Hi all,

Am posting here hoping i can answers to my queries. I have lost on Sunday 9/7/2017 my mavic at sea. The same day i email DJI attaching the flight log and asking if it is a user fault or a drone failure. One week after i have not received any answer and decided to go on dji chat support. I talk to a guy name Malvar and he said that my case was not posted which is very strange to me as i know that after sending my case it says email successfully send. A new case was opened by Malvar case number:CAS-803100-G9P5Q9. Malvar says i will get an email from Dji within 48hrs, but still nothing. I talk to another guy on the chat and he says an email was sent to my email address but i have not received any email from DJI.


As i have to finish some works on construction site and this can't wait for me and dji,  i bought a new mavic yesterday. But that does not mean that i consider the case closed because i need to know what reallly happen this day.


My flight data can be found here:  http://www.phantomhelp.com/LogViewer/55U21Y2N0HOR0OMELDB6/#

I have review the flight from the controller log and severals anomalies from the drone drop up, even that there were high velocity wind warning, like:

1. On RTH activation, at 42% battery, the aircraft does not descend to 60 meters as set in RHT altitude, why?
2. On RTH activation, no change in the aircraft orientation, why?

When i realize that RTH will not save the drone and took back the commands, the aircraft does not respond to command (see that on the controller while playing back)

I just hope a dji guy get into my case or an experience pilot analysis so that i know what really happen.

Thanks you in advance for your help.

Two questions:

1. Why did not you flown back manually and canceled RTH?
2. Why did you ignore the first battery warning?

For me this distance looks very risky, especially when you are flying over water.

Also it was windy that day ...

echterberliner Posted at 2017-7-19 11:45
Also it was windy that day ...

yes it was but as i said it did not drop to RTH set altitude and on the flight route i suceed bringing it back some 130 meters and at a point it refuse to obey the commands and did whaever he wants

During RTH the drone flies autonomously. If it is too windy or the drone has other problems, RTH must be canceled, otherwise it will not respond to manual control.
If I see this correctly, you did not cancel RTH.

Also:
Your height was 100 meters, the RTH was set to 60 meters.
If the drone was less than 60 meters, it would rise to 60 meters - if it is more than 60 meters, it remains at the previously flown altitude.

1. On RTH activation, at 42% battery, the aircraft does not descend to 60 meters as set in RHT altitude, why?

Echterberliner is correct; it never descends to the RTH altitude on return but only ascends to that height if it's initially below it.

2. On RTH activation, no change in the aircraft orientation, why?

Actually it did change orientation. Its heading was 35° when RTH was initiated, and it changed to 121° for the return trip.

This flight didn't have a lot going for it: Partially charged battery; Out of VLOS, Strong Winds etc

I'm sorry but it looks like pilot error (I'd be delighted to be wrong)...Can you upload the flight-record to Airdata and link here?

kenavata Posted at 2017-7-19 12:31
This flight didn't have a lot going for it: Partially charged battery; Out of VLOS, Strong Winds etc

I'm sorry but it looks like pilot error (I'd be delighted to be wrong)...Can you upload the flight-record to Airdata and link here?

Thanks guys for your clarification. Ok i understand why it did not drop down to 60 meters. I never wanted to fly so far, it gone by itself. I first initiate a RTH at 42% battery when it was about 350 meters but it did not respond and continue to flew away. I was waiting to see him back but when i realize i do cancel RTH and bring it back about 130 meters until low battery warning arrive and goes itself in RTH.

Copy and past this link you will have the flight data. http://www.phantomhelp.com/LogViewer/55U21Y2N0HOR0OMELDB6/#


Am not blaming the drone as i said, i need to understand what really happen. The battery was at 90% when i take off.

Now when i take hand and bring it back i was pushing the stick on the right and the head of the aircraft was pointing at my direction (seen from the controller flight log) it should not have come back in my direction. why?

fans64e5a3ef Posted at 2017-7-19 13:10
Thanks guys for your clarification. Ok i understand why it did not drop down to 60 meters. I never wanted to fly so far, it gone by itself. I first initiate a RTH at 42% battery when it was about 350 meters but it did not respond and continue to flew away. I was waiting to see him back but when i realize i do cancel RTH and bring it back about 130 meters until low battery warning arrive and goes itself in RTH.

Copy and past this link you will have the flight data. http://www.phantomhelp.com/LogViewer/55U21Y2N0HOR0OMELDB6/#

According to your flight data:

(1) The battery was at 80% on takeoff
(2) After the first Max flight distance warning, you flew a further 300m away before RTH was triggered.
(3) There is no record of you taking back control
(4) Even after RTH was initiated the AC did travel a further 150m away, before making any headway back, it looks like it was fighting the wind and failing

It appears as though the correct thing to have done once putting the drone into that situation would be switch to sport mode for the RTH flight so that it could fight the wind better . It was obviously being blown back by high winds . Remember that the wind even at 60 feet higher than you are standing can be quite higher . It is always best to pay attention to the speed readout on the display to tell if you are flying with the wind or against it . Always make the RTH flight with the wind .

echterberliner Posted at 2017-7-19 11:31
Two questions:

1. Why did not you flown back manually and canceled RTH?

I have seen several comments on the extra risk when flying above water, would you explain why the mavic would behave differently when it fly over land as compared to flying above water?

It may make sense when the altitude is low in relation to the water, however I do not seen how it would behave much differently, especailly in this case when the altitude is higher then the downward sensors' capacity.

Much appreciated.

fans64e5a3ef Posted at 2017-7-19 13:10
Thanks guys for your clarification. Ok i understand why it did not drop down to 60 meters. I never wanted to fly so far, it gone by itself. I first initiate a RTH at 42% battery when it was about 350 meters but it did not respond and continue to flew away. I was waiting to see him back but when i realize i do cancel RTH and bring it back about 130 meters until low battery warning arrive and goes itself in RTH.

Copy and past this link you will have the flight data. http://www.phantomhelp.com/LogViewer/55U21Y2N0HOR0OMELDB6/#

Hey man you might just have to put this one down to experience, I'm sure others will learn from it so putting up your log helps others.

There's very little to be said about the log I'm sure you can figure it ou yourself. Hope you might be able to get another AC soon.

Good luck.

My guess here is going to be a strong wind.  RTH calculation is fairly poor with a headwind and if its strong enough, the mavic cant make headway or will even drift backwards in P-GPS mode.  RTH also cant work against it.  There is a large wind velocity warning at one point there.
It'd be interested to upload that log to the Airdata site where it'll show the wind speeds and direction for those datapoints to see if that is the case

DronePix Posted at 2017-7-19 14:01
I have seen several comments on the extra risk when flying above water, would you explain why the mavic would behave differently when it fly over land as compared to flying above water?

It may make sense when the altitude is low in relation to the water, however I do not seen how it would behave much differently, especailly in this case when the altitude is higher then the downward sensors' capacity.

The difference is that the drone is now in the bay and you need a diver for the salvage. If the drone had flown over land, it would just landed.

kenavata Posted at 2017-7-19 13:47
According to your flight data:

(1) The battery was at 80% on takeoff

Yes you right, it continue to fly away because RTH does not adjust speed in function of wind

rydfree41 Posted at 2017-7-19 13:56
It appears as though the correct thing to have done once putting the drone into that situation would be switch to sport mode for the RTH flight so that it could fight the wind better . It was obviously being blown back by high winds . Remember that the wind even at 60 feet higher than you are standing can be quite higher . It is always best to pay attention to the speed readout on the display to tell if you are flying with the wind or against it . Always make the RTH flight with the wind .

Yes i understand now, i should have flew towards land, i would have save enough battery to search for a house and land. I was in a panic situation

hallmark007 Posted at 2017-7-19 14:14
Hey man you might just have to put this one down to experience, I'm sure others will learn from it so putting up your log helps others.

There's very little to be said about the log I'm sure you can figure it ou yourself. Hope you might be able to get another AC soon.

definitively yes, i've learn about my errors, and i  said the more important thing to me here is to know what jhappen so that i do not repeat the same errors again. I have already bought a new Mavic. Am now rassured.

gnirtS Posted at 2017-7-19 14:28
My guess here is going to be a strong wind.  RTH calculation is fairly poor with a headwind and if its strong enough, the mavic cant make headway or will even drift backwards in P-GPS mode.  RTH also cant work against it.  There is a large wind velocity warning at one point there.
It'd be interested to upload that log to the Airdata site where it'll show the wind speeds and direction for those datapoints to see if that is the case

Ok, can you tell me how to upload to Air data, any link? Is it the log from the controller? Thanks

echterberliner Posted at 2017-7-19 14:48
The difference is that the drone is now in the bay and you need a diver for the salvage. If the drone had flown over land, it would just landed.

I went to the last point GPS with 2 divers, it is 8 meters deep at this point, they dive one hour in very strong current at the bottom, for them its clear, the mavic has been taken away by the current

fans64e5a3ef Posted at 2017-7-19 20:47
Ok, can you tell me how to upload to Air data, any link? Is it the log from the controller? Thanks

Its the txt file from the mobile device.  You may need a paid account to see wind data though.

i admit my errors:
1. raise up at 120 meters with high wind velocity warning ( was on the charm on a small island)
2. try a POI in this condition
3. activate RTH where RTH does not adjust speed in function of wind (realize that too late)
4. Force returning manually at this distance with less battery
5, Should i gone towards land instead
6. Not using sport mode after RTH cancellation

I was so pannic in fact

I was counting on RTH and did not know that RTH is fix speed, If i was aware of that i would have bring it back definitively. I will never use RHT for sure, it does not even drop to RTH set altitude if the drone is higher, that also i did not know. Conclusion i lost too much time to realize all this and it was not a situation for losing time to take decisions.

I have a new Mavic now, and for sure i will not trust these functions where the drone took the hands, flight modes etc. I accept it is a user fault and just hope DJI take into consideration my new purchase and give me a discount as need to buy a phantom 3 standard for my son,

Thanks you all guys, really appreciate your help, please do continue to see the flight data may be there more errors I've done and i need to know, specially at the end of the flight where i don't understand the drone behaviour.

gnirtS Posted at 2017-7-19 20:57
Its the txt file from the mobile device.  You may need a paid account to see wind data though.

Ok i see, that no need, may be for future, yhe navic is in the bay now. Yes its the txt from the mobile. Its the end of the flight now that i need to understand.

Using RTH is fine , you just must understand how it operates and know its limitations .  After RTH is initiated you can still lower the altitude if you are above your preset altitude by lowering the throttle stick . You can also make small corrections with pitch , roll and yaw while in RTH . Also you can switch into Sport mode when you need more speed . This will cancel the current RTH but you can then put it into RTH again and it will RTH in Sport mode .

rydfree41 Posted at 2017-7-20 04:06
Using RTH is fine , you just must understand how it operates and know its limitations .  After RTH is initiated you can still lower the altitude if you are above your preset altitude by lowering the throttle stick . You can also make small corrections with pitch , roll and yaw while in RTH . Also you can switch into Sport mode when you need more speed . This will cancel the current RTH but you can then put it into RTH again and it will RTH in Sport mode .

Thanks that very for knowledge

rydfree41 Posted at 2017-7-19 13:56
It appears as though the correct thing to have done once putting the drone into that situation would be switch to sport mode for the RTH flight so that it could fight the wind better . It was obviously being blown back by high winds . Remember that the wind even at 60 feet higher than you are standing can be quite higher . It is always best to pay attention to the speed readout on the display to tell if you are flying with the wind or against it . Always make the RTH flight with the wind .

Sport mode actually consumes more battery / distance.  So, given his already low battery, Sport mode would not get him home.  His only chance would have been  to lower altitude manually to try to reduce head wind and perhaps try to make it safely to the nearest shore (Sport mode may be necessary).

Griffith Posted at 2017-7-20 06:33
Sport mode actually consumes more battery / distance.  So, given his already low battery, Sport mode would not get him home.  His only chance would have been  to lower altitude manually to try to reduce head wind and perhaps try to make it safely to the nearest shore (Sport mode may be necessary).

Sport mode doesn't always consume more power per distance traveled , it depends on the situation . If you fly around in sport mode like a dragonfly on crack then it will consume more energy but if you are simply trying to maintain a straight flight path and go faster it really doesn't .In this case it would have been best to start RTH in Sport mode and manually try to lower altitude a bit to lessen the effect of the wind .

rydfree41 Posted at 2017-7-20 10:43
Sport mode doesn't always consume more power per distance traveled , it depends on the situation . If you fly around in sport mode like a dragonfly on crack then it will consume more energy but if you are simply trying to maintain a straight flight path and go faster it really doesn't .In this case it would have been best to start RTH in Sport mode and manually try to lower altitude a bit to lessen the effect of the wind .

Sport mode doesn't always consume more power per distance traveled

Not to be argumentative. but ...
For the sake of discussion, you are technically correct.  It  isn't the fact that Sport Mode is used, it's the fact that speed efficiency declines toward the higher velocities that can be achieved in Sport Mode.   You can still fly at a snail's pace in Sport Mode.

This situation is analogous to the power curve most pilots are familiar with.  Its a combination of the power required to keep the AC aloft vs the additional power required to balance drag and any given velocity  (drag increases with velocity - and it's non-linear).  So there's a sweet spot somewhere in the power-vs-velocity curve where the efficiency is the greatest. Pilots make use of this curve  to maximize their fuel efficiency. Much like an automobile gas mileage vs. speed.

In aircraft, such specs are required to be published by the manufacturer, but unfortunately for us, DJI has not provided that information (and is not required to do so).  So we don't really know where the sweet spot is.  Perhaps it's actually above max speed in Normal mode.  But numerous others have reported diminished max distance when flying in Sport Mode - presumably at max Sport Mode speed.

There have been many discussions on this topic but that is perhaps for another thread . You can go faster in P-mode BTW if you turn off OA but you get more angle of attack plus speed capability to fight the wind in Sport mode . I think the general consensus of most efficient speed is 31MPH but that of course depends on the wind speed and direction at the time . The easiest method to calculate it in a pinch is to watch the motor RPM and power meter bars and keep them at the intersection of green and blue . This thread has some good info about this .
https://mavicpilots.com/threads/ ... .16568/#post-190075

anyone else think it would be good to have DJI add an option of RTH with Sports mode speed or a way to set speed for RTH return ?

Dirty Bird Posted at 2017-7-20 15:43
The aircraft does not descend to RTH altitude.  It will climb to RTH altitude if lower.  If already at or above RTH altitude it returns at its current height.

Yes you right

RCNJ Posted at 2017-7-20 14:23
anyone else think it would be good to have DJI add an option of RTH with Sports mode speed or a way to set speed for RTH return ?

As per this last experience encountered, i would definitively advice not to try RTH in windy situation even in sport mode. Whatever the situation, for me, i would use the wind direction and go with until i found a safe place to land, it would save battery this way, and with GPS and flight route you can find the drone. Lot of pilot fear not to see their drone back then make all that they can but in fact never realize that it is much more easier to go land and find it in a secure place 1 or 2 km away.

I think DJI also should give and indication of winds versus drone speed.

Sorry for your loss, just checked your case, we've sent you an email to ask for the info about 3 days ago. Did your receive it? Please check it , or you can check the spam.

DJI Diana Posted at 2017-7-20 22:24
Sorry for your loss, just checked your case, we've sent you an email to ask for the info about 3 days ago. Did your receive it? Please check it , or you can check the spam.[view_image]

Hi,

I 've check my email and there is nothing receive from dji. Ok i will upland the flight data from the controller so that you have a clear analysis. You have certainly saw here what have happen and what i consider as my responsibility too. Am not here to hide or blame. That no need, the drone is gone and i have already purchase a new one as i have some works which cannot wait.

i think, thank to the forum and its helpful members, to have understand what happen in the beginning of the flight, but for the last part am still not convince about bizarre behavior from the drone and am counting on you to establish what was happening.

I want to look forward, firstly not to do the same errors again and secondly as a good client would like to ask how dji can consider its contribution as i need to purchase a phantom 3 standard for my son.

i thank you for your consideration, co-operation and contribution to my request.

DJI Diana Posted at 2017-7-20 22:24
Sorry for your loss, just checked your case, we've sent you an email to ask for the info about 3 days ago. Did your receive it? Please check it , or you can check the spam.[view_image]

Ok, You right, the email was in the spam. You will get all the requested details.

fans64e5a3ef Posted at 2017-7-21 02:42
Ok, You right, the email was in the spam. You will get all the requested details.

Thank you, we'll take care of it once we received the details.

As a beginner with my Mavic, this forum has certainly increased my knowledge on the more complicated situations. At this stage, my only issues have been the faulty battery which I lost out on that one and a camera issue which I have been able to overcome with the advice of members on this forum.
it is obvious that there is a  great bank of knowledge on this forum, a great forum!

DJI Diana Posted at 2017-7-21 02:54
Thank you, we'll take care of it once we received the details.

I have sent by email all the details, and have synchronize all flight log from my controller, awaiting your reply

fans64e5a3ef Posted at 2017-7-21 06:50
I have sent by email all the details, and have synchronize all flight log from my controller, awaiting your reply

Which email address have you sent to? Just checked your case again, I didn't see your email for some reason. You can just reply our email or send an new email to support@dji.com.

DJI Diana Posted at 2017-7-21 20:11
Which email address have you sent to? Just checked your case again, I didn't see your email for some reason. You can just reply our email or send an new email to .

I reply on the email i received from dji,  support.us@dji.com and it says it gone. Thins thing begin to get me cray, am a patient guys but there a bit to much here. Please do check spam or what soever on your side. Thanks