Skeeter Honey Posted at 1-13 21:26
I tried to replicate this and it did not perform as yours did.

I was about 40 feet away from "home" and -5 feet in elevation.  I turned off the controller and it climbed to its 42M RTH altitude and started flying away.  In a panic, I turned on the controller as it started to leave and waited a few seconds (which seemed like an eternity) for it to re-bind.

Waow... sorry for this experience!
By flyaway, do you mean it was not returning to home??
The official explanation from DJI is :
"The aircraft switched into landing mode due to loss RC signal and close the home point"

What was the setting for the option "RTH at current altitude" ?For future experiences like this, I would suggest to disconnect only short enough to trigger the RTH and then reconnect again to be ready to cancel and better monitor what's going on

Eclair29 Posted at 1-13 22:54
Waow... sorry for this experience!
By flyaway, do you mean it was not returning to home??
The official explanation from DJI is :

It didn't go too far, and I turned the controller back on immediately once I saw it climbing well beyond what I expected (and up to my 42m RTH alt).

It flew on a vector that took it right above its RTH point and started to keep going it would appear.

So lesson learned there--ALWAYS keep your controller charged!

Eclair29 Posted at 1-13 22:54
Waow... sorry for this experience!
By flyaway, do you mean it was not returning to home??
The official explanation from DJI is :

It didn't go far and since I was under the awning of my porch I didn't see it at the time.  When the controller came back online it had flown 30 or so meters beyond the point above its RTH spot.  I have no idea how far it would have gone but I wasn't about to find out if I could help it.

I think it just stayed on the correct vector, and maybe it had stopped, but I just don't know.  I may try to replicate from another spot and with great visibility and clearance to get a read of the behavior.  I'm at least comfortable with the close proximity re-connect, so it might be worth a shot.

Skeeter Honey Posted at 1-14 22:12
It didn't go far and since I was under the awning of my porch I didn't see it at the time.  When the controller came back online it had flown 30 or so meters beyond the point above its RTH spot.  I have no idea how far it would have gone but I wasn't about to find out if I could help it.

I think it just stayed on the correct vector, and maybe it had stopped, but I just don't know.  I may try to replicate from another spot and with great visibility and clearance to get a read of the behavior.  I'm at least comfortable with the close proximity re-connect, so it might be worth a shot.

Hmm another strange and unexplained behavior...
For sure, every test like this should be in a clear empty field with unobstructed line of sight in case the drone wants to return to DJI rather than designated Home Point
Also, I strongly recommend to do a screen record which can be later analysed for a better understanding in addition to the log files.
As for RTH behaviors on connection lost, I believe there may be up to 24 cases to test with the assumption that a negative altitude could also play a role. See below.
I would hope for anyone to challenge / test / or confirm any of such expected behaviors. Once again, the option "RTH at current altitude is not explained in MA manual"


For my case, #17, DJI ruled that it landed due to close proximity to Home Point... "RTH at current altitude" was disabled.

Screen record would not have provided insights with controller off.

Skeeter Honey Posted at 1-15 04:59
Screen record would not have provided insights with controller off.

I speak in general. Beside, it needs only to be off the time to restart and reconnect. Whatever it records after may still be interesting.

Eclair29 Posted at 1-15 06:40
I speak in general. Beside, it needs only to be off the time to restart and reconnect. Whatever it records after may still be interesting.

It’s a lot to take in but it shows the importance of knowing the RTH procedures you need or have set before you fly, as an emergency RTH needs some attention.

Eclair29 Posted at 1-11 19:30
Thank you for your support guys, this just landed into my mailbox

Your request（#1645268）has been updated, please reply the email below:

I think you should get a new replacement or refurbished as new, good result hopefully you get it sorted soon.

Eclair29 Posted at 1-10 22:40
One thing is for sure, I will test all possible situations once I get my hands on a drone again!
Also it seems there are many differences between models. Mavic pro manual does not mention anything about a distance between HP and drone when RTH is triggered.
Older manuals mention different behaviors. This adds to the confusion.

That hits on two issues.
1) Manuals are unclear or vague leading to problems or crashes.
2) You can't get an answer out of DJI as to how things are supposed to work.

Eclair29 Posted at 1-14 22:23
Hmm another strange and unexplained behavior...
For sure, every test like this should be in a clear empty field with unobstructed line of sight in case the drone wants to return to DJI rather than designated Home Point
Also, I strongly recommend to do a screen record which can be later analysed for a better understanding in addition to the log files.

I would like to see an option to send all information that is recorded to drone's internal BlackBox sent to R.C. with info passed onto SmartDevice for failure analysis - for cases where drone is not recoverable.

If nothing else, in future versions of DJI drones and RCs, the RC have an optional microSD card slot for storing a real-time copy of drone's BlackBox information.

HedgeTrimmer Posted at 1-15 09:44
I would like to see an option to send all information that is recorded to drone's internal BlackBox sent to R.C. with info passed onto SmartDevice for failure analysis - for cases where drone is not recoverable.

If nothing else, in future versions of DJI drones and RCs, the RC have an optional microSD card slot for storing a real-time copy of drone's BlackBox information.

I couldn't agree more.

Having that kind of flight recording option would be good for DJI too.  They'd essentially (via the forum) crowdsource debugging.

That assumes, of course, that they'd act on it.

Too close to water?

Drameee Posted at 1-15 18:34
Too close to water?

For sure, next time I fly near water, the home point will have to be more than 20 meters away from the water to avoid a similar issue.
Without knowing, I did just that a few days earlier when flying near the beach, but that was because I did not want to take off from the sand beach. So I opted for a concrete slab which happened to be far enough from the water so I was safe. But then again, I had never experienced a disconnect at close range.

Eclair29 Posted at 1-15 18:40
For sure, next time I fly near water, the home point will have to be more than 20 meters away from the water to avoid a similar issue.
Without knowing, I did just that a few days earlier when flying near the beach, but that was because I did not want to take off from the sand beach. So I opted for a concrete slab which happened to be far enough from the water so I was safe. But then again, I had never experienced a disconnect at close range.

Your experience is really unfortunate and I'm sorry it happened to you, but thank you for sharing and expanding my understanding of my MA.  Your story probably helped to prevent several  future accidents.

if I launch mine from my back deck sometimes its like it takes off in beginner mode n fly about 8ft high the say max altitude reached then say home point updated and take off normal . I have tested this for possible glitches , it shows -altitude ft when I fly under the home point n RTH id doesn't hover  8ft  off the deck then fail it lands on the deck.  

Eclair29 Posted at 1-13 22:54
Waow... sorry for this experience!
By flyaway, do you mean it was not returning to home??
The official explanation from DJI is :

Hi Eclair,

Reading this answer makes me think uh ???

In the latest FM the option RTH at current altitide does not exist, see post #16 and 17 ?
#16 older manual, #17 last version MA manual.
At 10.1 meter away from HP it should do a normal RTH.

My MA is on the latest FM and does not have "the RTH at current altitude".i did a check just now again and its really not there!

So how can DJI refer to that ?? Can someone clarify this?  what do i miss for info ??
Screenshot is the setting for my SPARK, this is not seen in the MA menu.

cheers
JJB

Slight OT, but the Dynamic Home Point looks dangerous as well.
Update Home point to where the drone is currently, I'd expect in gesture mode to not be able to update the home point from the take off position, and in active track, it should in my opinion use the GPS location of the transmitter / controller / phone / tablet.

JJBspark Posted at 1-21 07:08
Hi Eclair,

Reading this answer makes me think uh ???

Hi!
This is strange. And this is why I want to make more tests as soon as my Mavic is replaced.
It is now in the hands of DJI at Hong Kong for its final assessment and hopefully I will get a replacement at no cost since they have ruled out pilot error.
Yet, before I sent it to DJI, I was able to reconnect to it and I browsed through the menus to make sure about the last settings I had (RTH at 40m, RTH when connexion lost, etc.)
I did find the option "RTH at current altitude" in the main controller parameters, it was off, and I had always dismissed that option because I did not want RTH at current altitude.
Yet, when I did select to activate it, I got a warning which said "when activated, unit will land immediately if RTH triggered less than 5m from Home Point" ok this is coherent with the manual.
Then it said "the unit will descend directly from its current position when RTH is activated within 20m from HP" which is not clear... If we want RTH at current altitude, why is it descending. And what about landing??
So I am puzzled by you saying that you don't see that option in your controller.
It seems DJI has some explaining to do here. There may be a conflict in the coding? At 10.1m, it should have climbed to +2.5m and RTH.
What about other users? Can you find the "RTH at current altitude" in the menus?
One thing for sure, it is not mentionned in the latest manual.
To be continued...

Eclair29 Posted at 1-21 18:16
Hi!
This is strange. And this is why I want to make more tests as soon as my Mavic is replaced.
It is now in the hands of DJI at Hong Kong for its final assessment and hopefully I will get a replacement at no cost since they have ruled out pilot error.

Hi,

Well, its not written in the last version of the manual, as you can see in #16 and 17 posts.at 10.1 meters away from HP it should do a RTH ! and not land immediately, so IMO DJI saying in post# 41 is wrong for the latest software.
Or is the iOS version different from the Android version ??

Guess it can depend on wich GO 4 app version is used, but .9 is not that old.It seems logical to me that the latest version of the manual is for the latest versions of the GO 4 app.

cheers
JJB

Skeeter Honey Posted at 1-13 21:26
I tried to replicate this and it did not perform as yours did.

I was about 40 feet away from "home" and -5 feet in elevation.  I turned off the controller and it climbed to its 42M RTH altitude and started flying away.  In a panic, I turned on the controller as it started to leave and waited a few seconds (which seemed like an eternity) for it to re-bind.

Did you figured out why your MA started to find fly away from home position? That's so scary, are you sure you recorded the home point with high GPS signal?

Eclair29 Posted at 1-11 19:30
Thank you for your support guys, this just landed into my mailbox

Your request（#1645268）has been updated, please reply the email below:

So glad to hear that, probably you will not receive the same unit but a refurbished one, this is the best scenario that you can claim. Hope your luck for the next fly, if I would be in you I would do several tests in a safe area, just to be sure that the disconnection was not due to your RC.

Fly safe,
cheers.

TwentyThrill Posted at 1-22 16:55
Did you figured out why your MA started to find fly away from home position? That's so scary, are you sure you recorded the home point with high GPS signal?

I always take off with precision take off and make sure I have 13+ satellites before I start moving.

That said, I'm questioning whether or not it was truly moving away or if that was due to the parallax of altitude from my vantage point.

BUT

In that proximity it should NOT have climbed to its 40M RTH altitude, so yeah.  It's weird.

So, no.  I haven't figured it out.  Nonetheless, I did have a flight recently where I lost connection (the drone was FAR away) and it did perform the failsafe RTH flawlessly. *shrug*

JJBspark Posted at 1-21 23:47
Hi,

Well, its not written in the last version of the manual, as you can see in #16 and 17 posts.at 10.1 meters away from HP it should do a RTH ! and not land immediately, so IMO DJI saying in post# 41 is wrong for the latest software.

I have an iOS device, DJI GO 4 and MA are updated to the latest firmware and I still have "RTH at current altitude" option.
I updated my DJI GO 4 about 2 weeks ago, and since this update magically the option "CSC Maneuver" disappeared! That's so dangerous! I didn't know that since DJI didn't inclued any changelog of the update. The same day I were flying indoor when ATTI mode has been triggered, so I did CSC Maneuver to shut down the motors and land in the carpet, but MA kept flying toward the wall and crashed, i broke 2 props and got some minor scratches.
Could you please check if you still have this option in the settings?


Thank you in advance,
Cheers.

TwentyThrill Posted at 1-22 20:56
I have an iOS device, DJI GO 4 and MA are updated to the latest firmware and I still have "RTH at current altitude" option.
I updated my DJI GO 4 about 2 weeks ago, and since this update magically the option "CSC Maneuver" disappeared! That's so dangerous! I didn't know that since DJI didn't inclued any changelog of the update. The same day I were flying indoor when ATTI mode has been triggered, so I did CSC Maneuver to shut down the motors and land in the carpet, but MA kept flying toward the wall and crashed, i broke 2 props and got some minor scratches.
Could you please check if you still have this option in the settings?

Hi,

CSC does not work for the Spark and MA !

see this > https://forum.dji.com/thread-172296-1-1.html

So RTH at current altiude does exist in iOS and not in Android GO 4 app !!  uh?  DJI  can you explain this?

cheers
JJB

JJBspark Posted at 1-22 23:45
Hi,

CSC does not work for the Spark and MA !

I am sure that 2 months ago (before the update) on my iOS DJI GO 4 app there was the option to enable CSC maneuver (default was off), I set it on because I tough that could be useful in an emergency situation, then they removed without sayng anything.
Aniway, now I just double checked with MA connected and yes, I still have RTH at Current Altitude, version of the app is 4.3.10

All right guys! So for you who have been following on my little misadventure, I want to bring this to a conclusion.
I have finally received a new unit almost 1 month after the crash. There was some delay with DJI finding the drone after they had signed for it, then there was Chinese New Year, and then some more delay with FedEx when it took them 1 week to travel from Hong Kong back to Cambodia (versus 2 days with DHL the other way)
Anyway, I'm back in the air and first thing I did was testing the configuration.
It turns out that my post #44 is pretty accurate.
In the range 5-20m, if you want the drone to come back to the Home point safe at +2.5m (as described in the manual) you need to activate the option "RTH at current altitude"
This is not described anywhere in the manual, but if you don't (like me) then on connection loss, the drone will behave the same as for 0-5m and it will land straight.

In that case, you better make sure there is no water within 20m of the Home Point!
Now, to be complete, I also tested what happens if the drone is beyond the 20m cercle. Well, even if you activate "RTH at current altitude" the drone will still climb to it safe altitude and RTH when you call for it or lose connection.

Now what remains a mystery is the complete loss of connection between RC and drone for the whole time it took it to land in the water (30 seconds based on the salvaged video)

So now you know, and me too. Be aware of that option.

By the way, at the sme time I have tested the situation when you set the drone to "hover" if connection is lost. After I selected that option (rather than RTH or land) I sent the drone about 30 meters away at a 10m altitude and I turned off the RC to simulate connection lost. The battery was already low but still in the yellow before the point of no return.
Can you guess what happened when it hit the low battery mark?
.

.

.

.

.

RTH at the safe altitude.

Eclair29 Posted at 2-13 07:42
All right guys! So for you who have been following on my little misadventure, I want to bring this to a conclusion.
I have finally received a new unit almost 1 month after the crash. There was some delay with DJI finding the drone after they had signed for it, then there was Chinese New Year, and then some more delay with FedEx when it took them 1 week to travel from Hong Kong back to Cambodia (versus 2 days with DHL the other way)
Anyway, I'm back in the air and first thing I did was testing the configuration.

Thank you very much for your testings, I'm very glad to know that you received a brand new drone, after reading your threat I started to keep "RTH at current altitude" always enabled. Also your last test was very useful! I was guessing that a land in position procedure would have been triggered, instead were triggered Low Battery RTH. It look like Low Battery RTH and Failsafe RTH have some special priority not only over the Smart RTH, but also on some other settings, very interesting, good job!

Eclair29 Posted at 1-11 19:30
Thank you for your support guys, this just landed into my mailbox

Your request（#1645268）has been updated, please reply the email below:

I've been reading about your experience and I has an almost identical thing happen when I took my Mavic Air to the Philippines.  I've been battling with DJI customer service for almost a month and they keep insisting that it's pilot error.  How did you get them to take care of this for you?  

Mine just froze and autolanded in the ocean 30m from where I was standing and the takeoff point on land.  Battery was at 27% and they told me it went into autoland because I had the throttle at full?

Sorry to dig up an old thread just ran across this searching for how safe it is to fly over water.
I am a rookie pilot myself, but I think I cracked the code as to what went wrong for this pilot.
I do fly over water a lot but I do not fly low altitude above water as I am also living in fear the drone will somehow sink (more on that in a moment) however competent with technology and networking technologies having done formal training in the fields.

After reading the first OP post and watching the last moments of the drone and roughly the first page of the thread, I have some thoughts.

1. Mavic Air and flying location
Wifi does not perform so great when it must travel through concrete or solid rock formation. The pilot was clearly flying quite close to large bodies of the earth rock without a direct line of sight to the controller IRC.
Exert from Google SearchThe Mavic Air does not have Ocusync, it uses WiFi instead,  this could have contributed to the loss of signal suddenly, <------

2. RTH was used
Shocking I know but from the footage, I would feel more comfortable if the drone was told to hover in place as being cavernous and over water, at the low height, I would not trust it to correctly detect the home point due to potential interferences from the rocks and or possible poor GPS signals when flying near the caverns. It may try to fly up and crash into the ceiling as those things do not have collision detection at the rear or the top or sides.

3. Pilot Error
DJI suggested a best practice to disable the Vision Positioning System when flying over water.

Direct Quote from DJI Website
"Disable Vision Positioning System (VPS)All DJI drones come equipped with VPS, a technology that maps the surface below to help position the drone. When flying over water, however, light reflecting off of the surface can cause issues with this technology. Because of this, it’s best to maintain a height of at least two meters above the water. If you have to fly below this height for a special shot, we recommend you turn off the VPS to avoid any unstable actions by the drone. Caution: When you disable the VPS of your aircraft and the distance between water surface and drone is smaller than 2 meters, you should fly the drone with a low speed in your FOV (field of view). Also, the height needs to be adjusted frequently since the aircraft could possibly drift downwards. Be aware that the minimum height has to be above 1 meter when flying over water."
Source:https://store.dji.com/guides/how-to-fly-safely-over-water/



So I think what may have happend here is a combination of loss of wifi signal or short intterupted burst in combination of drone being told to go home while being close proximity to the home point of which GPS accuracy would or may detect as close enough to begin to descend, ontop of a large body of flat water refracting the sensor reading of the VPS under the Mavic Air so it bugged out and procceded to land.

I could very well be wrong but that is just my opinion of the possible event leading to unforunate fate of this poor pilots cool drone.



P.S
I do fly over water though I prefer to fly at higher altittude so that in the event it does something strange I have ample time to manually take over, one other thing I am contemplating getting is water pontoone leg extentsion kit for times where I would be doing arial photography over bodies of water so in the event it tried to land on water it could safely do so provided the water is calm I could then simply just take off again and land it back ashore.



Edit
I see now the other user-posted the issue
"In the range 5-20m, if you want the drone to come back to the Home point safe at +2.5m (as described in the manual) you need to activate the option "RTH at current altitude"
Okay so basically that falls into my the close proximity thing I mentioned where GPS lock reckons it was close enough to descend near the home point. So future reference for me make sure my home point is a good 20m+ away from the body of water and manually set my failsafe and RTH height to something sane which I normally do.

Hi Eclair29, I know that this occurred some time ago, but I have a similar fault. I have been flying my DJI mavic 2 Pro on a minesite, and I would take off at the top of the pit and go down. It didn't  have a problem. At first and I was able to go -170meters down. I conducted several manevours going up, down travelled across the pit floor  and decided to go to the opposite side. I had to fly up to approximately-120 meters and across to  inspect another section of the pit where the floor was partially covered in water (300mm deep) in some areas. I found that when I was over or near water and I wanted to descend it decided that I was going to land. It was 50 meters from the ground, but it thought I was just off the ground. I was initially worried it was going to try to land and drop out of the sky into the water and I had to cancel the landing and take off. I  found out that it will still go down,but it doesn't like this and tries to fight over riding it. I found out that sun was

Hi Eclair29, I know that this occurred some time ago, but I have a similar fault. I have been flying my DJI mavic 2 Pro on a minesite, and I would take off at the top of the pit and go down. It didn't  have a problem. At first and I was able to go -170meters down. I conducted several manevours going up, down travelled across the pit floor  and decided to go to the opposite side. I had to fly up to approximately-120 meters and across to  inspect another section of the pit where the floor was partially covered in water (300mm deep) in some areas. I found that when I was over or near water and I wanted to descend it decided that I was going to land. It was 50 meters from the ground, but it thought I was just off the ground. I was initially worried it was going to try to land and drop out of the sky into the water and I had to cancel the landing and take off. I  found out that it will still go down,but it doesn't like this and tries to fight over riding it. I found out that sun was

djiuser_ajwOJj8N7iZx Posted at 5-6 16:20
Hi Eclair29, I know that this occurred some time ago, but I have a similar fault. I have been flying my DJI mavic 2 Pro on a minesite, and I would take off at the top of the pit and go down. It didn't  have a problem. At first and I was able to go -170meters down. I conducted several manevours going up, down travelled across the pit floor  and decided to go to the opposite side. I had to fly up to approximately-120 meters and across to  inspect another section of the pit where the floor was partially covered in water (300mm deep) in some areas. I found that when I was over or near water and I wanted to descend it decided that I was going to land. It was 50 meters from the ground, but it thought I was just off the ground. I was initially worried it was going to try to land and drop out of the sky into the water and I had to cancel the landing and take off. I  found out that it will still go down,but it doesn't like this and tries to fight over riding it. I found out that sun was

Reflecting off the water and confusing the sensors as the water was like a mirror. I think the fact it was also negative height, it may of confused its proximity to the ground. I found a few ways around this, but I can't trust descending over water on a sunny day.

@djiuser_ajwOJj8N7iZx
Thank you for this contribution.
My experience was a bit different. DJI never explained why but a short time after take off and some simple manoeuvers to position the drone I completely lost contact. The drone was less than 15 meters from me, at my level hovering over the water which was maybe 10 meters down.
The disconnection is the key to my issue.
Deep in the country side with no wifi, no radio signal, no buildings, not even a telephone signal. Just me, my friends, a bunch of trees and the waterfall.

Once disconnected, the drone went to its program to know what to do. Since it was less than 20 meters away from the takeoff point the program said: "land" when I was expected it would say "RTH"
This is configured in the options and i explained that in details above. If you don't tick that option, it will land instead of RTH. This is specific to the case of lost connection in the zone 5 to 20 meters from take off.
Further away and it will climb & RTH, closer than 5 meters it will land no matter what the option.
I witnessed the drone going down slowly to the surface, hovering a few seconds as it probably identified the water surface, and then it decided to continue the landing command (we can see the camera returning to a horizontal level, which is the sign for landing).

DJI replaced the Mavic Air (i was able to recover it from the river bed) and I sold it for a Mavic 2 zoom with the dedicated controller.
I never got such a scary experience again but I am now super careful of where I fly. The only time I experienced again a lost connection (twice on the same flight) the drone had triggered a safe RTH and I regained control after about 10 seconds (enough time to lose a few kg ). Drone was about 100m away in a clear line of sight. I was blaming some telephone relays but after a word on some forums I was advised to reload my firmware. Which I did. I flew the next week-end at the same location, distance, and height and nothing has happened since.

My advice, always play safe and always keep in mind that something could go wrong at anytime. If you respect the rules of line of sight and not flying over valuable property & people you will be safe if something does go wrong. Losing the drone is frustrating but it is just a $$ issue while getting someone injured is an entirely different outcome.

Be safe, fly safe and enjoy!