Loss of control of Mavic Mini - Pilot error or malfunction?

[avinoam83]

This happened last Sunday. I started my flight by ascending to 50 meters and setting the RTH height to 50 meters. I flew about 275 meters and came back. So far so good. Got an intermittent strong wind warning, but the wind didn’t appear to affect my flight, so I kept going (first mistake) and flew out to the same spot around 275 meters out. Started heading back with 55% battery left. This time I noticed that the drone was being pulled to the south. Got to within 100 meters of my house and I was pulled strongly to the south. Tried bringing it closer to my yard. Got a low battery voltage warning at 33%. Yikes. Struggled for a few more minutes, managed to get within 34 meters of my starting point. Saw I was at 17% battery and hit the RTH button (second mistake). The drone started flying in the opposite direction! Cancelled RTH to try again manually, at this point I got the “Low battery. Returning to home” message and the drone pulled further to the south. I ran after it (just down the block) to try to at least land in a controlled manner. I did re-establish line of sight, but ended up getting stuck in a tree on the way down. It was caught about 40 feet up in the tree, so I was unable to retrieve the drone on my own. It was rainy and windy on Saturday and the drone fell out of the tree. I broke one front arm and cracked the other. I'm attaching the text log. Here is the data from airdata.com:
Was this purely the result of flying in improper conditions, or was there something else at play?

Thanks!

 

[Thomas B]

Will be interesting to see the expert analysis. Your description sounds like the home point was not allowed to set at TO and occurred later in the flight... but the logs will tell us.

 

[Fly Dawg]

@avinoam83 Looks like more pilot error than aircraft. First, the wind warnings should have been heeded. Second, you cancelled both RTH events just as the aircraft was starting to make progress back. Wind was a factor, but not the primary cause IMO.

 

[avinoam83]

@avinoam83 Looks like more pilot error than aircraft. First, the wind warnings should have been heeded. Second, you cancelled both RTH events just as the aircraft was starting to make progress back. Wind was a factor, but not the primary cause IMO.

View attachment 92301

Thanks for taking the time to respond. Regarding my cancellation of RTH at 13 minutes, 23.6 seconds, I cancelled RTH there since the drone started moving backwards about two seconds before that. Was it wind that was causing it to be pushed back away from the home point? Are you seeing any wind data?

 

[Fly Dawg]

@avinoam83 During the last RTH that is correct. You were fighting the wind. As you climbed higher it got worse.

 

[slup]

Wind speeds from the flight ... they were not quite as high as shown below as Airdata.com still uses the Spark profile for the MM (approx 30% to high we think), but still over the Mini spec.

 

[avinoam83]

Wind speeds from the flight ... they were not quite as high as shown below as Airdata.com still uses the Spark profile for the MM (approx 30% to high we think), but still over the Mini spec.

View attachment 92336

Very helpful. Even if the data is relative and not absolute (because of the profile that was used), the data does show a correlation between the increased wind speeds and my loss of control. I'm surprised there was that much wind because of wasn't that windy at all at ground level. It appears that this was totally my fault. Bummer, but at least I know what I could have done differently. Any suggestions what I might do in the future if I find myself upwind of my drone when the wind picks up? Apart from descending, which should have been my first step.

 

[slup]

...Any suggestions what I might do in the future if I find myself upwind of my drone when the wind picks up? Apart from descending, which should have been my first step.

Switch to Sport mode, descend & maneuver manually, all at once ... then keep away from the RTH button. If the battle seems to be lost land while you have connection.

 

[avinoam83]

Switch to Sport mode, descend & maneuver manually, all at once ... then keep away from the RTH button. If the battle seems to be lost land while you have connection.

I hear that. Biggest screw up from pressing RTH is that it actually caused the drone to ascend to my RTH level (which was set pretty high to prevent the possibility of hitting anything). Now I have to decide if I'm going to pay to fix it (hopefully just the two arms) or completely replace it. Sigh.

 

[MAvic_South_Oz]

One thing to keep in mind with the Mini, is if lowering to get below wind, don't forget to keep decent signal LOS, or as it gets too low and loses connection, the RTH failsafe will kick in and the drone will then rise !!
Best is to not have RTH altitude set to 'pretty high', have it set to as high as needed with a little safety margin.

For sure if you get caught in wind, it's best not to use RTH, fly home manually at an adequate altitude, use the camera dead forward to clear obstacles, and as said in Sports mode to try and better the wind.

Hope you can fix it, or get a decent price on replacement.
Not sure how you will go just buying an aircraft ?

 

[avinoam83]

Thanks everyone. I posted pics of the damage at Repair advice for broken front arms of Mavic Mini?

 

[JAW]

I just checked the winds in Tuckahoe, NY via UAV Forecast. Surface winds are 10 mph, at 200 feet they are also 10 mph but are gusting to 33 mph. i’m guessing that the hilly terrain around there makes this a pretty common occurrence.

 

[avinoam83]

I just checked the winds in Tuckahoe, NY via UAV Forecast. Surface winds are 10 mph, at 200 feet they are also 10 mph but are gusting to 33 mph. i’m guessing that the hilly terrain around there makes this a pretty common occurrence.

Looks like I bit off more than I could chew. Are there other DJI models that could handle similar wind speeds?

 

[JAW]

I believe the max wind speed for a Mavic 2 is 22 mph (10 m/s). I’m sure there’s a lot of pilots that have flown in winds higher than that. The problem you can run into is when you fly away with a tailwind and then turn around and have to fight your way back through a headwind to reach home.There have been a couple incidents here where that was a direct cause of the crash.

 

[Mikey's]

Based on my own experience 50 m is simply too high in such conditions. Always watch the UAV Forecast for your location. Sometimes you will be surprised how quickly the wind speed increases with the altitude.

 

[avinoam83]

Based on my own experience 50 m is simply too high in such conditions. Always watch the UAV Forecast for your location. Sometimes you will be surprised how quickly the wind speed increases with the altitude.

You're right. Honestly, the only reason I was flying so high is that my area is fairly hilly and I wanted to account for the tallest trees and buildings (including after accounting for changes in elevation) when flying using the map. Any suggestions as to how I should be calculating minimum height in those conditions?

 

[slup]

You're right. Honestly, the only reason I was flying so high is that my area is fairly hilly and I wanted to account for the tallest trees and buildings (including after accounting for changes in elevation) when flying using the map. Any suggestions as to how I should be calculating minimum height in those conditions?

Doesn't look overly hilly ... or isn't googles view of it accurate?

Ascend with camera pitched to 0 degrees (leveled/horizontal), turn around & note what objects still is above horizon, if any ... ascend until they also are below or equal with horizon. There you have the free height.

 

[avinoam83]

Doesn't look overly hilly ... or isn't googles view of it accurate?

Ascend with camera pitched to 0 degrees (leveled/horizontal), turn around & note what objects still is above horizon, if any ... ascend until they also are below or equal with horizon. There you have the free height.

View attachment 92445

Thank you for this! I'm curious how you managed to display this angle. Is that through airdata.com? The hills aren't extreme, but there are definitely some steep inclines, and I don't think that comes across in Google. For example, on the street where the drone crashed, the incline is steep enough that I need to keep the car in second gear. I'll try to get some good video once my drone is repaired - Assuming that I have the guts to try again.

 

[slup]

Thank you for this! I'm curious how you managed to display this angle. Is that through airdata.com? The hills aren't extreme, but there are definitely some steep inclines, and I don't think that comes across in Google. For example, on the street where the drone crashed, the incline is steep enough that I need to keep the car in second gear. I'll try to get some good video once my drone is repaired - Assuming that I have the guts to try again.

Just download the .KML format of the log from Airdata.com & open it in Google Earth ... push Shift & at the same time use the mouse to tilt & turn.

 

[FoxhallGH]

It does come with experience but some lessons to be gained here are:
1) The wind speed at ground level is ALWAYS lower than it will be at 400ft
2) Use an app like 'UAV Forecast' or 'Ventusky' to show you the wind at altitude before you fly.
3) From the posted graphics, there are a lot of trees in the area you were flying in. Use them! Their tops will have been showing you that there was some difference between the ground-level wind-speed, and even 10 metres (30ft) up.
4) If you are not sure of your aircraft, fly away from yourself up-wind - not downwind. That way, when you realise that the Mavic isn't handling it well, it can be blown back to you rather than away from you.
5) Return to Home is not a 'Get-out-of-Jail-Free' card! Due to the cautious way we tend to set RTH altitude, the Mavic will usually pop up into even faster-flowing air, where it will have to fight even harder to get back to you. Get familiar with the Fly app' and what it shows you to give you the clues as to what way your drone is pointing and flying - and be prepared to get down to hedge-top height on a windy day to manually fly back to your home point.
6) Know that you will really upset your neighbours if you are flying over populated areas like this, and your Mavic falls out of the sky due to a motor fail! If you are training, do yourself a favour and fly in an open space where you'll do minimum damage to others in case of a problem.
7) Take some time on a rainy day to download and read the manual - Mavic Mini - Specs, FAQs, Videos, Tutorials, Manuals - DJI - so that you know what your Mavic is capable of and the tools that it can provide to help you in situations like you found yourself in ...

I hope you get the Mavic repaired OK and get to enjoy the hobby ... There are some weather limitations with the Mav' Mini, but on a calm day you'll see what this is all about ...
Have fun & fly safe