RTF (ready to fly) Electric Helicopters are very accurately set up at the factory. They are test flown, and all the components are thoroughly checked to ensure everything is balanced as it should be.
However, Electric Helicopters are so sensitive it doesn’t take much for things to go amiss. And what if your heli isn’t RTF, but kit built? Or you’ve recently upgraded some of the parts, or had a recent crash?
All of these things can cause RC Helicopters to behave in all sorts of unpredictable ways, even when the rotor and flybar are perfectly balanced.
But first of all, you need to know what a ‘normal’ helicopter feels like because, as you know, they are unpredictable things anyway. The following test will soon tell you if the helicopter you are flying is properly balanced, or if it needs adjustment anywhere.
Check if your helicopter has a clockwise or anti-clockwise rotor (this should be obvious) and that there isn’t any obvious juddering or odd transmitter responses, which would point to other problems such as unbalanced blades or tracking. (We will assume your RC is working accurately).
The first thing to do is remove any training kit you’ve got on the undercarriage. You want this bird to be unstable.
Next, get her hovering just off the ground, just enough throttle to keep her airborne. Yes, she will jump about like a ferret in a sack. Now note the drift. RC Helicopters with clockwise rotors tend to drift to the left, this is a natural effect of the torque, and remedied on the transmitter. Anti-clockwise is obviously a right-hand drift.
Increase the throttle, the head will swing sharply to the left, (for clockwise rotors) with some counteraction by the gyro. Decreasing the throttle will cause the head to swing right.
If this is all you experience, the swash and C of G are fine.
However, if the tail or head drop when you lift off, then the centre of gravity needs adjustment. RC Helicopters that drop to the left or right have a swash plate problem.
If the tail itself is swinging oddly, it’s the rudder and/or gyro that need attention.