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100 lines
5.2 KiB
Markdown
100 lines
5.2 KiB
Markdown
# Flight Termination Configuration
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The _Flight termination_ [failsafe action](../config/safety.md#failsafe-actions) irreversibly turns off controllers and sets PWM values to their parameter configured failsafe values.
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::: info
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Flight termination differs from the [Kill action](../config/safety.md#kill-switch) in that it is permanent until after reboot.
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:::
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::: warning
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This is _not_ an independent _Flight Termination System_.
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If power is lost or if the autopilot crashes completely, the failsafe devices will not be triggered.
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:::
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## Overview
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### Termination Triggers
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Termination may be triggered by:
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- [Safety checks](../config/safety.md) for RC Loss, geofence violation, and so on (on any vehicle type or in any flight mode).
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- [Failure Detector](../config/safety.md#failure-detector) trigger
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- RC termination switch (mapped to an RC channel using [RC_MAP_TERM_SW](../advanced_config/parameter_reference.md#RC_MAP_TERM_SW)).
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- The MAVLink [MAV_CMD_DO_FLIGHTTERMINATION](https://mavlink.io/en/messages/common.html#MAV_CMD_DO_FLIGHTTERMINATION) MAVLink command from a GCS or companion computer (see [MAVLink Trigger](#mavlink-trigger) below).
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There is no way to recover from flight termination.
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After triggering you should unplug the battery as soon as possible.
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You will need to reboot/power cycle the vehicle before it can be used again.
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### Termination Actions
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When _Flight termination_ is activated, PX4 simultaneously turns off all controllers and sets all PWM outputs to their failsafe values.
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Depending on what devices are connected, the PWM failsafe outputs can be used to:
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- Deploy a [parachute](../peripherals/parachute.md).
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- Extend retractable landing gear.
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- Move a PWM-connected gimbal to a safe orientation (or retract it) in order to protect the camera.
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- Trigger an inflatable device like an airbag.
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- Trigger an alarm.
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:::tip
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PX4 does not know what safety devices are attached - it just applies a predefined set of PWM values to its outputs.
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:::
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:::tip
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Failsafe values are applied to all outputs on termination.
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There is no way to configure independent time-based (or other) triggering of the motors or specific safety devices.
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:::
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## Hardware Configuration
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Any _safety device(s)_ (e.g. a [parachute](../peripherals/parachute.md)) that can be triggered by changing a PWM value can be used, and may be connected to any free PWM port (both MAIN and AUX).
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::: info
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If you're using Pixhawk-series board you will have to separately power the servo rail (i.e. from a 5V BEC, which is often also available from your ESC).
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:::
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## Software Configuration
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The [Safety](../config/safety.md) topic explains how to set the _flight termination_ as the [failsafe action](../config/safety.md#failsafe-actions) to be performed for particular failsafe check.
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The [Failure Detector](../config/safety.md#failure-detector) can also (optionally) be configured to trigger flight termination if the vehicle flips (exceeds a certain attitude) or if failure is detected by an external automatic trigger system (ATS):
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- Enable the failure detector during flight by setting [CBRK_FLIGHTTERM=0](../advanced_config/parameter_reference.md#CBRK_FLIGHTTERM).
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- [Safety > Failure Detector > Attitude Trigger](../config/safety.md#attitude-trigger) explains how to configure the attitude limits that trigger _Flight termination_.
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::: info
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During _takeoff_ excessive attitutes will trigger _lockdown_ (kill motors, but not launch parachute) rather than flight termination.
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This is always enabled, irrespective of the value of `CBRK_FLIGHTTERM`.
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:::
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- [Safety > External Automatic Trigger System (ATS)](../config/safety.md#external-automatic-trigger-system-ats) explains how to configure an external trigger system.
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For each MAIN output to which a safety device is attached, where "n" is the PWM port number, set:
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- [PWM_MAIN_DISn](../advanced_config/parameter_reference.md#PWM_MAIN_DIS1) to the device's "OFF" PWM value.
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- [PWM_MAIN_FAILn](../advanced_config/parameter_reference.md#PWM_MAIN_FAIL1) to the device's "ON" PWM value.
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For each AUX output to which a safety device is attached, where "n" is the PWM port number, set:
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- [PWM_AUX_DIS1](../advanced_config/parameter_reference.md#PWM_AUX_DIS1) to the device's "OFF" PWM value.
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- [PWM_AUX_FAILn](../advanced_config/parameter_reference.md#PWM_AUX_FAIL1) to the device's "ON" PWM value.
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Finally, set the `PWM_AUX_FAILn` and `PWM_MAIN_FAILn` PWM values for any motors.
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::: info
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Flight termination via ATS only works if `drivers/pwm_input` is included in the firmware for your board.
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If not, you need to add it manually to your board configuration using [boardconfig](../hardware/porting_guide_config.md#px4-menuconfig-setup).
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:::
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## MAVLink Trigger
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The [MAV_CMD_DO_FLIGHTTERMINATION](https://mavlink.io/en/messages/common.html#MAV_CMD_DO_FLIGHTTERMINATION) command can be used to trigger Flight termination from a ground station or companion computer.
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This is sent, for example, when you call the [MAVSDK Action plugin](https://mavsdk.mavlink.io/main/en/cpp/api_reference/classmavsdk_1_1_action.html#classmavsdk_1_1_action_1a47536c4a4bc8367ccd30a92eb09781c5) `terminate()` or `terminate_async()` methods.
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## Logic Diagram
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The diagram below shows the logical flow around flight termination.
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