P4 Crashed uncontrollable spin

[Rat Rambo]

Just returned from a couple of flights this morning. On the first flight everything was normal but then it just fell from the sky continually spinning.

Very lucky for me it's went down into a wheat field which substantially slowed its fall. It was only a few meters away and I retrieved it immediately.

The craft was upright, bird still on with no prop damage and camera/gimbal appeared OK.

I wiped it down, inspected the bird and decided to see if it still works.

So turned it off/on and it connected with the app and camera feed was fine. It located satellite's/home point and was ready to go.

I launched and the second flight went without any issues.

However I have lost total confidence in my bird. In almost any other situation I would have been bringing it back home in bits.

See DJI 4 flight replay:

Any ideas what happened?

 

[macoman]

You should perform calibration after the crash.

 

[With The Birds]

Your flight record will almost certainly provide greater insight. Upload to phantomhelp or airdata and post link here.

 

[Rat Rambo]

DJI Flight Record below

 

[Rat Rambo]

So having got home I have now fully inspected the bird and notice the following :
1) Have a small crack on the upper frame near the motor.

2) One of the motors is slightly higher than the others.

Third photo shows the bird as recovered from the wheat field. All seemed OK after a 40 meter fall

 

[Fester]

Is that high battery drain something you see on your flights? Are all able to rotate freely with no obvious bearing troubles?

 

[zgembit]

I recently bought used phantom 4 that has exactly same thing with one of the motors (spacing is about 3 times bigger then on other ones), see the picture. From previous owner I got to know that he once also had one minor crash.
I flew this one couple of times now with success, no issues at all. This higher motor doesn't make any speciell different sound or is getting warm. But its strange, I dont know will I trust it or not yet...

 

[Rat Rambo]

Any ideas why my bird span out of control and crashed? Uploaded flight record shows no clue. It was in my full view when it happened, no birds around or anything.

In reply to previous comments motors spin freely and no high battery drain.

 

[Capo]

A spinning fall usually points to a problem with a single prop/motor. I'd be very suspicious about that motor with the excessive gap. I'd be wondering if that might have caused the crash, not a result of the crash. If it got locked up that would explain the spin.

 

[rene van der meer]

A spinning fall usually points to a problem with a single prop/motor. I'd be very suspicious about that motor with the excessive gap. I'd be wondering if that might have caused the crash, not a result of the crash. If it got locked up that would explain the spin.

From all the lost prop discussions it is my understanding that a drone will drop down if one of the motors blocks.

 

[Rat Rambo]

Update..... OK my bird is on it's way to the Netherlands for repair. Reported incident to DJI who requested a return to service centre.

I still don't understand what went wrong? As I mentioned earlier once the drone had crashed I wiped it down, turned it on/off and then flew a test flight (Including sport mode) it was faultless.

 

[Capo]

From all the lost prop discussions it is my understanding that a drone will drop down if one of the motors blocks.

It'll most likely drop and spin. You have asymmetric torque (2 blades one way, 1 the other) which will cause a spin and insufficient lift to keep it up. This will cause a downward spiral, whether powered or during autorotation.

 

[FlashBuddy]

I saw the "obstructed motor" warning on your scree. Hmmm, do you think a motor could have been momentarily obstructed and thus caused the fall?

 

[Duchunter]

I got my p4 used and I noticed that one of the motors just didn't sound or feel quite right. I investigated a little deeper and I noticed a lot of movement in the bearing. I tried to post a video of it but it wouldn't let me. You can definitely see that its not the same as the rest. I haven't changed it out yet but I do have a new motor. I gotta do it but I'm debating just exactly how I want to go about it. I really don't want to soldier the board. I can and I will, I just hate to solder something that's not broke. What if it needs another new motor in the future? Now that's twice it would need to be soldered. Im thinking of putting quick connects on it and sealing each connection with shrink take. If I don't crash it, it may live a very long life and need several motors. I would rather put in new motors every so many flights than risk a failure. They are the only moving parts that will bring it down. The aren't expensive either. Quick connects just makes since to me.

 

[Duchunter]

It'll most likely drop and spin. You have asymmetric torque (2 blades one way, 1 the other) which will cause a spin and insufficient lift to keep it up. This will cause a downward spiral, whether powered or during autorotation.

I think the obstruction was it falling into the vegetation. I could be though that a motor over heated and locked up.

I've seen drones fly on 3 props, controlled flight and Im talking a quad with one motor shut down with a controlled decent. Why hasn't dji implemented this? I guess it sells more quads if every failure results in a crash but the technology does exist now to bring it down intact from a motor failure at altitude, and it has for some time.

 

[Capo]

I got my p4 used and I noticed that one of the motors just didn't sound or feel quite right. I investigated a little deeper and I noticed a lot of movement in the bearing. I tried to post a video of it but it wouldn't let me. You can definitely see that its not the same as the rest. I haven't changed it out yet but I do have a new motor. I gotta do it but I'm debating just exactly how I want to go about it. I really don't want to soldier the board. I can and I will, I just hate to solder something that's not broke. What if it needs another new motor in the future? Now that's twice it would need to be soldered. Im thinking of putting quick connects on it and sealing each connection with shrink take. If I don't crash it, it may live a very long life and need several motors. I would rather put in new motors every so many flights than risk a failure. They are the only moving parts that will bring it down. The aren't expensive either. Quick connects just makes since to me.

Don't be a afraid to solder. It's a much more reliable connection than using quick connects. This is why most quad racers also solder in spite of often changing parts. It can only take one minor failure to totally wreck a camera drone.

 

[DanMan32]

Just be sure you have a decent wattage iron, like 30-40 watts and very clean, we'll tinned tip.

 

[Rat Rambo]

Update.....

Drone has been repaired by DJI for free.

Interestingly it's also my original drone that came back i.e same serial no.

They have repaired motors, gimbal & camera.

And the icing on the cake, they sent it back with a new P4+ battery. I only sent the bird and controller back as requested.

So well done DJI I am very happy.

Now if only they can sort out the android DJI go 4 app!

 

[DocDiggler]

I think the obstruction was it falling into the vegetation. I could be though that a motor over heated and locked up.

I've seen drones fly on 3 props, controlled flight and Im talking a quad with one motor shut down with a controlled decent. Why hasn't dji implemented this? I guess it sells more quads if every failure results in a crash but the technology does exist now to bring it down intact from a motor failure at altitude, and it has for some time.

Mate a quadcopter with only 3 blades you going down sorry no way!!

 

[With The Birds]

Mate a quadcopter with only 3 blades you going down sorry no way!!

Not true, by yawing they can continue to fly, albeit not very elegantly- enough to allow a controlled landing however. DJI does not currently implement the algorithm to prove for it though.