Inspire 1 Raw fell from the sky -- what the hell happened?

[Ruckusman]

or perhaps the battery errors from the pilot log posted in earlier messages are the cause, occams razor in action

 

[Ewan Haggarty]

The Battery telemetry goes through the small 4-pin connections next to the larger power spades. I think it likely that there was spurious Battery TM due to it not being clicked in, so the contacts were intermittent or poor. That would also account for the strange multi-cell errors recorded. It seems much less likely that the Battery itself was at fault.

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[Andrei Voinigescu]

I did recover the drone after three days in the ocean -- thankfully, it was only in two meters of water at the top of the reef (which is why we didn't find it the first time -- we were looking deeper). So I was able to recover the video off the microSD card, including a video earlier in the doomed flight (from 40s - 88- into the flight). The drone wasn't recording at the time of the sudden failure though. I also couldn't recover anything off the SSD -- not sure if it's because there's corrosion on the connections, or internal damage, or what.

For what it's worth, the battery was firmly wedged in place when I found the drone. More amazingly, it was still intact -- I figured it would've just as likely exploded/burst into flame after being submerged in 2 meters of water, but maybe the pressure wasn't enough to penetrate the cell and there were no punctures.

Also, at the time of the disconnect, the drone was climbing and flying forward at somewhere between 20-40km/h. Aside from the force of gravity, the inertia would've been operating to keep the battery in place. It seems rather implausible to me that it would suddenly "pop out" at that point. Also, shouldn't there be some sign of these intermittent/poor contacts in the log?

Regarding DJI.. nothing conclusive yet. The language barrier makes interpreting the emails I've received from them a bit iffy, but as best as I can determine, they don't have a policy against refusing warranty claims for flights with 3rd-party apps per se -- they just categorically refuse to use the Autopilot telemetry log. Or at least the tech support person I've been communicating with refuses to. He's promised to put me in touch with another department though, so I'm hoping that'll be more productive.

 

[Ruckusman]

good job recovering the Inspire and yeah it was clear enough that the battery would be installed still...
Ewans attempt at a smokescreen wasn't a good one and was starting to look somewhat suspicious.

When battery communications are interrupted the error message is battery error and the rear LED goes solid red.

Distinguish that from the battery successfully communicating errors within the battery to the flight controller - which is what you have in your flight logs.

Good luck with DJI as their stance to this point is quite appalling

 

[Ewan Haggarty]

I've offered an opinion based on fact. I know suggesting the cause might be Pilot operational error could be taken poorly as personal criticism, this suggestion was not posted with that intention. People do make mistakes and there is a tendency to look for a 'thing' to blame for the consequences before considering human behaviour and actions. It is possible for a I1 to be flown with a battery not clicked in and I believe the result could be it unseating and disconnecting giving the crash symptoms you describe. What is the condition of the battery contacts? Perhaps corrosion from the seawater means there is nothing to make out. If the I1 hit the water upright, the force would have been in the right direction to seat the battery fully on impact.

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[andrew259]

Part of the analysis of faults is to find the simplest explanation that fits all the known facts - it's called 'Occam's Razor'. Please try this yourself - place the I1 battery in the bird, but do not press down until it clicks into place, you will find that the battery sits proud of the fully-fitted position by about 3mm. This more than halves the contact area for the battery connections to the bird. Switching the battery on will power the I1 and the ESCs will beep-beep-beep,beep as normal. DO NOT pull the battery up and DO NOT start the motors by CSC in this state, carefully power down by switching off the battery. It is entirely possible to fit the I1 battery into the airframe and not click it into place - its weight alone is insufficient to make it positively self-locate. Perhaps as part of the sequence of getting prepared for flight, the Pilot just failed to push the battery home until it clicked. A bit of negative-G by manoeuvring or a gust could then easily separate the battery from the bird, or, through over twice the current going through the available contact area, these burnt out.

Completely PLAUSIBLE - I think this is what may have happened to me....


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