Disaster

[Capt KO]

Batteries at rest after a flight nearly always give a false reading, you noticed this as a drop from 31% to 24% on startup. That was your first indication that the battery was about to lose power shortly. So sorry for your loss but telling DJI of your previous flight experience may be enough to get them to show compassion. That along with it only being a day old. Please contact customer service and hope for the best, and be sure to tell us about the outcome.

 

[NoBozos]

Good luck working it out with DJI. Thanks for sharing your experience.

 

[Coconut Island Drones]

@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:



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.


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).

View attachment 172248

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.

View attachment 172249

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).

View attachment 172250

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.

All very good points and taken onboard. Thank you very much once again for all your help. Contacted DJI this morning and it's being sent back so hopefully I get a good outcome. I'll let you know how things work out.

 

[Droning on and on...]

Batteries at rest after a flight nearly always give a false reading, you noticed this as a drop from 31% to 24% on startup.

Especially if they're warm. Allow them to get to room temp first.

But even then estimating remaining charge is an approximation at best. Things like natural changes in internal resistance, lost capacity with age, etc. affect how much usable charge remains at a given resting voltage.

The most accurate measure of a battery's State of Charge is "FULL".

 

[Coconut Island Drones]

Ok so finally an update. Just heard back from DJI and they're sending out a brand new drone. They declined to say why it's as straightforward as that and given the exact same thing happened to a guy who lives only a few miles from me I do suspect there has been a faulty batch of batteries that they're aware of. He had the same outcome, straight replacement, no questions asked. I have to say though DJI customer services are the best I've ever dealt with. Hat's off to them.
And once again thank you to the members on this fantastic forum for going out of your way to help me understand what went wrong. 10/10