Using Drone Flight Controllers for Airplanes

We will take a look at using a flight controller in your RC plane. Why would you use a flight controller in an RC plane in the first place? Because it’s a way to add a ton of functionality and different flight modes to your airplane, with a flight controller you can make your flight assisted with stabilization thanks to the built-in accelerometers or gyros, different ports allow you to connect external sensors and systems like a GPS that will make your airplane able to measure it’s altitude, ground speed and set up return to home, basically it will fly by itself. With the addition of a telemetry system, with a ground control computer, running a mission planner, you can now add way points for the airplane to navigate and fly all by itself.

A flight controller is basically a computer on board the airplane.

Important! We’ll only focus on drone flight controllers instead of the bigger ones made for fixed-wing aircraft.

First steps

In this article I’m assuming that you’re familiar with flashing the firmware to a flight controller and that you’ve used software like Betaflight before.

There are many different flight controllers in the market, for airplanes we normally choose more specialized FC’s for that task, since we need more PWM outputs and peripheral pins to connect more servos and sensors for more complex things, but to keep things simple let’s start by using a common FC normally used in racing drones (quadcopters), and we’re only using its gyros or accelerometers for stabilization, that’s all. But if it’s your first time using a flight controller this should be enough to get you started in this topic.

Flight controller selection

Any flight controller should be able to work for airplanes, the only problem is the PWM outputs available from the board, some boards have a more convenient layout than others, some will provide only 4 PWM outputs and others 8, to make life easier, buy a flight controller that offers at least 6 PWM outputs, if the outputs are arranged in a comfortable way to solder the pins in a single line the better, otherwise, you’ll have to make some awkward soldering like the one I did in the video but is not a big deal.

flight controller outputs

If you don’t get the 6 PWM outputs you won’t be able to connect all the servos.

If you use one servo per aileron, 1 motor, and the standard elevator and rudder it adds up to 5 channels, so why do you need 6? That’s because Inav by default assigns the first 2 outputs for motors even if you’re going to use only 1 motor, then if you also want to use flaps you add 1 or 2 channels more.

 

The FC on the left is an SP Racing and it has the 8 PWM outputs in a single rail which is perfect for soldering a connecting easier, the one on the right is the Omnibus pro V2, and as you can see it has highlighted in green 4 PWM outputs + 4 more but in an awkward position. Both are good for a setup of ailerons and flaps with separate servos for each surface, elevator, rudder, and 2 motors.

The Software and Firmware

You can download and install Betaflight, Inav, Cleanflight, or any similar one, I’m using Inav for its compatibility with my board, and also offers more options for airplanes, but the others will also be very similar.

Note: All code can be considered software, but firmware is a more specific code designed to run in a specific hardware, like the FC we’re using.

After downloading the software of your preference you need to open it, connect your FC to the PC in boot mode, here’s a video on how to do that in case you have trouble connecting your FC in DFU mode. Then load the right firmware to flash, flash it, and that’s it.

Calibrations and configurations

Now it’s all about configuring your parameters to make it work with your setup, we’re not going to cover that here but I can show you a video of what I did.

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