Radio Control Helicopter Vibration

All helicopters have some vibrations. Now, that does not mean they are eggbeaters either.

The model helicopter can be tricky at times to identify what might be causing a vibration. In the full helicopter business, we had devices we could hook up accelerometers to and identify the vibration's intensity and RPM. This would, in turn, give us an idea on what might be causing the issue (as most of the components ran at different RPMs).

What are some causes of vibrations? By definition, vibrations are a "mechanical phenomenon whereby oscillations occur about an equilibrium point." So, in short, an out-of-balance condition.

Let's identify the most common systems or components that could cause an out-of-balance condition. 

 1. Main rotor head and blades

 2. Tail rotor head and blades 

 3. Motor/engine

 4. Geartrain

In my experience, most model helicopter vibration stems from the main and tail blades and heads and, on occasion, the geartrain.

So how do we identify what is causing the vibrations? Main rotor vibrations are normally the slowest and most pronounced. Tail vibrations can usually be described as a buzz or high frequency. The geartrain is usually in the same category as the tail, presenting as a high frequency.

If you're having trouble identifying where the vibrations might be coming from, start with a process of elimination. Remove the main blades and run the helicopter up to flight RPM and see if the vibrations are gone. If they still exist, remove the tail blades and repeat.

If the vibration is resolved when removing blades, you now know where the issue lies. Your rotor blades and head can be perfectly balanced and still give you a vibration if the track is out.

Tracking a multi-blade head can be an entire article. With it being hard to gain an accurate reading with blade widths and profiles, we always recommend using turnbuckles and our angle plate that removes the blades and allows you to set up the blade grip very accurately. The blades can still fly out of track, but in our experience, for a high-quality blade you don't need further tracking after initial setup.

The smoother a helicopter runs, the happier it will be. Vibrations can cause cracking and premature component failure, along with just not looking very pleasing to the eye.