Drone Lost with Litchi (Airdata log attached)

[icculus]

Hi, I've flown w/ Litchi countless times but today something happened and the drone went into some auto landing mode w/o me pressing anything. My settings when it loses signal is to RTH at 300 feet. I was flying and visually started seeing the drone lowering altitude. So I used the stick to raise it back up. It then lost signal so I figured RTH was engaged and waited. Nothing. After 30 sec or so I hit the RTH button on the controller just to make sure. Still nothing. Can someone help me understand what happened? I went to the spot it landed at but the drone wasn't there, unfortunately Does anyone see any operator error here or was this some sort of LItchi bug?

Log file: Dropbox - 2018-04-08_13-38-30_Standard-1.csv

Thanks!

 

[msinger]

Please attach your Litchi flight log here too.

 

[Meta4]

Hi, I've flown w/ Litchi countless times but today something happened and the drone went into some auto landing mode w/o me pressing anything. My settings when it loses signal is to RTH at 300 feet. I was flying and visually started seeing the drone lowering altitude. So I used the stick to raise it back up. It then lost signal so I figured RTH was engaged and waited. Nothing. After 30 sec or so I hit the RTH button on the controller just to make sure. Still nothing. Can someone help me understand what happened? I went to the spot it landed at but the drone wasn't there, unfortunately Does anyone see any operator error here or was this some sort of LItchi bug?

You launched using a battery that had been sitting around discharging for some time.
Although the % indicator showed 50%, this is a false indication unless you start with a full battery.
Within one minute your battery cell value was down to 3.3V which triggers the critical low voltage autolanding.

 

[icculus]

Here's the Litchi Logs: Dropbox - 2018-04-08_13-38-29_v2.csv

You are right, I didn't fly for a few weeks but the battery was above 50% and I was going to go on a very quick flight.

Thanks for the info - expensive lesson learned, never fly unless you are at 100%.

 

[msinger]

Here's your uploaded log file:
DJI Flight Log Viewer - PhantomHelp.com

 

[msinger]

Litchi flight logs don't contain as much data as DJI GO flight logs, so I'm not 100% certain as to what happened. It appears the battery reached the critically low level and the Phantom auto landed.

Did you check the beach around the last known location? It was flying at ~35 MPH at the time, so it wouldn't have been at that exact location.

 

[icculus]

Thanks everyone. We did check that location out but no luck. Hoping someone may have found it and will report it somewhere. I never would have thought 1 minute into a flight a battery at over 50% would be critically low.

 

[msinger]

Was it windy? That combined with the speed and low charge level would be a perfect recipe for the low battery cell voltage (3.2 V) shown in your flight log.

 

[icculus]

Pretty calm day. The battery level in Litchi didn't seem to go down quickly either, I think it was above 50% the entire time.

 

[msinger]

The battery level was above 50%. However, the battery is deemed to be critically low when the cell voltage reaches a level where the aircraft determines it only has enough time to safely get back to the ground.

 

[icculus]

Thanks. What is a safe voltage level to start a flight with? I suppose if i get a new one that will be on the check list before taking off.

 

[sar104]

Pretty calm day. The battery level in Litchi didn't seem to go down quickly either, I think it was above 50% the entire time.

It was not particularly calm at 170 ft (Airdata UAV - Flight Data Analysis for Drones) but that was not a problem per se.

The aircraft went into autolanding due to the battery cell voltages, as mentioned above. The disconnect was the downlink only - the uplink was still full strength, so what happened afterwards depends a lot on whether you continued to send stick inputs.

At the point of downlink disconnect the aircraft was in autoland mode but traveling back at around 16 m/s under full forwards elevator and descending through 20 m - but that speed was actually slowing its descent rate below the normal 2.5 m/s.

If you continued to send full elevator then it will have continued that profile and may have taken 30 s to complete its descent. That's a possible further travel of nearly 500 m - i.e. virtually all the way back to the home point. On the other hand, if you discontinued full elevator or the uplink disconnected (although no sign of that happening), it will have stopped and landed in place. If you know what you did regarding stick inputs after disconnect you may be able to narrow it down - otherwise it is the full line from the last recorded point to the vicinity of the home point (its approximate direction of travel).

 

[Meta4]

I never would have thought 1 minute into a flight a battery at over 50% would be critically low.

50% is not 50% unless you start with a full battery.
Yours was probably more like 15%
The voltage is the important parameter - not the (false) percentage indicated.
Once your battery reaches 3.3V per cell, it's critical low voltage time and autolanding is unavoidable.

 

[icculus]

Thank you, that is an impressive amount of info. I went into panic mode so who knows what I was hitting on the sticks after it didn't come back. I'm guessing it's somewhere in the ocean.

 

[msinger]

What is a safe voltage level to start a flight with?

The aircraft will usually try to automatically back down the stick inputs if it detects the voltage is at the point where the critical low battery warning is going to be triggered soon. I don't see those messages in your flight log. Perhaps Litchi is unable to access them or it just doesn't display them.

To answer your question though, there really is no safe voltage level to start a flight. When on the ground, the voltage will always be higher since there isn't much load on the battery. So, it would be hard to guesstimate where the voltage will be once in the air and flying at full stick in windy conditions. Keeping that in mind, you should definitely start with a full battery if you know you're going to be flying at full stick and/or windy conditions.

 

[DigitalSkyPilot]

I lost control of my P3S when the app stopped. I had been using android with a 1.5 ram for awhile. . I got a new tablet with 4 gigs of ram and problem solved. May not be your situation but was for me. It wouldn't respond and had a mind of it's own coming down into the neighborhood. I managed to get control at the last minute.

 

[Harleydude]

Hi, I've flown w/ Litchi countless times but today something happened and the drone went into some auto landing mode w/o me pressing anything. My settings when it loses signal is to RTH at 300 feet. I was flying and visually started seeing the drone lowering altitude. So I used the stick to raise it back up. It then lost signal so I figured RTH was engaged and waited. Nothing. After 30 sec or so I hit the RTH button on the controller just to make sure. Still nothing. Can someone help me understand what happened? I went to the spot it landed at but the drone wasn't there, unfortunately Does anyone see any operator error here or was this some sort of LItchi bug?

Log file: Dropbox - 2018-04-08_13-38-30_Standard-1.csv

Thanks!

In these situations, I usually go with ATTI mode and full stick up. If your home point were good and RTH altitude high enough, there should be no problems. So...maybe your RTH was too low and/or your home point wasn't set correctly? Does Litchi maintain that data?

 

[paulmorel]

In these situations, I usually go with ATTI mode and full stick up. If your home point were good and RTH altitude high enough, there should be no problems. So...maybe your RTH was too low and/or your home point wasn't set correctly? Does Litchi maintain that data?

yup. this is exactly what i would do.

 

[Ged2217]

I've read about this happening before with the Litchi app, when pressing RTH it lands where ever it is rather than returning home. This bug in the app is exactly whats stopped me from using it, sorry for your lose buddy

 

[sar104]

I've read about this happening before with the Litchi app, when pressing RTH it lands where ever it is rather than returning home. This bug in the app is exactly whats stopped me from using it, sorry for your lose buddy

No - that wasn't the problem. It autolanded due to critically low battery, not because of a Litchi bug in RTH.