Suggestion: being able to define an RTL "approach path". i.e. "Approach RTL"

I fly in the same location often - with much rising terrain - which requires me to set my RTL altitude very high - which also means arriving over the home point very high - and results in a LONG (time) descent over the landing point.

I’d like to be able to define “RTL” as more-or-less an AUTO mission - so I can define a particular/safe approach path - so the frame arrives over the landing point at a MUCH lower altitude.

Now I know I can set the receiver failsafe to switch flight modes to AUTO, but then I can’t even use AUTO for flying AUTO missions, plus receiver-failsafe switching to AUTO doesn’t cover non-transmitter RTL events.

Of course if I fly somewhere else, I’d need to remember that my “approach RTL” is set up for another location and make the necessary changes.

Anyway, I’d like to be able to define RTL for my particular “field”, so I always clear obstacles AND arrive over the landing point MUCH lower than traditional RTL.


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Hi @wsalopek,

Copter-4.2 includes support for DO_LAND_START mission items. If MRTL is used instead of RTL then it will follow the waypoints defined after the DO_LAND_START command. It looks like we haven’t added DO_LAND_START to MP’s list of available commands on the Plan screen so I’ve raised an MP issue to get them added.


@rmackay9 Do we have this explained in the wiki somewhere? I would like to test it out. Thanks!

In the meantime can it be configured by selecting “Unkown” and the command ID? 189? and a description of the fields?

@dkemxr Hi Dave, I’m understanding this feature will give us the ability to return to home following past mission waypoints.

RTL is a straight line, and makes it difficult to return to home when you have obstacles. Smart RTL keeps record of the flight path, but sometimes it has buffer issues and the pruning logic affect curves too much. So if this MRTL mode exists it will be best return to home ever for those of us who only fly auto missions.

If you have any instructions on how to use, I would love to test it out.

Kind regards.

I don’t but I can certainly see it’s usefulness. My question was abut whether we can use the “Unkown” command in MP and then the Command ID for it. But, we would need to know what the fields are to do this if it’s possible. I’m sure they will be added to MP Planner screen this would be a short term fix if it can work.


For clarification…does this mean MRTL is only available for use during AUTO missions?

And for clarification of my question, I’d like what is being called “MRTL” to be a selectable fail-safe option.

So in other words, I’d have the choice of selecting regular RTL, or MRTL, (or LAND or SMART RTL, etc) where if a failsafe occurs, or if I switch flight mode to RTL, the frame will fly an approach, defined by me (using waypoints/altitudes), but which have nothing to do with AUTO missions.

So that anytime I’m just flying around at my flying field, and if I failsafe (or switch to the RTL flight mode), the frame will fly a multi-waypoint approach back to the home point.


I’m not sure how MRTL is implemented, but I think a smart option might be to allow the user to select from the following entry behaviors:

  • Always start MRTL at WP1
  • Start MRTL at a user specified/updateable WP index
  • Calculate the nearest MRTL WP and begin the MRTL path from there

Would It work the same (or can it be used the same) as DO_LAND_START in plane?

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As @Allister says, it works very similar to how DO_LAND_START works in Plane. So it when the vehicle is switched to AUTO_RTL mode (sorry, I said “MRTL” but it’s actually “AUTO_RTL”) it will execute any commands after DO_LAND_START.

  • the DO_LAND_START command doesn’t have any arguments (or more accurately it does but AP doesn’t use them)
  • AUTO_RTL can be setup as the action for the RC failsafe (aka “radio failsafe”, aka “throttle failsafe”), GCS failsafe and battery failsafe (e.g. FS_THR_ENABLE = “6” is “Auto DO_LAND_START or RTL”)


Flashed AC 4.2.0 RC4 on a quadcopter.

Found “Auto_RTL” as a flight mode and RC/radio/THR failsafe.

“Do_Land_Start” is not in my MP|PLAN commands list though.

EDIT: shoulda read Randy’s reply. Eagerly awaiting this function.

The DO_LAND_START command has been added to beta mission planner so feel free to give it a try! MP can be updated by going to the Help screen and then push the “Check for BETA Updates” button.

Basically any mission commands that appear after a DO_LAND_START command will be executed if the vehicle is switched into Auto_RTL mode (a new mode). This new mode can be setup as any of the various failsafes (e.g. FS_THR_ENABLE = 6, BATT_FS_LOW_ACTION=6, etc).



Loaded AC4.2.0 RC4 and updated MP with the latest Beta.

DO_LAND_START works as advertised.

Is there a recommendation for building the operation at the beginning of a mission or the end, or does it make any difference?

RC/THR/Radio F/S set to AUTO-RTL.

Only other odd thing I saw was my OSD reported the flight mode as “F27”.


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Thanks for the report. I’ve created an issue to update the OSD’s list of flight modes.