Phantom 4 Pro hits bunker air vent.

[Yt2]

Hi guys,


I had my first accident today after some strange things happened. I believe I am a competent pilot, so I am looking to the experience of the group to see if it was pilot error or not.

• I charged two battery's in my DJI charging hub and noticed that one battery charged for a bit then it started charging the second battery. It started charging the first battery again once the second battery was full.
• I could not fly the same day, and naughty, I flew today. I only wanted to do a few small flights as I had been having issues with Dronelogbook and battery reporting. I realise that you should always fly with freshly charged batteries.
• I put the battery in the P4 that had issues charging and auto took off. It only remained in the air for about 5 seconds and started landing with all led's blinking Red. I removed and replaced the battery again and shut down A/C and controller, but the same thing happened again.
• I swapped batteries and fired up everything, when the bird started shaking on the ground with the props in idle. Shut down everything again and restarted and all was good.
• I decided to fly in ATTI mode to keep my skills up and headed towards an old ammo bunker with 4 air vents sticking up above the roof my about 1.5 metres. These air vents are about 2.5 meters apart. The whole roof is made of metal, as are the vents. Correct me if I am wrong, but I believed if I was in ATTI mode, I would not have compass errors. Is that correct?
• As I was going to be flying between the vents I made an altitude adjustment to get higher above the roof, just before the vents, then when I thought I was past the vents, I made a right hand turn, and to my amazement, the bird bounced off the vent with a sicking thud, and took off. I gained control and brought the bird home and landed.
• Damage was one bent arm, well creased and the gimble is now continually quivering. Surprisingly all props are in perfect condition.

DJI Flight Log Viewer - PhantomHelp.com
Not sure if the above is how you post the link.

I would appreciate all you guys with the expert knowledge of reading the logs and giving me a report as to if it was pilot error or not. Thanks in advance.

Yt2...

 

[Yt2]

The battery issue log.
DJI Flight Log Viewer - PhantomHelp.com
Yt2

 

[Fly Dawg]

As for the battery, I see no reason that it should have commenced "critical battery" auto land. Might be a silly question, but what is your "critical battery" level set at in the app? According to this, the AC went in to Autoland at 17.5 seconds and 96% battery, which makes no sense.

 

[Fly Dawg]

As above, I can't explain the autoland. As for the full flight, I don't see much out of the ordinary to say it is anything other than pilot error unfortunately. The impact point appears to be at 381 seconds, simoultaneously with speed errors, which could be expected with an impact.

 

[Yt2]

Hey Fly Dawg,
Swift work on the logs, thanks... A bit late here now to check but will post back tommorow. They should be the default DJI settings, as I had formatted my pad the day before and reinstalled everything.
That battery was the one that did not charge correctly, but the lights on the battery were showing full charge.
I do have the second attempt to fly with that battery. I shut it down, removed and reinstalled battery and fired up again, but it did the same thing. Is that worth posting.
I then swapped to the other battery for the crash flight only minutes later, so if the settings were up the creek, it should have done he same thing and not taken off, I would expect.

 

[Fly Dawg]

I then swapped to the other battery for the crash flight only minutes later, so if the settings were up the creek, it should have done he same thing and not taken off, I would expect.

I agree with the same expectations. Before using that battery again, try a deep discharge then recharge and try it again. Should it exhibit the same response, you might just have to write that one off. It is odd though that the cell voltage's never reached anywhere near the cutoff values, not did the reported total voltage or the percentage value. That is just a bit odd.

 

[Fly Dawg]

Instead of uploading another flight, as you mentioned. Upload the .dat file from the aircraft itself of the battery issue flight. If you have not done this before, finding the correct one can be tricky, and you can't directly upload it here. You will need to upload to a share site such as Dropbox, Google Drive, etc....and share a link to that back here. These files can get quite large. For instructions to get the files, follow this link: How to retrieve a V3 .DAT File from the AC

 

[Meta4]

The whole roof is made of metal, as are the vents. Correct me if I am wrong, but I believed if I was in ATTI mode, I would not have compass errors. Is that correct?

The Phantom can fly without GPS (that's what you are doing in atti mode) but it can't fly straight without the compass.

 

[sar104]

The Phantom can fly without GPS (that's what you are doing in atti mode) but it can't fly straight without the compass.

It may appear that way, but in fact the FC is ignoring the compass in ATTI mode. It is holding altitude and attitude and beyond that, elevator directly controls pitch and aileron directly controls rudder. Rotation is detected and controlled using the input from the rate gyros.

 

[Yt2]

Ok,

In view of that, could the steel roof contributed, as I was concerned about being so close to metal.
I surspect that as I had just reloaded all software and made a rookie mistake of not going into setting to check all settings, that all the avoidence stuff is off by default or is it that in ATTI mode it is turned off.
I could have sworn that I had passed the air vent when I made the turn. Lesson learnt, back to the books for me...
Yt2...

 

[Techcop50]

As far as the battery behavior you described, it sounds to me like this: You powered up the hub, at which point it measures the level in each battery, then charges the highest level one first. It briefly charged the first battery, then swapped to charge the other one first, leading you to think that it was full. The first flight was on a battery that was almost empty, perhaps?

 

[Fly Dawg]

The first flight was on a battery that was almost empty, perhaps?

The first flights battery levels are charted in Post #3 above. According to this it was at 97% but the autoland is still a mystery to me. I can't explain that one.

 

[Techcop50]

Thanks, Dawg.

 

[Yt2]

Hi Dawg,

Here, I hope, is the link to the battery file you asked for.

Dropbox - DJI_ASSISTANT_EXPORT_FILE_2018-06-13_22-45-18.DAT

Is there any point linking the crash file here as well...

Yt..

 

[Fly Dawg]

Here, I hope, is the link to the battery file you asked for.

That is not the correct file. It is only a short power on, no motor start. The file you are looking for should be much larger than 50meg. As I mentioned, finding the correct one can be a bit tricky.

 

[Russ43Phantom]

The battery hub, when charging more than one battery, will first test the charging level of each battery. Then it will select the battery with highest charge to charge first. That gets you into operation quickly by topping off the first one. So what you shared shows no battery issues. Radical flight behavior is a symptom of magnetic interference or compass error. I experienced radical flight take off behavior from a wooden picnic table that had metal legs.

 

[Yt2]

Hi Dawg,

This should be the file.

Dropbox - DJI_ASSISTANT_EXPORT_FILE_2018-06-16_23-11-22.DAT

 

[Yt2]

Hi RUSS43Phantom,
You are correct about the charging hub, I have flown from this location many times before, I had no compass/magnetic interferiance that I know of. I swapped out the battery and took off from the exact same location 2 minutes later with no problems.

I fully discharged the battery and recharged again, and it is now seems Ok.
It was due for a full discharge as it had had done 22 charges and Airdata UAV recommends doing a full discharge at 20 charges.

Thanks for your reply.
Yt2...

 

[BangBangDroneDead]

Wowzer-i know exactly why it autolanded. How many charge cycles do you have on the failing battery? I'm not sure if it's the same for all phantom batteries, but hold down the button on the battery without it plugged into the phantom and keep holding for 5 seconds. That will show you the battery LIFE, not charge. If all 4 lights hold, its between 90-100 life, 3 lights, 80-90, and so on. Flying with battery life below 90 or 80 would be risky, and if it starts blinking all red that means you need a new battery, as that one has worn out and doesnt provide enough voltage. If you have more than 100 charge cycles and you've been not treating them optimally, you may get this error. This can even happen at 60-80 charge cycles. The battery is simply worn down and doesnt provide enough power, hence the autoland. If your battery life is 90-100 and has few charge cycles or as been treated optimally, I'm stumped. Goodluck buddy

 

[Fly Dawg]

This should be the file.

This is the exact same file as you previously posted in Post #14 above. FLY317.dat .....dated 2018-06-10T08:37:20Z at power on.