Navigation Mode: Return to Home
Return to Home (RTH) has quite a few settings, so would benefit from a page of it's own. RTH will attempt to bring copter/plane to the home position, or safehome if used. The home position is defined as a point where aircraft was first armed, by default. RTH will control both position and altitude. You will have to manually control altitude if your aircraft does not have an altitude sensor (barometer).
With default settings RTH will land immediately if you are closer than 5 meters from launch position. If further away it will make sure to have at least 10 meters of altitude. A plane will fly home at cruise throttle, then loiter or land, depending on settings. A copter will start going home at 3m/s, and land. It will disarm itself if so configured, otherwise you will have to manually disarm once on the ground.
Return to Home is activated by the NAV RTH flight mode.
There are two altitudes that can be used with RTH: nav_rth_altitude and nav_rth_home_altitude.
nav_rth_altitude is used in conjunction with the RTH Altitude control modes to decide the altitude that the model returns home at. See below to see how the two are combined.
nav_rth_home_altitude sets the altitude that a plane will loiter at when it arrives at home. If above the nav_rth_altitude, the plane will start loitering, then loiter down to the home altitude. The default, 0, means that the feature is disabled. In which case the plane will loiter at the RTH altitude.
RTH sequence can control altitude in several different ways, controlled by nav_rth_alt_mode and nav_rth_altitud (the altitude in centimetres) parameters.
Default setting is NAV_RTH_AT_LEAST_ALT - climb to preconfigured altitude if below, stay at current altitude if above.
- nav_rth_alt_mode = CURRENT
- nav_rth_altitude is ignored
The Actual RTH Altitude is the altitude that the model is currently flying at.
- nav_rth_alt_mode = EXTRA
- nav_rth_altitude defines extra altitude margin
The Actual RTH Altitude is the altitude that the model is currently flying at, plus the nav_rth_altitude.
- nav_rth_alt_mode = FIXED
- nav_rth_altitude defines exact RTH altitude above launch point.
If the model is below nav_rth_altitude it will climb to desired altitude prior to flying back home. If the model is above the desired altitude, it will turn and fly home and descend on the way. That defines the Actual RTH Altitude.
- nav_rth_alt_mode = MAX
- nav_rth_altitude is ignored
The Actual RTH Altitude is the highest altitude during the flight.
- nav_rth_alt_mode = AT_LEAST
- nav_rth_altitude defines the minimum RTH altitude above launch point.
If the aircraft is below nav_rth_altitude it will climb to desired altitude prior to flying back home. If the model is above the desired altitude, it will turn and fly home at the current altitude. This defines the Actual RTH Altitude.
- nav_rth_alt_mode = AT_LEAST_LINEAR_DESCENT
- nav_rth_altitude defines minimum RTH altitude above launch point.
If the aircraft is below nav_rth_altitude it will climb to desired altitude prior to flying back home. If the model is above the desired altitude, it will turn and fly home, and descend on the way (on a linear straight line). This defines the Actual RTH Altitude. Aircraft will descend in a way that it'll reach the nav_rth_altitude altitude only when it reaches the home point. So aircraft can save energy by doing an easy descend on it's way back home.
The nav_rth_climb_first option sets how the model will initiate the RTH.
- If nav_rth_climb_first = OFF, the multirotor will turn to home, and immediately fly towards it, climbing on the way to the Actual RTH Altitude.
- If nav_rth_climb_first = ON, the multirotor hover and increase altitude. When it reaches the Actual RTH altitude, it will fly towards home.
If nav_rth_climb_first = OFF, the plane will turn towards home, and climb to the Actual RTH altitude on the homeward journey.
If nav_rth_climb_first = ON, the plane climb to the Actual RTH altitude in the direction it is currently flying. Once the Actual RTH Altitude is reached, it will turn and fly towards home.
If nav_rth_climb_first = ON_FW_SPIRAL, the plane climb in a loiter to the Actual RTH altitude. Once the Actual RTH Altitude is reached, it will turn and fly towards home.
