Mavic crashed into office building...what did I do wrong?

[esm123]

I take that back..the motor current happened at the last moments. It had crashed at that point. What is speed error? This is becoming more confusing.

 

[Robbyg]

What kind of GPS issue would cause erratic flight? I've never heard of such a thing.

msinger, Budwalker do you think based on his low altitude in between so many high rise buildings that it might have been GPS signal reflections that caused it?



I remember a YouTube video, I think it was from Casey. He took off between high rises and the Mavic went Berserk.

Rob

 

[BudWalker]

I was expecting but don't see any evidence that the Yaw value was incorrect at launch. This would have been indicated if it looked like the Mavic moved the wrong way in response to stick inputs. E.g. if it looked the Mavic moved sideways in response to elevator input that would indicate that the Yaw value is 90 degrees incorrect.

It's a little hard to tell, but, it seems that the response to stick inputs is correct. The top speed is about 16 mph (7 m/sec)


I'm gonna speculate that environment caused errors with the GPS positioning resulting in the erratic flight. When the gpsHealth dropped below 4 at 27.8 secs that resulted in the GPS_POSITION_NONMATCH

 

[esm123]

msinger, Budwalker do you think based on his low altitude in between so many high rise buildings that it might have been GPS signal reflections that caused it?

View attachment 12350

I remember a YouTube video, I think it was from Casey. He took off between high rises and the Mavic went Berserk.

Rob

I've flown in the parking lot across the bridge in the picture in between the three skyscrapers many times and I never had an issue.

 

[esm123]

I was expecting but don't see any evidence that the Yaw value was incorrect at launch. This would have been indicated if it looked like the Mavic moved the wrong way in response to stick inputs. E.g. if it looked the Mavic moved sideways in response to elevator input that would indicate that the Yaw value is 90 degrees incorrect.

It's a little hard to tell, but, it seems that the response to stick inputs is correct. The top speed is about 16 mph (7 m/sec)
View attachment 12352

I'm gonna speculate that environment caused errors with the GPS positioning resulting in the erratic flight. When the gpsHealth dropped below 4 at 27.8 secs that resulted in the GPS_POSITION_NONMATCH
View attachment 12351

I did initially move sideways after going up vertically but as soon as I noticed the mavic started to move on its own..I stopped and then it went all haywire. Is that what you are seeing?

 

[esm123]

Posted the video!
Will take it down later - it's unlisted. Sorry for the language!

 

[msinger]

I've flown in the parking lot across the bridge in the picture in between the three skyscrapers many times and I never had an issue.

Where did you take off this time? Where did you calibrate the compass?

 

[esm123]

I took off from the pool area. If you see the link of the log, it has a picture of where I took off. I calibrated it the compass there.

 

[msinger]

Is the pool area concrete?

 

[esm123]

I think so. The floor seems like concrete.

 

[msinger]

Most concrete is full of magnetic metal. That would be my best guess as to what caused the erratic flight behavior. You calibrated the compass and then took off near a magnetic metal source.

 

[esm123]

Okay - I assume that will fall under pilot error from DJI's perspective. From what you guys can see, is there any possibility of software (since I had just updated it) or other defect that would have caused what happened?

 

[msinger]

I assume that will fall under pilot error from DJI's perspective

Yes -- if they deem that to be the cause. You should never do either of those things.

is there any possibility of software (since I had just updated it) or other defect that would have caused what happened?

I've never seen or heard of software causing something like this.

 

[Robbyg]

I was expecting but don't see any evidence that the Yaw value was incorrect at launch. This would have been indicated if it looked like the Mavic moved the wrong way in response to stick inputs. E.g. if it looked the Mavic moved sideways in response to elevator input that would indicate that the Yaw value is 90 degrees incorrect.

It's a little hard to tell, but, it seems that the response to stick inputs is correct. The top speed is about 16 mph (7 m/sec)
View attachment 12352

I'm gonna speculate that environment caused errors with the GPS positioning resulting in the erratic flight. When the gpsHealth dropped below 4 at 27.8 secs that resulted in the GPS_POSITION_NONMATCH
View attachment 12351

I assume when you say environment you mean the high rise buildings. That's what I am thinking at this time.
Msingers compass calibration idea was my first thought.
Without the DAT file can we ever know for sure

Rob

 

[esm123]

Okay thanks everyone. Theres A good chance DJI will have to send it back to me. (I don't think it's repairable or atleast it would be cheaper to replace).. if they send it back I will upload the DAT files from the aircraft.
I had no idea it had internal storage for flight records outside of the SD card.
Thank you

 

[Robbyg]

BTW sorry about the comment about the helicopter pads and power line. It seems that there might have been a cache problem with my software and it kept the Map framework from a previous flight analysis. When I re-ran the software a bit later the map was the correct one.

Rob

 

[geigy]

A city is one of the most unpredictable places to fly your Mavic. An unstable GPS lock can happen easily when tall and/or reflective buildings are nearby. Check this by making sure that your tablet/phone's map view matches your actual location, and the home point is where it should be to within a few feet.

If your first GPS lock is off base, you are riding on a knife's edge, and should not take off. If you do, a bad lat/lon may be set by the Mavic as the home point and current location. It could be a hundred meters or more from your actual location. When GPS gets a new position lock, it may differ greatly from the first one, even though the Mavic has not moved much. It will cause the Mavic to register a position error, and attempt to fly "back" to the first lat/lon where it thinks it should be located, resulting in a fly away.

 

[BudWalker]

I did initially move sideways after going up vertically but as soon as I noticed the mavic started to move on its own..I stopped and then it went all haywire. Is that what you are seeing?

Not exactly. I think you're referring to time 24.2 when you noticed the Mavic moving on it's own. There was no stick input for the next 3 seconds. But, then the rest of the flight had many stick inputs.


As I mentioned in the previous post it looks like the Mavic is responding to stick inputs. (To see this you'll need to run CsvView and observe the GeoPlayer as you're moving the value tracker in a SigPlayer like the above.) Also, the Mavic is trying to control the position, but it's relying on compromised GPS location info. It may have seemed like the Mavic was either ignoring your inputs or responding incorrectly. I think what you experienced was you and the Mavic both trying to control it.

I noticed in the video that the Mavic said "ATTI mode". But, the log doesn't have the switch to ATTI mode. I don't know what to make of this. The Mavic behaved as if it didn't switch to ATTI. Could you please provide all of the video of that flight?

 

[esm123]

Not exactly. I think you're referring to time 24.2 when you noticed the Mavic moving on it's own. There was no stick input for the next 3 seconds. But, then the rest of the flight had many stick inputs.
View attachment 12373
View attachment 12374
As I mentioned in the previous post it looks like the Mavic is responding to stick inputs. (To see this you'll need to run CsvView and observe the GeoPlayer as you're moving the value tracker in a SigPlayer like the above.) Also, the Mavic is trying to control the position, but it's relying on compromised GPS location info. It may have seemed like the Mavic was either ignoring your inputs or responding incorrectly. I think what you experienced was you and the Mavic both trying to control it.

I noticed in the video that the Mavic said "ATTI mode". But, the log doesn't have the switch to ATTI mode. I don't know what to make of this. The Mavic behaved as if it didn't switch to ATTI. Could you please provide all of the video of that flight?

That is all the video I took. Your description seems correct. When i was controlling it, it would receive the input but it was also moving on its own.

 

[m0j0]

If you take compass into an area with a lot of metal it will read incorrectly. That is why a properly calibrated Mavic will say it needs calibration when you carry into an area full of metal objects. When you calibrate it in this bad location the mavic will think it is properly calibrated but once you get it up in the air and far from all the metal the Mavic will suddenly be out of calibration and will behave erratically.

You always need to calibrate in a open location away from any buildings and metal. Once that is done ignore any calibration warnings that occur when your near building and metal. I have only calibrated my Mavic 3 times in 5 months.

Rob

I have you beat. I'm actually embarrassed to say... I have never calibrated the compass on my Mavic. Not a single time. I don't recommend doing what I have done. But my bird came fine right out of the box. I checked sensors and continually monitor the flight characteristics and have not seen even the slightest indicator that calibration is required so I have left it alone. Additionally I have not received any application prompts requesting a calibration so I won't do it. As a matter of fact, I have never calibrated anything aside from the visions sensors. It flies straight as an arrow and the only time I had a compass error was the time I intentionally flew near a 150 metal structure at a sawmill. I literally flew about 20 feet from the metal dome before I saw the compass error warning. I've been flying the mess out of my Mavic from day one back in November and I have not had a single issue with it.. none, nada, zilch. I absolutely love the thing it is in another category from the other birds I own and operated before. So, I'm going to say this crash is likely the result of a bad calibration.

Why exactly did you calibrate it anyway?