Archive for category Helicopters

Just over a year ago I got into radio controlled helicopter flying. I started with a couple of 4 channel co-axial helicopters, moved up to a fixed pitch single rotor, and most recently took the step up to 6 channel collective pitch with a new Align T-Rex 250.

With the two single rotor helicopters, I find they tilt to the right whilst hovering, whereas the co-axial models don’t. Got me wondering why?

The answer is something called “translating tendency”, and really it’s obvious when you think about it. The tilt comes from the thrust of the tail rotor. The tail rotor is pushing against the natural torque of the main rotors to keep the helicopter on a heading, but of course the tail rotor is mounted below the hub of the main rotors. This basically causes the helicopter to pivot slightly.

This happens with most helicopters, models or not, apart from co-axial or tandem rotor helicopters which have no tail rotor. In a real helicopter, significant levels of left foot input are needed to keep the helicopter straight whilst hovering, and it would be normal for the aircraft to be leaning slightly to the right or the left. In fact, European helicopters will lean right, whereas American helicopters will lean left. This is because the main rotors spin in different directions on American and European helicopters. (Not sure if this is the case with radio controlled models.)

It can be a little disorientating at first, because the temptation is to provide a little cyclic input to correct the lean, but if you do, the helicopter will start to drift in that direction. You just have to get used to it. At least on my model the heading hold gyro takes care of the yaw, so I don’t have to - real helicopter pilots don’t have that luxury! As difficult as it is flying a full 6 channel radio controlled model, it’s nothing compared to doing it for real. Maximum respect to those guys!