Failsafe Protection

Go to Autopilot Setup -> Safety Protection to configure the handling logic for common faults.

Low Battery Protection

Low voltage protection has three levels, corresponding to the warning, critical and emergency battery levels, as shown below:

No.	Level	Battery level	Description
1.	Warning	BAT_LOW_THR=15% (default 12%~40%)	Alerts the user
2.	Critical	BAT_CRIT_THR=7% (default 5%~10%)	Below this level the UAV should return at once
3.	Emergency	BAT_EMERGEN_THR=5% (default 3%~7%)	Below this level the UAV should land at once

System protection is configured using the COM_LOW_BAT_ACT parameter, as shown below:

No.	COM_LOW_BAT_ACT	Action	Remarks
1.	0	Warning	Not recommended
2.	1	Return
3.	2	Land in place
4.	3	Return when critical, land in place when emergency

RC Signal Loss Protection

RC signal loss protection only takes effect in manual modes such as Stabilized (Stab), Altitude (AltCtr) and Position (PosCtr); it does not apply to most automatic mission modes. It is mainly controlled by the following parameters:

• COM_RC_LOSS_T: sets the loss detection time, default 0.5 s;

• NAV_RCL_ACT: the action performed after loss is detected; commonly Hold mode, Land mode or Return Mode.

The protection logic for each mode is shown below:

No.	NAV_RCL_ACT	Manual mode	Automatic mode	Remarks
1.	Hold	Ground station alerts, UAV holds its current position	No response, continues the mission
2.	Return	Ground station alerts, UAV starts to return	No response, continues the mission
3.	Land	Ground station alerts, UAV starts to land	No response, continues the mission

Data Link Loss Protection

Data link loss protection only takes effect in automatic modes such as MISSION, LOITER and ORBIT. It is mainly set by the following two parameters:

• COM_DL_LOSS_T: sets the loss detection time, default 10 s.

• NAV_DLL_ACT: sets the protection action after loss, including Disabled, Hold mode, Land mode and Return Mode.

  The protection logic for each mode is shown below:

No.	NAV_DLL_ACT	Manual mode	Automatic mode	Remarks
1.	None	No response	No response
2.	Hold	No response	Ground station alerts, UAV holds position and altitude
3.	Return	No response	Ground station alerts, UAV returns
4.	Land	No response	Ground station alerts, UAV lands

GNSS Failure Protection

Once the satellite loss protection logic is triggered, the loiter altitude, throttle and roll angle can be configured.

The relevant parameters are shown below:

No.	Parameter	Description	Recommended value
1.	NAV_GPSF_ACT	0: loiter and heading flight 1: always heading flight 2: always loiter	Must be set to 2 when no heading is available after satellite loss
2.	NAV_GPSF_R	Fixed roll angle	15 deg
3.	NAV_GPSF_P	Fixed pitch angle	0 deg
4.	NAV_GPSF_TR	Fixed throttle (used when altitude and speed are invalid)	30%
5.	NAV_GPSF_ALT	Loiter altitude (above 10001 means use the current altitude)	10001
6.	NAV_GPSF_ARSPD	Cruise speed (set to 0 to use the configured cruise speed)	0 m/s

Engine Failure Protection

Once the engine failure protection logic is triggered, the pitch angle and return altitude can be configured.

The relevant parameters are shown below:

No.	Parameter	Description	Recommended value
1.	EF_APT_PITCH	Commanded pitch angle	-5 deg
2.	EF_ROLL_MAX	Roll angle limit	35 deg
3.	EF_MC_ACC_RAD	Multirotor lead distance	100 m
4.	EF_RTN_ALT	Return altitude	60 m
5.	EF_TRANS_ALT	Fixed-wing to multirotor transition altitude	50 m
6.	EF_LOITER_RAD	Loiter radius	150 m

Geofence Protection

The UAV supports two forms of geofence:

1. A cylindrical fence, configured using the maximum horizontal distance (GF_MAX_VER_DIST) and maximum vertical distance (GF_MAX_HOR_DIST) parameters;

2. A circular or polygonal area composed of multiple coordinate points, edited on the mission planning screen.

Both forms can be active at the same time; touching any fence triggers the protection logic. Use the GF_ACTION parameter to set the mode switched to when protection is triggered. The available options are None, Warning, Hold mode, Land mode and Return Mode, with parameter values 0, 1, 2, 3 and 5 respectively.

Once geofence protection is triggered, the protection logic is as follows:

No.	GF_ACTION	Manual mode	Automatic mode	Remarks
1.	None	No response	No response
2.	Warning	Ground station alerts	Ground station alerts
3.	Hold	Ground station alerts, UAV holds its current position	Ground station alerts, UAV holds its current position
4.	Return	Ground station alerts, UAV starts to return	Ground station alerts, UAV starts to return
5.	Land	Ground station alerts, UAV starts to land	Ground station alerts, UAV starts to land