Help Please: Mavic 2 Pro Lost Yesterday

[PTBperegrine]

DJI Flight Log Viewer - PhantomHelp.com

I need the help of the Forum gurus to shed any light they can on whether this was the result of a malfunction or my own stupidity..

Below is an excerpt that I sent to the National Park office for this area. Yes, we are allowed to fly here in Australia:

"I'm a disabled motorcycle rider who uses a 3 wheel motorcycle to get out into the world and explore.
For the MANY places I can't actually get to see, I use a Mavic Pro 2 drone to view and photograph these areas.

Yesterday I visited the Purling Brook Falls (car park) and flew my drone carefully over the trees and avoided flying over people and paths.
My drone descended about 40m from the falls for a clear view and to take photographs, when I lost the connection.
Supposedly, if the drone loses contact, it climbs to 50m above my launch height (to clear the trees) and then returns to me, whether or not the signal
is re-established. Immediately after connection loss, a message appeared on the controller, "Obstacle Avoidance Not Available On Return To Home",
which is NOT what is supposed to happen. Friends travelling with me took my controller down to the Lookout but were unable to re-establish contact.
After 45 minutes fruitless searching (the battery has enough power for a 30 minute flight) we abandoned the search and left."

 

[DanMan32]

There are situations where OA can be an issue.
Low sun for example can be interpreted as an obstacle that OA can't get out of.

Other times the AC can't see itself around an actual obstacle, though you did indicate you set your RTH height adequately to go over any obstacles.

That "OA not available in RTH" troubles me though. Did you have it on?
If you had it on and adequate height, then phantom obstacle (sun for example) could be the issue.
If you did inadvertently turn it off and had adequate height, then there shouldn't be an issue.
Sport mode will turn off OA, but RTH which is a flight mode in its own right, should turn it back on, assuming it's enabled for RTH.

30 minutes is in ideal conditions, and from 100% to 0%. I usually get 23 minute flights.
Still, it would RTH on low battery. Might not make it though if it encounters too much headwind.

 

[RayOZ]

Most likely, the loss of connection was user error. The trees probably blocked connection from RC to AC.
I don't see the "Obstacle Avoidance Not Available On Return To Home" message in the flight log. There's a setting where you can disable AO on RTH, not sure if this is the case.
There was about 10s between the last 2 logs, it was descending. Would it have hit the water?

 

[PTBperegrine]

Thanks DanMan32 and RayOZ!
Time was almost midday so low sun should not have been an issue.
The obstacle avoidance message came up on the controller when my phone screen was saying "Connection Lost". I pushed the hardware "Return Home" button on the controller as it was still saying "Connecting"..

I rely on the excellent sensors with this model and would never turn them off. The message that they were off horrified me, I couldn't see why that had happened and basically assumed from that point that I would lose my drone...

The drone was in a large clearing about 40m from a waterfall, the top of the falls themselves were about 200m from me and about 30m below my height. There was a fair amount of tree cover between myself and the top of the falls, which is why I was getting intermittent signal loss. This didn't concern me too much as I knew that signal loss would trigger a climb to well clear of any tree height for a return to home. I also believed that the climb would reestablish my connection with the drone.
Sadly that didn't happen.
A couple of friends are going down there tomorrow to see if they can find anything in the trees on a direct line to the home point. If the drone didn't climb, it should have impacted the trees in the north west corner by the pool.
As I understand it, DJI Care Refresh won't cover this??

 

[ff22]

If the drone is recovered, then I believe, DJI care refresh does cover accidental damage. Sorry and I hope you can retrieve it. Some of these guys are great at figuring out where it might have gone down.

 

[RayOZ]

As long as you can find and retrieve your drone, DJI Care Refresh will cover it, even if it's user's fault. Probably not a good idea to push it beyond it's limit and rely on back-up software to save you. Tree's can cause signal loss, but solid rock will block signal altogether.
I think your throttle was pulled all the way down until it lost connection. It seemed to continued to descend until 10s later, which by then had descended another 15m.
It definitely should've ascended on loss of connection. If you can retrieve your drone and sent it to DJI, if they found it was a malfunction, they would replace it for you under warranty and you won't need to use your DJI Care Refresh.

 

[PTBperegrine]

Thanks ff22 and RayOz, I'll cross my fingers....

 

[sar104]

The GPS reception plummeted as you descended the aircraft towards the falls:



It was on the verge of dropping into ATTI mode when the connection was lost, and so would not have been able to RTH.

If you look at the wind direction it would then have drifted towards the falls. Unfortunately it likely either collided with the terrain or, if VPS kicked in, held position until it had to autoland due to low battery.

 

[Meta4]

Supposedly, if the drone loses contact, it climbs to 50m above my launch height (to clear the trees) and then returns to me, whether or not the signal
is re-established. Immediately after connection loss, a message appeared on the controller, "Obstacle Avoidance Not Available On Return To Home",
which is NOT what is supposed to happen

The message was telling you that there would be no obstacle avoidance for a return to home so the comments above about the sun sometimes acting as an obstacle are irrelevant.
One possible reason might be that RTH obstacle detection might not have been enabled?

As Sar104 mentioned, GPS was seriously impaired below -28 metres with the terrain masking too much of the sky.

You were pushing things with that wide band of tree cover between you and the Mavic, and made things harder by going down deeper without a clear line of sight.
You had a number of warnings of signal problems with loss of downlink for 2.2 secs, 1.8 sec and 9.8 sec towards the end of the flight data.
With the downlink lost, you still had control signal but by pushing lower, you were bound to lose signal.

Normally losing signal wouldn't be a disaster and RTH would save your bacon but pushing down where GPS wasn't available nixed that.
Sar's analysis looks like the most likely explanation for what would have happened.[/QUOTE]

 

[PTBperegrine]

The GPS reception plummeted as you descended the aircraft towards the falls:

View attachment 59079

It was on the verge of dropping into ATTI mode when the connection was lost, and so would not have been able to RTH.

If you look at the wind direction it would then have drifted towards the falls. Unfortunately it likely either collided with the terrain or, if VPS kicked in, held position until it had to autoland due to low battery.

Wow, great information, thank you!

 

[PTBperegrine]

Thanks Meta4 for your insight as well! I definitely had obstacle avoidance for RTH in the ON position but I admit not keeping an eye on my GPS satellite situation.

 

[Meta4]

Thanks Meta4 for your insight as well! I definitely had obstacle avoidance for RTH in the ON position but I admit not keeping an eye on my GPS satellite situation.

There are other possible reasons for OA to be unavailable (eg lighting) but OA or not OA only matters if there are obstacles to avoid and makes no difference when there's no GPS.

 

[denar]

I love this forum!

 

[Nutcracker]

Wow you guys are amazing ... just bought my first drone Mavic Pro been been reading all your posts on all subjects learnt so much ... I can’t have enough info ... all the does and donts ... so much to learn .... I think that where some people get into trouble by not reading enough here .... turn it on and go fly ....once. And it’s gone .... i’am still reading and getting ready to fly ..... many thanks again to the experts out there for all the help in many subjects

 

[PTBperegrine]

The assistance and wisdom from this forum is awesome! Thank you everyone! I’m back there today with a couple of friends who will search using the feedback from Forum members as a headstart.

 

[Jackcutrone]

The assistance and wisdom from this forum is awesome! Thank you everyone! I’m back there today with a couple of friends who will search using the feedback from Forum members as a headstart.

+1

 

[Goldengate98]

PTB, sorry for your misadventure.

JohnTX posted this link back in April, 2014. Just knowing that there is something called a Fresnel Zone has helped me to think differently about the signal line between me the bird. I hope your friends find yours.

Here is a calculator (and basic explanation) that some may find interesting:
http://www.proxim.com/products/knowledg ... -zone#feet

 

[Jackcutrone]

PTB, sorry for your misadventure.

JohnTX posted this link back in April, 2014. Just knowing that there is something called a Fresnel Zone has helped me to think differently about the signal line between me the bird. I hope your friends find yours.

Here is a calculator (and basic explanation) that some may find interesting:
http://www.proxim.com/products/knowledg ... -zone#feet

That’s great info about a topic I have wondered about for a long time. Thanks

 

[paulatkin73]

Hi, it is an extremely informative and helpful info. I wonder - is there any functionality in dji settings to program a default reaction to a loss of radio link, prior to RTH to climb up to a certain altitude above the current one? I have that set on my arducopter models and it is quite helpful.

 

[sar104]

Hi, it is an extremely informative and helpful info. I wonder - is there any functionality in dji settings to program a default reaction to a loss of radio link, prior to RTH to climb up to a certain altitude above the current one? I have that set on my arducopter models and it is quite helpful.

The M2 (and MA) retraces its last 60 seconds of flight path to attempt to regain uplink before resorting to RTH. It's not a setting - it's the default behavior.