it a more compact model.
Things to consider
The speed of the rotors should be appropriately controlled and maintained. The stability of a coaxial R/C helicopter
greatly depends on the 2 rotors’ synchronization such that any deviation may result to damaging effects. Another downside
is the possibility of the rotors getting into each other especially during extreme flight maneuvers.
Recently, several R/C helicopters began adopting a simplified coaxial design. This new model consists of a coaxial
unbending rotor system with fixed-pitch blades and a swashplate. One thing is clear, dual-rotor R/C helicopters are sure
to make a wave in the next couple of years.
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