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Issue No 39, 14 August 2023
By: Anthony O. Ives
I intially learned to fly fixed wing RC aircraft because I was told it was easier than learning to fly RC helicopters. My experiences of learning to fly fixed wing RC aircraft were frustrating and it seemed to be neverending not to mention I was not having any fun. RC helicopters were also more expensive when I started learning to fly RC aircraft, but then with the introduction of Lipo batteries and small electric micro helicopters, flying helicopters became more accessible. I immediately enjoyed learning to fly helicopters even though it was probably not easy I never noticed because I was having more fun.
Not to say some of my less enjoyable and frustrating experiences with fixed wing RC aircraft probably helped me and maybe made it a bit easier for me to learn to fly RC helicopters. However, when I decided to try to learn to fly a full sized aircraft I just went straight to helicopters. Of course these experiences might be reversed for other people so its probably important to test both fixed wing aircraft and helicopters intially to see which one you is for you and which you will enjoy the most. The one thing I did enjoy about RC fixed wing aircraft which I have mentioned in some previous articles is building them, as you can build a fixed aircraft from wood in a similar way you can build a boat.
If you decide RC helicopters is something you want try you are better to start with as stable a helicopter design as possible such as a micro electric helicopter with contra-rotating rotors instead of single main rotor and tail rotor. In a contra-rotating rotor helicopter there are two rotors one above another with one spinning clockwise and the other spinning counter-clockwise so one rotor counter acts the torque of the other rotor as per Newton's 3rd law [1]. An example of RC contra-rotating rotor helicopter is giving below:
The helicopter in the picture is an extremely stable design which anyone can fly with very little practice, as it can hover without the need for any input from the pilot. This helicopter is really only capable of yawing [2], moving forward and vertically. So this helicopter cannot move sideways or maneuver in the way as a conventional helicopter can, so you not going to learn fly a RC helicopter using this particular helicopter but it does give a good idea of the features you can use to make a helicopter more stable.
A RC helicopter should actually be unstable in order for it to be able to maneuver however, you include certain features such a flybar and contra-rotating rotors to make it less unstable and slightly easier to hover. The effect of the flybar will be discussed in more detail in some further articles however, you can get an explanation in a book about helicopter theory [3]. You can opt to start off with a conventional helicopter design as in the picture below:
The picture above gives an example of conventional helicopters both electric micro scale and a larger scale model. The picture also shows the training aid that can be used to protect both helicopters and preventing it from tipping over. The larger scale helicopter could not be operated safely in the space shown, it only shown here for demostration purposes. There is a number of advantages of learning to fly with a smaller scale electric helicopter these include the following points:
Less space is required for small scale RC helicopters, hence you can possibly fly a small helicopter indoors even in your living room
The ability to fly a small scale Helicopters indoors also makes it easier because you do not have wind and gusts
Small scale helicopters are lighter in weight, hence less momentum which means lower risk of damage if you crash
Small scale helicopters can be less expensive, as will be their spare parts when you need them
The main disadvantage of a small scale helicopter is the advantage of larger scale helicopters which is that a large helicopter is more stable. This is kind of a catch 22 as the lightweight helicopter can be lowered to ground quite quickly without any damage whereas a heaver helicopter would probably get damaged. However, a lightweight helicopter has less inertia making it more unstable. Some small scale helicopters such as the one shown in the picture use fixed pitch rotor blades which can also make them more unstable. Overall a small scale helicopter is better to start with until you can hover comfortable and master gentle landings, then when you try a larger scale helicopter it will feel a lot easier.
The transmitter controls on a RC helicopter give the similar movements to those on fixed wing RC aircraft [4]. The laterial cyclic control generates the same movement as the aileron controls hence uses the same transmitter stick and movement as does longitudial cyclic control with elevator. The yaw control is achieved using the tail rotor pitch control which uses the the same transmitter stick and movement as rudder control. Throttle and collective control are combined which both control vertical movement.
The typical way to start learning to fly RC helicopters is short hops. Increase the throttle slowly until the helicopter startes to become light on the skids, you have to also be ready to use tail rotor anti-torque control (same as rudder on a fixed wing aircraft as already discussed). Once the helicopter lifts off do not let it get too high but try to control its position over the same point using the cyclic controls (same as aileron and elevator on fixed wing aircraft as discussed above). If the helicopter wanders too close to something that it could crash into lower the throttle and land it. Then can move it back to the starting point by physically lifting and placing it there. You can repeat this process until the battery needs charged. It is a good idea to practice once a day for about 10 to 15 minutes depending on how long your battery lasts. Overpracticing can be frustrating and you always improve after a break generally because you get time to think about what you did wrong and how you will correct it next time.
You will intially learn to hover the helicopter tail in which means the helicopter tail rotor will be closer to you than the nose. It is easier to learn to hover tail in as all the controls generate the same intutive movements as though you were sitting the helicopter cockpit. However, hovering nose in which means the helicopter nose will be closer to you than the tail rotor and it will be more difficult as the controls do not generate the movement which are intutive in fact the lateral cyclic controls are reversed to what they would be if you are sitting the cockpit. Therefore once you have learned to hover tail in, you should practice turning the helicopter until you can hover slightly turned tail in, then turned sideways, etc until you finially able to turn it round and hover nose in. As with learning to hover you should do it in small increments and be ready to turn back to a position you are comfort with or reduce the throttle and land. For nose in hovering one way to remember which way to move the lateral cyclic (or aileron) stick in the nose in position is to move the stick under side of the rotor you want to level or raise. That was something I learned from fixed wing RC aircraft when the aircraft was flying toward you, you would turn the stick so that it is under the wing you wanted to raise or level almost as if you were using it to prop up the wing.
Once you have learned to hover comfortably to can remove the training aid which actually will make hovering easier as the ping pong balls create some unstability due to the rotor wake blowing on them, however you need the training aid intially to protect the helicopter. Hovering nose in can be quite difficult to learn in a tight space, to be honest I never found time to learn it and then I got distracted and decided to learnt to fly full size helicopters. However, if you keep practicing you can learn to do all sort of things with RC helicopters.
Please leave a comment on my facebook page or via email and let me know if you found this blog article useful and if you would like to see more on this topic. Most of my blog articles are on:
Mathematics
Helicopters
VTOL UAVs (RC Helicopters)
Sailing and Sailboat Design
If there is one or more of these topics that you are specifically interested in please also let me know in your comments this will help me to write blog articles that are more helpful.
References:
[1] http://www.eiteog.com/EiteogBLOG/No25EiteogBlogNewton.html
[2] http://www.eiteog.com/EiteogBLOG/No5EiteogBlogStability.html
[3] Principles of Helicopter Flight, 2nd Edition, W. J. Wagtendonk, 2006, Aviation Supplies & Academics
[4] http://www.eiteog.com/EiteogBLOG/No14EiteogBlogRC.html
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