Quick Answer
Failsafe is the safety system that tells your FPV drone what to do when it loses signal from your radio. In Betaflight, you can configure it to drop, hover, or fly home using GPS rescue. Setting it up correctly prevents flyaways and keeps your drone recoverable.
What Is FPV Failsafe?
When the link between your radio transmitter and the drone's receiver breaks, the flight controller enters failsafe mode. Without a configured failsafe, your drone could fly away, crash into something, or keep running its motors at the last throttle position.
Failsafe can trigger for several reasons: flying behind a building or tree that blocks the signal, a battery voltage dip under load, or a loose antenna connection. Whatever the cause, the behaviour after signal loss is determined entirely by your failsafe configuration.
Modern ELRS receivers like the RadioMaster RP1 V2 maintain a robust 2.4 GHz link, but even the best links can drop. Failsafe is your last line of defence.
Failsafe Stages Explained
Most flight firmware uses a two-stage approach. First, the receiver detects signal loss and enters receiver failsafe, configured in your ELRS Lua script. You set the channel values the receiver outputs when the link drops: typically throttle to zero and all other channels to mid position.
Second, the flight controller detects these special values and switches to its programmed procedure. In Betaflight, you choose between three options: drop (motors off, drone falls), stage 1/2 (attempt recovery then drop), and GPS rescue (fly back to launch point).
GPS rescue is the preferred option for most pilots. It needs a GPS module like the Holybro M10 GPS Module, but gives you the best chance of recovering your drone intact.
Setting Up Failsafe in ELRS and Betaflight
Start by configuring receiver failsafe in the ELRS Lua script on your radio. Set the failsafe mode to "No Pulses" so the flight controller's own failsafe handling triggers immediately.
In Betaflight, go to the Failsafe tab. Enable the feature and set your preferred procedure. For GPS rescue, configure the rescue altitude (30 to 50 metres), minimum distance (at least 20 metres), and return-to-home angle.
Test on the bench before flying: arm the motors with props off, then turn off the radio. Confirm the failsafe triggers correctly via the Betaflight OSD.
GPS Rescue: How It Works
When GPS rescue triggers, the drone climbs to a safe altitude, rotates to face the launch point, flies back, and descends slowly. The whole process takes 30 to 90 seconds depending on distance.
GPS rescue relies on a working fix with at least 8 satellites. Indoor flights, heavy interference, or poor satellite coverage reduce its effectiveness. For long-range flights, combine it with a stable receiver like the Happymodel EP1 TCXO, which uses a temperature-compensated crystal oscillator for reliable frequency performance.
Failsafe Best Practices
Set up failsafe before your first flight with any new build. Check your receiver connections are secure and the antenna is properly positioned. Enable low battery warnings to trigger well before voltage sag could cause signal issues.
If you fly with telemetry enabled, your radio can warn you before link quality drops to failsafe levels. Our ELRS telemetry setup guide covers how to configure LQ warnings on your transmitter.
For more on adding GPS, see our GPS modules guide. For broader flight controller configuration, check the Betaflight setup guide.
FAQ
Q: What happens if failsafe triggers during a flip?
A: The drone stops the current manoeuvre and executes the configured failsafe procedure. If GPS rescue is enabled, it levels out and begins the return sequence.
Q: Does GPS rescue work without a compass?
A: Yes. Betaflight determines the home direction using GPS course over ground data. A compass can improve accuracy in some conditions but is not required.
Q: How far can I fly before failsafe triggers?
A: It depends on your receiver, antenna setup, and environment. ELRS on 2.4 GHz can maintain a link for several kilometres with a good antenna. Monitor your telemetry LQ percentage to track link health in real time.