FPV Drone Failsafe Settings Mastered — All Techniques for Safe Landing on Signal Loss

Failsafe is a feature designed to automatically return an FPV drone to a safe state in unexpected situations such as signal loss, low battery, or sensor errors. This post covers everything you need to know to avoid losing your drone, from the types of failsafes to Betaflight setup and real-world testing.

What is Failsafe?

Failsafe means 'safe failure'. It is a function designed to automatically return to a safe state when unexpected situations like signal loss, low battery, or sensor errors occur. Even if the signal is lost during flight, the drone automatically lands or returns, greatly reducing the chance of loss.

Main Types of Failsafe

1. RX Failsafe (Receiver Failsafe) This activates when the receiver does not receive a signal for a certain period. It is the most common and important failsafe. The signal loss detection time is usually set between 500-1000ms; too short and it reacts to noise, too long and the reaction is delayed.

2. Battery Voltage Failsafe The drone automatically lands when the battery voltage drops below a set value. For 4S batteries, it is typically set to activate below 3.0V/cell. This feature alone can prevent losses at sea or in forests.

3. GPS Failsafe For drones equipped with a GPS module, this initiates an automatic return when the GPS signal is lost. However, not all FPV drones have GPS.

Setting Up Failsafe in Betaflight

In the Failsafe tab of the Betaflight configurator, set the following:

Failsafe Delay: Determines how many milliseconds after signal loss detection the failsafe will activate. 100-500ms is usually recommended.

Failsafe Procedure: Choose what action the drone will take when failsafe activates. There are three main options: - Disable Gyro Protection: Turns off gyro stabilization and allows free fall (not recommended). - Land: Slowly reduces throttle and lands (most drones). - GPS Rescue: Returns using GPS (requires a GPS module).

Failsafe Throttle: The throttle value during landing. Usually set around 1000-1050. Too low results in free fall, too high results in ascent.

RX Failsafe Setup (Receiver Settings)

For wireless protocols like ExpressLRS or Crossfire, you must also set up failsafe at the receiver level.

For ExpressLRS: Select the Failsafe Mode in the receiver web UI. - No Pulses: Maintains a no-signal state (recommended). - Channel Failsafe: Fixes specific channels to set values.

For Crossfire: Use the Crossfire Agent software to set per-channel failsafe values. The throttle must be set to its minimum (1000), and roll/pitch to center (1500).

Battery Voltage Failsafe Setup

In the Power tab of Betaflight, set the following:

Battery Voltage: Accurately enter the number of cells (3S, 4S, 6S, etc.).

Min Cell Voltage: Set the minimum voltage per cell. 3.0V is generally recommended, and 3.2V for a more conservative approach.

Critical Cell Voltage: If the voltage drops below this value, the drone will land immediately. Usually set to 2.8V.

Practical Failsafe Testing

You should test on the ground first.

Step 1: While not flying, remove the receiver antenna to cut the signal. Verify that the failsafe activates.

Step 2: At a low altitude, turn off the transmitter. Verify that the drone slowly descends.

Step 3: After discharging the battery, take off in a low-voltage state to confirm failsafe activation.

Common Mistakes

Excessive Failsafe Throttle Setting: If set too high, the drone will ascend and continue to hover or fly in circles.

Signal Loss Detection Time Too Long: If too long, it activates too late in a real signal loss scenario, increasing the chance of loss.

Mismatch Between Receiver and FC Failsafe: Both levels must be configured to work correctly.

Incorrect Battery Capacity Input: Incorrect voltage calculation prevents failsafe from activating.

Conclusion

Failsafe is an insurance policy against the worst-case scenario of losing your drone. While it may seem complex to set up initially, once properly configured, it provides peace of mind for years. It is especially crucial for drones with important components or expensive batteries. Check your failsafe settings now.

Rafdy FPV