Mavic Pro suddenly spiraled downward into seawater beach - What caused it, and is there a way I can repair it?

Flight Log:

Hello everyone here, I was hoping you guys would help me with this tragic event…

We were in a beach-lagoon area which was surrounded by large mountains. We wanted to get some good photos and video of the area, so we decided to launch the drone from the beach. When we turned it on, it couldn’t pick up a proper GPS signal, even after letting it sit for a minute. This was kind of expected, since the beach was right up against a steep rock wall mountain. My partner and I decided to have it take off in OPTI and slowly bring it out over the water, away from the mountains so that it can get a clear signal. I put it up at the max altitude allowed for OPTI mode, and slowly crept it forward. I was ready to pull it back just in case the visual sensors suddenly decided to make it descend into the water, with the altitude stick pushed up at full so that it can immediately ascend away the moment it switches to GPS mode. At around 1:36, it does so and I was able to fly up and away. Between then and 1:49, the drone appeared to be totally fine.

At 1:49, that’s when it suddenly everything just went wrong. I couple seconds prior I was slowly bringing it forward and rotating counterclockwise while ascending for a cinematic video shot. I was looking down at the display when suddenly everything turned into a blur, and at that same moment I heard the drone’s motors going haywire. I look up just in time to see it spiraling nose down into the water. It was submerged for about 20-30 seconds before a bystanding beachgoer grabbed it out of there. Aside from a scuff mark on the battery, and a couple broken propellers, the Mavic appeared to be undamaged.

We were still clueless as to what had caused it to suddenly spiral out of control like that. I do not recall seeing any error message the moment it started spiraling downward. One of my family members gave a clue- she said she was watching the drone the entire time. Shortly before it spiraled down, she noticed what she described as one of the propellers being “out of sync”, like it wasn’t spinning correctly with the other three. She couldn’t tell which one exactly. I theorized that one of the propellors must have broken midflight.

My partner wiped down the drone, and blew into the motors and ports. He then decided it was a good idea to pop in a new battery and try to turn it on again, despite it had being dunked in salt water 5 minutes ago. As expected, the drone failed to power on. The two front red LEDs lit up, but there was nothing else, not even a startup tone. When we got back to our hotel room, he blew it with a hair dryer for several minutes. We tried it again the next morning, but still the same thing- the front LEDs light up, but nothing else. We fear it’s completely dead.

So I have two questions. What caused it to suddenly spiral downward? The flight log viewer at doesn’t seem to say much, so I’m wondering if you guys can figure something out.
And is it possible to fix up the drone to be usable again? I read in a couple of forum threads to try washing it in distilled water or alcohol - something we can’t really do until we get home in the next couple of days, unfortunately. Thanks in advance!

It does appear that you may have lost a prop and or motor. Taking a wag…the left rear, just judging from the available data. However, for whatever reason approx 2 -3 seconds after that you gave full down throttle which sped up the descent and left it there until the data ends. Not sure why you did that, but the results would be basically the same with or without that point. That said, the only way to determine for certain would be to see the aircraft .dat file, but if you cant power the aircraft it is a mute point.

Hi, thanks for the reply! As for the throttle down, the moment I saw it was going down I broke out into a run straight into the water, holding the remote in one hand. My thumb must have been pushing down on the left stick without me really knowing it, which explains why there was so much throttle down in the last few seconds.

A couple questions, did the drone log any sort of failure state or message, or anything as to why the propellor failed? Also is it possible it can be fixed without needing to send it in to DJI? Thanks!

If you notice in the above graph, shaded in blue, approx. 1 second after the aircraft went out of control, the “not enough force” flag went true, which indicates an issue with a motor ( Most likely a prop ). At the very end of the data the "is propeller catapult " flag also went true. There is really no way to be 100% certain of the exact cause from this data. The aircraft data file would be the only method that would give a clearer explanation. That file contains the motor data, which this one does not. As for repair, I can’t advise you on that other than to say that sea water is, generally speaking, fatal to the aircraft no matter how much cleaning you do. The corrosion process starts pretty much immediately. Fresh water you have a chance to flush and dry.

The drone is only able to detect a prop is missing since that causes the motor to spin faster than usual. The common causes for a lost prop are:

  • Improper installation
  • Using a damaged prop
  • Using 3rd party props (they might not fit properly)