Unusual VERY IMPORTANT Safety Tips from a rookie Mavic Mini pilot

Unusual VERY
IMPORTANT Safety Tips
from a rookie Mavic Mini pilot

Okay, you probably know my story since you're here, so you know I learnt the hard way and I have couple of tips to share. In case you wonder... no, I haven't lost my drone in the wind but still better be prepared than caught by it. So I won't bother you with the traditional EMPTY notices like: the control sticks work inverted when the drone is facing you, do not smash into power lines (actually it's pretty easy... you don't even notice them) and so on... just don't tangle with your fiancée's hair, this isn't really a beginner's guide to begin with, but possibly still very interesting.

Pre-flight checks...

First a bit of environmental checking, speaking of which... the UAV Forecast app. I think there's not better app around (that I know of) than this one. It's incredibly easy to understand and easy to use, straight to the point, all you need to know in one screen. Basically it's like a pre-flight check panel: everything must be green to go fly. Check the weather, check the light, the temperature, wind, clouds, sats, geomagnetic interference (Kp)... did I say check the wind once?

UAV Forecast app for Android and iOS

Now, what I learned going through the forums is that Mavic Mini rookies are hundred of times more likely to get caught by the wind than everyone else: new, old pilots, Mavic, Phantoms, the lot. I plea every Mavic Mini owner please, PLEASE CHECK THRICE the WIND every time before you fly, always plan your flight in advance, don't reach higher altitudes (above 25m or 75ft) unless you're super sure there won't be stronger wind, avoid inhabited zones and flying near the water in your first weeks, fly where it would be easy to retrieve should it get down. Keep in mind the wind resistance is 8 m/s even compared to how stable it flies in winds near that level, it's less than 30kph or 17mph.

Be prepared! It's still early days for the Mavic Mini, its firmware and companion Fly app, features might be introduced (subject tracking is within its range, should DJI decide to implement it), and errors stand to be corrected. I noticed several (forum) cases of Mavic Mini dropping unexpectedly from the sky, but I've also read it is possible to counter and arrest this tendency. The same can be said for the wind, sometimes it seems to fail to acknowledge the high wind condition and it just counters it with lethargic movements... and is carried away! Be prepared to act quickly (bring it down as soon as possible) to save your beloved Mini if you don't wanna skip directly to the next step (search and recovery). The wind is always likely to be stronger at higher altitudes.

Did you notice a warning in the UAV app (airport nearby)? Even if you're quite far-away and going to elevate 30 meters be careful. Now the position in which I was meant that if something was flying that altitude it probably would have crashed, but still be considerate and it's good to know even of minor airports several kilometers away.

Set your max altitudes in the Fly app. Set a Return to Home altitude that you know for certain will be higher than anything in your surrounding but still as low as possible to avoid winds or disturb the airspace (and spare time, battery). Personally I've set the wind level in the UAV Forecast app @60m (or 200 ft) and the max altitude for the Fly app accordingly.

Now onwards, we go FLY!!

... hey, wait a minute! Where do you plan to fly? In case you don't plan to fly on Mars (which for slight physical inconveniences might not be possible) chances are you're going to fly near some place that is using 2.4 GHz band, i.e. Wi-Fi, and guess what... our drone operates on the same frequency. This is probably the main reason I've lost the connection with my Mavic Mini after just 300 meters, how is it possible when the range is 2000 m (in 2.4 GHz) for the CE version?

Well, when cumulatively sampling all the flight distances (up to 300m) and heights (33m) of my flight it is entirely possible that whole 2.4 GHz spectrum was busy, but the 5.8 GHz band was pretty much clear from ground (and within range). So what happened is... most probably, the drone couldn't keep up changing frequency with the Auto channel program and the signal strength meter did not give any warning of signal degradation until complete and sudden link loss. I received two brief notices mid-flight (about halfway, minutes before link loss) that quickly disappeared. They were about -adjusting antennas- and -signal interference-, a couple of seconds each for a 7+ minutes flight, the video downstream remained perfect. You know how it ended.

I can't stress long enough even if you're a paranoid like me and already use a Wi-Fi scanner app (you should definitely use one) and also go around surveying from the ground every bit of airspace you plan to fly in, please be aware before DJI can fix this in a firmware update, the signal strength meter and warning information system in the Fly app ARE NOT reliable for the Mavic Mini, at least in my case within a very challenging frequency airspace (for the 2.4 GHz spectrum) the Mavic Mini couldn't cope with that, it probably couldn't switch to 5.8 GHz fast enough, neither it showed the signal degradation with multiple and steady warning information notices on the screen and the signal meter stayed full. You're warned... please be aware you should not trust these two systems, especially the signal indicator. Should you ever get a notice for a couple of seconds and then it disappears stop there immediately... get your drone back, make multiple scans before you fly again in the same environment because what followed after is not something you want to get through... a period of anxiety, frustration and worse possibly impeding liability.

  

Scan the Wi-Fi spectrum

In case you're wondering what apps I use for Wi-Fi scans here and here
https://play.google.com/store/apps/details?id=com.vrem.wifianalyzer
https://play.google.com/store/apps/details?id=cz.webprovider.wifianalyzer
I have my strict requisites: form over function, no ads (or as least as possible), no parasitic activities (and permissions).

Ideally you might want to scan the complete 2.4 GHz channels (1 to 13) and the 5.8 GHz ones (CH 144 to 169, 5.725-5.850 GHz). I had problems scanning the whole spectrum with an older Note3n but my S9+ can effortlessly sample all the frequencies. If you notice from the ground something beyond -80dBm that's usually a green light for flight, but if you notice something in the mid region of -65 to -80dBm depending on where you are, you might want to consider those channels occupied, because that level of signal strength could compete with your remote connection and cause interference. Then there's the obvious occupied channel that sits higher than -65 dB, that is a solid signal you should be aware of and consider that channel busy. Keep in mind that a 2.4 GHz Wi-Fi transceiver tuned on a specific channel extends its influence to adjacent channels as well. If you have the 6th channel occupied like in the above screenshot (the blue dome is my mobile access point) the influence extends up to 4th and 8th channel. So it is highly advisable not to pick adjacent channels (like 5 or 7) because they could not even work, and avoid the 4 and 8th channel because you'd have strong interference. Ideally to use the full bandwidth of that channel you need to stay at least 4 channels away and resort to use CH2 or CH10.

Naturally all of this is handled automatically by your Mavic Mini (unless you disable the Auto channel program which I advise not to do) so you have a nice hassle free flying experience and despite the occupied bands the drone will always fly in the least busy channels... unless well, radio waves are not exactly linear things, and all sort of interference might happen along the road, something that you can easily miss from the ground, or just checking the departure and destination points. So you need to be considerate even of the puniest signal, because it might become a beast in other places you can't reach personally.

Tracking your drone (ready for search and rescue)

Ideally your very first tries of a drone should be in some kind of farmland, so if the worst happen you won't make damage to other's property, you don't hit anybody and you can easily retrieve your drone (without falling in a ravine).

Obviously you don't want you drone being carried away... but sometimes you just get caught by the events and you have no control, so better be prepared for it. Retrieve your flight log data is essential to better understand your flight and make projections of where it might have ditched. Using this very useful guide https://mavicpilots.com/threads/flight-log-retrieval-and-analysis-guide.78627/ I was able to find my logs (Fly app logs are in your phone internal storage, DJI » dji.go.v5 » FlightRecord)​. After this I also learned a couple of very interesting online website that help you translate that ocean of bits into something graphically meaningful, one is https://app.airdata.com/flight/ (registration required) and the other is https://www.phantomhelp.com/LogViewer/upload/

Essentially what you can reproduce (replay) in your DJI fly app is what you will see in the online program plot, only better. And of course the files can be processed further more the determine the projection of the possible drone crash/landing area.

The DJI program

Now that you've learned how to check the environment let's say you want to gain some experience and execute some ZERO risk tests... (well, unless you tumble from your chair). Now, how dare you destroy perfectly working drones because you're a complete dud! Introducing the DJI Simulator... smash your drone no more (or smash it in virtual reality only) with this beautiful piece of software that helps professionals and amateurs get better at piloting a drone. If you like me are using the free version you'll have to deal with some important limitation, like the inability to access training programs... but you're free the play and explore many environments with it, and it gives you a pretty good idea what it's like to fly and control a drone. The graphics are pleasant and the menu is a joy to behold with all the various DJI models a in perfect 3D reality replica.

Unfortunately there's no Mavic Mini in this simulator but there's the Mavic Air which is the most closely related product probably, and last but not least you can use your DJI remote with it! Despite not having official compatibility the Mavic Mini controller works perfectly with the simulator, the top control sticks, the RTH button, the photo, video, and gimbal tilt dial they all work beautifully. Honestly I think the help provided by this program is almost invaluable... you can even set your own weather and test your drone in heavy winds.

https://www.dji.com/simulator/

Now that you've arrived at the end of my unusual safety tips it should be safe to assume you already went through all the other normal beginner guides and it's about time to head for the farmlands. Let's not make the mistake of consider ourselves learned... still having such a baggage of knowledge certainly could help to avoid quite embarrassing situations, not least avoid filling up the maps of the lost Mavic Mini drones.

Happy flights...