How to Abort an Autolanding

A landing-abort mechanism is provided to allow you to abort a autolanding sequence in a safe, controlled, and expected way. Custom abort behaviour can be pre-programmed as part of the mission or you can use the default abort mechanism. To enable autolanding abort feature, set param LAND_ABORT_THR = 1.

There are three aspects of this feature:

  1. Triggering an abort

  2. The behavior during the abort

  3. The mission state after the abort completes

Step 1) Abort land triggers

The are three ways to trigger an auto-landing abort. All of them will only work while in AUTO mode and currently executing a NAV_LAND waypoint mission item:

  • Send the ``MAV_CMD_DO_GO_AROUND`` command using a GCS. Mission Planner has a button labeled “Abort Landing” on the FlightData Actions tab.

  • RC input Throttle > 90%. This will trigger an abort while staying in AUTO mode. The throttle only needs to be high briefly to trigger it. Don’t forget to lower it!

  • Mode change. For human piloted landing abort you can switch out of AUTO mode into, for example MANUAL/STABILIZE/FBWA, and navigate the aircraft safely however you’d like. Using this method will skip abort behavior step 2 because it is being done manually. When switching back to AUTO the mission will resume as described in step 3 below.

Step 2) Abort land flight behavior

The abort behaviour has a default configuration and does not require a pre-planned mission. The default abort behavior is to simulate an auto-takeoff: pitch up at least 10 degrees and set throttle to TKOFF_THR_MAX and hold the heading until it reaches a target altitude of 30m. It is possible to override the pitch and altitude to allow for a customized behavior.

  • Pitch minimum. If there was a NAV_TAKEOFF ever executed on this mission then the same minimum pitch (param1) will be re-used here.

  • Target altitude. If NAV_LAND param1 is >0 then it is used as a target altitude in meters. Else If a NAV_TAKEOFF was ever executed on this mission then the same altitude (param7) will be re-used here.

This step is skipped if the abort trigger is via mode change because it is assumed the pilot manually took over and flew the aircraft to a safe altitude at the pitch and throttle of their choosing.

Step 3) Mission state after an aborted landing completes

Once an abort land has completed, by either reaching the target altitude or switching back to AUTO, the mission index will have changed and you will no longer be executing a NAV_LAND command. The mission index will change to be one of these three options and checked for in this order:

  • If the NAV_LAND mission item is followed by mission item CONTINUE_AND_CHANGE_ALT with param1 = 0 or 1 then the mission index will increment once to that command and execute it like normal. This can be followed by further post-abort mission planning for any custom planned mission behavior.

  • Else If there is a DO_LAND_START in the mission then it jumps to that index.

  • Else the mission index decrements once to be the index before the NAV_LAND. This will ensure the same landing approach is repeated.