Hi everyone, I'm new here and I hope you can help me.

Last week I was flying my spark. Probably a minute before take off, and 15 m away and 51 m height, the drone suddenly disconnected. At first I thought it was just the normal thing (despite it was pretty close and with the RC). I was flying over a river, and I started noticing that the drone was slowly losing altitude. I was trying to gain connection again but it wasn't working, and of course pressed the RTH button several times with no effects. I opened the app again and nothing, the drone simply lost connection. It stopped descending 50 cm above the water, so I thought I may have aprox. 13 minutes to figure it out since the battery was fully charged. But a few seconds later it kept descending until it finally sunk in the river.

There was evidently no pilot error, and as I said the return to home didn't worked when drone disconnected. I sent a message to DJI and they responded:

Dear Customer,




Thanks for your patience.


For your case CAS-2002522-B5L5X8, we have finished the data analysis, and the result is as follows:


1. The aircraft worked in GPS mode in the flight;
2. The aircraft flew back and ascended after the pilot pulled back the pitch stick and pushed up the throttle stick, then the flight record ended at t=00:38, h=51 m, d=15 m.


The record ended without any sign of abnormality, so we could not verify what happened afterward.


We truly appreciate your support for DJI. If you could not recover the product and would like to purchase a new one, we can offer you a 30% off coupon for a new Spark(Alpine White).



That's it. That's their response. Of course they can't know what happened next because the drone lost connection. From the flight record you can see that it lost connection when flying over water. Of course I couldn't get it back because I'm talking of a big European river, impossible to find it (and probably illegal to try to dive in).


I don't think that a 30% discount is fair, I actually think it is abusive. "We sell you a horrible drone and if it fails you can buy next one 30% off. "


What should I do? Thanks everyone!

Upload your flight log record to this site:  http://www.phantomhelp.com/LogViewer/

You will need to post the resulting URL here. There are people here who can tell you a lot from your log results.

N2QLT Posted at 2018-7-14 03:14
You will need to post the resulting URL here. There are people here who can tell you a lot from your log results.

Hi N2QLT, thanks for your reply.

Here is the URL, hope it helps:

http://www.phantomhelp.com/LogViewer/2812Z29OXKVSXRTFJHI6/

Hi Shalabid,

Sorry for your loss.

No errors in your flightlog. I would go back to DJI and ask for a better explanation.
When you had a disconnect it should RTH, well it did not! HP was recorderd and disconnect time 4 secs, after 3 it should RTH (if using RC)

Your RTH height is 30 meter, means that it will fly home at current height at disconnect.
So why it slowly went down and went for a swim....DJI should explain.

cheers
JJB

JJBspark Posted at 2018-7-14 05:04
Hi Shalabid,

Sorry for your loss.

JJB,

Spark went down for a swim because "RTH at current altitude" was not enabled in DJI GO.
When signal disconnected, Spark started correct RTH sequence which in this case, since it was closer than 20 meters from home point, was to land. This was correct behaviour.

At 30 cm above water it stopped waiting for instructions from pilot to land. Its VPS sensors have been fooled by flowing water and it lowered its altitude sinking.

Everything is correct outside of the fact that it lost signal at such short distance.

Either strong WiFi interference (cell towers nearby - pilot is in the middle of the city) or DJI h/w failure.
I bet on WiFi interference from some nearby sources. I have seen case where, at that altitude, AC is in the direct line of signal from parabolic antennas and the signal is disrupted. Some LTE bands are very close to 2.4GHz or 5.8GHz frequencies (e.g. Band 40 for 2.4 GHz).

However, in this case, I would come back to DJI asking for much better explanation of why the signal broke at such short distance. This could be their h/w failure (I doubt that, but possible - DJI needs to check).

Mirek

Mirek6 Posted at 2018-7-14 06:02
JJB,

Spark went down for a swim because "RTH at current altitude" was not enabled in DJI GO.

Hi mirek,

make sense, wich parameter is the CSV file for that?

cheers
JJB

JJBspark Posted at 2018-7-14 06:10
Hi mirek,

make sense, wich parameter is the CSV file for that?

JJB,

What parameter are you asking about in csv?
I made my conclusions purely on very clean csv record, the fact that HP and landing spot were less than 20 m away (from GPS co-ordinates in csv) and the fact that logs end as cut by a razor blade.

LTE tower disrupting AC at 50 metres was the case of 62+ in South Africa last month. I referred to this case in yesterday's discussion on AC sinking in Maine.

I do not know which csv parameters show quality of WiFi signal. There must be some in the extended csv file since Airdata is able to analyze and measure that. Perhaps you know?

Thoughts?

Mirek

Mirek6 Posted at 2018-7-14 06:23
JJB,

What parameter are you asking about in csv?

I meant the "RTH at current altitude" was not enabled in DJI GO.
Cannot find it yet wich True/False value is for this option.

JJBspark Posted at 2018-7-14 06:26
I meant the "RTH at current altitude" was not enabled in DJI GO.
Cannot find it yet wich True/Value is for this option.

Ahhh - OK, I should have said: "Spark went down for a swim most likely because "RTH at current altitude" was not enabled in DJI GO." My apologies for confusion.

No, I don't know if there is a paramater for it in csv file (good chances are that there is).

I made an educated assumption based on several observations (not from csv file):

• Spark's behaviour after disconnect (based on pilot's description)
• The fact that "RTH at current altitude" is disabled by default in DJI GO App and most pilots don't ever bother to enable it.
  

Spark's behaviour in this case was 100% consistent with failsafe RTH (confirmed by signal loss followed by Spark's landing) with "RTH at current altitude" disabled and with HP and Spark position between 3 and 20 metres (confirmed by GPS).

Mirek

Question:
I see "GPS-Atti" all over the log picture from JJB
If disconnected AND in Atti, shouldn't it land, anyway?

S-e-ven Posted at 2018-7-14 06:43
Question:
I see "GPS-Atti" all over the log picture from JJB
If disconnected AND in Atti, shouldn't it land, anyway?

S-e-ven,

GPS_ATTI in detailed csv logs which JJB is using (not the ones available from phantom site but rather ones after conversion using TXTlogToCSVTool) is equivalent to P-GPS mode. Spark was entire time in GPS. You can also see it by the color of the line drawn by phantom application - green.

Mirek

Hi. I am sorry to know what happened to your DJI Spark. I will be forwarding this thread to the proper DJI department for further help on this issue that we are facing today. Thank you.

Hi everyone,

Thanks for the time you've taken to respond.

I have two questions:
1. Is it normal that being so near the home point the AC just descends instead of moving to the exact point? (i mention this because of Mirek's response).

2. In your experience, what does DJI reply in this kind of situations? What should I expect?

Thanks!

Shalabid Posted at 2018-7-14 11:05
Hi everyone,

Thanks for the time you've taken to respond.

Hi,

Thinking of what happend here ; my best to do is to takeoff at a distance > 20 meter of the waterline! (if possible ofcourse)
So in case the connection is lost flying over water it will RTH with dry feet.
( when RTH at current alt is disabled )

Is my logic correct?

cheers
JJB

By the way, there is an accessory I saw that allows Spark to land in water. They are flotation balls that attach to the feet. I am vacationing near water next month and plan to get them. Not sure if it would have helped you, since I don't know if you would have access to the river it landed in. But it may be helpful if you get another Spark.

Shalabid Posted at 2018-7-14 11:05
Hi everyone,

Thanks for the time you've taken to respond.

Shalabid,

Your question 1: What you saw is absolutely correct behaviour of Spark. JJB attached appropriate DJI Spark manual pages (above) which explain that. I tend to keep "RTH at current altitude" on - it is safer (in my opinion). Keeping default setting doomed your flight.

Your question 2: This is anybody's guess. DJI is, in my opinion, very good at servicing or replacing Spark if they determine that fault was on their side. In this case the only question is - "why did signal broke?" Was it h/w failure or strong interference? If it was interference, should pilot have know about it (in other words - did pilot fly in an area which was obvious that there might me interference)?

If I were DJI I would have scrutinized your surroundings for cell towers. If there is one within 200 metres and it is visible, you may get you 30% rebate and asked to be happy about it. Also, I would have checked my firmware - why DJI GO did not warn you about bad signal? Was it bad from the very beginning? Was it visible to the pilot. If it was bad and was not visible to the pilot - why?

This case is not black and white and only DJI can determine if the fault lies on their side and if they should accept full responsibility. You did correct thing to question their response and asking forum for help. They will read our analysis and they will go back and re-discuss it. DJI is not here to cheat or take advantage of their customers - they are here to help (although sometimes this help is not sufficient :-)) and keep us reasonably happy.

Good luck and please let us know what was the conclusion of your re-opened case with DJI.

MIrek  

N2QLT Posted at 2018-7-14 11:58
By the way, there is an accessory I saw that allows Spark to land in water. They are flotation balls that attach to the feet. I am vacationing near water next month and plan to get them. Not sure if it would have helped you, since I don't know if you would have access to the river it landed in. But it may be helpful if you get another Spark.

N2QLT,

Nothing wrong with the Big Balls for Spark :-) Highly recommended for beginners and in certain situations (see below). It is just that it is added weight and air drag so your flights will be shorter (battery will deplete few minutes earlier - which may be important if your average flight time is short anyways).

I would recommend to use them when you are in dynamic situation on water. For example, you are canoeing on the lake and Spark is tracking you while you are canoeing. Directing Spark to land in your canoe while you are alone and wind and waves push your canoe around while you are steering Spark may be tricky. Big Balls are a very useful insurance policy in such case.

If you fly over water, I believe it is much more important to stay at altitude at least 2 metres up (to be perfectly safe you need 8 metres up or more so VPS switches off) and watch Spark all the time. VPS can get confused by water reflections very easily and Spark may suddenly start loosing altitude. You need to be ready to raise it up any moment.

Let's not get paranoid too much about it though - I trust my Spark - it is a marvel of technology, but I also keep its calibration in tip top shape and I know what dangers to look for and avoid.

Many thanks for actively joining this forum - happy to see you in these discussions.

Mirek

Mirek6 Posted at 2018-7-14 13:16
N2QLT,

Nothing wrong with the Big Balls for Spark :-) Highly recommended for beginners and in certain situations (see below). It is just that it is added weight and air drag so your flights will be shorter (battery will deplete few minutes earlier - which may be important if your average flight time is short anyways).

Thanks, Mirek. Yes, it seems that a lot of Spark users (like myself) are beginners. I do understand that any added weight would cut the already short flight time. I considered adding a bluetooth finder despite this, but found that their range is quite limited. I am still paranoid about a flyaway, hence the idea of Big Balls when flying near water. I was unaware that Spark could become confused over water. I have flown mine less than 0.5 meter over the swimming pool (oops). That could have turned into another awful lesson. I don't recall seeing a way to turn off the VPS on Spark. Anyway, this forum is informative and enjoyable. I don't believe that DJI could sell the products at the price they do if they had to provide extensive tech support. So it looks as if they provide the forum so that the community can work things out together.

N2QLT Posted at 2018-7-15 05:21
Thanks, Mirek. Yes, it seems that a lot of Spark users (like myself) are beginners. I do understand that any added weight would cut the already short flight time. I considered adding a bluetooth finder despite this, but found that their range is quite limited. I am still paranoid about a flyaway, hence the idea of Big Balls when flying near water. I was unaware that Spark could become confused over water. I have flown mine less than 0.5 meter over the swimming pool (oops). That could have turned into another awful lesson. I don't recall seeing a way to turn off the VPS on Spark. Anyway, this forum is informative and enjoyable. I don't believe that DJI could sell the products at the price they do if they had to provide extensive tech support. So it looks as if they provide the forum so that the community can work things out together.

Yes - as you noted, no way to turn VPS off in Spark.

And yes - I do fly a meter or so over water with Spark but I do watch it like a hawk - it happened to me several times that it suddenly dipped down. Fortunately, my reflexes are still sharp and I do expect that behaviour :-).

The most dangerous situations are when you see Spark's own wind (created by Spark's propellers) is starting disturbing water below. This is a sign that it is dangerously low and VPS may get confused any second. Either get it up or have your thumb on throttle stick ready to intervene in a split second.

Do not take my 2 metres above water as gospel. I said that since, in my experience, I never had trouble flying 2 or more meters above water but I did have trouble (sometimes) flying lower. I have also seen, that in some extreme situations, Spark can dip down even if it is higher than 2 metres above water, as long as its VPS system is still engaged - hence my (very conservative) advice for beginners - fly above VPS sensor range - 8 metres or up.

Mirek

Hi guys,

I received a new answer from DJI:
Dear Customer,


Thanks for getting back to us.

We really want to figure out why the aircraft didn’t return to home. Because if it’s pilot error, we want to give advice to the customers and also if it’s not, we want to improve our products.

However for this case, the cause was not recorded.

The aircraft showed no signs of a manufacturing defect or malfunction. Since we did not find any conclusive information to explain the detail of the incident, a 30% discount was offered.

We are sorry about the frustrating experience you have had. We assure you we do not deliver this result lightly. We carefully examined your case, and are confident the data assessment is accurate.

We have offered you the 30% discount, as a sincere gesture of our apology. The offer will be valid for a month for you. You are not obligated to re-order the lost product, but if you choose to do so, we are here to help.

Again, we apologize for your lost.

--------

I don't know. I still think their answer is weak. They can't assure it was h/w or s/w error but can't either assure it was pilot's error. I feel like that 30% discount it's just their easy way for not responding any further.

What do you think?

DJI answer is weak. You lost your drone not because of pilot error but because you lost connection between RC and Spark.
DJI did not even bother to check why you lost connection. Was it strong interference? They should be able to see it in the logs (unless this data went down with Spark's blackbox).
I do not know where to check for signal interference in Spark's logs but I do know it is possible since you can get pretty good diagnosis of it through airdata.com. This means that 3-rd party somehow can get to this - so should DJI be able to.
If there was interference DJI could attribute it to pilot's error - pilot should be aware of their surroundings.  If there was an interference and Spark disconnected you can have one of two possibilities: pilot switched off RC or there was an error on RC/Spark part.

Mirek

Mirek6 Posted at 2018-7-15 13:46
Yes - as you noted, no way to turn VPS off in Spark.

And yes - I do fly a meter or so over water with Spark but I do watch it like a hawk - it happened to me several times that it suddenly dipped down. Fortunately, my reflexes are still sharp and I do expect that behaviour :-).

Thanks for that info! Yes, my Spark has made some ripples on the water! Thank goodness, it didn't go down at all. Although, my thumb is always on the joystick. I won't do it again. Not until I get Big Balls anyway  :-)

N2QLT Posted at 2018-7-16 05:52
Thanks for that info! Yes, my Spark has made some ripples on the water! Thank goodness, it didn't go down at all. Although, my thumb is always on the joystick. I won't do it again. Not until I get Big Balls anyway  :-)

Yeah :-)

For your reference - snippet from Spark's manual with appropriate sentences applicable to flying over water highlighted.

One thing that this unfortunate issue brings to my mind, is the RTH preset/default behaviour when RTH is initiated less than 20 meters from the home point?  Why is it this way?  Why does it need to be different than when you are 500m away?

Shalabid Posted at 2018-7-14 11:05
Hi everyone,

Thanks for the time you've taken to respond.

Mirek is right on this action by SPARK during a RTH.  

Mirek6 Posted at 2018-7-16 06:12
Yeah :-)

For your reference - snippet from Spark's manual with appropriate sentences applicable to flying over water highlighted.

And I was always told that instructions are for people who don't know what they're doing...  ;-)

Same crap from dji that I had the rth does not work half the time. They will just say pilot error as normal as they don't want to admit there drones have a serious issue.dont waste your time you will get nothing from them !!!