Well, one of the shittiest and most destructive things that could happen to a UAV happened to me today. Accidental low-battery LAND failsafe set my 3DR Y6 down... into a pool. I retrieved it immediately and disconnected the battery. Now I'll wait for a few days for it to dry out before doing some system tests, but I'm curious what your expectations for system function will be at this point. Crappy? I think so. It was smoking when i pulled it from the water. Oy. 

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Ouch - You are living one of my biggest nightmares. First off, I am very sorry, but hopefully we can salvage as much as possible. While I don't have a experience with the drones electronics, I have salvaged more stuff than I should have from water damage (including the keyboard I am using) by doing the following.

1. The battery is gone - get a new one. I wouldn't trust it after this.

2. Disassemble the drone completely. 

3. Look for melting on any wires and / or burn marks on any circuit boards. If you find any, that component needs to be replaced.

4. Dry everything off as best as you can. Use compressed air, if you have it, to blow out any residual water.

5. Ideally, get some silica gel. You can buy 100% silica gel cat litter. If that isn't available, get a bag of dry rice (not instant rice)

6. Every component (motors, ESC, power distribution board, Pixhawk/APM, GPS, anything else) goes into it's own zip top plastic bag. 

7. Add enough rice / silica gel to each bag to to completely cover the component.

8. Let them sit for 3 very long days.

9. Pull everything out of the bags and blow out any residual gel / rice and any dust.

10. Bench test each component, see what works.

11. Replace any parts that don't work; reassemble and get into the air again.

I hope that this helps. I really do feel your pain. Good luck!

I agree with everything Paul said, and want to add that you're almost assuredly going to lose your ESCs.  Motors are very likely ok.  Everything else is up for grabs, good luck!

Fresh water, or saltwater pool ?

Anyway, first rinse everything in distilled water, then alcohol, then dry with hair dryer on gentle heat.

Fresh water you might stand a chance, salt, well luck of the draw.

Smoke never is good :-(

Hardest part is getting the smoke back in :)  I once washed a GPS/compass in washing machine with my pants, I took it out of the case and dried it immediately in a warm oven, surprisingly it works just fine, but it wasn't powered on.  I also flipped a quad in shallow water once and got the APM and GPS wet, dried them out in the oven and they still work fine.  I get motors wet all the time on my Aquacopter APM, they run underwater too, motors will definitely be fine.  I expect your ESC's will be toast.  I am assuming fresh water, I would definitely rinse any chlorine residue off.

Hi,

I got 2 times this hard experience, once in rapids in the river... after 2 hours of search, we got it back.No damage except the wifi part of the gopro 3 (mounted on tarot guimbal). I guess we still use the 5000 mAh batery. And we saved 1 hour footage.... maybe lucky.... 2 times....

It's actually possible to set the battery failsafe to RTL instead of LAND.  This feature is sadly not visible in the mission planner's battery failsafe setup page nor is it documented on the wiki page.

I'll fix the wiki page.  Until then, for those that are reading this, it's possible to set it to RTL by setting the FS_BATT_ENABLE parameter to "2".

Sorry for the troubles.

This is a classic example of why users must have a detailed and clear picture of exactly how all of the failsafes work and what the implications are.  Sadly, many people enable the failsafes and say "now I'm safe."  Not understanding how and when they work can at best ruin your equipment, and at worst cause serious property damage or injury.

RTL is the safest battery failsafe action because you know it will be landing right where it took off.  With the battery failsafe set for LAND, it might be landing in a pool, on a road, someone's roof, or a bystander's head.  BUT, what if you are flying somewhere with overhanging tree branches?  What if there are other RC aircraft in the sky around you.  What if you are indoors?  All of these things would be highly detrimental when the RTL tries to take it up to 150ft.

Do you know how much flying time you have after your battery failsafe voltage or MAH remaining kicks in?  If you arbitrarily set it for something because "that's low battery", and there isn't enough juice left to fly home, you've made the situation even worse.

Have you tested your transmitter failsafes to make sure it acts as you expect?  I've made that mistake and almost lost my aircraft.

Randy, I thought the default battery failsafe behavior was already RTL, not LAND? If not, we should totally make that the default. 

yes but what's happen if the drone is far away.... RTL could be far away...

=> RTL if near from Home else LAND....

"Far away" is a relative term.  There is no such programmatic definition for "far away".

If you are too far away to RTL, then the problem is the pilot who failed to manage flight time.  That is not a scenario you can automate.  It is a huge pilot screw up that will end up with a mangled aircraft at best, and possibly damage/injury on the ground.  Arbitrarily crashing into the ground a mile + away from home because you didn't monitor your flight time and battery power is unacceptable pilot behavior.

Hi ben.

My IRIS as been under the water for more than 1hours a few days ago. I ve removed all the components and put them into a plastic box with rice. 

After 48 hours i've re-mounted all the components (including 2 GPS , A sonar + a Gimball, ...)

And it works perfectly ! 
I've been flying hours, and did not encounter any issue.

"...and want to add that you're almost assuredly going to lose your ESCs. "

Why?  Your boards with lots of surface-mount devices and tiny traces are far more likely to get some corrosion damage.

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