Spark lost altitude and crashed on RTH

[Nick R]

I decided to fly my spark today over an open field trying to see how far I can go with it before it loses signal and come home.. So on a fresh battery I let it flew thinking if it doesnt come home on its own.. I will hit RTH when battery hits 60% trying to be safe.

About 2000 ft in.. I lost signal .. and sure enough it turned around and started coming home.
But then it never came home... I ended up spending the next hour.. in a field looking for it.
With the last know coordinates.. I eventually found it.

If there is a DJI support person monitoring this thread..
I would love to know why my bird lost altitude and crashed.

I am attaching a video...
At about 1:00 min mark I lost signal.. and the bird turned around and started its climb to RTH altitude of 60m.
Then at about 1:23 it begins its flight home. Then about 1:40 it rapidly lost altitude and eventually crashed.
No bird strike.. no nothing.. Just gradually went down.

Why ?

Here is the youtube clip of what happened.

 

[aviscomi]

Post your log file for others to diagnose:

DJI Flight Log Viewer

 

[msinger]

If there is a DJI support person monitoring this thread..

You'll have to post over in the official DJI forum if you want an answer from DJI support.

If you want some feedback from people in this forum too, then upload your TXT flight log at the link above and post a link back here.

 

[Nick R]

Here is the flight record

DJI Flight Log Viewer - PhantomHelp.com

Post your log file for others to diagnose:

DJI Flight Log Viewer

 

[msinger]

Your flight log shows your Spark was descending while the throttle stick was in the center position. That's pretty odd.

Did you have any 3rd party accessories installed on your Spark at the time?

 

[Nick R]

Your flight log shows your Spark was descending while the throttle stick was in the center position. That's pretty odd.

Did you have any 3rd party accessories installed on your Spark at the time?

How do you determine what position my stick was in looking at the available data ?
No there was no 3rd party accesssory on the bird.

In fact when the bird went down.. I totally lost contact with the UAV.
First .. RC Signal lost.. Then I got a message that says "Aircraft Disconnnected"

 

[msinger]

How do you determine what position my stick was in looking at the available data ?

Look at the CSV file for the flight log you linked above.

The "RcThrottle" column shows the position of the throttle (which commands the Spark to ascend/descend). "1024" means the stick was in the center position. A value greater than 1024 means you were commanding the Spark to ascend. A value less than 1024 means you were commanding the Spark to descend.

 

[Nick R]

Look at the CSV file for the flight log you linked above.

The "RcThrottle" column shows the position of the throttle (which commands the Spark to ascend/descend). "1024" means the stick was in the center position. A value greater than 1024 means you were commanding the Spark to ascend. A value less than 1024 means you were commanding the Spark to descend.

All the RC numbers at the last record in the CSV .. are the same as at the point when the RC signal was lost. All 1024 except the rudder which was 1018. Rudder controls the yaw of the aircraft .. not elevation.. which could simply mean the aircraft may have tried to adjust heading during RTH

What is puzzling to me is .. why the last known altitude is at 55.1 ft. ??
Almost look like the aircraft once disconnected.. stopped registering the flight log.
But the RTH behavior should still return to HOME or Hover .. not descend rapidly as clearly seen in the youtube video.

 

[msinger]

What is puzzling to me is .. why the last known altitude is at 55.1 ft. ?

DJI GO only logs data to the TXT flight log while the downlink is connected. If you want to see the full flight log, you'll need to retrieve the DAT flight log from your Spark like this.

 

[Nick R]

DJI GO only logs data to the TXT flight log while the downlink is connected. If you want to see the full flight log, you'll need to retrieve the DAT flight log from your Spark like this.

I tried that.. the .DAT file that were downloaded were not ascii and not readable. How do you use it to glean information >?

 

[msinger]

You can use DatCon to view the DAT flight log data.

 

[NewYorkJack]

DroneShield: The DroneGun can shoot UAVs 1.2 miles away | WIRED UK

 

[Blue Baron]

Looks like a defect to me. Although the telemetry says satellites ok and descending. So no false record of altitude.

However, the RTH looks very bumby, not like it should. Where the craft starts to descend, footage almost looks like the drone was hit by something. Maybe, the output from motors became too weak?