My Mavic Pro lost connection and landed in a brook - want to find the reason

[ylmavicpro]

Hi, all there

I have been flying my mavic pro more than one year without much problems - I always thought it is really a marvelous bird. Two days ago I was flying in an open mountain site near a lake. By the third flight, the system showed "the aircraft lost connection ... ". I got a big panic and I remembered vaguely that one should shut down the apps and switch on again, it could connect again. I did - once, twice, no success. Later, way way too much later, I found my mavic in the middle of a brook. I don't know what caused this mishap. Here are the flight record .txt and .dat files, which I downloaded directly from my android phone.

I would be grateful, if your expert here can make an analysis for me: a mistake by the pilot or a system error.

thanks a lot!

 

[sar104]

The behavior was created before the app disconnected.



At 252 seconds you initiated RTH. At 267 seconds the aircraft was back above the home point. At 272 seconds it started to land but then, at 282 seconds, you applied 3 seconds of full left airleron. It was facing just north of west, and so it moved 15 m SSW, and continued autolanding. The app appears to have disconnected later on the descent, but it continued in autoland and looks like it ended up where you found it.

Pilot error.

 

[ylmavicpro]

The behavior was created before the app disconnected.

View attachment 80398

At 252 seconds you initiated RTH. At 267 seconds the aircraft was back above the home point. At 272 seconds it started to land but then, at 282 seconds, you applied 3 seconds of full left airleron. It was facing just north of west, and so it moved 15 m SSW, and continued autolanding. The app appears to have disconnected later on the descent, but it continued in autoland and looks like it ended up where you found it.

Pilot error.

Thank you very much for your analysis, Sar104!

Does it mean that when the RTH commend is given, I should not do any other commends during descent? Sometimes during the decent, the camera has different angles and views, I press the shutters again. So in the future I should conduct manual decent rather than auto landing or RTH`?

Best regards

 

[sar104]

Thank you very much for your analysis, Sar104!

Does it mean that when the RTH commend is given, I should not do any other commends during descent? Sometimes during the decent, the camera has different angles and views, I press the shutters again. So in the future I should conduct manual decent rather than auto landing or RTH`?

Best regards

I think it's fine to take photos etc, and autolanding isn't cancelled by control commands. However, if you drive it off the home point it's not going to come back by itself, and if you then lose connection you can create a situation like the one that you experienced.

 

[silverdragon]

From what I am gathering, when the drone was right above the take off point during RTH if it came straight down it would of most likely landed on the ground not in the brook. It's ok to use the RTH command but you still have to keep a close eye on the drone in case it does land off of the Take off point. I believe you pushed full left airleron and made the AC go into the brook.

 

[ylmavicpro]

I think it's fine to take photos etc, and autolanding isn't cancelled by control commands. However, if you drive it off the home point it's not going to come back by itself, and if you then lose connection you can create a situation like the one that you experienced.

If I want it to fly to another direction, I should cancel the original RTH action and set a new RTH commend?

But what caused the disconnection?

 

[ylmavicpro]

From what I am gathering, when the drone was right above the take off point during RTH if it came straight down it would of most likely landed on the ground not in the brook. It's ok to use the RTH command but you still have to keep a close eye on the drone in case it does land off of the Take off point. I believe you pushed full left airleron and made the AC go into the brook.

Yes, with the new handling, it changed the Home Point and went to the place where the new action pointed.

 

[sar104]

If I want it to fly to another direction, I should cancel the original RTH action and set a new RTH commend?

I'm not sure I understand the question. If you don't want it to RTH then yes, cancel the command.

Yes, with the new handling, it changed the Home Point and went to the place where the new action pointed.

The home point was not changed.

But what caused the disconnection?

That's a persistent problem with certain Android devices, so that may have been the cause.

 

[gnirtS]

App disconnect is often USB cable/plug related but you usually retain control via the RC.

When landing you should always be (i) watching it and (ii) finger on that pause button to stop auto land the instant you notice it going wrong.

 

[ylmavicpro]

App disconnect is often USB cable/plug related but you usually retain control via the RC.

When landing you should always be (i) watching it and (ii) finger on that pause button to stop auto land the instant you notice it going wrong.

Thanks you very much for your kind advice.

If I am conducting a manual landing/return, the connection is broken between USB cable/plug, are the sticks on RC still active for guiding the AC to come back?

best regards

 

[gnirtS]

Yes. The app and the RC are different things. Its perfectly possible to fly the mavic pro back to use using the telemetry and RC with no app.
Any time the drone is in an intelligent flight mode you really want that finger next to the pause button, app or no app.

 

[MAvic_South_Oz]

If I am conducting a manual landing/return, the connection is broken between USB cable/plug, are the sticks on RC still active for guiding the AC to come back?

Yes, provided you still have signal to the MP.
Obviously easy if you have a visual on the MP, but even without this, you can still get back.

Either . . .
Press RTH on the controller, of course before flight, you must be sure to assess the location for each flight to enter correct settings in case it is needed like this.

Or, using the altitude and distance readout, you can ensure safe height, then do short runs of forward stick, and watch the numbers.
If decreasing it's coming back, if not, turn a bit and try again until it is counting down to home.

 

[ylmavicpro]

Thanks you MAvic_South_Oz and gnirtS!

Somewhere I read in the forum, but I can not remember exactly, that it is better to operate manual flying back than auto RTH. Is it true? and why

 

[gnirtS]

No reason not to use auto RTH unless maybe its really windy (in which case altitude and profile might need to change).
There's no "skill" difference in holding a stick forward vs pressing a home button. Use whatever you want.
But you should *always* monitor RTH and all other modes in case it goes wrong, goes off course, finds a wind, obstacle or anything else. Monitor the telemetry, monitor the screen and drone visually and be ready to take manual control instantly if it starts to do something unexpected.

 

[ylmavicpro]

Thank you, gnirtS

I had experienced some cases that the AC goes a few meters way rather than to the RTH point, in those cases I immediately cancelled RTH and did manually.

 

[dannybgoode]

Thanks you MAvic_South_Oz and gnirtS!

Somewhere I read in the forum, but I can not remember exactly, that it is better to operate manual flying back than auto RTH. Is it true? and why

I trust RTH 100% to function exactly as it is described. Don’t forget it you have not flown far (less than 20m from memory) and activate RTH the drone will land straightaway and not return to the take off point. This is fully documented in the manual but people have still drowned their drones etc by not realising it.

The other behaviour I am always conscious of is the RTH minimum altitude. If you are say flying in a forest and lose signal which activates RTH the drone will try to reach that altitude and could well strike a branch on ascent or have the obstacle avoidance stop its ascent so it just hovers until the battery runs out.

Also RTH plots a straight line back to yours home point so if you flew round an obstacle on the way out it may need taking into account on the inward leg.

Understand how it works thought and practice a few scenarios and you’ll get very comfortable with its capabilities.

 

[The Editor]

Also RTH plots a straight line back to yours home point so if you flew round an obstacle on the way out it may need taking into account on the inward leg.

Not with APAS active. It's in the manual fully documented.

 

[dannybgoode]

Not with APAS active. It's in the manual fully documented.

Fair. I’d still keep a close eye on it though and from memory it’s a straight line regardless from over 1km out or thereabouts?

 

[InvisibleName]

Fair. I’d still keep a close eye on it though and from memory it’s a straight line regardless from over 1km out or thereabouts?

It will try & retrace it’s flight path for the the first 60 seconds. If it fails to regain contact with the RC, it then straight lines the rest of the RTH.

Ps should point out that this is for a MA. not sure it’s the same for an MP

 

[InvisibleName]

Thank you, gnirtS

I had experienced some cases that the AC goes a few meters way rather than to the RTH point, in those cases I immediately cancelled RTH and did manually.

The best way to get an accurate RTH (within cms) is to take off vertically up to approx 10m & hover. This allows it to record an accurate GPS & an image directly below itself. This has been demonstrated in a very good video somewhere on YouTube.

Ps should point out that this is for a MA. not sure it’s the same for an MP