Let's Talk Ground Resonance, I wanted to talk about ground resonance and why as model helicopter pilots, you want to be aware of this potentially damaging event.
Ground resonance, in the very simplest of terms, is an induced out-of-balance rotor disc. How the rotor disc becomes out of balance has to do with the lead and lag of the blades.
Just think of a two-blade rotor and both blades ending up on the same side of the mast. A big reason model helicopters are more susceptible to ground resonance is the head design.
Full-size helicopter rotors/blades have been designed to mitigate ground resonance. There are a few factors that can contribute to your model helicopter experiencing ground resonance.
How tightly do you tighten your blades in the grips? A too-loose blade can contribute to a ground resonance. The surface you are flying off can also be a factor.
A hard surface can greatly increase your chances of inducing ground resonance because there is no dampening. Grass and soft surfaces have a much less chance of getting into resonance. When can ground resonance occur?
Anytime you are on the ground running, the potential is there. What happens if you do get into ground resonance, and how do you get out of it? There are two ways. The first is to just take off.
By breaking away from the ground, you no longer have anything to bounce off of, thus breaking the cycle. The second is to shut down power and coast down. If it's already in resonance this won't be ideal, but sometimes you don't have the option to take off. Below are some links to videos of ground resonance and how fast and violent it can be.
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