Recovery from near Disaster

[SteveMLexington]

I thought I would share a recent experience in hopes that if any of you have a similar experience you may be able to recover from it.

I have had my Phantom 4 about two months and have flown around 10 hours. I feel pretty confident in my abilities, but realize I have much more to learn.

Three days ago I decided I wanted to fly the drone low over a very beautiful river we have running through our county between high mountain peaks. I went down by the river to a beautiful flat rock and got my drone set up on the edge of the rock. Upon taking off the drone moved over the edge of the rock, paused (while it’s sensors wondered what the hell happened to solid ground) and slowly teetered into the water. After I caught my breath, I reached down and grabbed the landng gear. It was submerged about 3-4 seconds, or as I refer to it as “2-3 glugs”.

I'm convinced that the steps I took next helped me to save my drone from certain death. Maybe this will help you if you find yourself in a similar situation.

• Immediately after fishing my drone out of the water, I yanked the battery out. I felt that cutting electricity to any of the internal circuits immediately was the best thing I could do.

• I quickly turned it sideways and drained as much water as I could out of the now empty battery compartment. Once that slowed, I turned it in every other direction, and watched in horror as water came out in all directions. (Luckily this was crystal clear mountain stream water, not muddy river water or salt water!) I rushed to my car and proceeded to fill the battery compartment with paper towels and took any excess water off of the outside..

I then placed paper towels on the floor of my car, removed the propellers and turned the drone upside down to drain any liquid out of the motors.

It took me about 20 minutes to drive home, trying desperately to stay within the speed limits, and slow my breathing and heartbeats. Upon arriving home I pulled out all of my tools, which I commonly used for working on computers and laptops. Immediately I searched YouTube for a teardown video and was lucky enough to find the one linked here. https://www.youtube.com/watch?v=dA_MQiNmTUI

With the help of spudgers and some patience I was able to carefully disassemble the aircraft. The best thing you can do at this point is take photos of each step of the disassembly. You WILL forget where all of the antenna wires go, and which screws go into which holes. The pictures will save your sanity.

After I had disassembled the outer shell and carefully disconnected the wires I took each piece into the garage and, using my shop vac, blew compressed air into every possible nook and cranny. I was surprised at how much water still came out using that method.

I then made a quick trip to my local home improvement center and purchased some bags of desiccant called “DampRid”. Use this instead of rice. It’s much more effective.

Even after having blown out most of the excess water with the shop vac my biggest concern was the moisture inside the camera lens. I used a hair dryer to see if that could help evaporate some of the liquid but it was only partially effective.

I took the camera lens and placed it in a small Tupperware container with the desiccant on the bottom and a small piece of shop towel over the desiccant and sealed it. I used additional containers of dessicant for the top of the drone, camera/gimbal assembly and battery. After 12 hours I first checked the camera lens and it was totally clear of any moisture. The same was true for the other large components.

I then began the process of reassembling. Because of the photos I had taken, this actually went quickly and easily. Yesterday I was finally ready to test the craft to see if I had been able to save it. I'm happy to report that it seems to be as good as new! If you are ever in this situation, I wish you the same good fortune!

P.S. Now I am older and my close-up eyesight might not be as good as it once was, but having a pair of inexpensive jewelers magnifier headband is a lifesaver. http://amzn.to/2fLcdtp

 

[drm]

Wow. Your quick response saved you! But I am still wondering why the bird took a swim in the first place.

 

[Waylander]

Hi Steve

Quick thinking saved the day, fresh water is non-conductive, and provided you don't leave gallons of it inside the craft you will be OK.

A little story of mine in a similar vein, I worked in the offshore Oil industry, as a diving, and some time ROV technician.
One night in a bad storm the on deck container in which our control station was housed was breached, some hours later when I went in to survey the situation, I found that the Sony Betamax video cassette recorder, which was housed under the control consul, about 1 foot above the deck, was soaking wet through with sea water. We only had the one machine ( cost $ 1000's to get a new one to the vessel) so I set about stripping it down to attempt a repair, Took the outer casings off and slowly poured fresh water from a bucket all over chassis. then as you did, I blew out the excess water with compressed air, from every nook and cranny, took it down to the engine room ( very warm down there) and packed bags of Silica-gel all around it.
24 hours later I had it re-assembled, connected it to the mains, switched on and it worked first time, (The cassette tape of course went straight in to the trash).
As I said before fresh water is relatively non conductive, ( provided it is fresh), so water should not cause harm provided you get rid of it.

Glad your bird survived
Waylander.

 

[eaglegoaltender]

I thought I would share a recent experience in hopes that if any of you have a similar experience you may be able to recover from it.

Thank you for posting that info - compressed air never a good thing with electronics due to "static" - however I think you were using the shop-vac to blow which would be ok and somewhat warm.

There have been issues with the P4's VPS when hovering over moving water - like the river you mentioned. Whereas the VPS sees moving water and will follow it - if it gets confused by this it can sometimes drop in altitude. Since you can't turn off VPS in the P4 some have used electrical tape to cover up the sensors when doing this type of flying. The video below will explain what likely happened to your P4 and how to avoid it.

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But I am still wondering why the bird took a swim in the first place.

 

[SteveMLexington]

Wow. Your quick response saved you! But I am still wondering why the bird took a swim in the first place.

My understanding is that I forgot to turn off the vision positioning sensors on the bottom of the craft, so when I took off from the rock and moved over the water, the sensors could not process the movement in the water. I have since realized that I need to turn those off when flying close to the surface of the water. The latest version of the DJI Go app allow you to do that.

 

[SteveMLexington]

Thank you for posting that info - compressed air never a good thing with electronics due to "static" - however I think you were using the shop-vac to blow which would be ok and somewhat warm.

There have been issues with the P4's VPS when hovering over moving water - like the river you mentioned. Whereas the VPS sees moving water and will follow it - if it gets confused by this it can sometimes drop in altitude. Since you can't turn off VPS in the P4 some have used electrical tape to cover up the sensors when doing this type of flying. The video below will explain what likely happened to your P4 and how to avoid it.

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​

Thanks for posting this video!

 

[eaglegoaltender]

Thanks for posting this video!

You're welcome Steve - looks like that might be a bit dated as I am reading that you can turn off the P4's VPS via the DJI Go App - as of April/16. I haven't tried myself but since your post on the incident, I now have further info on my P4 - so thank you again for posting that.

 

[SteveMLexington]

Hi Steve

Quick thinking saved the day, fresh water is non-conductive, and provided you don't leave gallons of it inside the craft you will be OK.

A little story of mine in a similar vein, I worked in the offshore Oil industry, as a diving, and some time ROV technician.
One night in a bad storm the on deck container in which our control station was housed was breached, some hours later when I went in to survey the situation, I found that the Sony Betamax video cassette recorder, which was housed under the control consul, about 1 foot above the deck, was soaking wet through with sea water. We only had the one machine ( cost $ 1000's to get a new one to the vessel) so I set about stripping it down to attempt a repair, Took the outer casings off and slowly poured fresh water from a bucket all over chassis. then as you did, I blew out the excess water with compressed air, from every nook and cranny, took it down to the engine room ( very warm down there) and packed bags of Silica-gel all around it.
24 hours later I had it re-assembled, connected it to the mains, switched on and it worked first time, (The cassette tape of course went straight in to the trash).
As I said before fresh water is relatively non conductive, ( provided it is fresh), so water should not cause harm provided you get rid of it.

Glad your bird survived
Waylander.

Thanks for the story! I somehow never realized that pure water is a bad electrical conductor. I know that oxidation is the condition that ruins most electronics. Thanks for teaching me something new!

 

[SteveMLexington]

You're welcome Steve - looks like that might be a bit dated as I am reading that you can turn off the P4's VPS via the DJI Go App - as of April/16. I haven't tried myself but since your post on the incident, I now have further info on my P4 - so thank you again for posting that.

Yeah, it takes a concerted effort to keep up with all the changes that are made with every software or firmware update!!

 

[eaglegoaltender]

Yeah, it takes a concerted effort to keep up with all the changes that are made with every software or firmware update!!

As I continue my search on the P4 and updates to firmware and/or updates to same - came across this site that seems really up to date on this.

DJI Phantom 4 Common Issues​

 

[eaglegoaltender]

As I said before fresh water is relatively non conductive, ( provided it is fresh), so water should not cause harm provided you get rid of it.

Interesting to note with the fresh water - did not know that so thank you for posting. I suppose "deionized" water (despite being hard on metals/copper) is even less conductive.

Tip of the hat to you man, that is a dangerous job you have out there on the rigs - being a diver in particular. Stay safe.

 

[Cougar68]

If fresh water is less damaging, would it be helpful to wash out a drone that was submerged in salt/dirty water when repairing?

 

[Waylander]

If fresh water is less damaging, would it be helpful to wash out a drone that was submerged in salt/dirty water when repairing?

Hi Cougar

Absolutely, if you need to, you could carry some extra drinking water, just make sure it has no mineral or salt content, if you put it into one of those plastic isotonic drinks containers, ( make sure you wash it thoroughly) then you have a ready made jet of water to get to the tricky parts.

PS. I have used low pressure air jets for cleaning PCB's for years, never had a static problem, ( I know it is theoretically possible, but....! ), anyway a shop-vac can generate static if the nozzle is not earthed/grounded.

Regards
Waylander

 

[GMack]

I wonder if flushing out with water is a good idea as the drone may have a small IC chip on it for the barometer that often has an exposed small hole for the pressure. If water were to get in there could it damage the IC? I was surprised to see that light entering that small hole could damage it too (Top of page 12 under "Handling Recommendations" here: http://cache.freescale.com/files/sensors/doc/data_sheet/MPL115A2.pdf ) if this indicative of those types of IC's that DJI might use. If light damages them, might explain why the altitude is all over the place with some drones if they are assembling without the caution of the barometer chip maker.

Some post PC board assemblies use some sort of flux solvent to clean them which might not be water based and dries quickly, or they only clean specific spots.

I wonder too about the crashes where some damage may occur to the accelerometers and gyros within those small chips too that might permanently be destroyed if hit too hard an the entire board is replaced. Dunno.

 

[Waylander]

I wonder if flushing out with water is a good idea as the drone may have a small IC chip on it for the barometer that often has an exposed small hole for the pressure. If water were to get in there could it damage the IC? I was surprised to see that light entering that small hole could damage it too (Top of page 12 under "Handling Recommendations" here: http://cache.freescale.com/files/sensors/doc/data_sheet/MPL115A2.pdf ) if this indicative of those types of IC's that DJI might use. If light damages them, might explain why the altitude is all over the place with some drones if they are assembling without the caution of the barometer chip maker.

Some post PC board assemblies use some sort of flux solvent to clean them which might not be water based and dries quickly, or they only clean specific spots.

I wonder too about the crashes where some damage may occur to the accelerometers and gyros within those small chips too that might permanently be destroyed if hit too hard an the entire board is replaced. Dunno.

Hi GMack

Yes you make a good point, I did not know about the environmental sensitivity of the Barometric Pressure sensor, it would seem therefore that precautions must be taken when opening the Drone for repairs, if light sensitivity is an issue, one could cover the hole in the sensor with black tape,
it follows that an air jet/stream should not be directed at the sensor.
The datasheet does not say anything about water ingress, but then you would not expect fluid ingress during normal use, natural evaporation of fluid would seem to be the only solution, possibly aided by the use of a desiccant, (silica Gel or similar), it would appear from the OP's experience that the Barometer was not apparently damaged by fluid ingress. Here is a view of the hole in the Barometer IC. (picture extracted from datasheet)
I'm sorry that I do not have a picture of the circuit board where the IC is located, perhaps another OP could post one here.

Regards
Waylander

 

[Rjeffw]

I have learned from first hand experience that water, fresh clean water, is not the end. While yours was close to the water, mine fell 20 ft into the water. Like you I drained it out. I howerver didn;t get home till much later. All I did was leave it in the sun rotating it every so often till I got home. There is no need to break them down. All I did was sit mine under a fan, rotating it every so often, for 24 hrs or so. Took right off.

 

[drm]

Concerning the light sensitivity of the barometer...according to the data sheet, light exposure affects sensitivity and accuracy during operation, but does not damage or otherwise affect the device when it is not in operation.