Hi all,

I had a crash recently that made no sense to me.  I posted the log to another thread and was given the (correct) answer that since my drone was within 65 feet of home when the battery hit 30%, the drone immediately initiated a RTH landing without prior warning.  In my case though, I was hovering just over some bushes so the drone descended into the bushes and crashed before I had a chance to break RTH.

SO, no need to post the flight log again, the drone operated "As Programmed".  But my question is WHY is it programmed to do this?

1) I thought it was only supposed to initiate a failsafe RTH (basically a controlled drop out of the sky) when it was at 10% battery.  

2) I'm also surprised that it didn't shoot up to its RTH altitude before landing... 30% is quite a bit of power still.

3) Why would it instantly try to land at 30% if it is so close to home?  It doesn't try to do this if it is farther than 65 feet from home.

4) Why is RTH so accurate if the drone is farther away, but if it is within 65 feet when it hits 30% power, it will just basically drops out of the sky and doesn't even try to get near its liftoff point?

Something about this makes no sense to me... and my drone crashed because of it.

Any pointers to help me better understand the logic of this would be good.  Thanks so much.

If you find an answer to this,  please post it here.  Because no one knows and DJI aint saying.

Mabou2,

Did you start your flight from a freshly charged battery?
Or was it partially charged ?
The Quad will land if it's within 20m of the home point. I agree that it not ideal, but I'm guessing that on a low satalite count there may be some distance error, so a 20m/65foot radius around the home and the quad lands..

A while ago I had the opposite problem. I landed the aircraft in my back yard, and without resetting the home point, I went indoors to drain/cycle the battery. At 10% the quad decided to RTH to the home point that was set to my back yard, and shot straight up and got stuck to the ceiling props turning max speed. I had to physically, pull it down, and switch off from the battery. Luckily there was no damage.. - I was expecting it to land instead of shooting up to the ceiling to get to RTH altitude.

You need to turn off the "Smart RTH" option.

As Second Officer Kneepuck says, DJI have never explained this phenomenum, but my guess is that it does this because of people flying indoors. It RTH kicks in while you are indoors, and therefore fairly close to where you started, there are no GPS satellites visible to go to the proper home point and the last thing you want the aircraft to do is fly up to the RTH hieght and crash into the ceiling.

If you initiate RTH within 20 meters of take off point it will land where it is, same with P3

This will happen on low battery as well, right? if within 20 meters, it just lands?
When you press RTH or lose signal, this will happen as well, right?

Phantomski Posted at 2016-5-24 15:23
This will happen on low battery as well, right? if within 20 meters, it just lands?
When you press R ...

Yes, correct.

People will be asking this FOREVER!!!!  And the manual really does not explain it well.... it is confusing..
DJI really needs to make it a feature for indoor flying, not the default for all of us, outdoor monkeys!When i throw some seed down, I do not want my bird landing 15 meters away! i want him to come right to the seed and peck it!

Sorry for your crash, Mabou2. I'd suggest you to download the flight data of that day and send it to support.us@dji.com for the data analysis.The flight data contains more details of the drone.

What's happening if Phantom 4 is flying over the pool near me (less than 20m) with Smart RTH option activated and the battery gets low?

Unless its a seagull over a pond then it'll be a very expensive electronic catastrophy.

Don't you all think that this will mean we have to have a clear and safe area within a radius of 20m from us pilots if RTH kicks in within the proximity??

Yep... this functionality is not correct.  There is no scenario I can imagine where it makes sense for the drone to just drop out of the sky with 30% power when within 65 feet of home with 13+ Satellites connected....  Yet if the drone was more than 65 feet away, I could have flown off another 20% of the battery without an issue.  So in essence, the drone will drop anywhere within a 130 foot circle if it hits 30% power (and is within 65 feet of home)?  This really doesn't make any sense at all.

DJI-Paladin Posted at 2016-5-24 02:42
Sorry for your crash, Mabou2. I'd suggest you to download the flight data of that day and send it to ...

HI DJI... I sent the crash log to the email address you provided.
Thanks

It is a PITA that the craft will initiate a landing out to that distance. DJI could mitigate the problem by simply giving a 10 second delay before initiation. Like "RETURN TO HOME ACTIVATED, 10....9...8....7.....etc". This would give you the opportunity to abort.

you know, DJI is meant as a filming platform.. even though people do fly it far and high, it really is meant to do majority of it's work rather near the takeoff point.... So that makes this 20m rule even more undesirable, unless it's something you can actually configure, in case you are indoors....

100% agree that the 20 meter radius landing should be optional and for most cases it should just come back. And I didn't know there was no heads up for the rth when within that 20 meters, that's ridiculously stupid. Why would I be given a chance to keep flying when I'm far away, but not get the chance when near by, especially the later scenario giving me way more time to eventually bring it home...
I'm always very cautious when flying nearby, as I don't want the drone landing somewhere it shouldn't, but now knowing it will not even give me a heads out, that's scary.. Usually where I fly (over water, launching off shore, mountain sides) I never want the drone landing anywhere other than where it took of, and with far away rth heads up, I've been able to cancel the rth before it starts.

1) I thought it was only supposed to initiate a failsafe RTH (basically a controlled drop out of the sky) when it was at 10% battery.  
There is 4 RTH procedures as stated in the manual:- User initiated (press button on the app or control)
- Emergency (lost of signal)
- Smart RTH (at X% battery, configured straight in the app also choosing wich procedure will do, hover or land)
- Critical Battery (at 10% battery, not configurable)

2) I'm also surprised that it didn't shoot up to its RTH altitude before landing... 30% is quite a bit of power still.

Within some radius (20mts from take off point) User RTH is supposed to land in the same spot. If Smart RTH kicked in, then it's supposed to do what you configured in the app. If Critical Battery kicked in, then it's supposed to land. Not sure about the behaviour in Emergency RTH when close to take off point.

3) Why would it instantly try to land at 30% if it is so close to home?  It doesn't try to do this if it is farther than 65 feet from home.

If kicked by Smart RTH, and you set to land, it will land or hover where it is, no matter the distance. Hover is specially usefull when going on a boat and you don't want to let it go back home and instead just hover to do a hand catch in the reimaining time. Land is usefull when doing great distance and can't go back to home point and instead you land where it is and drive to recover it (instead of just crashing midair)

4) Why is RTH so accurate if the drone is farther away, but if it is within 65 feet when it hits 30% power, it will just basically drops out of the sky and doesn't even try to get near its liftoff point?



Because flying close could mean that you're indoor, and going up 20mts to return home (lowest height that can be set) isn't a good idea when you have a roof (or tree top) just 5mts above. If you're so close to the drone you could perfectly cancel the RTH and land/return home manually.


Hope this clarifies a little bit. You could also use the user manual and configure your app correctly according to the guidelines/pre-flight checklist

LordNeo Posted at 2016-5-26 13:48
1) I thought it was only supposed to initiate a failsafe RTH (basically a controlled drop out of t ...

Hi Neo,
Your answers do clarify a few things.  The biggest clarification being that DJI needs to rethink the logic in this scenario.  If I am flying indoors, I should be able to tell the drone I am flying indoors to modify the behavior.  Not have some unilateral strategy imposed on all flyers whether indoors or out.

Bottom line, at 30% power, and within 65 feet of the home base, the drone should not go into any RTH mode.  Pretty simple.  

If the drone is going down and you don't want it to, press up. This will stop the descent.

Phantomski Posted at 2016-5-27 03:33
you know, DJI is meant as a filming platform.. even though people do fly it far and high, it really  ...

"even though people do fly it far and high, it really is meant to do majority of it's work rather near the takeoff point"

That makes no sense and it's never been suggested by DJI.
The P3/4 drones are made to be able to easily fly several miles from launch point.

Are you kidding?
P4 often lost the signal after 500 meters or sometimes less.

I think what Geebax said makes a lot of sense.

"...but my guess is that it does this because of people flying indoors. It RTH kicks in while you are indoors, and therefore fairly close to where you started, there are no GPS satellites visible to go to the proper home point and the last thing you want the aircraft to do is fly up to the RTH hieght and crash into the ceiling."

I tested my P4 indoor (without propellers) and to my surprised it declared that it was ready to fly after a long period of initiation. I guess it gave up locating the satelites and switched to ground sensor mode. I can imagine that if I were flying my P4 indoors (which I will never do), chances of my quad being more than 20 meters away are remote and if I accidentally pressed the RTH button, the craft would land where it is. This is good as I can't imagine it being clever enough to find it's way to back the take off spot with walls and corridors to negotiate. Maybe the P5 or P6 will be a super intellegent craft that can negotiate walls, doorways and corridors etc.

John Osmo Posted at 2016-5-27 08:14
I think what Geebax said makes a lot of sense.

"...but my guess is that it does this because of peo ...

Hi John... in thinking more about this whole discussion... I think RTH should not exist at all when flying indoors.  Indoors means flying in very very close quarters.  As you mentioned, RTH could mean flying through hallways or between racks (in a warehouse), around lighting fixtures, etc.  RTH should be disabled indoors all together.

markaguille Posted at 2016-5-26 16:35
If the drone is going down and you don't want it to, press up. This will stop the descent.

Hi Mark... I wish that were true.  I tried the sticks up during the two or three seconds I had before the auto-descent landed it in a bush.  No go.  I had no control over the bird (that I could tell).  It was doing an emergency landing, as if it were less than 10% battery.

Mabou2 Posted at 2016-5-27 18:54
Hi John... in thinking more about this whole discussion... I think RTH should not exist at all whe ...

There's certainly room for improvement here. When GPS is lost, RTH should not be activated. The craft should hover until GPS is available or runs of battery? Difficult one.

Mabou2 Posted at 2016-5-26 15:25
Hi Neo,
Your answers do clarify a few things.  The biggest clarification being that DJI needs to r ...

So it should just warn and fall down when battery is over? You can do that too, just set the smartrth at 10% so it will only have enough power to land.

Mabou2 Posted at 2016-5-27 13:56
Hi Mark... I wish that were true.  I tried the sticks up during the two or three seconds I had bef ...

SmartRTH (30% or set by user) can be cancelled pressing the RTH button, just as normal RTH.

LordNeo Posted at 2016-5-30 13:56
So it should just warn and fall down when battery is over? You can do that too, just set the smart ...

Hi Neo....  I'm not arguing with you... just saying that if the drone is within 65 feet of home and the battery hits 30% power, there is no reason whatsoever for the software to suddenly take control from me and drop the drone wherever it is.  In my case, the drone unexpectedly dropped into a bush and crashed.  I would not have even had time to hold the RTH button for the three seconds to stop it.
And the last thing in the world I would want my drone to do is auto drop at 30% power when shooting indoors in a tight space.  Makes NO SENSE at all.

John Osmo Posted at 2016-5-27 14:04
There's certainly room for improvement here. When GPS is lost, RTH should not be activated. The cr ...

Hi again John... agreed.  A little bit complicated.  But in some ways very simple.  RTH does not auto land the drone at 30% battery when the drone is more than 65 feet away.... why does it take control and auto land at 30% battery when within 65 feet?  Doesn't make a single bit of sense no matter how you look at it.  

If I am flying indoors (as others have suggested might be the reason for auto landing at 30% power), the LAST thing in the world I would want to have happen in such a confined space is that the drone takes over from me and drops onto whatever might be below it indoors.

Mabou2 Posted at 2016-5-31 15:23
Hi again John... agreed.  A little bit complicated.  But in some ways very simple.  RTH does not a ...

"...and drops onto whatever might be below it indoors."

LOL! Like your Grandma?

Interesting turn of events... DJI took a look at my flight log and think something is wrong with my drone.. they have asked me to send it to them.  UNSURE about this...  I can't afford to send it in just so they can do due diligence....  so I started another thread asking if anyone else has seen this problem.

Mabou2 Posted at 2016-5-31 10:17
Hi Neo....  I'm not arguing with you... just saying that if the drone is within 65 feet of home and ...

Sorry, wasn't trying to argue or anything. English isn't my native language so sometimes i sound harsh.

Back on topic, i was trying to tell that you can pre-configure that behaviour, either by changing the smart rth to "hover" or by lowering down the battery % so it will not trigger at all until the critical battery warning (10%). It can't go lower than 10% because of the voltage protection (so it doesn't just fall like a brick and can try to land as last resort). As i said before, you should add that (RTH behaviour configuration) to your pre-flight checklist, so you don't end up with the drone either landing in a dangerous area or crashing into a building (because of low RTH height).

LordNeo Posted at 2016-6-1 16:56
Sorry, wasn't trying to argue or anything. English isn't my native language so sometimes i sound h ...

Hey Neo... No problems buddy.. All good.  I appreciate your input.