Mavic Mini out of control - saved by RTH

[miker570]

Yesterday I attempted a short flight to video ice fishing activity out on the middle of a lake. The temp was about 32F/0C and very light winds. The battery was at 46% at takeoff.

All pre-checks at take off seemed normal, I was just going to fly strait up to about 100 feet, pan around and land.

As soon as it reached 100+ feet it started to fly away to my south. It did not respond to controls. It issued a max power warning and high winds but it was not windy and I was not giving any power inputs. It then spun around and started heading west and then went into an uncontrolled spin. At that point I hit the RTH and it flew directly back to the exact RTH point and landed precisely where it took off.

Lucky I was out in the open or it would have probably crashed into trees again. I had a similar out of control spin last November that resulted in a bad crash and was discussed here. DJI sent a replacement at no cost for that incident.

Flight logs attached. I have a video of the flight that I will post later
Thanks for your help to understand what happened.

View attachment DJIFlightRecord_2020-02-01_[16-50-38].txtView attachment 2020-02-01_16-50-20_FLY052.zip

 

[miker570]

Here is the video from the flight

 

[Starz]

Curious. Location of pilot?

 

[BigAl07]

Yesterday I attempted a short flight to video ice fishing activity out on the middle of a lake. The temp was about 32F/0C and very light winds. The battery was at 46% at takeoff.

All pre-checks at take off seemed normal, I was just going to fly strait up to about 100 feet, pan around and land.

The mere idea of launching at just 46% is asking for problems. Keep in mind that battery % is a guestimate (at best) and it's never a good idea to start a flight at such a low battery level. Even if the % estimate is accurate you don't have much flight time and you're not leaving any "Uh oh" time as a safety factor.

 

[Lastrexking]

Curious. Location of pilot?

Buffalo. Says under the name of each poster where they’ve provided the info.

 

[miker570]

I was in the window of my fish house. There were no battery warnings and RTH worked perfectly. So unlikely the battery level was an issue for this short flight. I was running my batteries down for storage, otherwise I always fly with a full charge.
I have flown many similar flights from inside the fish house observing from the window. I have range extenders on my RC and it has never been a problem on several previous flights.

 

[Fly Dawg]

@miker570 Problem #1 You took off with too few sattelites aquired. NavHealth was zero.
Problem #2. All of the spins were due to your rudder inputs.

 

[miker570]

I think it had 10 sats when the RTH home point was set. The RTH was exact. It is possible that the GPS signals got confused or were intermittent causing the fly away. The home point was correct and RTH was precise.

 

[slup]

@miker570 Problem #1 You took off with too few sattelites aquired. NavHealth was zero.
Problem #2. All of the spins were due to your rudder inputs.

View attachment 92913

Yup ... agree to both the navhealth & the rudder commands leading to the yaws we see in the clip.

Messages in the logs:



Wind ... no, don't think so, Airdata reports around 5,7m/s (being like 30% to high for the Mini).



But this looks like a compass error ... we have a heading speed increase from 0m/s to 13m/s without neither aileron or elevator inputs between 59sec to 65sec. The whole flight path looks like the famous bathtub curve ... Even Airdata throws an compass error in the end.





We need the DAT log ...

 

[Fly Dawg]

@slup The .dat log is posted above...

 

[miker570]

I zipped up the DAT in the attachments of the first post.

It only allows the DAT attachment when zipped. I will try again.

View attachment 2020-02-01_16-50-20_FLY052.zip

 

[Fly Dawg]

@miker570 You were in the air 26 seconds before the home point was set. Your sat count was never more than 9.

 

[miker570]

@miker570 You were in the air 26 seconds before the home point was set. Your sat count was never more than 9.

Yes that is correct. I took off from the ice quickly, and usually let it hover until everything is locked in. Since I was planning to just fly strait up and pan around directly above I wasn’t expecting it to start flying away like it did.

 

[Fly Dawg]

I wasn’t expecting it to start flying away like it did.

It appears the wind picked up at ~37 meters in altitude. It was blowing at a brisk pace at that altitude it appears judging by the aircraft speed with few stick inputs.

 

[Starz]

Buffalo. Says under the name of each poster where they’ve provided the info.

Video showed takeoff and landing from point x. No pilot in view. Op has answered the question.

 

[miker570]

“Fly Dawg, It appears the wind picked up at ~37 meters in altitude. It was blowing at a brisk pace at that altitude it appears judging by the aircraft speed with few stick”


If it really was wind, why did it stop and turn and then fly in straight line when RTH kicked in?

I suspect the GPS signals were confused and once it got locked in again it came straight home. I had no control, but good thing the RTH worked to get back home.

 

[slup]

@slup The .dat log is posted above...

Thank's ... missed it

Well, if I'm not wrong here the disagreement between Yaw & magYaw started at approx 13sec were the magMod spikes. And that was a factor through out the flight ... usually this leads to a "bathtub" curved flight path and a crash, think OP were lucky this time. All of this due to a start near that camp wagon or 4-wheeler probably ?

 

[BudWalker]

Thank's ... missed it

Well, if I'm not wrong here the disagreement between Yaw & magYaw started at approx 13sec were the magMod spikes. And that was a factor through out the flight ... usually this leads to a "bathtub" curved flight path and a crash, think OP were lucky this time. All of this due to a start near that camp wagon or 4-wheeler probably ?

View attachment 92923

I was getting ready to post the same. A clear case of geomagnetically distorted launch site.

Fortunately, the ascent was directly over the launch site and the HP got set correctly when enough sats were acquired and navHealth got to 4.

 

[miker570]

I have flown many flights from my ice fishing shack and never had an issue before. I did purchase a new fish finder that also has GPS lake mapping capability. Could a fish finder GPS interfere with my MM flying far away?

 

[slup]

I have flown many flights from my ice fishing shack and never had an issue before. I did purchase a new fish finder that also has GPS lake mapping capability. Could a fish finder GPS interfere with my MM flying far away?

GPS didn't have anything to do with this ... and if I may add, luckily. You were though a bit reckless there regarding your drones navigation possibilities ... give it time before getting airborne.

This was all about you taking off in a magnetic interfered area close to large magnetic things ... like your camp wagon or the 4-wheeler. As soon as you ascended out from the disturbed area the drone yaw angle didn't match the compass anymore ... the Mini didn't know to which direction it should counter the winds affecting it, and away it went.

All about this in the manual ... below from page 36, get it here --> https://dl.djicdn.com/downloads/Mavic_Mini/Mavic_Mini_User_Manual_v1.0_en_1.pdf