Had a fly away that landed in the lake

[Marcius]

How close drone was to the water? I had some problems when it was close to water, drone went out of control, my heart stopped beating, after about 5 seconds i turn on sport and problem gone, I believe it was something to do with bottom sensor, it doesn't like when drone near water.

 

[boblui]

Analysis of the .DAT flight log file indicates that the selected IMU ( IMU1 ) was indeed faulty as the track sensed by the other IMU ( IMU0 ) matches that of the GPS much better :

 

[boblui]

How close drone was to the water? I had some problems when it was close to water, drone went out of control, my heart stopped beating, after about 5 seconds i turn on sport and problem gone, I believe it was something to do with bottom sensor, it doesn't like when drone near water.

This is my M2P flying at full speed in P mode 1 meter above water surface. All sensors were on. There was no issues at all. In your case something else must have gone wrong. So far I have not seen any incidence proven by flight logs to be caused by water surface affecting the bottom sensors.

 

[Marcius]

Yes, all good but when you fly, but difrent story when drone hoovering.

 

[boblui]

Yes, all good but when you fly, but difrent story when drone hoovering.

Hovering :

 

[fguthrie]

Although this idea is commonly held, it is completely wrong.
Compass calibration has nothing at all to do with where you are, how far you are from somewhere else or magnetic declination.
If you don't understand what compass calibration actually does, everything else you believe about compass calibration is probably wrong.
You;ll find a good explanation of what compass calibration is really about in the first post here:

A short explanation of compass function, calibration and errors.

BACKGROUND The aircraft compass is often misunderstood, both in terms of function and purpose, but it is important to understand what the compass measures, why, and what happens to that information. At the most basic level the purpose of the compass is to measure the earth’s magnetic field in...

mavicpilots.com

Without analysing the flight data from your flights, we can't tell what your issue might have been.
But understanding what compass calibration does and what it can and cannot affect, we can be sure that taking your drone from one location to another many miles away and not recalibrating, was not the issue.

The reference documentation you provided from @sar104 is excellent - thank you. It definitely cleared up some of my questions and created a few more. I switched out Tripod mode for ATTI mode on my M2P and have had at least 1 occasion where the M2P was flying unpredictably shortly after takeoff in GPS Mode (P) and switching to ATTI mode gave me control of the aircraft back. I was able to safely land the AC, re-calibrate the compass and take off again and the AC was stable. I was receiving the compass error message message during the first flight. That is the flight I was referencing above. One unrelated note concerning Tripod mode - I've learned that for me Tripod mode is more useful that Sport mode and I have since replaced Sport Mode with ATTI mode, I use Tripod mode more for filming purposes along with ATTI mode. I have flown faster (with the wind) in ATTI mode then I can in Sport mode anyway.

 

[boblui]

.... M2P was flying unpredictably shortly after takeoff in GPS Mode (P) and switching to ATTI mode gave me control of the aircraft back. ......

The problem of ATTI mode is that auto RTH will not be possible. Fly-away due to the compass being off can easily be avoided by checking whether the direction of the arrow representing the craft is correct on the map prior to taking off. I do it every time.

 

[slup]

... have had at least 1 occasion where the M2P was flying unpredictably shortly after takeoff in GPS Mode (P) and switching to ATTI mode gave me control of the aircraft back. I was able to safely land the AC, re-calibrate the compass and take off again and the AC was stable ...

The cause for that incident was most probably not a compass in need of a calibration ... instead you probably had powered on your M2P with a magnetic disturbed compass due to a magnetic compromised place which made the IMUYaw initialize in a wrong direction. Then airborne with a IMU with a wrong heading direction the AC applied thrust to the wrong motors to hold position making it fly "unpredictably". Having access to a ATTI switch in that situation will save the day as all horizontal position hold are left over to the pilot ... & by that stop the uncontrolled flyaway.

DJI's compass calibration prompt when the AC is placed in a magnetic disturbed power on spot is wrong ... a calibration in this situation will not prevent a IMUYaw error with following flyaway. If you get a calibration prompt in your app you should always question that ... you should rather power down & move away to another place. Then when powered on again check so that the drone icon on the map view in the app have the same direction to other objects there as the AC have in reality.

 

[slup]

The problem of ATTI mode is that auto RTH will not be possible ...

I'm not sure if this is different on Mavics than for Phantoms ... but on a Phantom, if you manually select ATTI mode during flight and lose signal the drone will RTH providing you have a GPS connection (it kind of swich mode to RTH that have horizontal position support). If the drone auto switches to ATTI as GPS is lost then no ... could be worth a try if you have a modded Mavic with a ATTI switch.

 

[Meta4]

The problem of ATTI mode is that auto RTH will not be possible.

If your drone loses control signal and is receiving GPS satellite signals, it will initiate RTH, switch to RTH mode and come home.
It makes no difference if you were flying in P-GPS, Sport, Tripod or Atti mode.

Of course if you are in Atti mode because you are flying in a cave or somewhere GPS is not available, RTH is not possible.

 

[fguthrie]

If your drone loses control signal and is receiving GPS satellite signals, it will initiate RTH, switch to RTH mode and come home.
It makes no difference if you were flying in P-GPS, Sport, Tripod or Atti mode.

Of course if you are in Atti mode because you are flying in a cave or somewhere GPS is not available, RTH is not possible.

That is good to know! Thank you.

 

[fguthrie]

If your drone loses control signal and is receiving GPS satellite signals, it will initiate RTH, switch to RTH mode and come home.
It makes no difference if you were flying in P-GPS, Sport, Tripod or Atti mode.

Of course if you are in Atti mode because you are flying in a cave or somewhere GPS is not available, RTH is not possible.

I was doing some research for ATTI mode and found this in a comment in a youtube video:

Flight switch position parameters
fswitch_selection|g_config_control_control_mode[0] = Tripod : factory value = 12 (Tripod)
fswitch_selection|g_config_control_control_mode[1] = Sport: factory value = 8 (Sport)
fswitch_selection|g_config_control_control_mode[2] Position (GPS): factory value =7 (Position GPS)

Switch parameter values
0 = Manual Mode (GPS position and Altitude Stabilization are disabled)
1 = GPS - no noticed difference
2 = GPS - no noticed difference
3 = ATTI Mode (Altitude Stabilization)
4 = GPS mode indicated, sport mode speed for some reason
5 = GPS - no noticed difference
6 = Beginner
7 = PGPS Mode (Normal)
8 = Sport Mode
9 = FARM Mode (Altitude stabilization with RTH capability)
10 = GPS - no noticed difference
11 = GPS - no noticed difference
12 = Tripod mode

What interests me is number 9. I have not validated the parameters above, but it implies that RTH works in FARM mode but not in ATTI mode ... thoughts?

 

[Slloyd]

Analysis of the .DAT flight log file indicates that the selected IMU ( IMU1 ) was indeed faulty as the track sensed by the other IMU ( IMU0 ) matches that of the GPS much better :

View attachment 109789

Thanks for that info. Is there anything I can do to not let this happen again? Settings? I did compass calibrate before launching. Any advise appreciated. Been flying over a year and never had this issue before.

 

[Slloyd]

The cause for that incident was most probably not a compass in need of a calibration ... instead you probably had powered on your M2P with a magnetic disturbed compass due to a magnetic compromised place which made the IMUYaw initialize in a wrong direction. Then airborne with a IMU with a wrong heading direction the AC applied thrust to the wrong motors to hold position making it fly "unpredictably". Having access to a ATTI switch in that situation will save the day as all horizontal position hold are left over to the pilot ... & by that stop the uncontrolled flyaway.

DJI's compass calibration prompt when the AC is placed in a magnetic disturbed power on spot is wrong ... a calibration in this situation will not prevent a IMUYaw error with following flyaway. If you get a calibration prompt in your app you should always question that ... you should rather power down & move away to another place. Then when powered on again check so that the drone icon on the map view in the app have the same direction to other objects there as the AC have in reality.

Thanks for this info.

 

[Meta4]

What interests me is number 9. I have not validated the parameters above, but it implies that RTH works in FARM mode but not in ATTI mode ... thoughts?

I don't know what that's about but it does not say that RTH won't work in atti mode at all.
But I do know that what I put in post #30 is true and accurate. and easily proved.

 

[fguthrie]

I don't know what that's about but it does not say that RTH won't work in atti mode at all.
But I do know that what I put in post #30 is true and accurate. and easily proved.

Thanks. I've never seen that table until today. It is interesting, but how acccurate it is I don't know. If you know the RTH works in ATTI mode that is good enough for me.

 

[Alloy]

I failed to notice if APAS or obstacle avoidance was switched on. Does an IMU error override the sensors?

 

[mm crashed]

Crap! Had the same thing happen to me today on a MM drone that is less than a month old. No warnings about loss of signal. I viewed my GPS track on the phone and it shows 86% battery, full signal,12 satellites, in cinema mode (so not even flying fast)! Has anyone had success with DJI in getting warranty service? Clearly I cannot turn the drone into them since it is at the bottom of a body of water. Any suggestions in dealing with them before I call? I imagine I may only get one shot at replacement.

 

[Meta4]

Has anyone had success with DJI in getting warranty service?
Clearly I cannot turn the drone into them since it is at the bottom of a body of water.
Any suggestions in dealing with them before I call? I imagine I may only get one shot at replacement.

Lots of people have received replacements from DJI but the key point is that they have to be able to show evidence that the cause of the incident was a DJI issue.
When the drone is not able to be retrieved, that can make things difficult.
Sometimes the recorded flight data is enough to show the cause of the incident - sometimes not.

Crap! Had the same thing happen to me today on a MM drone that is less than a month old. No warnings about loss of signal.
I viewed my GPS track on the phone and it shows 86% battery, full signal,12 satellites, in cinema mode (so not even flying fast)!

You haven't given enough information about your incident for anyone to be able to make any helpful comments on it.
What happened?
What does the recorded flight data show?

 

[mm crashed]

Lots of people have received replacements from DJI but the key point is that they have to be able to show evidence that the cause of the incident was a DJI issue.
When the drone is not able to be retrieved, that can make things difficult.
Sometimes the recorded flight data is enough to show the cause of the incident - sometimes not.

You haven't given enough information about your incident for anyone to be able to make any helpful comments on it.
What happened?
What does the recorded flight data show?

Thank you Meta! I am new to this, so I just figured out how to view my flight log with Air Data. I attached it. I was also able to view my flight and controls through the DJI app. I don't see me pressing down on the left joystick for it to descend.

Here is a link to the AirData page: I also attached the notifications from AirData, flight log and *.DAT file if that helps