Why did I trust RTH?

After a lovely flight, I was showing a friend the nifty Return to Home feature. I'd flown my P4 out of this location, and the location was stored as Home. But the aircraft was over a tree, and instead of flying horizontally to a spot above Home, it immediately descended straight down, right into a tree below it, crashed and fell about 35' to the ground. The damage is serious, I think.

I feel like this is a flaw in the software - shouldn't it have detected the tree branches directly below it?

Very frustrating.

Was the P4 within 20m or the home point? If the P4 is 20m or closer to the home point it will just descend. Why only DJI will know but its in the manual..

Well that must have been embarrassing.. lol. You gotta read the manual and definitely understand all of the RTH features. If you're within 20m of the home point, the aircraft will just land.

Probably you selected land and not rth, no?

There is also no down facing object avoidance on the P4

"shouldn't it have detected the tree branches directly below it?"

No!

It will avoid the ground during landing procedure????

How long can it fly so????

Sorry to hear of your loss, were you operating any of the sticks when you pressed RTH button on RC ?

Reason I ask is that left stick pushed down to the right & RTH button push at the same time will shut down the motors on a P4.

I am sorry for your crash, my recommendation to everyone even before they get the aircraft is to read the entire manual. This is a amazing aircraft with lots of features and you really need to fully understand ALL the features and limitations.
Whenever I purchase a new aircraft, I download and print the manual and sometimes read it several times so when the new aircraft arrives, I'm fairly ready to try out all the features of it.

Return To Home is more like Return To Control. Once you get it back in control range, you should take over and land it. Humans are still better at piloting drones than the drones are themselves (although not for too much longer hopefully). This is why I say again that automatic RTH should first return along its path about 100 meters before returning to home as an option to put the drone safely back under control as quickly as possible with the least amount of battery power.

DJI-Ken Posted at 2016-5-10 10:41
I am sorry for your crash, my recommendation to everyone even before they get the aircraft is to rea ...

This does beg the question:Why do the forwards cameras work for collision avoidance but the downward ones do not?

grangerfx@gmail Posted at 2016-5-11 02:19
This does beg the question:Why do the forwards cameras work for collision avoidance but the downwa ...

The bottom cameras are for keeping the aircraft locked into position.

grangerfx@gmail Posted at 2016-5-10 13:19
This does beg the question:Why do the forwards cameras work for collision avoidance but the downwa ...

If they did then you would never be able to land.   

You keep DJI in business.

There is a margin of error that can be up to 40 feet with the GPS. This is the norm for all GPS. I made a comment last week about this when using RTH. You have to consider things overhead for a wide swath around the Home Point Tree limbs, overhead wires to name a couple. When using RTH as soon as I have the Phantom within sight I bring it in for the landing myself. The other issue that you have to consider is your RTH height as well. And no on the branch detection below it or in front of it. They are to small. I have brought mine up to a 4" fence post and it will sound the warning and hover but it has to be right on but it does work. Sorry about your crash and hopefully it can be repaired inexpensively.

DJI-Ken Posted at 2016-5-10 12:55
The bottom cameras are for keeping the aircraft locked into position.

Locked horizontally but not vertically? Even the downward facing audio sensors don't seem to be used for collision avoidance.

EdM Posted at 2016-5-10 14:43
If they did then you would never be able to land.

You are probably correct about that. This occurred to me after I posted my question. Easy to solve though. Just disable the vertical collision avoidance when close to the home point or when the user tells the drone to land. Otherwise I pretty much never want my drone crashing into the ground.

grangerfx@gmail Posted at 2016-5-28 01:13
Locked horizontally but not vertically? Even the downward facing audio sensors don't seem to be us ...

The bottom cameras keep it locked horizontally and the sonar/barometer locks it vertically.
Only the front facing sensors are for obstacle avoidance.

DJI-Ken Posted at 2016-5-10 11:41
I am sorry for your crash, my recommendation to everyone even before they get the aircraft is to rea ...

You know Ken, and other DJI friends, not sure how to "force people" to do this.. but perhaps it needs to be the fist item on the quick start page that comes with the drone, on the box, and on any forum here, for beginners - bit letters...
People do not realize how important it is to REALLY read and UNDERSTAND the manual.. DJI is by far the most complex drone I ever flew, and due to it's features and abilities, it has a lot of functionality that is NOT intuitive, and people really need to understand - do not fly the damned thing, until you've red the manual and did research on at least 3 things that seemed confusing. If you read it and have no questions, you did not read it well! I dealt with RC for 10 years, flow various quads for 3 years, still took over a week to do my first flight on the DJI.. and guess what, I still find things I did not know, on the forums, daily! This is not a simple toy.. it's what I would call a professional and feature rich aircraft, and it should be treated as such.. u cannot guess things and assume things, and hope u will figure them out as you fly.....

I can see why people continue to crash this drone, even on this thread after several people have explained about reading manual, about downward sensors and how it all works, some people don't have the savvy to be able to work out advice given to them it all sounds very practical to me, tearing my hair out....

Like others have mentioned, RTH is very good from a long distance away but as soon as you can see the Copter then revert to self landing, safest way imo

Phantomski Posted at 2016-5-27 13:59
You know Ken, and other DJI friends, not sure how to "force people" to do this.. but perhaps it ne ...

well said and true,

I often say The Phantoms are Ready To Fly, its The OPERATOR not so much!

have had p1,p2,p3a,p3p,p3s
and Still check procedures, hints, tips before doing and testing things.
Easier to look up how to do it vs looking up how to FIX it!

Now, do not kid yourself, there will be crashes...
So reading manual is not "take care of it all" - but it's a starter for ideas on what to do and what not to do....
More DJI GO info in the manual would be cool too.
In no way am I pointing my finger at the thread owner here, but I do appreciate him sharing his experience - so we can all learn from it.
I have learned a lot from mishaps and experiences of others.. but I wish there were less accidents...!

DJI-Ken Posted at 2016-5-27 10:30
The bottom cameras keep it locked horizontally and the sonar/barometer locks it vertically.
Only t ...

Sounds like the latest firmware update may help with ground collision avoidance. Need to test that soonish.

grangerfx@gmail Posted at 2016-6-1 08:18
Sounds like the latest firmware update may help with ground collision avoidance. Need to test that ...

There is no ground collision avoidance. The down facing camera is for stability. Read the manual and check the advice you give is in fact good advice.

grangerfx@gmail Posted at 2016-6-1 08:18
Sounds like the latest firmware update may help with ground collision avoidance. Need to test that ...

As far as obstacle avoidance, the latest firmware improved propeller guard recognition.
The downward facing cameras are only for lateral positioning stability.

DJI-Ken Posted at 2016-6-1 07:31
As far as obstacle avoidance, the latest firmware improved propeller guard recognition.
The downwa ...

What about the downward facing acoustical sensors? Aren't those supposed to measure the distance to the ground?
And if you can do this for Active Track, why not for normal flight mode when the user tells the drone to fly forwards (not descend) when the ground is rising?

"Optimized altitude adjustment logic so that the aircraft automatically adjusts its altitude according to changes in the terrain when using ActiveTrack (available when the aircraft is flying within 10 meters of the ground)."

grangerfx@gmail Posted at 2016-6-8 01:44
What about the downward facing acoustical sensors? Aren't those supposed to measure the distance t ...

No, those are cameras that keep the aircraft in position horizontally and the sonar sensors keep the aircraft positioned vertically (measures the distance) while in VPS range.

DJI-Ken Posted at 2016-5-11 01:41
I am sorry for your crash, my recommendation to everyone even before they get the aircraft is to rea ...

What is the logic behind this feature when the bird is within a radius of 67 ft. approx., for the bird to just land rather than first climbing, then going to the recorded home point, then landing.  I have tried and tried to understand why anyone would want or need the bird to do this.  It just makes no sense, and it caused me to have my only accident, which by the way is going to cost me approx. $400 to repair.  And I did read the manual, but I totally forgot about this ridiculous setting.  Please explain.

I agree, same thing happened to me, I cannot for the life of me understand the logic behind this hard coded setting?  Makes no sense at all!  And it cost me about $400 to repair.

gcoan2000@yahoo Posted at 2016-7-26 01:35
What is the logic behind this feature when the bird is within a radius of 67 ft. approx., for the  ...

They designed it that way, maybe they think there's no reason to get into a RTH from that close.
I'm really not exactly sure why.

My only accident was also caused by the bird dropping straight down when RTH was initiated.  I understand it is in the manual, and as such, it was totally my fault.  But this still makes no sense to me that I could have the P4 out a thousand or more feet, hit RTH, and it will return, landing within a few feet of takeoff point.  But if is within 65 feet of home when RTH initiates, it will just drop out of the sky.  Really doesn't make any sense to me.

Phantomski Posted at 2016-5-28 01:59
You know Ken, and other DJI friends, not sure how to "force people" to do this.. but perhaps it ne ...

Well it is very simple.  Would you read the manual after buying the new Corvette. Of course not!!  You would get in the car and find the longest road to check out how fast it can really go.  It is all about human nature.
New toy we dont read the book first?  But in the case of drones we MUST READ first before we try to fly.  Just that simple

No idea why but I feel much safer just manually flying my P3P back. I haven't used RTH once yet.

gcoan2000@yahoo Posted at 2016-7-26 01:40
I agree, same thing happened to me, I cannot for the life of me understand the logic behind this har ...

I think DJI should get rid of this code, and just go to the designated altitude, return to the home point, then land.  And they should reimburse everyone that this has happened to, like myself.

I also thought about this as well, and my conclusion, (based upon pure speculation) was that DJI development/Q.A. felt that if you can see the P4 which is flying close to you, and you press RTH, you may have an RC stick issue and you can not land it manually. So it lands it using the RTH button.  You may also be flying under trees like I do when testing it, and you do not want to fly it upwards to reach the RTH altitude.


I have used RTH twice so far; one time just testing it and the other time when I lost complete communication.  In both cases though, I manually landed it.  No reason to rely on it's landing procedure, which sometimes may cause an issue as it descends rapidly and it starts wobbling due to standard laws of physics.

gcoan2000@yahoo Posted at 2016-7-26 03:35
What is the logic behind this feature when the bird is within a radius of 67 ft. approx., for the  ...

"I have tried and tried to understand why anyone would want or need the bird to do this. "

And I've tried and tried and can't understand why anyone wants to use RTH when their Phantom is less than 60 feet away.

tm0054 Posted at 2016-7-26 04:28
No idea why but I feel much safer just manually flying my P3P back. I haven't used RTH once yet.

You probably should.
The day you need to use RTH is a very bad day to start learning how it works and how to initiate it.

Agreed, certainly get used to RTH... u definitely want to know EXACTLY how that function works - read-up and practice. DO NOT use when within 20 meter radius from take off point.

DJI-Ken Posted at 2016-7-25 13:50
They designed it that way, maybe they think there's no reason to get into a RTH from that close.
I ...

I agree, but it should just tell you that it won't initiate it and to land manually,  rather than just immediately descending.  I just wanted to test it out, and didn't realize I was too close, and it cost me a lot of money!