How to Set Up Failsafe in ArduPilot for Safe Drone Operation

To set up failsafe in ArduPilot, configure parameters like FS_THR_ENABLE and FS_BATT_ENABLE to activate failsafe on throttle loss or low battery. Use the Mission Planner software to set these parameters and define the failsafe actions such as RTL (Return to Launch) or Land.

Syntax

Failsafe in ArduPilot is configured by setting specific parameters that control when and how the drone reacts to failures like signal loss or low battery.

• FS_THR_ENABLE: Enables throttle failsafe (1 = enabled, 0 = disabled).
• FS_THR_VALUE: Throttle PWM value below which failsafe triggers.
• FS_BATT_ENABLE: Enables battery failsafe (1 = enabled, 0 = disabled).
• FS_BATT_VOLTAGE: Voltage threshold to trigger battery failsafe.
• FS_ACTION: Defines the action on failsafe (e.g., 1 = RTL, 2 = Land, 3 = Terminate).

These parameters are set using Mission Planner or directly via parameter files.

shell

param set FS_THR_ENABLE 1
param set FS_THR_VALUE 975
param set FS_BATT_ENABLE 1
param set FS_BATT_VOLTAGE 10.5
param set FS_ACTION 1

Output

Parameters updated successfully

Example

This example shows how to enable throttle and battery failsafe using Mission Planner's command line interface. It sets the drone to return home (RTL) when failsafe triggers.

shell

param set FS_THR_ENABLE 1
param set FS_THR_VALUE 975
param set FS_BATT_ENABLE 1
param set FS_BATT_VOLTAGE 10.5
param set FS_ACTION 1

Output

Parameters updated successfully

Common Pitfalls

Common mistakes when setting up failsafe include:

• Not enabling the failsafe parameters (FS_THR_ENABLE or FS_BATT_ENABLE set to 0).
• Setting incorrect threshold values that never trigger failsafe or trigger it too early.
• Forgetting to set FS_ACTION, so the drone does not know what to do on failsafe.
• Not testing failsafe in a safe environment before flight.

Always verify parameters after setting and test failsafe behavior carefully.

shell

param set FS_THR_ENABLE 0  # Wrong: disables throttle failsafe
param set FS_ACTION 0      # Wrong: no failsafe action

# Correct setup
param set FS_THR_ENABLE 1
param set FS_ACTION 1

Output

Parameters updated successfully

Quick Reference

Parameter	Description	Typical Value	Notes
FS_THR_ENABLE	Enable throttle failsafe	1	Set to 1 to enable
FS_THR_VALUE	Throttle PWM threshold	975	Below this triggers failsafe
FS_BATT_ENABLE	Enable battery failsafe	1	Set to 1 to enable
FS_BATT_VOLTAGE	Battery voltage threshold (V)	10.5	Voltage to trigger failsafe
FS_ACTION	Failsafe action	1	1=RTL, 2=Land, 3=Terminate

Key Takeaways

Enable failsafe parameters like FS_THR_ENABLE and FS_BATT_ENABLE to activate failsafe.

Set appropriate threshold values to trigger failsafe at the right time.

Define FS_ACTION to specify what the drone should do on failsafe (e.g., RTL or Land).

Use Mission Planner or similar tools to set and verify failsafe parameters.

Always test failsafe settings safely before flying your drone.