By combining my readings of rcgroups.com and my personal experience, I try to outline what you need to know about transmitter features that you should look out for in order to start flying a tricopter.
This one is pretty easy, you need a minimum of 4 channels:
All transmitters on the market support 4+ channels. Don’t worry about having extra channels they might come in handy if you have accessories (retractable landing gear maybe?) that you need to trigger mid-air.
As a tricopter newbie, you need to know about D/Rs and Expos and you need to use them. Flitetest made an awesome video with some demos of how these things work.
Basically, dual rates reduce the throw of your servo. For example on your tricopter, the rudder stick controls the yaw mechanism. By configuring the Dual Rates of your rudder control on your transmitter, you can reduce the throw (or the total angular movement) of your yaw mechanism. This will prevent the tricopter’s response to a rudder command to be an extreme movement that could result in an unwanted crash.
Expos, like Dual Rates, modify the throw response of your servos but use exponential curves instead of limiting the total throw of your servo. This allows you to configure your transmitter to reduce or increase the sensitivity of its controls. For example, if you use expo values that reduce sensitivity, you’ll get very precise control and movement response on your tricopter. This is important because as a newbie you’ll be overcompensating for every movement of the tricopter and the transmitter will “soften” those “overcompensations” and let you learn to fly.
Warning: Expos can be configured with both negative and positive values and with different transmitters those mean different things. For example positive expos on my transmitter means that the sensitivity is reduced near the center of the control for fine tune and precise flying (good for newbies). Negative expos on the other hand will turn the center of the control very sensitive for acrobatic flying. Make sure you understand how to configure your transmitter before flying because this might be hazardous to your tricopter. David Windestål does recommend you fly with these features disabled before configuring them because you want to calibrate your controller board on the tricopter first and configure your transmitter second.
On mid-range transmitters, you can configure both individual Expos and Dual Rates settings for your aileron, elevator and rudder controls. I personally found Expos to be the most useful feature as a beginner. I’ve read that some transmitters don’t allow for “simultaneous” D/R and Expo configurations (it’s one or the other) so you should take that into consideration when purchasing your first transmitter.
These are my current D/R and Expos settings.
As you learn to fly your tricopter, you’ll probably want a mode 2 transmitter: the left stick is rudder and throttle and the right stick is aileron and elevator (you can read up more on the different transmitter modes on here). Throttle curves are a feature specific to helicopters and generally this feature will be found in the “helicopter” settings of your transmitter.
When you’re a newbie and using a mode 2 transmitter, you’ll want to configure a throttle curve and here is why: when the throttle response is linear and you’re learning to fly a helicopter for the first time, it is very difficult to maintain a nice stable hover. Like I explained in the Expos section, the stick is very sensitive and as a newbie you’ll be overcompensating a lot trying to keep the tricopter from hitting the ground, which will result in it gaining a lot of altitude which you’ll overcompensate by making it fall to the ground (and so-on). In addition, your rudder is on the same stick so as you’re learning to use the rudder, you’ll accidentally hit the throttle and the response might be exaggerated, again making you loose control of the tricopter.
Throttle curves, like expos, allow you to reduce the sensitivity of your throttle stick in a specific range. This means that at the throttle level where your tricopter hovers (about 50% throttle for me), you can configure your transmitter to reduce its sensitivity for further throttle input. This allows you to control very precisely the hover of your tricopter. I noticed that my transmitter had a verynice (and manageable) default throttle setting when I switched it to helicopter mode, so you may want to start with that and then configure it to your liking. As you can see on my transmitter at the 0 throttle position, the throttle output is almost 50% (slightly below hover throttle), the rest of the curve is flattened to soften the throttle input. If you do more reading on this topic, the more advanced helicopter pilots never allow their throttle to go to zero during flight (this is a safety feature preventing them from cutting throttle, which you should never do until your helicopter is on the ground).
So there you have it, these are the key features that I found very useful getting started with a tricopter. You’ll also want to learn about trimming your tricopter. You can read up on trimming in the forums or discuss it in the comments section of this article, but that’s the easy and fun part. If you’re curious, I bought this transmitter and I’m quite happy with it. It’s easy to understand and it has the features you need to get started at a decent price. Also, if you’re new to the hobby, transmitters and their receivers are sold individually or in a package so be mindful of what you buy (I bought the transmitter and receiver package).
About me: After watching David Windestål and “the Joshes” on flitetest fly a tricopter, I was sold and I decided to jump into the hobby. I have never flown an RC plane before and never owned any RC equipment, so these are my learnings from getting into the hobby from scratch.