Disaster

[Coconut Island Drones]

Just got my mini 4 pro yesterday and flying it half an hour ago and got a low battery warning. I had 22% battery power and it went into a forced landing which I couldn't cancel. I was at a height of 82m and around 180m away when it decided to descend and an incredible rate and nothing I done would halt it. Couldn't cancel the forced landing and couldn't get control over the drone. Long story short the drone is knackered. Haven't had time to buy the care refresh thing so where do I stand with this ?

Same thing happened to another guy I know who bought the mini 4 just a few weeks ago. He was flying at around 30m on a perfect windless day and it just dropped out of the sky.

 

[Meta4]

Same thing happened to another guy I know who bought the mini 4 just a few weeks ago. He was flying at around 30m on a perfect windless day and it just dropped out of the sky.

You said that yours went into auto landing but his just fell from the sky?
That doesn't sound like the same thing.

Perhaps if you post your flight data, people will be able to see what actually happened to your drone.

 

[Coconut Island Drones]

You said that yours went into auto landing but his just fell from the sky?
That doesn't sound like the same thing.

Perhaps if you post your flight data, people will be able to see what actually happened to your drone.

I got a warning of low battery at 22% and that battery power suddenly dropped to I'm sure it said 9% then the drone literally fell out of the sky. No option to cancel the forced landing, nothing. The drone fell in a spin. All I could do was watch it spinning round until it hit a tree then fell into a puddle. Front sensor is smashed, as is the camera and gimbal. I'm not new to drones so know not to venture out too far when the battery is getting low. Flew the mini 2 for a long time and when the low battery warning flashed up it wasn't an issue as I knew I had plenty of time to bring it home. I'm honestly starting to thing there might be an issue with these drones or possibly the batteries.

 

[Meta4]

I got a warning of low battery at 22% and that battery power suddenly dropped to I'm sure it said 9% then the drone literally fell out of the sky. No option to cancel the forced landing, nothing. The drone fell in a spin. All I could do was watch it spinning round until it hit a tree then fell into a puddle. Front sensor is smashed, as is the camera and gimbal. I'm not new to drones so know not to venture out too far when the battery is getting low. Flew the mini 2 for a long time and when the low battery warning flashed up it wasn't an issue as I knew I had plenty of time to bring it home. I'm honestly starting to thing there might be an issue with these drones or possibly the batteries.

Any chance you'll post your data for this incident?

 

[msinger]

@Coconut Island Drones you can find instructions for locating the TXT flight log here. If you post it here, we can take a look and help you figure out what happened.

 

[GFields]

Sorry for your loss. I know you do good work. I enjoy watching your videos. I suggest, in addition to uploading your flight log here, but also contact DJI Support.

 

[Coconut Island Drones]

Thanks folks. Going out on a 12 hour dayshift so will try to upload them when I get home tonight.

 

[dave canada]

shouldn,t need care refresh if you just got it yesterday ,just time for the replacement

 

[Droning on and on...]

The missing piece here is RTH. The drone should have warned and tried to return home at the appropriate battery level. Going straight to emergency forced landing says something was wrong, probably with the battery. The logs should show this, and DJI should replace the drone under warranty... that's typically their behavior in incidents like this.

But they'll need the logs.

 

[Coconut Island Drones]

The missing piece here is RTH. The drone should have warned and tried to return home at the appropriate battery level. Going straight to emergency forced landing says something was wrong, probably with the battery. The logs should show this, and DJI should replace the drone under warranty... that's typically their behavior in incidents like this.

But they'll need the logs.

Right just home from work and my memory is a bit clearer than it was last night. When I charged the battery up it took almost 3 hours to fully charge. I went out with the drone around an hour later and noticed the battery had already drained to 92% and it hadn't been switched on. The flights I done were pretty normal. Finished up with the battery at around 32% then took it out again just for a quick up to get some pics. Wasn't intending being in the air for anymore than 5 mins. Shortly after take off I got critically low warning but noticed the battery was saying 24% which made no sense. Anyway this was still plenty for what I wanted to do I carried on. The battery then suddenly dipped to 9 or 7% and the drone immediately went into a forced landing and I could clear it. I could also see the drone and could tell it was coming down fast. The fact it's smashed indicates it was no normal forced landing.
Just going to see if I can work out how to get these logs and post them here. Bear with me.

 

[Coconut Island Drones]

Not sure if this is the right thing or not.

 

[slup]

It's not very clear how you used the battery... if it had been laying around in between the different flight you made or not. If the flights were made, like the same day... the battery may have been bad & you should take it with DJI.

But the fact is that the battery voltage crashed (went as low as 2,85V/cell)... you already got the first on screen message about it at 79sec into the flight... then from about 122sec battery warnings dominate the message stream in the log... you should really have tried to land immediately.

Below a chart with the important data... flight starts to the left with motor start, then flight in N-mode (pink) & ending with a forced critical low voltage landing (yellowish) from where I've placed the chart marker at 150sec (it's from here the values in the legend comes). The meaning of the graphs is below the chart in the legend there.

The purple graph shows the vertical speed... during the first phase of the landing it reached 11mph (=5m/s) which is according to spec, so this wasn't any freefall speed, just max descend speed.

(Click on the chart to make it larger)


And here the message stream... have marked the timepoint where the first battery warning comes & when the forced landing starts. A lot of warnings in between that you ignored unfortunately.

(Click on the pic. to make it larger)

 

[Coconut Island Drones]

It's not very clear how you used the battery... if it had been laying around in between the different flight you made or not. If the flights were made, like the same day... the battery may have been bad & you should take it with DJI.

But the fact is that the battery voltage crashed (went as low as 2,85V/cell)... you already got the first on screen message about it at 79sec into the flight... then from about 122sec battery warnings dominate the message stream in the log... you should really have tried to land immediately.

Below a chart with the important data... flight starts to the left with motor start, then flight in N-mode (pink) & ending with a forced critical low voltage landing (yellowish) from where I've placed the chart marker at 150sec (it's from here the values in the legend comes). The meaning of the graphs is below the chart in the legend there.

The purple graph shows the vertical speed... during the first phase of the landing it reached 11mph (=5m/s) which is according to spec, so this wasn't any freefall speed, just max descend speed.

(Click on the chart to make it larger)
View attachment 172230

And here the message stream... have marked the timepoint where the first battery warning comes & when the forced landing starts. A lot of warnings in between that you ignored unfortunately.

(Click on the pic. to make it larger)
View attachment 172231

That's the thing though, these warnings weren't appearing on screen. The first I knew something was really wrong was when it went into a forced landing and the jump from 24% to 9 or 7% was instant, on screen at least. RTH never appeared at all. My intention was to get into position to take a couple of pics and when I got there that's when it all went wrong. I literally didn't even have the time to start bringing it home before it started it's forced landing.

 

[slup]

That's the thing though, these warnings weren't appearing on screen. The first I knew something was really wrong was when it went into a forced landing and the jump from 24% to 9 or 7% was instant, on screen at least. RTH never appeared at all. My intention was to get into position to take a couple of pics and when I got there that's when it all went wrong. I literally didn't even have the time to start bringing it home before it started it's forced landing.

But he battery voltage percentage didn't suddenly jump from the 24% you took off with... down to 9-7%. Look at the red graph.

And the message stream in the log should be visible on screen... sure you didn't miss them when trying to keep the drone in visual sight?

A low battery RTH will logically only occur if the circumstances is normal... not when the battery voltage crash, there the main priority is to prevent free fall by auto command the drone to land immediately.

 

[Coconut Island Drones]

But he battery voltage percentage didn't suddenly jump from the 24% you took off with... down to 9-7%. Look at the red graph.

And the message stream in the log should be visible on screen... sure you didn't miss them when trying to keep the drone in visual sight?

A low battery RTH will logically only occur if the circumstances is normal... not when the battery voltage crash, there the main priority is to prevent free fall by auto command the drone to land immediately.

I can see from the graph the voltage seems to have decreased in the normal way albeit very quickly but not on screen. I flew this flight looking at the screen with only the occasional glimpse up to see the drone. As I said, on screen everything was normal until the sudden decrease in battery power and the forced landing. I'm normally quick at reacting to any sudden changes or battery getting low but this was so sudden it completely caught me out. I had no controll over the drone and it was turning constantly on the way down.

 

[slup]

...As I said, on screen everything was normal until the sudden decrease in battery power and the forced landing...I had no controll over the drone and it was turning constantly on the way down.

What's shown on screen regarding battery percentage is taken from the same source as what's recorded in the log...

And the drone didn't rotate uncontrollably on the way down... all yaw movements it made came from rudder stick commands you made...

Dashed green is the stick command (value 1024=neutral)... red is yaw on a 360 degree axis (where 0 is North).

 

[Coconut Island Drones]

What's shown on screen regarding battery percentage is taken from the same source as what's recorded in the log...

And the drone didn't rotate uncontrollably on the way down... all yaw movements it made came from rudder stick commands you made...

Dashed green is the stick command (value 1024=neutral)... red is yaw on a 360 degree axis (where 0 is North).

View attachment 172234

I get that and the spinning might well have been me trying to regain control to be fair but as for the on screen warnings they simply weren't there and the battery power on screen took a sudden plunge. I reckon DJI aren't going to play ball on this one.

 

[slup]

If the battery didn't have been laying around on those 24% for several days... instead it had been fully charged the same day & used during several flight that day... the battery most probably were sick, & DJI would probably take this. Contact them.

Here you can replay the flight & study percentage, messages & stick moves...

DJI Flight Log Viewer - PhantomHelp.com

 

[Coconut Island Drones]

If the battery didn't have been laying around on those 24% for several days... instead it had been fully charged the same day & used during several flight that day... the battery most probably were sick, & DJI would probably take this. Contact them.

Here you can replay the flight & study percentage, messages & stick moves...

DJI Flight Log Viewer - PhantomHelp.com

I had used it that same day, maybe just over 2 hours before. When I landed on the previous flight the battery was showing 30-31% and had decreased to 24% upon starting up. I didn't see this as being an issue as I was only planning a very short flight anyway. Thanks for all your help it's very much appreciated and I'll contact DJI in the morning and see what they have to say.

 

[slup]

@Coconut Island Drones , would also like to end this with sketching up some lessons learned, in all friendliness (hope you don't mind)... both for you in future flights & for others that might read this later.

It covers good judgement, panic & what a pilot remembers vs. what actually happened.

Good judgement:

...I'm honestly starting to thing there might be an issue with these drones or possibly the batteries.

...When I charged the battery up it took almost 3 hours to fully charge.
...I went out with the drone around an hour later and noticed the battery had already drained to 92%
...Finished up with the battery at around 32% then took it out again... after take off I got critically low warning but noticed the battery was saying 24% which made no sense.
...Anyway this was still plenty for what I wanted to do I carried on.

...When I landed on the previous flight the battery was showing 30-31% and had decreased to 24% upon starting up. I didn't see this as being an issue

Have stacked up some bits of your story about the battery behavior & your decisions forward... As the battery is one of the most critical components to keep your craft airborne, this isn't the correct decision process... you got several early warnings & you shouldn't have proceeded.

Panic:

When panic hits you, a lot gets mixed up & it's easy to get a "tunnel vision"... sticks are being moved in a counter productive way & observations gets misinterpreted.

...the drone literally fell out of the sky.
...The drone fell in a spin.
...All I could do was watch it spinning round until it hit a tree then fell into a puddle.

...I could also see the drone and could tell it was coming down fast. The fact it's smashed indicates it was no normal forced landing.

None of these observations & conclusions correlates to what actually happened... you actually manoeuvred the drone the whole way into the tree.

This regarding the descent... speeds & what you commanded. As seen in below chart you actually commanded a descent with the throttle stick yourself in the beginning. Furthermore you can see that you actually gained height every time you held the throttle stick fully forward. The drone then never reached any speeds that could be considered to be "falling out of the sky"... it reached those 11mph or 5m/s that are specified (blue graph, z-speed= vertical speed where positive value is a descent).



Then this with "All I could do was watch it"... you were very much active on the sticks the whole way into the tree.

During nearly the whole decent you had the right stick nailed forward (elevator)... in the end you also applied some right stick right inputs also (aileron). All this made your drone to gain a heading speed, just before the crash the speed was 11,5mph, mainly generated by your maxed out stick input.



It was similar regarding "the spinning"... all came through your stick inputs. The drone turned nicely every time you applied a rudder command (which you did during 4 main instances).



What a pilot remembers vs. what actually happened:

All above gives a really good example around how big of a difference it can be regarding reality & what a panicked pilot remembers.

The battery was most probably the main issue here of course... but the decisions made, up on early warnings in the battery behavior, warnings during flight & panicked state made the issue worse. If you had put that battery aside before flying with it... or if you had calmly applied full throttle for a slower ascent when the landing set in, pointed your camera down & looked for a suitable landing spot already higher up, manoeuvred it there & then just handed over to the auto landing... your drone most probably had been without damage now.