Mavic Pro 2 lost at sea - what could I have done differently

[acrossthenight]

Hi

I lost my drone (Mavic 2). I’m happy to assume I’ve made a bunch of mistakes - sure there are loads to find! DJI is looking at the logs. What I’d to understand is:

(A) what happened to the drone after I lost connection and

(B) what could I have done differently.


It was a windy day but it is always windy here and if I never flew the drone with a wind warning I’d almost never fly it. I get them all the time and have had no issues before.

My plan was to send it out, check it was ok in the wind and then keep going if it was ok. It took me a while to realize it was drifting in the wind - and at first assumed it was set to FPV mode which is why camera was titled (it wasn’t). I also turned it to cinematic mode which looking back may have made the drift much worse (?)

When I realized what was happening eg the wind was pushing the drone out, I tried to bring it lower but probably took too long to do that. I also tried to manouver it behind one of the two headlands but it seemed a bit futile until it got much lower. When it wasn’t making any real headway I panicked and put into RTH mode and with the lower altitude it was making decent headway with about 70% battery and only around 800m to make it to land (not the home point - the land on the headland - would have switched off RTH when it go adjacent to the land and steered it over).

But the connection dropped out while it was over a km away. I moved around the beach to try and open up the signal but the connection never came back. My assumption is the drone has crashed into the water but I don’t know how or why exactly. If it is not making headway due to wind does it just land even if over water?

I’m clutching at straws here but assuming could identify an approximate position, what are chances it could be found on sea floor (assuming the water is shallow enough to dive). Drone is so light my assumption is that when it hits the water it would deviate a bit with any current until it hits the bottom. Does this mean that even if I could identify a pretty good search area there is almost no chance of finding it on the ocean floor? Reason I ask is I have Refresh. A few questions


1. Did putting it into cinematic mode make the control much worse?

2. If I had been able to switch to sports mode before I lost signal would it have made it back? Winds were coming and going but at one stage it was travelling well even with wind gusts against it.

3. Did I need to have switched off auto land over water? Read that they can just land if they are getting stuck

4. What would have happened in this scenario eg after I lost signal where did the drone go/what did it do?

5. Is it strange that it lost signal and wasn’t able to land when it had so much battery left? Did something happen to drone which affected the connection?

6. Any ideas where it would have landed...? How quick do they sink...?



Thanks

 

[Thomas B]

Welcome to the forum. Hope you can get the hulk of your drone back... if not, at least a discount from DJI.
to answer your questions:
1. Cinematic mode slowed your controls and limited possible speed of flight.
2. Sport mode would have given you the highest speed possible. Remember that winds aloft are often much higher than near surface... so descending just enough to clear obstacles would help.
3. When batteries get low enough the drone will land where it is... you can use the sticks to try forward motion to change actual touchdown location... and try “climbing” which will slow descent. You can’t stop a forced autolanding.
4. If signal is lost to the M2P it will retrace it’s path for a limited time. 10 seconds I believe. After that it would follow the settings you programmed, RTH is default, but this is slower than regular flight modes making it harder to overcome winds... again, descending helps. Eventually the drone will land itself wherever it is when critical battery level is reached.
5. An answer w/o review of the logs would not be useful... one of our resident experts.. maybe @sar104 will chime in.
6. Sinks like rock....see answer #5. However, it is possible the drone made it to terra firma or at least shallow water.

 

[Fly Dawg]

For the sake of asking the question. I assume you were aware that you were using a custom setting on your remote. This really has no bearing on the wind issue, but your control inputs are reversed from the norm.

 

[acrossthenight]

Welcome to the forum. Hope you can get the hulk of your drone back... if not, at least a discount from DJI.
to answer your questions:
1. Cinematic mode slowed your controls and limited possible speed of flight.
2. Sport mode would have given you the highest speed possible. Remember that winds aloft are often much higher than near surface... so descending just enough to clear obstacles would help.
3. When batteries get low enough the drone will land where it is... you can use the sticks to try forward motion to change actual touchdown location... and try “climbing” which will slow descent. You can’t stop a forced autolanding.
4. If signal is lost to the M2P it will retrace it’s path for a limited time. 10 seconds I believe. After that it would follow the settings you programmed, RTH is default, but this is slower than regular flight modes making it harder to overcome winds... again, descending helps. Eventually the drone will land itself wherever it is when critical battery level is reached.
5. An answer w/o review of the logs would not be useful... one of our resident experts.. maybe @sar104 will chime in.
6. Sinks like rock....see answer #5. However, it is possible the drone made it to terra firma or at least shallow water.

Thanks for your to the point responses. Does this mean if right away I had flicked it to sports mode I might still have a drone...?

 

[acrossthenight]

For the sake of asking the question. I assume you were aware that you were using a custom setting on your remote. This really has no bearing on the wind issue, but your control inputs are reversed from the norm.

View attachment 94359

Yeah I actually did this because I found in the very beginning when I first used a DJI spark 2-3 yrs ago) that my instincts were to use my right hand for altitude - I think it comes from playing too much XBox when I was younger where right hand up controlled looking up or something.

 

[Thomas B]

Thanks for your to the point responses. Does this mean if right away I had flicked it to sports mode I might still have a drone...?

Very possible depending on winds.

 

[Fly Dawg]

Assuming this is fairly accurate. The winds were quite high and blowing out to sea....

 

[slup]

Yup, a clear blow away... with several pilot mistakes done once the drifting were noticed due to lacking knowledge about his equipment and the circumstances he decided to fly in.

Below the event in a couple of points (instead of a colorful chart ) ... have colored the disastrous actions in red & the good/or better ones in green.


-Mainly you started to drift out sideways with the wind at the time you switched over to Cinematic mode, at 39sec.

-From here at 78m height you did put in full positive throttle (as stick mode 3 meaning elevator) but without rotating the AC back towards the HP.

-At 75sec you also add in full positive elevator (as stick mode 3 meaning throttle) and ascend up to 195m height making the winds even stronger, still drifting sideways not heading HP.

-At 115sec you for the first time direct the AC back towards the HP ...still on 195m height.

-Shortly after, you get it ... now with the AC directed towards the HP you nail the sticks for descending & full speed forward, but still drifting out to sea.

... All above still remaining in Cinematic mode which only seems to gives max 15 degrees pitch angle ... instead of switching over to Sport and made 35 degrees possible.

-Then shortly after at 159sec you give up & goes for RTH ... then at 148m height. This makes it possible for the AC to use a 25 degree pitch angle & the drift speed goes from approx 8m/s down to 2,5m/s

-During the RTH phase you continued to apply negative elevator (as stick mode 3 meaning throttle) in periods ending up on 102m height when you get disconnected for the first time.

-You seems then to continue applying negative elevator (as stick mode 3 meaning throttle) during the video/log stream disconnect but were probably still in control of the AC as it is on 33m height when the video/log stream continues. You are now also making way towards the HP

- But short after you lost connection for good ... the battery were then down to 59% with 1517m to go to reach the HP & a coming land battery level of 10%. The heading speed then were roughly 2-3m/s in the right direction & the log reports 674sec useful battery time left (not sure if it's to auto landing or to 0%) meaning in best case 674sec of flight with 3m/s still left in straight line to HP (and nearly half of that remaining distance to HP consisted of ground). But I leave that judgement to @sar104, he's the best of those kind of estimations.

 

[Fly Dawg]

@slup With all due respect, your analysis is quite good. However, I would like to offer some practical advice from a long time telemetry analyst. Extreme detail in every analysis is quite often ( More times than not ) unnecessary. You should consider that any OP who may ask for assistance may not fully grasp the concept of such a detailed report and lead to confusion. I admit that I have made that same mistake a few times. Stick to the point, and as the old saying goes ( KISS ), such that the pilot requests can be answered in simple terms that are easily understandable. Also for other pilots that may read the thread and not understand the fine details. Just a bit of advice. Nothing else....??

 

[slup]

@slup With all due respect, your analysis is quite good. However, I would like to offer some practical advice from a long time telemetry analyst. Extreme detail in every analysis is quite often ( More times than not ) unnecessary. You should consider that any OP who may ask for assistance may not fully grasp the concept of such a detailed report and lead to confusion. I admit that I have made that same mistake a few times. Stick to the point, and as the old saying goes ( KISS ), such that the pilot requests can be answered in simple terms that are easily understandable. Also for other pilots that may read the thread and not understand the fine details. Just a bit of advice. Nothing else....??

The intention with the color markings & this time skip the chart (which many doesn't grasp if not explained) was just that ... think the answers to at least question 1-4 is in the red but point taken.

 

[acrossthenight]

Thanks for the feedback. Is it fair to say that if I had dropped the altitude earlier or changed to sports mode the result is different? Would it have been easier/possible to not try to fly direct into the wind but try to push the drone north or south onto the headland to try and land it or get some cover from the wind? Is there an altitude that is considered optimum to avoid the wind in those conditions eg with waves and the occasional boat/mast?

The problem I had besides feeling rushed is that landing it on either cliff face would have been problematic to recover the drone for a number of reasons - but I guess it’s a much better scenario to have to find or negotiate back my drone if it’s somewhere on the land.

In a practical sense, what would have happened after I gave the last command - the drone just keeps trying to fly to the HP until it hits 10% battery or do the engines get overwhelmed and it seeks to land because it is not making any headway? Does the loss of signal have anything to do with the wind/drone drifting or are they completely unrelated?
Thanks again

 

[Meta4]

Is it fair to say that if I had dropped the altitude earlier or changed to sports mode the result is different?

You acknowledged that it was a windy day ...

It was a windy day but it is always windy here and if I never flew the drone with a wind warning I’d almost never fly it. I get them all the time and have had no issues before.

My plan was to send it out, check it was ok in the wind and then keep going if it was ok. It took me a while to realize it was drifting in the wind

But showed very little awareness of how to deal with the wind.
A couple of points about flying with a significant wind:
1. The wind is always stronger up higher.
If you go higher, you will have a bigger wind problem to deal with.
If you go lower, you have less wind to deal with.

2. If it's windy, don't fly away with the wind.
Fly into the wind and you'll quickly see how the wind is affecting the drone.
If you can only make slow progress flying into the wind, you can see how difficult it would be to get back if you ended up downwind and fighting a headwind.

If you look at your flight data towards the end of the flight, the Mavic was making good headway in RTH once it was down below 200 ft.
At 80 ft it was making 6-8mph toward home.

Would it have been easier/possible to not try to fly direct into the wind but try to push the drone north or south onto the headland to try and land it or get some cover from the wind?

You should have dropped altitude much earlier and you could have easily made it home.
You should not have gone south at all because that created another problem.
By going south hoping for shelter behind the headland, you put the drone in a bad situation.
As it got closer to shore you lost signal because the headland blocked your line of sight and the headland became a large obstacle blocking the RTH path.

Is there an altitude that is considered optimum to avoid the wind in those conditions eg with waves and the occasional boat/mast?

The answer to this Q is to look at your screen.
Your app display will show you what speed you are making and what height you are at.

In a practical sense, what would have happened after I gave the last command - the drone just keeps trying to fly to the HP until it hits 10% battery or do the engines get overwhelmed and it seeks to land because it is not making any headway? Does the loss of signal have anything to do with the wind/drone drifting or are they completely unrelated?

Losing signal initiates RTH, the drone flies until it reaches critical low voltage and it autolands to prevent falling from the sky when it runs out of juice completely.
You lost signal because the headland blocked your line of sight.

The problem I had besides feeling rushed is that landing it on either cliff face would have been problematic to recover the drone for a number of reasons - but I guess it’s a much better scenario to have to find or negotiate back my drone if it’s somewhere on the land.

Since it did not return home, there's a chance that it's there somewhere.
It was coming home at 6-8mph at 80 ft.
On losing signal it would have climbed to 100 ft where it would have managed 3-5mph toward home.
It would have reached the headland in about 4 minutes and the battery was sufficient for that.
At 100 ft it would have cleared the headland on the straight line from last signal to home.
But if it was set just a little further south, the rocks are higher than the RTH height and could have caused a problem since you did not have obstacle avoidance enabled.
That cliff line (or below it) looks like the place to search to recover your Mavic.

 

[acrossthenight]

Thanks this is really useful feedback appreciate it

 

[sar104]

The aircraft was making progress at 31 m altitude, but it was struggling to hold a course to get to the home point.



On the other hand, it did have enough battery reserve to make it to land.



Unfortunately that track intersects the headland that is higher than the RTH height of 30 m. Since RTH obstacle avoidance was not enabled, the flight will likely have ended just short of the yellow pin below, taking into account vegetation height. Note, however, that the winds were quite variable, and so there is significant potential error in that location estimate. Whjat might be worthwhile is to search the 30 m contour on that headland.

 

[new2mavic]

It's perfectly OK to fly in strong wind but you have to make sure that the drone will be returning home in tail wind.

This video shows what more you could have done :

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[acrossthenight]

The aircraft was making progress at 31 m altitude, but it was struggling to hold a course to get to the home point.

View attachment 94426

On the other hand, it did have enough battery reserve to make it to land.

View attachment 94427

Unfortunately that track intersects the headland that is higher than the RTH height of 30 m. Since RTH obstacle avoidance was not enabled, the flight will likely have ended just short of the yellow pin below, taking into account vegetation height. Note, however, that the winds were quite variable, and so there is significant potential error in that location estimate. Whjat might be worthwhile is to search the 30 m contour on that headland.

View attachment 94429

View attachment 94430

I don't know quite how you do this but its very cool and extremely helpful. I will give this a try. Thanks so much

 

[acrossthenight]

It's perfectly OK to fly in strong wind but you have to make sure that the drone will be returning home in tail wind.

This video shows what more you could have done :

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Thanks I'll take a look

 

[Meta4]

I don't know quite how you do this but its very cool and extremely helpful. I will give this a try. Thanks so much

It's just illustrating what I already told you in post #12.

 

[slup]

Think you got all needed info to fully understand what & why thing's went wrong ... and from this learn & be able to avoid similar situations in the future. Just a pity that it became a costly learning process. Always flip to Sport mode, drop altitude & manually maneuver back as quickly as possible in case of a starting blow away situation.

Will just add one more piece into this to give you a visual picture how little maneuver space you had & how little time that was available to react with the correct actions.

Mainly once out of zone 1 below you faced a serious higher risk considering the strong wind. In zone 2 your only option were to decrease height until you licked the waves or got progress either in HP or solid ground direction. Once in zone 3 you more or less were doomed to lose connection & only be left to rely on RTH.

 

[E90RAW]

It's perfectly OK to fly in strong wind but you have to make sure that the drone will be returning home in tail wind.

This video shows what more you could have done :

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Very informative thanks