Using an autoland mission sequence with RTL_AUTOLAND is highly recommmended to prevent failsafes simply returning and loitering at home until battery or fuel runs out and the plane glides randomly down to earth on the loiter path. But that means you have to know and program a mission with the correct landing approach direction.
ArduPiot has just merged into “master”, or also know as “dev or 4.7dev”, code a new flight mode: AUTOLAND. If an automatic takeoff has occurred, either by a mission NAV_TAKEOFF, or Mode TAKEOFF, mode AUTOLAND will automatically land a fixed wing mode plane or a QuadPlane if capable of fixed wing landings) like a normal mission based autolanding.
It will setup a parameterized base leg and final approach waypoint and altitude, opposite the home location from the takeoff direction, and proceed to it and switch to an automatic landing at home. It can also be selected as a FS_LONG_ACTION for failsafes.
This is useful when programming a mission with a DO_LAND_START landing sequence is not convenient since it requires a GCS on a laptop or phone, such as traveling with impromptu stops to fly FPV or photograph. Simply use Mode TAKEOFF or a simple mission that was loaded before travel with a single NAV_TAKEOFF waypoint. It is also useful for fields which have varying wind directions, which would prevent using a single home-loaded autolanding mission or require using the MissionSelector LUA script to select from several missions with different approaches.
To use simply make an automatic takeoff and at any point later, switch into AUTOLAND. A final approach waypoint will be created behind the HOME landing target at :ref:AUTOLAND_WP_DIST<AUTOLAND_WP_DIST> (400m by default) at :ref:AUTOLAND_WP_ALT<AUTOLAND_WP_ALT> (55m by default)using the takeoff direction plus :ref:AUTOLAND_DIR_OFF<AUTOLAND_DIR_OFF> (“0” default) and land using all the parametrics of a normal autolanding. A base leg to the final approach waypoint is also created at the same altitude and 1/3 :ref:AUTOLAND_WP_DIST<AUTOLAND_WP_DIST> from the final approach waypoint as shown below:
LAND parameter defaults are usually acceptable for most planes in the 1-2m wingspan, <2kg class) and should yield a safe, if not optimally tuned, autolanding. LAND parameters can be optimized with test flights.
see file: https://ardupilot.org/plane/docs/mode_autoland.html
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