A Litchi Mission Go Awry-or so I thought

[Marco Cantieni]

From what I have just learned, I would not change apps in flight. If you have both DJI and Litchi installed, usually when you plug in the USB it asks which app to open unless you told it to always open one app or the other.
So you plug USB in first before opening app.
I might be wrong but I first start tablet then turn on controller connected to tablet. It asks if I want to use Litchi when plugging usb in tablet, I say "0k'" and then I power on Mavic Pro.

With the latest version of iOS, DJI go and Litchi a change of apps works flawless. However I deactivate DJI or Litchi app in iOS task manager before switching apps.

 

[lisadoc]

I've usually come back and landed, made sure everything was set up and working, and then take off again.

No need to come back and land. Just hover and you'll be fine.

Question: When this happens do you reseat the USB cable to fix it, do you close the app you're switching to first and then reseat the cable and restart the app, or just reseat the cable without closing and the app will pick up the connection?

Just reseat the cable (with the app you want to use open) and it picks up the connection. Make sure to close the other app you're not using (prior to reseating the cable) and you should be good to go.

My protocol goes like this (typically): Open DJI Go. Make sure all the settings are how I want them. Check for any error codes (other than the constant warnings to upgrade my firmware ). Take off with DJI Go. Make sure home point is set. Hover in place. Close DJI Go. Open Litchi (or Hangar 360, etc.). Most times the signal catches and I'm good to go in that app. Occasionally, I don't get a signal, so I pull and reseat the USB cable. Almost without fail, the new app picks up the signal at that point, and I head out using the new app. Very rarely, I have to pull the cable and reseat it a second time (generally if I've accidentally forgotten to shut down DJI Go.)

 

[jedburgh01]

Hello.
I have flown Litchi Missions ever since I bought my first Phantom 3 Standard, and my drone has always returned even though the signal was often lost for a few moments.
I have flown Litchi missions with my Mavic, but only a few.
I made a nice 8 minute mission, loaded it on my tablet, and headed for my location.
I started the Mavic Pro as usual, tested the movements and tap to focus and got it in position before loading the mission.
The Mavic was directly above me and maybe a little behind me before I loaded the mission. As soon as I hit "go", the screen said signal loss. I had no video feed or satellite map--they were frozen.
This had never happened to me right from the start.
And off went my Mavic Pro.
After wrapping my head around the problem I decided to stop the mission while I could see the drone.
It seemed to stop. I tried bringing it back but convinced myself that it was out of my control.
And off it went out of sight.
I tried leaving the waypoints screen, changing to fpv, and back to waypoints. Still no signal.
No video.
No drone.
I finally checked the controller screen. Altitude was being adjusted and distance increasing. .And I recognized the heights as waypoints that I set, so the mission was being run.
The tablet which is a Nvidia K1 Shield still said no signal.
The Mavic went by me as it finished its last leg of the programmed flight.
When it finished and hovered above me. I easily brought it back down and landed.
But the tablet screen and Litchi had never recovered the signal.
I decided to start it back up and fly a short flight. Everything was back to normal and Litchi had a signal and video feed.
I wonder if when I first raised the Mavic above me that the controller momentarily lost the signal as the mission loaded. For some reason, Litchi loaded the mission then lost the signal.
Every time I have almost lost faith with Litchi, Litchi comes through!
P.S. If anyone is interested I can post the video which shows the mission being stopped by me, then reversing a bit, then Litchi continued on with the mission.

That's why DJI screwed up not putting a screen on the MA controller. The info on the screen should be enough to bring it home.

 

[RobH2]

This is a really interesting thread. I need to go do some testing of all of your techniques. It's really good disaster training.

I do have a question. It was mentioned that even if all telemetry with the tablet or phone is lost, the craft is still controllable, like a car with a dead dash pod. But, if the aircraft was being flown away from the Home point and the connection was lost, wouldn't it just continue to fly the last input it received, meaning, it keeps going away? My scenario supposes a Litchi mission is not running, just manual flying. If so, then some fast reconnection would be prudent so it doesn't get too far away to have enough battery to return. That's always my fear, that I'll be flying away and 20mph and I lose connection and it just keeps going.

 

[lisadoc]

I do have a question. It was mentioned that even if all telemetry with the tablet or phone is lost, the craft is still controllable, like a car with a dead dash pod. But, if the aircraft was being flown away from the Home point and the connection was lost, wouldn't it just continue to fly the last input it received, meaning, it keeps going away?

No. You've been worried for nothing. The Mavic stops and hovers without input from the RC (i.e. lost connection). The aircraft will then wait a few seconds (waiting for a reconnection), and then initiate it's RTH protocol (if that's what you have it set for in the settings) if no further connection is forthcoming. This is why it's critical to have your "Loss of signal" settings properly configured.

 

[MileHighSi]

Thanks for sharing your story. I will reconsider to set the end of my missions to RTH instead of hovering.

I've been having a few gos of Litchi this week. So far, so impressed. It is quite harrowing, though, watching your drone fly off haha... The idea of having Litchi do anything but RTH after a 'mission' scares me. You can always cancel it if hovering is safe.

 

[MileHighSi]

Just to add another real-life Litchi drama to the thread, in case anyone finds the information useful..
Yesterday I cycled over to a river with my drone and a Litchi mission all set up to fly down the stream, following its path - hopefully to see a crocodile! I kind of anticipated that after it flew over the tree line (losing VLOS) I'd have a lost connection. That didn't make it any less stressful, though, when sure enough the video feed and all telemetry ceased updating. The mission was roughly 11 minutes long, I had a full battery and I'd set the action for mission end to RTH - so I felt confident enough to let the mission continue without any feedback (not that I had a choice at that point..). Not less than a minute after losing connection (less than 3 minutes in to the mission), however, despite me being cautious about the weather, I felt drops of rain. I panicked and tried to cancel etc. but obviously it was no use. Anyway, as luck would have it, the rain was pretty light. 9/10 here rain = thunderstorms and my poor MA would have been the highest conductor of electricity for a mile each way. Got away with it. 5-6 heart-wrenching minutes later the controller started beeping, signalling that my drone was making it's merry way home. I slung it in to Sport mode and landed it ASAP. We hugged. I promised never to do it again - probably a lie tbh.

Just a cautionary tale about losing connection during autonomous flights and weather.
Also, while I remember, the controller turned itself off mid-flight, whilst disconnected. I wonder if this is a battery-saving feature which activates when the controller has been disconnected from a drone for a certain amount of time. Something else to be cautious of.