It’s important to setup failsafe properly on your mini quad for maximum safety and preventing fly-away. In this tutorial I will explain what failsafe is, and how to set it up in Betaflight as well as on your Taranis TX radio transmitter and receiver.
What’s a Failsafe?
A failsafe is basically something you want your RC model to do when there is a connection loss between your radio transmitter and receiver. A failsafe can happen when:
- radio is out of range when you fly too far away
- signal is getting blocked by obstacles
- TX or RX is switched off, lost power or malfunctioning
- receiver is accidentally disconnected from the flight controller
What Does a Failsafe Do?
You can program your receiver or flight controller to do whatever you want when you lose radio signal. For example, to hold its last stick position, or keep throttle at 20% for it to slowly descent etc. But it’s generally advised to cut throttle when failsafe happens. This should disable or stop all the motors, and your quad should just drop vertically to the ground.
A quadcopter with uncontrolled spinning propellers can be extremely dangerous. It’s better to crash your quad and repair it later, rather than hurting someone badly.
When you lose video signal, you can also just disarm or switch off transmitter to emergency-land your mini quad. This can prevent it from wandering around further, making the search harder.
Many flight controllers, transmitters and receivers support failsafe feature. You should set up failsafe in at least one of them, and it doesn’t hurt to setup all of them to have extra layers of safety.
For Frsky Taranis users, you only need to set it up on the Taranis and you can just leave Betaflight and the RX at default. If you don’t have the Taranis, you might have to set it up in the flight controller or receiver.
Anyway, don’t just take my words for it, make sure you test failsafe thoroughly before taking off.
Further Reading: My Tools, Gears and Quads
Setup Failsafe on Taranis Radio TX
Go to the Setup Page on your Taranis, scroll down to “Internal RF Module”.
I recommend “No Pulses”. You also get the following options and here is what they do:
- Not Set, this is the default; When failsafe happens the quad will just fall to the ground (same as No Pulses as far as I can tell, but you sometimes get an annoying prompt at power up asking you to choose another option)
- Hold, it will hold the last stick/switches positions; Maybe useful for planes and wings, but not a good idea for multirotors especially racing or acro quads as you might be doing a flip when FS happens and the quad will keep rolling until it crashes into the ground, or it might simply fly away…
- Custom, it might be useful if you use angle mode (self level), you can set a lower throttle level and the quad will slowly descent. This might be useful in case you can regain control before it hits the ground; But you don’t always know what would be below the quad, landing a quad without control with spinning props can be dangerous
- No Pulses, when failsafe is triggered, the quad will just stop and drop to the ground, in my opinion the ideal failsafe option for mini quad
- Receiver, failsafe on the TX will depend on the FS setting on the RX
Setup Failsafe on the Receiver
Some receivers’ failsafe is setup during binding, they remember the stick (throttle) positions when they are bound together. Rebinding can reset failsafe.
For most Frsky receivers, there is a dedicated failsafe button (F/S or FS button), when pressed it remembers the stick position. To cut throttle at failsafe, make sure the throttle stick is at its lowest position when you press the button.
If failsafe is not set or enabled, the default behaviour is to hold last stick position when the signal is lost, which you should avoid.
Check out this list of Frsky receivers for mini quads.
It’s explained pretty well in the Frsky receiver manual how to do this step by step:
- Bind the receiver first and turn on both the transmitter and receiver;
- Move the controls to the desired failsafe position for all channels;
- Held down the F/S button of the receiver (for a second). The GREEN LED of the receiver will
flash twice, indicating the failsafe position has been set in the receiver.
- To disable/reset the failsafe function, re-bind the receiver.
Failsafe Configuration in Betaflight
If you have failsafe setup in your TX and/or RX, the defaults Failsafe configuration in Betaflight is just fine. All that matters is your motors stop spinning when you turn off the radio.
But if you can’t setup failsafe in neither your TX or RX, here is how I normally setup failsafe in Betaflight.
- Enable Expert mode, and a new tab “Failsafe” will appear
- Enable Failsafe Stage 2
- Check “Drop”, I don’t recommend using “Land” unless you are experienced enough and know what you are doing
- Only change the failsafe delay if you know what you are doing, otherwise leave it at default (e.g. you might want to increase delay if you fly over water and want to buy some time in case the radio link can recover by moving the TX around)
Note that after flight controller failsafe, you won’t be able to arm the quad unless you turn the FC off and on. However if it was just a RX failsafe you can just arm it again (because the FC didn’t detect it). This is important to understand because there are times you can get stuck in trees and need to arm the quad to get out of it :)
Once you have setup failsafe, make sure to test it and it works exactly the way you want it to.
REMOVE propellers and simulate all the possible radio failures you can think of. For example, arm the quad, give it 50% throttle, then turn your radio off to see what happens.