Lost Mavic Mini - Croatia

[alx32]

Hello Pilots,

Sadly this is my first post, but upon reading the success stories on the forum I got a glitter of hope.

I've went to a bicycle trip today and upon climbing a pretty long hill I wanted to record some of the surroundings and take a rest.

So I startup my Mavic Mini v1 and start to fly around, exploring the area from the air.
At the home point there was no/very little wind so I assumed it's safe to fly.

At first I got Max Power Reached warning but i ignored it. Not so long after I got Strong Wind Warning and lost control of MM so I hit RTH. I was flying in P mode the whole time,

Foolishly, I assumed there won't be issues with RTH so I waited for drone to regain control instead of landing it immediately.

As I waited the signal was lost. Went to the last seen location but I was unable to get connection.

I would really appreciate if I could get approx location on where to look.

Here is the log file - DJI Flight Log Viewer - PhantomHelp.com
DAT file in the attachment

Thank you in advance!

 

[Deleted member 103366]

Did the wind remain fairly constant after you lost connection?
I am asking about the wind because the drone had a a lot of battery left at loss of connection and so had the potential to have been blown quite some distance.
Do you think the heights shown on the Phantomhelp page are true?
The saving grace might be, was this across a valley? If so are the hills on the far side of the valley higher than your go home height which seems to have been 31m? If so and the wind kept up then it may have flown into the hills and or their bushes or trees. But you need one of the folks here that can work with topographic maps etc. to give estimates.
From what I see the average downwind drift appears to be around 4.25m/s over the last 200second.

 

[Yogi053]

I am very inexperienced when it comes to analysing flight logs so bear with me. Looking at the display representing stick inputs, were you increasing the height of the drone near the end of the flight?
Others of greater experience than I, will, I'm sure, be along to give you good advice and further information as to the cause of your loss. Hope you do recover your AC.

 

[Prismatic]

Hello Pilots,

Sadly this is my first post, but upon reading the success stories on the forum I got a glitter of hope.

I've went to a bicycle trip today and upon climbing a pretty long hill I wanted to record some of the surroundings and take a rest.

So I startup my Mavic Mini v1 and start to fly around, exploring the area from the air.
At the home point there was no/very little wind so I assumed it's safe to fly.

At first I got Max Power Reached warning but i ignored it. Not so long after I got Strong Wind Warning and lost control of MM so I hit RTH. I was flying in P mode the whole time,

Foolishly, I assumed there won't be issues with RTH so I waited for drone to regain control instead of landing it immediately.

As I waited the signal was lost. Went to the last seen location but I was unable to get connection.

I would really appreciate if I could get approx location on where to look.

Here is the log file - DJI Flight Log Viewer - PhantomHelp.com
DAT file in the attachment

Thank you in advance!

I'm sure @slup, @boblui, or someone else will be along soon to provide a thorough analysis.

But despite their skills, I would caution against great hope in recovering your drone. At last contact, it was being blown downwind at 30 km/h with 60% of its battery remaining. It would have traveled a very long distance before it landed due to low battery, and every meter adds uncertainty to its final resting spot.

Consequently, the best estimates of the experts here are likely to point at a very large search area, probably somewhere west of the A7, over by Bakarac.

I hope I'm wrong. Good luck.

 

[slup]

Hello Pilots,

Sadly this is my first post, but upon reading the success stories on the forum I got a glitter of hope.

I've went to a bicycle trip today and upon climbing a pretty long hill I wanted to record some of the surroundings and take a rest.

So I startup my Mavic Mini v1 and start to fly around, exploring the area from the air.
At the home point there was no/very little wind so I assumed it's safe to fly.

At first I got Max Power Reached warning but i ignored it. Not so long after I got Strong Wind Warning and lost control of MM so I hit RTH. I was flying in P mode the whole time,

Foolishly, I assumed there won't be issues with RTH so I waited for drone to regain control instead of landing it immediately.

As I waited the signal was lost. Went to the last seen location but I was unable to get connection.

I would really appreciate if I could get approx location on where to look.

Here is the log file - DJI Flight Log Viewer - PhantomHelp.com
DAT file in the attachment

Thank you in advance!

I'm sorry ... but in this case it will be impossible to estimate any touch down location ... it can be all from the last position shown in your app with the "Find my drone" function ... or over 4,8km away from the last position.

All this due to that your Mini suffered from the dreaded "Uncommanded descent" decease due to deformed props that no longer could tilt the AC according to specification. In relation to your case this meant that the AC was very prone to drift with even lower wind speeds, much lower than what a healthy Mini could manage ... furthermore your Mini had lost so much thrust due to the deformed props that it actually no longer could maintain the height ... it was constantly slowly descending.

Your RTH height was set to 31m but your Mini just managed to reach 21m until it started to either keep a constant height or lose it.

From the chart below produced from your log I have pictured a part from the RTH period where the maximum height was reached (red graph) ... we see that the AC drifts (with a average speed of just above 4m/s) with the wind as the distance to HP increases (light blue graph). No stick inputs is made there at the top height but the AC looses height & have in average a tilt angle (dark blue graph) of just 10-15 degrees (according to spec it should be 20). So most probably your 2 rear props couldn't produce enough thrust to set the AC to the correct tilt & at the same time the thrust was so bad that it couldn't keep the height... or ascend to the 31m that the RTH height was set to.



If we compare the vertical speed with what was commanded (you were in RTH & the AC was in progress to ascend to 31m = full throttle input generated from the RTH automation).

We see that you applied a lot of manual throttle inputs also (black graph) despite being in RTH ... mostly for ascending. But despite this the AC looses height (red graph) & the vertical speed (dark green) shows mostly positive values ... which is in the direction of descending.



So the problem here is that we don't know if the height instability improved later when the connection was lost or if the loss of height continued ...

Taking the very last values from the log gives a very long remaining battery until auto low battery landing should kick in (which was defined automatically to 5%) ... but the touch down could have happened much faster due to the "Uncommanded descent".

The big white gap in the chart below is a period where your RC was disconnected ... so no log could be recorded to your mobile device. But later you recovered the connection shortly & the AC was accelerating & had a drift speed of 8,6m/s (yellow graph), the battery consumption ... if interpolated, was around 1% per 10,3sec. So with 55% battery left gives further 565,2sec of flight until low battery landing, this means a maximum drift distance of approx. 4,8km. But that speed is most probably a bit high ... the average calculated drift speed during the disconnect was 4,25m/s ... but that gives 2,4km anyhow ...



And hoping for some higher object in the drift path that might stop the AC is in vein unfortunately (if the height in the end of the log remained) ... this is how the terrain looked like in the drift direction, you took off from a high point & all terrain in the drift direction was lower. The distance to the water was approx. 4,5km.

This Mini is lost unfortunately ...

 

[Deleted member 103366]

I wondered why the heights were so 'odd' and not 'climbing' during RTH or...... if I was going bananas.
Does the plot on what might be google earth? show the height above the ground or the height above the take off point etc.?
How do you plot such things on whatever that imagery is? Thanks

 

[slup]

I wondered why the heights were so 'odd' and not 'climbing' during RTH or...... if I was going bananas.
Does the plot on what might be google earth? show the height above the ground or the height above the take off point etc.?
How do you plot such things on whatever that imagery is? Thanks

It's a .KML file downloaded either from Airdata or Phantomhelp ... & opened in Google Earth.

Here the full elevation profile ... marker placed on the highest point, in the end it was a disconnect (except for the very last seconds) so that's why the profile seems to be so flat, the profile is interpolated between the disconnect & reconnect.




And from here he started ... look at the view, only downhill.

 

[Meta4]

It won't help the OP but for any other owners of the original Mini, this problem was because the Mini was using very old firmware (V 1.0.244).
Normally firmware updates don't make much difference to the way a drone flies.
But the Mini had a serious issue when it was released and V1.0.5 fixed the problem.

Any Mini owners should make sure they aren't using firmware earlier than V1.0.5.

 

[alx32]

You guys confirmed what I was afraid from the start. Due to downhill terrain, strong wind and large amount of battery the AC is gone with the wind.
This could easily be prevented by lowering the altitude or landing the AC, lesson learned the hard way, Now only thing I can do is to save up for a new AC.

Anyway the analysis was awesome, I'm really impressed with the amount of data that can be pulled of and also interested in learning more myself.

Thank you very much for your effort in analyzing the logs and providing explanation, you guys rock!

 

[slup]

...But the Mini had a serious issue when it was released and V1.0.5 fixed the problem.

You're saying that the new firmware fixes the problem by only warning the pilot that the motors are rotating to fast & beeping with the ESC on the motor that are revving to fast & putting up a message on screen advising the pilot to change the props ... right?

Or have I missed anything... was it more in that FW update?

 

[Meta4]

You're saying that the new firmware fixes the problem by only warning the pilot that the motors are rotating to fast & beeping with the ESC on the motor that are revving to fast & putting up a message on screen advising the pilot to change the props ... right?

Or have I missed anything... was it more in that FW update?

There were incidents of uncommanded descent and failing to maintain appropriate pitch angles, multiple times each week before V 1.0.5, many resulting in lost drones.
Since the update such incidents are very uncommon.

 

[boblui]

I think the new firmware does not really fix the problem but just gives a warning to the user in case some of the motors are dectected to be spinning abnormally fast and suggests the user to replace the associated props. The craft will still descend uncommanded until the deformed props are replaced.

 

[Meta4]

I think the new firmware does not really fix the problem but just gives a warning to the user in case some of the motors are dectected to be spinning abnormally fast and suggests the user to replace the associated props. The craft will still descend uncommanded until the deformed props are replaced.

So what happened to all the incidents?
Why aren't we seeing so many lost Minis?
Cases like this are now rare, but they were very, very common before the update.

Of course the firmware fixed things.

 

[boblui]

So what happened to all the incidents?
Why aren't we seeing so many lost Minis?
Cases like this are now rare, but they were very, very common before the update.

Of course the firmware fixed things.

A more logical reason is that many youtube tutorials were subsequently made and people replaced the deformed props before the problem occur.

If you have looked into those uncommanded descent cases in depth, you would have noticed that it happens only if the craft tries to pitch forward by a relatively large angle either to counter the wind or follow stick inputs. If there is little wind and the pilot just flies the craft around gently. Nothing will happen but still the "prop spinning too fast" warning will show up on the APP and the correspnding motors will beep and twitch after landing. The owner then replaces the bad props so no more such incidents.

Makes sense ?

 

[Meta4]

Makes sense ?

No .. the Mini came out 14 months ago.
You joined here 8 months ago.
Firmware 1.0.5 came out 2.5 months before you joined here.
You didn't see how many of these incidents were showing up before the firmware correction.
It was a disaster and that cleared up like magic as soon as the firmware was released.

 

[slup]

No .. the Mini came out 14 months ago.
You joined here 8 months ago.
Firmware 1.0.5 came out 2.5 months before you joined here.
You didn't see how many of these incidents were showing up before the firmware correction.
It was a disaster and that cleared up like magic as soon as the firmware was released.

Well ... I was in here when they launched the Mini1 & it soon there after started to rain from the sky if that matters.

Haven't seen or heard that something else was implemented in the FW besides the screen message of to fast revving motors & beeping ESC to guide the pilot to the failing motor ... think that message had a big impact, in fact so large that people became p1ssed-off, considered it as a bug & wanted to down grade to get rid of the beeping. As soon as pilots in general understood why this feature were implemented they more willingly accepted the pop-up & beeping & changed their props accordingly.

This of course doesn't exclude some minor changes elsewhere in the FW ... but we can only speculate around that.

But in general you're right ... having the newest FW with all the annoying beeping will force pilots to pay attention to their props & by that the "Uncommanded descent" cases will slowly fade away.