The X8’s default failsafe configuration is optimized for close-range manual flight in open areas with strong GPS signal. For flying in areas with poor GPS signal or for flying missions, we recommend changing the following failsafe settings for improved fault tolerance.
Some flying areas have poor GPS signal strength due to physical obstructions or lack of available satellites. (If you receive a pre-arm check failure for lack of GPS 3D lock on your ground station, it is likely that you are flying in an area with low GPS signal.) To fly without GPS lock, change the failsafe configuration to disable the horizontal geofence. This will remove the system requirement for GPS lock prior to takeoff and disable all GPS-dependent flight modes, allowing you to fly only using manual control (standard – altitude hold mode).
To Disable the Range Failsafe (Horizontal Geofence):
Connect the X8 to Mission Planner. Select Config/Tuning and Standard Params. This display shows the most frequently used ArduCopter parameters for easy access. Locate the Fence Type parameter; it will be set to Altitude and Circle by default. Switch to Altitude to disable the range failsafe, and select Write Params to save the changes to the X8.