Watch the Compass at 2:29.  He hit RTH and saved her.  

Pretty sure he took off from the hood of a vehicle, that might have screwed the compass readings from the get go.

Wow, that was a huge compass jump counterclockwise at 2:29, but looking again the MM heading did not change.  No wonder the flight sofware went crazy trying to correct for this.  He was one lucky individual to get the MM back.  Thanks for sharing this video Minnesota.

Is the hood to blame or the wires?   

Minnesota Posted at 1-19 07:36
Is the hood to blame or the wires?

I would think it was the hood and he was lucky, what normally happens I’ll explain below.

The best way I can explain this is. If you put your Aircraft on the ground in normal circumstances, start it up, then lift it up and turn it 90 degrees to the right both your compass heading and IMU will both move together 90 degrees and no problems.
If you put your Aircraft on the ground and there is magnetic interference only the heading of your compass will change, your aircraft will still take off. But when it clears magnetic interference compass will then move to correct heading which you would think was great. But No, what happens is IMU is then conflicted and confused because of this sudden movement by compass, so you receive IMU exceptional heading warning, your aircraft cannot deal with data conflict so decides to switch to Atti mode dropping gps in favour of compass simply because aircraft can fly without gps but not compass.

While I can’t be certain OP picked up interference from the ground or surrounding area it is the most common cause.
I have seen many cases where people start their aircraft in or on their car in their house and then bring it outside so damage is already done and we will see exact same warnings and and reaction from aircraft.

Although these warnings weren’t admitted it certainly looked like atti mode and I think log will show that it probably was .

It looks like many problems are associated with RTH or programmed smart behaviour of MM in general (in combination with interference)...I guess that manual return could end up differently. Once I got sensor error warning being on one side of the road (Mini and controller) with power lines on the other side. No more warning when I changed place...

Note how it hit 44 MPH ...

I think mavic mini is really poorly Programmed. This is not the only fly away i saw and in all of the the mavic mini did not Switch to atti mode. As the operator is also not able to do this there is no was to control the drone but hoping that it clears the interference. This is really worrying

Wow scary recovery, flights logs could shine some light.

What is interesting it that it crashed into a tree and somehow regained its balance and then began a RTH.  It's like it needed the IMU to be shaken, then did some type of reset.
How important is the compass during RTH?

Minnesota Posted at 1-19 07:36
Is the hood to blame or the wires?

Good question.

Different opinions ofcourse.

If compass was interfered because of the hood of the car than this is seen after taekoff, after yaw inputs it goes crazy.

After takeoff and in forward flight the arrow of the aircaft orientation indicator points the correct heading. This ofcourse if the OP did look at his drone and had his RC in front of him, wich is how we all stand and watch opur drone.
Beacuse of this good orientation and beacuse the compass goes weird after 2.29....do not think its because of the hood.
Guess not in ATTI as he pressed RTH and on the screen says going home, and watch the arrow; its points towards home as craft is flying steady.

44 MPH probably not reached, when data inputs are wrong the speed calculation goes often wrong as well.
Love to see this flightlog.

Seen few files now where compass goes crazy like this after some minutes, DJI did investigate and replaced those MM (and a MA)
And seen few files where the RTH did bring the compass back in normal yaw values again, like this one.

cheers
JJB

Minnesota Posted at 1-19 09:42
What is interesting it that it crashed into a tree and somehow regained its balance and then began a RTH.  It's like it needed the IMU to be shaken, then did some type of reset.
How important is the compass during RTH?

I think when Rth comes on craft was not heading towards home until it eventually straightened up so it looked totally confused if it was in correct Rth it would not have reacted this way, it looked like no gps lock and I believe your correct it looked like IMU was correcting itself and that’s how craft got back on track .
As I said earlier compass affected on hood but as soon as it clears hood it corrects itself that doesn't mean IMU can, we have seen so many yaw problems well into flight .

hallmark007 Posted at 1-19 10:34
I think when Rth comes on craft was not heading towards home until it eventually straightened up so it looked totally confused if it was in correct Rth it would not have reacted this way, it looked like no gps lock and I believe your correct it looked like IMU was correcting itself and that’s how craft got back on track .
As I said earlier compass affected on hood but as soon as it clears hood it corrects itself that doesn't mean IMU can, we have seen so many yaw problems well into flight .

Looks like he initiated RTH at 2:31, just seconds after it began Flying Away, it's almost as if he had experienced this before.  He didn't panic.

First, I don’t see how RTH could save such a situation, I don’t think it had any effect on it. Except maybe accentuating the problem (the RTH was asking the drone to go one way, the bad compass was causing it to move the other way and the actual position was getting further and further from the desired position, causing the drone to accelerate more and more). In any other way, RTH is working with the same data, it can’t bring it home when the drone’s systems no longer know the correct position and heading. The fact that the problem corrected itself after a crash I think points to a hardware problem within the drone. Maybe some contact problem?...
Second, I was wondering... if something like this happens... what’s the best course of action the pilot could take? I think I would first check if i’m low enough to land immediately. If not, I would take it high as fast as possible to ensure not hitting anything and to prevent losing contact if it goes beyond an obstacle of some sort. Then I would try yawing the drone and see if that causes it’s running away to stop. If that fails, try the right stick but most likely the drone is already gone...

Minnesota Posted at 1-19 11:39
Looks like he initiated RTH at 2:31, just seconds after it began Flying Away, it's almost as if he had experienced this before.  He didn't panic.

I see it different ;

If you look at the aircraft orientation indicator ;
first a rapid heading change (see the arrow move other direction),
than moving backwards,
followed by the OP to initiate a RTH.

cheers
JJB

As I see it: AC saved it despite him hitting RTH and taking off from the bonnet.

Minnesota Posted at 1-19 11:39
Looks like he initiated RTH at 2:31, just seconds after it began Flying Away, it's almost as if he had experienced this before.  He didn't panic.

If he habitually takes off from the hood of his truck, then very likely he has had this happen before. And the error happens long before the aircraft takes off. It happens as soon as he powers it up while it is sitting on the hood of the truck. The compass error does NOT clear when he lifts above the hood, it remains, and has no effect until a manouvre is made that requires use of compass data. Normal flying does not use the compass, it only happens when one of the semi-autonomous actions is invoked.

I think DJI makes amazing products which is why I have so many after having the Spark but with the DJI Mavic Mini.. it's just bad.  47mph+ on the telemetry when it says the top speed is only 30mph while losing altitude and people think it's user error?

All the DJI products I have never scared me like this.

Minnesota Posted at 1-19 07:36
Is the hood to blame or the wires?

Looks like wires.
Had it been hood**, would have been problems within a meter with a short time delay in seconds.

**Assuming hood is even metal.

Geebax Posted at 1-19 17:24
If he habitually takes off from the hood of his truck, then very likely he has had this happen before. And the error happens long before the aircraft takes off. It happens as soon as he powers it up while it is sitting on the hood of the truck. The compass error does NOT clear when he lifts above the hood, it remains, and has no effect until a manouvre is made that requires use of compass data. Normal flying does not use the compass, it only happens when one of the semi-autonomous actions is invoked.

"Normal flying does not use the compass,"

Compass is in used through out flight.  Drone's need to know their facing direction to calculate which motors to increase / decrease in speed, to travel in specified flight direction;  Flight direction which may or may not be direction drone is facing.

It is interesting that at he crossed over the power lines 10 - 20 seconds earlier and the compass didn't glitch.  

Geebax Posted at 1-19 17:24
If he habitually takes off from the hood of his truck, then very likely he has had this happen before. And the error happens long before the aircraft takes off. It happens as soon as he powers it up while it is sitting on the hood of the truck. The compass error does NOT clear when he lifts above the hood, it remains, and has no effect until a manouvre is made that requires use of compass data. Normal flying does not use the compass, it only happens when one of the semi-autonomous actions is invoked.

That's not how the compass works. The AC would get confused as soon as he got far enough from the hood if that was the cause. The compass would switch to the correct position, while the IMU would indicate no rotation. It's pretty clear the hood was not the issue.

HedgeTrimmer Posted at 1-19 23:00
Looks like wires.
Had it been hood**, would have been problems within a meter with a short time delay in seconds.

Agree   see #13


Taking off with a interfered compass will show once the drone is commanded to do YAW moves.
As this happens after many yaw inputs and after more than 2 minutes....

No compass problem at the beginning in flight.  Btw  Aircraft Orientation Indicator shows correct function after take off.

IMU is just processing and measuring data fron its own and external sensors, could not be interfered by a hood of a car (or other metal stuff).

cheers
JJB

The issue seems to happen as soon as the AC is above some kind of power lines it kind of looks similar to this one
https://youtu.be/pG2xc6PxBYQ

djiuser_6BBFyi9TSaue Posted at 1-20 01:01
The issue seems to happen as soon as the AC is above some kind of power lines it kind of looks similar to this one
https://youtu.be/pG2xc6PxBYQ

The poster says the power lines had been disabled for years.  DJI has not closed his case as yet.

I don't understand how *any* interference could cause such a massively violent reaction. Even if the compass changes to a totally different heading, shouldn't the drone just start flying in a random direction? In that video it almost looks like it suddenly tumbles over...

HedgeTrimmer Posted at 1-19 23:00
Looks like wires.
Had it been hood**, would have been problems within a meter with a short time delay in seconds.

Under the hood you've got an engine, usually, and it's made out of alu, iron and alikes. All around you've magnetic interfering items.

Ice_2k Posted at 1-20 02:33
I don't understand how *any* interference could cause such a massively violent reaction. Even if the compass changes to a totally different heading, shouldn't the drone just start flying in a random direction? In that video it almost looks like it suddenly tumbles over...

Some comments suggest a bird-strike, resulting in some damage not allowing stable flight.

Minnesota Posted at 1-20 03:33
Some comments suggest a bird-strike, resulting in some damage not allowing stable flight.

unfortunately that doesn't explain why the compass is all messed up post strike....

Minnesota Posted at 1-20 03:33
Some comments suggest a bird-strike, resulting in some damage not allowing stable flight.

As I explained earlier what happens when you get magnetic interference pre take off, the video will explain exactly what can occur how to avoid etc.

hallmark007 Posted at 1-20 05:25
As I explained earlier what happens when you get magnetic interference pre take off, the video will explain exactly what can occur how to avoid etc.

https://youtu.be/ZL6NbpzJVJI

If it was a pre-takeoff issue, is there any explanation of why the fly-away happened, when it happened, and where it happened during his route?  It was not doing much for 15 seconds or so before the indicator flipped 90 degrees, and it appeared that the indicator and camera were in good sync once the drone was  on course.

Minnesota Posted at 1-20 06:07
If it was a pre-takeoff issue, is there any explanation of why the fly-away happened, when it happened, and where it happened during his route?  It was not doing much for 15 seconds or so before the indicator flipped 90 degrees, and it appeared that the indicator and camera were in good sync once the drone was  on course.

It is wholly to do with IMU and compass working together and the problem is nearly always caused at take off, it’s very hard to encounter magnetic interference while flying, not impossible but difficult , so while everything seems in order it can just take a sudden yaw left or right and cpu realizes something is not correct, in this instance it looks like recovery came quickly, I don’t think it was the Rth as much as the systems recovery.
I have noticed in all new dji craft this recovery improving greatly over the years going back 2 years this would have been a disaster and most likely a crash .

And all of this is speculation because we haven’t seen flight log, but it’s an experienced guess .

HedgeTrimmer Posted at 1-19 23:00
Looks like wires.
Had it been hood**, would have been problems within a meter with a short time delay in seconds.

Wires have no effect on the aircraft. If you wish to challenge that, then please reply with a scientific answer.  The hood or other ferrous items in the car are the culprit, nothing else.
I have a friend who uses a P4 to do close-up inspections of 220,000 volt transmission lines and they do not affect his aircraft.

HedgeTrimmer Posted at 1-19 23:09
"Normal flying does not use the compass,"

Compass is in used through out flight.  Drone's need to know their facing direction to calculate which motors to increase / decrease in speed, to travel in specified flight direction;  Flight direction which may or may not be direction drone is facing.

In normal flying, the compass is only used for direction indication, it is only in the advanced flight modes plus the autonomous modes when the compass comes into play to control the direction of the aircraft, and that's when erratic flying commences.

Didnt anybody catch his comment, " OH %^^$, I CRASHED IT AGAIN", I would like to know if his first crash was of the same type?

fans7e30011f Posted at 1-20 13:36
Didnt anybody catch his comment, " OH %^^$, I CRASHED IT AGAIN", I would like to know if his first crash was of the same type?

Just look at his channel.  He had previously posted a video of him crashing into a tree by a lake.

I also found that comment particularly funny because he was videoing the construction of his church.  Lol!

44.6 MILES??? Ahaha this probably is going to be the fastest MM ever!

As most of you said, there are 2 things that I suspect;
1) He's taking off from the damn metal car hood, I experienced it myself, and it's the worst idea. If the drone thinks it's normal on the hood, it'll be crazy as hell in the air.
2) At the exact time the compass data screws, he is flying over the electric lines. I'm not a professional so I don't know what is the voltage there and what is the magnitude of magnetic field that it creates. But it seems like a rare coencidence right?

AntDX316 Posted at 1-19 21:54
I think DJI makes amazing products which is why I have so many after having the Spark but with the DJI Mavic Mini.. it's just bad.  47mph+ on the telemetry when it says the top speed is only 30mph while losing altitude and people think it's user error?

All the DJI products I have never scared me like this.

In regards to the 47+ mph, that is nothing!  My original Mini hit almost 65mph in a very similar looking video (minus the launching from a vehicle and minus any power lines).

With rotor aircraft like a quadcopter or a helicopter, horizontal and vertical speed is all about tilt angle and RPM of the motor.    To hover, a given RPM has to be maintained with nearly zero tilt.  However, if the tilt is increased, more of the thrust is directed in a horizontal direction, thus decreasing lift and increasing horizontal movement.

In the video, you can see that the tilt increases past the maximum capabilities of the gimbal, so it is not surprising to see it accelerate horizontally and lose altitude vertically.  That is what would be expected with the unexpected increased tilt while the IMU was losing its mind.

I would agree with it being user error taking off from the hood of his vehicle.  However, I'm very surprised that the software didn't throw up some sort of warning or error about the compass before takeoff.  You can see shortly after he takes off, the compass heading of the drone does a nearly 90 degree turn without an associated turn of the physical device.  Quite honestly, I was surprised the flight went as well as it did for as long as it did.

KlooGee Posted at 1-20 14:06
In regards to the 47+ mph, that is nothing!  My original Mini hit almost 65mph in a very similar looking video (minus the launching from a vehicle and minus any power lines).

With rotor aircraft like a quadcopter or a helicopter, horizontal and vertical speed is all about tilt angle and RPM of the motor.    To hover, a given RPM has to be maintained with nearly zero tilt.  However, if the tilt is increased, more of the thrust is directed in a horizontal direction, thus decreasing lift and increasing horizontal movement.

Yeah, I didn't want to put 65mph+ as no one here who has seen that video would make sense of it in their mind so I omitted from saying it.

Having a drone with problems only adds to the stress in life.  Having a drone that works that just sits is boring.
Coming up with all sorts of reasons why the drone didn't work without truly understanding that something is wrong with the design internally is not doing it right.  The M2s are built super well.  The DJI Mini makes DJI look bad.

Geebax Posted at 1-20 12:55
Wires have no effect on the aircraft. If you wish to challenge that, then please reply with a scientific answer.  The hood or other ferrous items in the car are the culprit, nothing else.
I have a friend who uses a P4 to do close-up inspections of 220,000 volt transmission lines and they do not affect his aircraft.

When your friend inspects transmission lines, does he impact drone into wires?  Betting he doesn't.

Whereas, in video, it looks like pilot flew drone into wires, and drone got very briefly tangled up; resulting in drone loosing stable flight, and having problems recovering.