Drone crash - what did I do?

[Mav1c]

Because I got my M2P the day before Thanksgiving and I’m in the Northeast US(Vermont) it’s been rather cold during every flight so far. Therefore, I’m usually always powering on somewhere where it is warm like a house or a car and then going outside for takeoff. Because of this I am ALWAYS having to do a compass calibration. I do my little spinning dance and then I’m good to go. I get the error even if I do power up away from magnetic interference because almost every time I land, I scurry back into the warmth and download footage to the phone before powering down..

The end result is I am so used to this process it’s just become part of the pre flight process. Just as important as folding out the arms and removing the gimbal clamp. Too risky on a drone that costs this much.

 

[Meta4]

Because of this I am ALWAYS having to do a compass calibration. I do my little spinning dance and then I’m good to go. I get the error even if I do power up away from magnetic interference because almost every time I land, I scurry back into the warmth and download footage to the phone before powering down..

The end result is I am so used to this process it’s just become part of the pre flight process. Just as important as folding out the arms and removing the gimbal clamp. Too risky on a drone that costs this much.

That's a rather confused idea of what compass calibration does.
Calibrating the compass doesn't "fix" anything and doesn't make your flight any safer.

 

[BudWalker]

Because I got my M2P the day before Thanksgiving and I’m in the Northeast US(Vermont) it’s been rather cold during every flight so far. Therefore, I’m usually always powering on somewhere where it is warm like a house or a car and then going outside for takeoff. Because of this I am ALWAYS having to do a compass calibration. I do my little spinning dance and then I’m good to go. I get the error even if I do power up away from magnetic interference because almost every time I land, I scurry back into the warmth and download footage to the phone before powering down..

The end result is I am so used to this process it’s just become part of the pre flight process. Just as important as folding out the arms and removing the gimbal clamp. Too risky on a drone that costs this much.

You could probably achieve the same results by letting the Mavic rest on the ground for the length of time it takes you to do the compass calibration. The Yaw value was initialized from the magnetometers which are incorrect indoors. Outdoors the magnetometers become correct but the Yaw value isn't because there is a delay in correcting Yaw.

 

[Mav1c]

That's a rather confused idea of what compass calibration does.
Calibrating the compass doesn't "fix" anything and doesn't make your flight any safer.

Maybe I’m mistaken as I’ve never experienced any erratic issues other than some slight drifting in my back yard that I now attribute to poor gps signal (took off too soon). I figured that not doing a compass calibration could cause what happened to the OP.

Can you educate me on what the compass calibration does from a technical standpoint? I am of the understanding that the magnetic interference gets the compass a little out of whack and so getting away from the metal source and moving it around 360° ensures that there is no more metal interference. I remember doing this years ago when the first iPhones came out with compasses. I honestly hadn’t put that much more thought into it. I do love to learn though!

 

[Mav1c]

You could probably achieve the same results by letting the Mavic rest on the ground for the length of time it takes you to do the compass calibration. The Yaw value was initialized from the magnetometers which incorrect indoors. Outdoors the magnetometers become correct but the Yaw value isn't because there is a delay in correcting Yaw.

Good to know! I didn’t know that. I thought that the only way to get rid of that error was to do what it says and move 360° But then again, I am not entirely sure I understand the compass calibrations. See above

 

[sar104]

Good to know! I didn’t know that. I thought that the only way to get rid of that error was to do what it says and move 360° But then again, I am not entirely sure I understand the compass calibrations. See above

I put a fairly detailed functional description of the compass and its calibration process in this post:

Mavic compass needs to be calibrated before each flight

The compass is one of the most misunderstood facets of drone flying. Possibly but i understand them well enough given i have to use the things in my daily job outside of it. It's not possible because moving any distance makes no difference to compass calibration. Distance specifically no...

mavicpilots.com

 

[Mav1c]

I put a fairly detailed functional description of the compass and its calibration process in this post:

Mavic compass needs to be calibrated before each flight

The compass is one of the most misunderstood facets of drone flying. Possibly but i understand them well enough given i have to use the things in my daily job outside of it. It's not possible because moving any distance makes no difference to compass calibration. Distance specifically no...

mavicpilots.com

Thank you sar104! I always thoroughly enjoy reading your analysis on flight data.

 

[BudWalker]

Good to know! I didn’t know that. I thought that the only way to get rid of that error was to do what it says and move 360° But then again, I am not entirely sure I understand the compass calibrations. See above

I should add that if you do try this that you need to wait until the red triangle heading indicator on the map display is consistent with the actual heading of the M2P. It will be slowly turning to the correct orientation and may not have finished before the magnetic interference warning goes away.

 

[Kilrah]

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.

It is not technically possible to give a warning about the situation the OP was in. Only the pilot can verify the information.

 

[Mav1c]

I should add that if you do try this that you need to wait until the red triangle heading indicator on the map display is consistent with the actual heading of the M2P. It will be slowly turning to the correct orientation and may not have finished before the magnetic interference warning goes away.

Also good to know. Is there a minimum amount of time to let the bird “warm up” if you will? Just to ensure that everything has time to acclimate? What steps do you guys go through before take off?

 

[Benton BS]

All,
Great info. Much to learn and try and understand. I'll go back to my first post.....Everything looked to me to be a very
normal take-off. When the MP2 reached approx. 20ft I sent the bird on it way. After a couple seconds it took off.
54 miles an hour.....circled and the 5lb unit crashed into a granite tombstone and shattered.
1. What if that had been a person? Unit was uncontrollable - from what I tried in the 30-some seconds it was in the air
2. Is there something from DJI that should be made a little more clear in the operators manual regarding this interference
issue?? Currently I would be concerned about anywhere I would take off.
3. I'll admit - when that thing came zooming down and crashed - I was very concerned and nervous as I had NO IDEA
where it was going.
My point is simply that it looked to me that I had a normal take-off - then it was gone.
Scary and concerning. As noted...MUCH to learn

 

[DanMc]

You should absolutely send the flight log to DJI and ask some very polite questions. I'm betting that they'll send you a new drone.

 

[Benton BS]

You should absolutely send the flight log to DJI and ask some very polite questions. I'm betting that they'll send you a new drone.

Thank you DanMc. I'll do that.
I also will tell all of you...that when the Unit crashed the battery flew about 15ft from point of impact, which was a poor souls granite tombstone....that by the time I was able to run and start picking up the parts...the battery had ignited in flames and started a small fire.
Think about that if you experience a crash out in the woods or some remote location.........................

 

[Bigbird48]

There are two factors to consider.
The size of the steel object
The distance between the compass and the steel object.
A good sized steel screw at one inch has a bigger magnetic effect on the compass than 100000 tons of steel at this distance:

wow who would think a wood screw in a 2x4 would cause compass errors, thats crazy.

 

[Mossiback]

... I’m usually always powering on somewhere where it is warm like a house or a car and then going outside for takeoff...

You could power up the RC and your display device and have Go 4 running before you go outside and power up your Mavic. That way you should not have to mess with any calibrations. Just make sure the Mavic and Go 4 indicators agree on the direction it is pointed before takeoff.

 

[awood35]

Sounds like the same magnetic interference experience I had days ago...I had (enough) control left to bring it back towards me and hit a tree.

DJI conducted their assessment and have either fixed mine or are sending me another.

FYI, mine was bought from B&H less than 5 months ago so it’s covrred under Warrenty

 

[BudWalker]

Also good to know. Is there a minimum amount of time to let the bird “warm up” if you will? Just to ensure that everything has time to acclimate? What steps do you guys go through before take off?

There have been several posts with before launch checklists. They all seem to miss these two;
1 - Check that the AC orientation is consistent with red triangle heading indicator on the map display. The suggestion above is essentially this. But, it also can be used to detect and prevent the scenario where the AC is launched from a geomagnetically distorted site.
2 - Wait until the gpsHealth is 4 or 5. This means that the FC has confidence in the Lat/Long it's computing from the GPS, IMU and magnetometer data. It's shown in the bar graph display on the Go App display and on the controller.

 

[BudWalker]

wow who would think a wood screw in a 2x4 would cause compass errors, thats crazy.

As they say, it's not the size that counts. It's a question of whether the magnetometer is within the distortion extent. The Phantom series has the magnetometer in the bottom part of the leg all but touching the ground. A well placed buried steel washer is enough to be a problem. Detecting this would be almost impossible with any other method besides determining if the red triangle heading indicator in the map display is consistent with the AC's actual heading.

 

[DanMan32]

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?

Simple: GPS delta. If the AC flies a few feet in what it thinks is north based on compass, but GPS says it moved east, then the compass is wrong and flight control should offset the compass dynamically.

If one of my old phones not having a compass/magnetonometer could figure out heading just by GPS when moving, so can the flight control.

In no case should the AC go flying 50mph without the pilot directing it to do so.

 

[DanMan32]

Note that many (most?) Android devices will have their compass frequently needing calibration to correctly read north. That could distort your map view.
IOW if you are facing north, and your AC is facing north, then all being correct, your AC should point up on your display. However if your device compass believes you are facing east, the AC will be pointing left.
The radar N should be correct though in it being north, no matter which way the N is pointing.