Field test of advanced RTH

[k0200679]

I would like to share small video I have made of how advanced RTH feature works in real life.

Last weekend I was flying on my Mavic 3 and suddenly was caught by tall building standing right between me and my drone.
Signal went from max to zero in less than one second and advanced RTH was activated automatically.
RTH altitude was set to 120m, visual sensors On, normal visual conditions.
At time of advanced RTH was activated drone was exactly behind the building.

Mavic 3 advanced RTH

 

[GadgetGuy]

Had this been at night, it would have been fatal. For me, the only purpose of loss of signal set to RTH is to restore signal, so I can continue, and not to immediately return to home. The Standard RTH ascends first to a preset height above the launch point, set high enough to be above all obstructions enroute. Should you drop below or behind any such obstruction, ascending to the set RTH will always restore any blocked signal within seconds, and allow you regain full control immediately. Advanced RTH is the current default setting for loss of signal response. I recommend changing it back to Standard.

 

[k0200679]

Had this been at night, it would have been fatal. For me, the only purpose of loss of signal set to RTH is to restore signal, so I can continue, and not to immediately return to home. The Standard RTH ascends first to a preset height above the launch point, set high enough to be above all obstructions enroute. Should you drop below or behind any such obstruction, ascending to the set RTH will always restore any blocked signal within seconds, and allow you regain full control immediately. Advanced RTH is the current default setting for loss of signal response. I recommend changing it back to Standard.

Manual says that advanced RTH only work in normal visual conditions, otherwise advanced RTH works exactly as "normal" RTH. Had this been at night, it would not have been fatal because drone would simply ascend to 120m and return.
There is a drawback of normal RTH. If you fly for example to 5km above sea, winds at high RTH altitude might be a reason you will never see your drone again.

But I agree, there are significant risks with advanced RTH. Actually, that was the reason why I made this video and opened this thread, to help other members decide of is it worth the risks or not

 

[Gagey52]

Thanks for sharing.
Regards

 

[GadgetGuy]

Manual says that advanced RTH only work in normal visual conditions, otherwise advanced RTH works exactly as "normal" RTH. Had this been at night, it would not have been fatal because drone would simply ascend to 120m and return.
There is a drawback of normal RTH. If you fly for example to 5km above sea, winds at high RTH altitude might be a reason you will never see your drone again.

But I agree, there are significant risks with advanced RTH. Actually, that was the reason why I made this video and opened this thread, to help other members decide of its worth the risks or not

Thanks for clarifying the normal visual conditions condition. However, even during the day there can be wires that the drone cannot detect at lower altitudes below your set RTH elevation. Personally, I want nothing to do with Advanced RTH. As to your hypothetical, the winds at higher altitudes will not interfere with your control signal restoration, which is priority number one. Once signal is restored, either switch into Sport mode to get back in front of the obstruction, or fly downwind laterally until you can get past the obstruction that caused signal loss, and descend again to continue your mission, or return home under full manual control.

The one time where I can see that the Advanced RTH would be very useful is in a range test, where the loss of signal is due to being out of range, instead of due to any intervening obstruction. In that one case, Standard RTH, especially if set at 800 feet designed for mountain climbing, as it would first ascend to 800 feet, further weakening the lost signal along the hypotenuse of the triangle, wasting more battery, while still needing to descend that extra height on the return, making it back very unlikely, especially if you were at 50% battery when you lost signal. Advanced RTH would be perfect here! That's what it is really designed for: battery conservation during return to home along a straight line glide path at the lowest altitude safely possible.

 

[Yorkshire_Pud]

Regarding post no3 and a flight to a range of 5km and over the sea. That's a thought provoking post.
My first thought was why would you need a high RTH height when flying over the sea?
I could see it being necessary if you flew from a cliff top but you would almost certainly be back inside control range LONG before the height was needed to clear the cliff top and therefore be able to resume manual control.
It then occurred to me that the minimum M3 RTH height is likely to be 15m but that that is relative to the take off point and thus, when taking off from a cliff top, already high relative to the sea. I have flown from cliff tops over the sea and it makes me wonder if there shouldn't be a facility to set a negative RTH height.
I am also wondering if, over open sea, the wind's velocity gradient is as dramatic as it is over land.

With regards to post no5. At sea I have flown an drone out to loss of signal, by oversight I had a high RTH height set. The flight over the sea was at a height of under 100ft, the drone actually climbed back into stable connection during the RTH ascent.
I have also been stood beside a Mavic Mini pilot who, from the shore, flew their CE spec Mavic Mini over the sea to well beyond DJI's quoted control range. As they flew the outbound leg and the signal strength weakened they had raised the drone and regained signal strength. The pilot's bottle ran out before the signal failed.
I would venture that the hypotenuse consideration is not applicable in every instance.
Oh yyeess, it takes an awfully long time to get the drone down from excessive height, in the flight of mine that I mentioned it took most of the return flight to lose the excess height, and even longer when you are battery level watching lol.

BTW I now know that with some, if not all, of the DJI drones you can cancel an climb to excessive RTH height by moving the throttle once the drone is above a height of 20m, the drone then starts flying towards home.

 

[bkushner]

Another tip is check your RTH settings after firmware upgrade. Last few have reset Normal RTH to Advanced.

 

[mobilehomer]

Regarding post no3 and a flight to a range of 5km and over the sea. That's a thought provoking post.
My first thought was why would you need a high RTH height when flying over the sea?
I could see it being necessary if you flew from a cliff top but you would almost certainly be back inside control range LONG before the height was needed to clear the cliff top and therefore be able to resume manual control.
It then occurred to me that the minimum M3 RTH height is likely to be 15m but that that is relative to the take off point and thus, when taking off from a cliff top, already high relative to the sea. I have flown from cliff tops over the sea and it makes me wonder if there shouldn't be a facility to set a negative RTH height.
I am also wondering if, over open sea, the wind's velocity gradient is as dramatic as it is over land.

With regards to post no5. At sea I have flown an drone out to loss of signal, by oversight I had a high RTH height set. The flight over the sea was at a height of under 100ft, the drone actually climbed back into stable connection during the RTH ascent.
I have also been stood beside a Mavic Mini pilot who, from the shore, flew their CE spec Mavic Mini over the sea to well beyond DJI's quoted control range. As they flew the outbound leg and the signal strength weakened they had raised the drone and regained signal strength. The pilot's bottle ran out before the signal failed.
I would venture that the hypotenuse consideration is not applicable in every instance.
Oh yyeess, it takes an awfully long time to get the drone down from excessive height, in the flight of mine that I mentioned it took most of the return flight to lose the excess height, and even longer when you are battery level watching lol.

BTW I now know that with some, if not all, of the DJI drones you can cancel an climb to excessive RTH height by moving the throttle once the drone is above a height of 20m, the drone then starts flying towards home.

Just a reminder, home point altitude is from launch. If you fly/launch from a clifftop, your rth altitude only needs to be enough to get you over obstacles there. It probably only needs to be minimum, but could be several hundred feet above sea level.

 

[Yorkshire_Pud]

Just a reminder, home point altitude is from launch. If you fly/launch from a clifftop, your rth altitude only needs to be enough to get you over obstacles there. It probably only needs to be minimum, but could be several hundred feet above sea level.

Yep thanks.

 

[Drone on...]

Yep thanks.

This is exactly the info I was searching for! I want to be absolutely sure I understand correctly. An example: I am starting my flight on top of a high hill. I set my RTH altutude at 50 meters. Then I fly the drone over a deep valley (let's say the valley is 100 meters deep). If I activate rth at that time, the drone will ascend to 150 meters before heading home. Is this correct?

Also, I am new to forums. Hope I am posting in right place, and replying to right person.

 

[Yorkshire_Pud]

This is exactly the info I was searching for! I want to be absolutely sure I understand correctly. An example: I am starting my flight on top of a high hill. I set my RTH altutude at 50 meters. Then I fly the drone over a deep valley (let's say the valley is 100 meters deep). If I activate rth at that time, the drone will ascend to 150 meters before heading home. Is this correct?

Also, I am new to forums. Hope I am posting in right place, and replying to right person.

A better and less ambiguous wording of your question would be,

"I am starting my flight on top of a high hill. I set my RTH altutude at 50 meters. I fly the drone out over the valley and cause it to descend to 70m below the take off point. If, at that point, I then activate RTH will the drone climb 120m, to 50m above the take off point, and fly home?"

The answer would, yes.


Why the quibble?
Simply and literally "flying over the valley" could mean the drone was 100m+ above the valley floor, it could even already be above the RTH height, in which case it would simply return home at its current height and then descend when over the home point. That assumes it doesn't have one of the 'fancy' power saving RTH schemes.
If however it was below the RTH height it would climb to the RTH height, 50m above the take off point, and return home.
Alternatively if the valley was 100m deep and you sent the drone down into the valley, to 100m below the take off point, the drone is likely to have landed and stopped its motors. After that a relaunch from that point would set the home point to the new take off point and the RTH height to 50m above the valley floor

 

[Drone on...]

Fair enough! So suffice it to say, my drone would not crash into the side of the mountain I am standing on. That's nice.Thanks! I don't even have one yet, but I am seriously considering the DJI Mini 2 ($$$ is a big consideration), and I tend to research things to a rediculous level. ;-)

 

[Yorkshire_Pud]

Fair enough! So suffice it to say, my drone would not crash into the side of the mountain I am standing on. That's nice.Thanks! I don't even have one yet, but I am seriously considering the DJI Mini 2 ($$$ is a big consideration), and I tend to research things to a rediculous level. ;-)

That's a good thing to do with these drone's, they are complicated beasts.

Also I would suggest you read, several times, the manual for your drone of choice. There are words, phrases and phrasings in there that it is likely that you will miss the significance of, I know I did.
Question anything you even think you do not understand, within reason there are no stupid questions, we all have to start somewhere.

Pay particular attention to the RTH section and the differing behaviours related to its distance from the home point. Every drone I have has caught me out with some part of their RTH behaviour.
Just to 'demonstrate' and it is a scenario that has just come to mind. Say you take off from the top of a vertical cliff and fly out over the whatever, but by only a few metres, and then descend and, when below the take off point ( heights will show in the negative), initiate an RTH, there is a chance that the drone WOULD fly into the cliff face, or even start to land.
Why? Because, within a certain distance of the home point, some DJI drones DO NOT climb to RTH height before heading for home, if the RTH is initiated even closer still they just land where they are. I have NOT tested that at significant negative heights to see if the programmers foresaw a problem in that situation.

Download, instal and browse, as best you can, the relevant control app, probably the Fly App, BEFORE you get the drone, quite a few have been rather 'annoyed' to find out the app is incompatible with their phone.