Litchi Waypoint slows Mavic after lose signal, preventing Mavic from fly mission at speed

[adiru]

So I did a long waypoint mission and wanted to do some tests to calculate max range from where I live. I wanted the Mavic to always keep a speed of 32 mph if it can sustain it (no winds).

However, after 3/4 mile, my RC connection is lost, but Mavic still continues the mission based on pre-programmed Litchi waypoints. All is well except after losing signal the Mavic slows down significantly, even though I did not tell it to slow down.

I used a stopwatch and estimated re-acquisition of signal to be in 3 minutes, when the three minutes came and gone and still no drone, I was starting to feel like how Mission Control in Houston must have felt after Apollo 13 didn't timely report back after reentry. I waited a full six and a half minutes until signal was recaptured at the 3/4 mile marker.Almost felt like I just lost $1500 since DJI Care doesn't cover flyaways.

Here is the issue:

On the Litchi help page it indicates that the Mavic in waypoint mode will continue to fly the rest of the mission at the speed it was flying while signal was lost... But obviously after reviewing my logs it seems this was not the case at all.

Before loss of signal I was doing 32 mph, and after lose of signal I did only 16mph. The entire rest of the mission took way longer than it should have, and it lose signal while still going outbound, based on my calculations, it slowed down to 16mph right after lose of signal, and wind was not a factor coming back in. There was no head or tail winds. I checked wind speeds for all altitudes that I had set waypoints for.

Is this a bug? How can it be fixed? At 16mph my range is significantly reduced, luckily I did not do a longer flight otherwise I would not have made it back!! Why can't it maintain the programmed 32 mph after signal lose? Even the website stated this should have been the behavior of the Litchi Waypoint functionality.

Also, I had turned off RTH and Smart RTH on both the DJI app and the Litchi app. And upon reacquiring signal, it was still in Waypoint mode and not in any RTH modes.

 

[BD0G]

Please send this well documented "feature" to Lichti's support email address and post in this thread with the potential resolution to this issue. Perhaps they will develop a resolution into their next update.

[email protected]

 

[adiru]

Please send this well documented "feature" to Lichti's support email address and post in this thread with the potential resolution to this issue. Perhaps they will develop a resolution into their next update.

[email protected]

Help - Litchi

Help - Litchi

""Speed: The speed at which the aircraft will travel from this waypoint to the next. By default the aircraft will use the mission's cruising speed setting, but the cruising speed can be overriden for each waypoint using this setting.
Warning This setting is only in effect when the aircraft is in range of the remote controller. If signal is lost during the mission, the aircraft will continue the mission at the speed it was travelling at when it lost signal. ""


Okay I emailed them!

 

[BD0G]

Lets see what they say. Kinda interested.

 

[arachnida]

Interesting! Let's make it more extreme, if your speed was say 2 mph when the connection was lost you would never have seen your 1500 USD again. That's a huge issue that should be fixed.

 

[Logger]

You cannot turn OFF the RTH feature for Litchi WPT. You can alter Litchi signal loss behaviour to prevent RTH for manual flying which you were not doing. So had your Mavic tried to continue the route at 2mph it would have only done so until a low battery RTH was triggered. At this point it would fly home at the regular RTH speed using the firmwares inbuilt RTH process.

 

[adiru]

You cannot turn OFF the RTH feature for Litchi WPT. You can alter Litchi signal loss behaviour to prevent RTH for manual flying which you were not doing. So had your Mavic tried to continue the route at 2mph it would have only done so until a low battery RTH was triggered. At this point it would fly home at the regular RTH speed using the firmwares inbuilt RTH process.

It did not RTH after losing signal, it still flew the entire route, only way I knew that was by watching the video afterwards since the Litchi flight logs stopped capturing right after signal loss. It still flew all the waypoints, only at a much much slower pace, and that was the issue since Litchi states that when in waypoint mode if signal is lost it will continue at the same speed at the time signal was lost, so based on Litchi's own documentation, it should have flew the rest of the waypoints at around 32 mph instead of 16 mph (I had also set the cruise speed to 32 mph, and it was exactly at 32 mph the very moment signal lose occurred so it should never have slowed down to 16mph)

 

[Logger]

YES I understand that. I was responding the two of you being concerned about the low speed leading to loss of aircraft.

" ...luckily I did not do a longer flight otherwise I would not have made it back!!"
&
"...I had turned off RTH and Smart RTH on both the DJI app and the Litchi app."
& arachnida:
"..if your speed was say 2 mph when the connection was lost you would never have seen your 1500 USD again. That's a huge issue "

You cannot turn off RTH in Litchi WPTs and therefore your Mavic would have made it back regardless of the low speed enroute.

Could you perhaps have pulled the left stick back a little after the initial signal loss inadvertently telling it to slow?

 

[Native Hawk eye]

Any updates?

 

[Michael Lee]

I've been using Litchi as well...experienced similar (if not same) issues as the OP. I had more success after turning off the front collision avoidance sensor, after seeing how it causes the drone to stop/pause mid-flight while facing the Sun at a critical angle.

 

[Dusty3]

Excuse Me! I had the impression the mission is uploaded to the quad and the craft flies the mission as designed autonomously. This thread tells me the quad need to maintain signal throughout the mission? I have flown Litchi around buildings.. could not see or hear the quad and all went well. I am now flying a Mavic

 

[davmcw]

GS Pro doesn't have this issue. And its new update last week closed the feature gap w Litchi Waypoint as well by adding curved turns, focus options, etc. I've found Litchi to be...well...glitchi.

 

[PaoloOne]

Is there anybody knows something new about this bug?
I just got this screenshot:
Imgur: The most awesome images on the Internet

 

[Mitch]

Does anyone here know if this still an issue with Mavic and Litchi?

 

[kidroc]

i use litchi all the time on very long waypoint missions with signal loss.. and it all ways continues at the cruising speed for me..maybe i've been lucky to have signal loss when it was going in a straight line every time who knows..watching this closely...

 

[Logger]

Could be simply a wind issue here? Perhaps the DJI Waypoint mode which Litchi programs, is set up hold a pitch angle to achieve the desired speed and then hold that pitch until the next speed change is commanded.

OPs data suggests a constant pitch of -14 or -15 degrees through out and pretty much a 180 degree course change between fast and slow speed.. So after signal loss..... follow the route and maintain the pitch (not speed). The yaw shows it has switched direction by 172 degrees or effectively done a U turn once it has slowed up.
Lets say -15 pitch equates to the mavic flying at ~ 39 km/h / 24mp/h in nil wind. Now consider flying with and against the wind at this constant pitch. A mild wind of just 13km/h or 8 mp/h will alter the GS from 16 to 32 mph. Ball park figures that match the log, but you get the idea.

When connected the litchi App sees the speed error and commands a correction. Seemingly the aircraft WPT mode cannot do this autonomously. If the wind is light or signal is lost when flying into wind it might go unnoticed.

 

[Aerial Gopher]

Did anyone notice data not consistent?

I am making the assumption like you said the data log file is complete, and this point is where the speed changes is the signal lost point. I make the assumption that data was not removed or modified... but....

Altitude changes from 440 to 405 feet? How did that happen so quick?
Speed Mph 32.17 to 16.65 ? Ok that is your complaint... but keep reading
distance 4393 changes to 3352? Light speed!
datetime UTC 54:09.9 to 00:47.4 Instant time warp? I never looked at logs to know what 54 is or 47, they are in different positions, how long was this flight? the difference is at least about 54:00.0 that's not minutes is it? How long dos your mavic fly?
Satelites still 18, sure..
Voltage 11.96 even after the really long flight? Remaining power was 92 then to 62, but why didn't the voltage drop?
velocities are what they are, no info to confirm any of these.

Interestingly the YAW deg is approx. 180 deg out, was this drone going the opposite way when you claimed the speed reduced by half?

Its either wind that slowed it down, but that doesn't explain the inconsistencies with the data in this log file.

I suspect the data was modified before posting the image.

 

[Logger]

@Aerial Gopher
You are misreading the log and the times in particular. (read it as MM:SS.s not HH:MM).
There is a 6min & 37sec gap from 54:09.9 until 00:47.4. The hour of the day is not shown in the log probably to do with the way it is formatted in excel. But for arguments sake, the signal loss occured at 09:54am and ended at 10:00am, 6 minutes later. More precisely 09:54:09.9 until 10:00:47.4. = 6 min 37.5 sec.
This is commensurate with the 30% reduction in remaining power.

The line with the red coloured data, OP has no doubt highlighted to show the signal regain point, not signal loss.This was a log from the mobile device App and not the aircraft, hence the gap. So the altitude and distance changes you speak of are simply explained by the loss off signal time period.

Yes the direction pretty much reverses and you can see that in the log too. Prior to signal loss it is flying SW with distance increasing. After the 6.5 minute gap when signal returns it is flying NE and the distance is reducing. I see no conspiracy here. Just a very similar pitch while flying in more or less opposite directions. To me the only likely explanation is wind.

 

[Aerial Gopher]

@Aerial Gopher
You are misreading the log and the times in particular. (read it as MM:SS.s not HH:MM).
There is a 6min & 37sec gap from 54:09.9 until 00:47.4. The hour of the day is not shown in the log probably to do with the way it is formatted in excel. But for arguments sake, the signal loss occured at 09:54am and ended at 10:00am, 6 minutes later. More precisely 09:54:09.9 until 10:00:47.4. = 6 min 37.5 sec.
This is commensurate with the 30% reduction in remaining power.

The line with the red coloured data, OP has no doubt highlighted to show the signal regain point, not signal loss.This was a log from the mobile device App and not the aircraft, hence the gap. So the altitude and distance changes you speak of are simply explained by the loss off signal time period.

Yes the direction pretty much reverses and you can see that in the log too. Prior to signal loss it is flying SW with distance increasing. After the 6.5 minute gap when signal returns it is flying NE and the distance is reducing. I see no conspiracy here. Just a very similar pitch while flying in more or less opposite directions. To me the only likely explanation is wind.

But why is the battery voltage still the same ?
I also did not see the 09 hrs in that field, nor the 10 just 54:09.9 and 00:47.4

 

[Logger]

I made the 09 and 10 up to try an explain to you how the time is being displayed with the hours hidden. If you have MS Excel, just select format cells > custom and set "mm:ss.0" as the time display type and you will see how it hides the hours from the display. It is simply formatting, not a conspiracy.
Dunno about the voltage. Maybe the field was recording max voltage and that was what he took off at.
Anyway the issue is the speed changing when it was not programmed to do so.