Phantom Pro 4 crash

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We run drones to perform surveys at a mine in Laos. Thankfully there are no government imposed flight restriction within the mine area, although of course we follow safe guidelines, stay well away from people and blasts and generally have had a very good run with high quality surveys being collected. A few weeks ago however, we had an usual flight which ended up with a written off drone. The pilot claims that near the start of his flight, his ipad went black. He hit the RTH button on the remote and waited, about 5 minutes later the controller turned-itself off and the drone never returned. Using the map, he located the drone which has sustained significant damage, of note is that the battery was found about 10m away from the drone. We use GSP with fully pre-programmed flight paths. From the flight logs (attached and linked below), I can see a rapid forward flight showing in the horizontal speed starting 1 min 24.7 seconds into the flight with accompanying pitch change, then the log stops. Battery condition was fine. My guess is that the battery became disconnected mid-air but would really appreciate some experts looking at the log to see if I am missing anything. Thanks for your time!



 

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Meta4

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From the flight logs (attached and linked below), I can see a rapid forward flight showing in the horizontal speed starting 1 min 24.7 seconds into the flight with accompanying pitch change, then the log stops. Battery condition was fine. My guess is that the battery became disconnected mid-air but would really appreciate some experts looking at the log to see if I am missing anything.
The data shows the drone ascending to 495 ft and then starting to fly south at approx 22 mph.
At 1:16.6 the Phantom pitches backward to slow and comes to a stop at 1:20.1 and hovers until 1:24.7, when it accelerates again.
It gets to 12 mph at 1:27.2 and the data just stops.
Battery is full and there's no sudden change in pitch roll and yaw which would be characteristic of a collision or motor problem.

We've run out of data to work with and have to guess from here.
The most likely explanation is that the drone suffered a sudden power loss and came down.
The battery being found some distance away might be because the battery came loose in flight .. or it could have separated in the crash and been thrown away (probably more likely).

Do the contacts in the battery look normal - not scorched ?
 
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It is unlikely that the battery was blown 10 m away from the drone at the time of impact unless it was on the hill slope and rolled down.
 
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If a drone & battery came down from 495' altitude, it might very well have enough energy to bounce 10 meters (33') away. I consider that event unlikely, although it also seems improbable that a battery would land that close to the drone if separated from the craft while moving and then fell independently for 495' feet. Just based on the distance between the drone & the battery, I would speculate that the battery didn't fully come out of it's port until the motors had stopped and after the device began spinning fast enough to fling it out of the port during free fall. The trajectory of the two once separated might be similar or widely disparate depending entirely on their orientation with respect to gravity at the moment of separation.

I wouldn't think that the battery would be separated at all from the drone unless it was the cause of the crash. I have never seen a drone fall, but it seems likely that if the battery was properly installed, they wouldn't be able to crash at such an angle that the battery was ejected unless it was directly downward from the battery port. Under those circumstances, the battery would be slammed downward and not fly a great distance from the drone. The sustained damage would mostly be shown on the battery port side of the drone.

A close inspection of the damage should reveal which side of the drone contacted the earth first. This should reveal the potential for battery ejection after the crash, except for how well the drone might bounce high and then spin after striking the earth. Big bounces with spinning seem unlikely unless it landed on a very hard surface like pavement or rocks. If that were the case, you should see other parts scattered for a great distance in addition to the battery.

Does anyone know how much or how far these things bounce when they hit the ground?
 
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Meta4

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I wouldn't think that the battery would be separated at all from the drone unless it was the cause of the crash. I have never seen a drone fall, but it seems likely that if the battery was properly installed, they wouldn't be able to crash at such an angle that the battery was ejected unless it was directly downward from the battery port. Under those circumstances, the battery would be slammed downward and not fly a great distance from the drone.
It is very common for the battery to be ejected in a crash when the case is deformed enough (it doesn't take much) for the safety to be released.
Falling drones can hit the ground at any angle.
 
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It is very common for the battery to be ejected in a crash when the case is deformed enough (it doesn't take much) for the safety to be released.
Falling drones can hit the ground at any angle.
That's true. I just said that it would be unlikely that after an impact when the force of the impact is directed straight down a battery would be blown up and away. If it dislodged during the flight it depends only on the speed of the drone how far from it will be. We only don't know if the ground was horizontal or sloped which could make a big difference.
Anyway the 'dat' file should revealed that.
 

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