Drone crash - what did I do?

cybervet · Mar 28, 2019

If the aircraft gave no warning for compass interference and dji will not let you switch to Atti mode then DJI should replace the drone under the guarantee .

Meta4 · Mar 28, 2019

cybervet said:
If the aircraft gave no warning for compass interference and dji will not let you switch to Atti mode then DJI should replace the drone under the guarantee .

It's quite normal ... the compass error only shows when the magnetic field is strong enough

cybervet · Mar 28, 2019

Meta4 said:
It's quite normal ... the compass error only shows when the magnetic field is strong enough

Yeap Thats what I say also , if it is quite normal that you can't safely fly due to this kind of interference and you still don't get a warning then it's DJI fault and should be replaced. Just consider what will happen if you have a human injury during the flyaway, who will be responsible?

AnzacJack · Mar 28, 2019

We do have some responsibility here i believe, but thats me speaking from years of experience. Im guessing this is not something that someone new to this pastime is going to know anything about.
I think that it should at least be well documented in the manual, that should be in the box with clear instructions.
They make these things easier and easier to fly with little or no skills, and are not interested in education

Simmo · Mar 28, 2019

cybervet said:
Yeap Thats what I say also , if it is quite normal that you can't safely fly due to this kind of interference and you still don't get a warning then it's DJI fault and should be replaced. Just consider what will happen if you have a human injury during the flyaway, who will be responsible?

You DO get a warning, if you are diligent in your Preflight checks!!!
When the lovely young lady says, "Your Homepoint has been set, please check it on the map".............
Do exactly that!!!! Check it on the map!!
Is the HP in the correct location, and is the AC facing the right way on the map as on the ground??
If it is all right.. take off!!!

Wher I do agree with you though, and others, is that this is not SPECIFICALLY spelt out in the manual.
More often than not, people learning this valuable knowledge, are learning it after thier flight logs have been analysed...

AnzacJack · Mar 28, 2019

Simmo said:
You DO get a warning, if you are diligent in your Preflight checks!!!
Wher I do agree with you though, and others, is that this is not SPECIFICALLY spelt out in the manual.
More often than not, people learning this valuable knowledge, are learning it after thier flight logs have been analysed...

I know that here in Australia, most of the reputable dealers have the CASA cards about rules inserted into the box.
Maybe a decent preflight checklist is needed, and then a small booklet explaining the check list. It doesn’t need to be crazy in depth. Or maybe something built into the DJI Go apps

AnzacJack · Mar 28, 2019

DJI aseem to be happy imposing restrictions on us in the name of safety, surely check listing can be introduced in the name of safety

Meta4 · Mar 28, 2019

cybervet said:
Yeap Thats what I say also , if it is quite normal that you can't safely fly due to this kind of interference and you still don't get a warning then it's DJI fault and should be replaced. Just consider what will happen if you have a human injury during the flyaway, who will be responsible?

We know the issue and what causes it.
We know how to check before flying to ensure everything is correct.
If you want to avoid this sort of thing, it's quite simple.

Simmo said:
You DO get a warning, if you are diligent in your Preflight checks!!!
When the lovely young lady says, "Your Homepoint has been set, please check it on the map".............
Do exactly that!!!! Check it on the map!!

That only checks that you have got a GPS location fix.
It does nothing to check that your compass has correctly identified where north is.

Simmo · Mar 28, 2019

If the AC is pointing SSE, and the App/map shows it pointing SSE, surely it knows where North is?
I dont see that the Cardinal point makes a differance??
Or am I totally wrong in my thinking???
@sar104

Benton BS · Mar 28, 2019

I am positive my AC was in ATTI mode - probably should not have been, but I used it like that previously with no issues.
The concern I have now with this Mag interference issue - and as Meta4 noted, that it's probably too late once you notice it....
This is a bit concerning with a $1,400 unit and a crash a near certainty. If the lack of control I had is the result of the interference, then what would we be looking for at take -off? I only ask that because it appeared I had a "all green lights"
and ready for take-off. Again, it got in the air and it was gone until it hit the tombstone.
would anyone send this back to DJI? Or do I have an operator issue and contemplate purchase of another unit?

sar104 · Mar 28, 2019

Simmo said:
If the AC is pointing SSE, and the App/map shows it pointing SSE, surely it knows where North is?
I dont see that the Cardinal point makes a differance??
Or am I totally wrong in my thinking???
@sar104

That's right. Any initial direction will do as long as the aircraft gets that direction correct.

sar104 · Mar 28, 2019

cybervet said:
If the aircraft gave no warning for compass interference and dji will not let you switch to Atti mode then DJI should replace the drone under the guarantee .

And how do you propose that the aircraft is going to be able to check whether the magnetic field that it sees is just the earth's magnetic field, and hasn't been distorted by local ferromagnetic material?

Tbredhed · Mar 28, 2019

Do the compass, IMU and GPS eventually come into agreement if the flight was to last long enough?

I usually fly from my deck at home or dock at camp and orient the drone facing south and check the app to ensure this.

My thought at both locations would be to apply full elevator and climb and hope the error resolves.

Dave A · Mar 28, 2019

I think this question is still on topic.
I've had my MPP for about a year and never have I had to do a compass or IMU calibration.
Before I take off I do check that my MPP and the arrow indicator on the map are pointing in the same direction........or lat least "close" to the same direction.

My question is there has always been about a 10 degree difference between the arrow on the map and the actual direction of the drone. How much deviation is too much? Do we know when it's enough to cause a problem?

Note; I use a Crystalsky and there also has been a certain amount of arrow wobble.

sar104 · Mar 28, 2019

Tbredhed said:
Do the compass, IMU and GPS eventually come into agreement if the flight was to last long enough?

I usually fly from my deck at home or dock at camp and orient the drone facing south and check the app to ensure this.

My thought at both locations would be to apply full elevator and climb and hope the error resolves.

If the disagreement is large, generally no. The initial response of the FC appears often to be to slowly rotate the aircraft while holding the IMU yaw constant until the compass yaw agrees with the IMU yaw. In principle that seems like a reasonable approach, although I would probably have gone with the converse - reset the IMU yaw to the compass yaw. Since the compass yaw defined the initial IMU yaw and since magnetic interference at the takeoff location appears to be far more common than magnetic interference in flight, I cannot see how that strategy could cause more problems than it solves.

In any case, for large errors, uncontrolled flight generally occurs before the FC manages to complete its correction strategy, leading either to a crash or a switch to ATTI mode.

sar104 · Mar 28, 2019

Dave A said:
I think this question is still on topic.
I've had my MPP for about a year and never have I had to do a compass or IMU calibration.
Before I take off I do check that my MPP and the arrow indicator on the map are pointing in the same direction........or lat least "close" to the same direction.

My question is there has always been about a 10 degree difference between the arrow on the map and the actual direction of the drone. How much deviation is too much? Do we know when it's enough to cause a problem?

Note; I use a Crystalsky and there also has been a certain amount of arrow wobble.

A consistent 10° offset is a bit surprising. It seems that either it would have to be due to you always taking off with exactly the same level of external interference or, if it is due to a magnetic component on the aircraft that has not been calibrated out, always taking off with the aircraft pointing in the same direction. Depending slightly on the details, I'd probably recommend calibrating.

bobscheel53 · Mar 28, 2019

Would switching to sport mode stop the runaway?

sar104 · Mar 28, 2019

bobscheel53 said:
Would switching to sport mode stop the runaway?

No - but it might make it run away faster.

Dave A · Mar 28, 2019

sar104 said:
A consistent 10° offset is a bit surprising. It seems that either it would have to be due to you always taking off with exactly the same level of external interference or, if it is due to a magnetic component on the aircraft that has not been calibrated out, always taking off with the aircraft pointing in the same direction. Depending slightly on the details, I'd probably recommend calibrating.

Amazing. As usual your help is spot on. I neglected to mention in my question that in fact I do usually take off from the same location, 90% of the time, and start facing in the same direction. How did you know this......I guess because you understand how the compass works in relation to it's surroundings and flight. Thank you.