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Flying from a boat

Ashtojr

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Just a warning to you all (and interested in any feedback on your experiences)

Just lost my Mavic Air after launching off a boat and it immediately ditching into the water during the launch sequence (i.e. no pilot input other than starting the launch)

Sent flight logs to DJI who are claiming that launch from a ‘moving platform’ should not be attempted and was the reason for the loss.

(Note that this was my third launch from the boat so it’s not a ‘thing’ that happens every time)

I tried to get more info on the specifics of the fault that caused the crash but have not managed to get anything out of them other than ‘don’t launch from a moving platform’ and ‘pilot should evaluate every launch and only launch if safe’ (but there is no reference to moving platforms in any manuals that I can find!?!! So not quite sure how that evaluation is supposed to take place)

Quote from DJI below:

“Thanks for getting back to us.

1. The reason why the aircraft crashed immediately after take-off was due to the moving platform.

2. As we stated previously, it is impossible to have exactly the same condition and flight environment, just as there won't be exactly the same people in this word. So each flight is supposed to based on the current situation, and couldn't be compared with other flights.

3. The User Manuel, instruction or the documents at the DJI website will not cover every detail. And whether the environment is proper to launch the aircraft should be determined by the pilot themselves, instead of the aircraft. We appreciate your kind feedback which will be forwarded to the related department who will check if it is possible to add this warning into the documents.

4. Indeed the pilot cannot cancel the process of auto launch, but the key point is that the pilot is not supposed to launch the aircraft from the moving platform.”

So - fair warning - Mavic may crash immediately on take-off from any moving platform!!!
 

msinger

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Taking off from a moving platform is not likely the reason that caused it to crash.

Anything interesting in the flight log? You can upload and view it online here. If you'd like other people to review and comment on your flight log, then please post a link back here after you upload it.
 

Meta4

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Sent flight logs to DJI who are claiming that launch from a ‘moving platform’ should not be attempted and was the reason for the loss.
DJI make great drones but they aren't very good with their communicating.
It would be very interesting to see what the flight data shows about that flight as it takes more than just launching from a moving boat to cause it to crash.
Follow the instructions you'll find at the link given in post #2 to share your data and probably get a better explanation than DJI will give you.
It would also help if you can give a description of how you launched and what you think happened.
 
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Ashtojr

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It would also help if you can give a description of how you launched and what you think happened.
At work at the moment but will do the upload tonight when I get to a laptop;

But the below is the log in spreadsheet form; (if that is of any use?)

CFDDF33C-1FB3-47BC-8987-FBD3B11A2A12.png

The scenario at launch was the the drone was on the rear (dropped down) deck of a yacht; (yacht is moving slowly forwards but on flat calm waters)
Drone was in ‘Ready to GO’ (ie GPS, compass all good)
Pressed the ‘Launch’ command (it Take-Off or whatever it is called)
Drone rose up as usual
(In the past 3 successful flights the yacht had then moved away as the drone held station - so in effect it looked like the drone was going backwards but in fact it was the yacht slowly going forwards)
This time, rather than just hover in place, it immediately dropped vertically into the water at speed.
Total time in the air was probably 2-3 seconds.
No pilot input from me at all (all happened too fast to react)

Would really welcome some input?
I wonder if downward facing camera got ‘confused’ by apparent forward motion of the ground (ie the boat) at launch?
 

Meta4

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Would really welcome some input?
I wonder if downward facing camera got ‘confused’ by apparent forward motion of the ground (ie the boat) at launch?
According to the downward sensors data the drone never gained altitude ?

As it was all over in 2 seconds, there's not much to work with.
I've not used the auto takeoff - is it slow to lift off or fast?
The data doesn't show any change in the VPS altitude and there's no data for the IMU altitude.
How far did the drone lift?
At 2.2 sec the drone is pitching and rolling and then at 2.4 sec the error message suggests the motors have stopped.

It's hard to see from this what's caused the problem.
For boat launching, it's usual to hand launch rather than launch from the deck and a manual take off is used to get the drone up quickly.
 

PhantomFandom

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A bit of speculation here based on the limited data from the logs. However my take is that due to using auto-launch from a moving platform (and even worse over water), the VPS system got totally confused. This caused the drone to crash in somehow trying to determine where it was and trying to correct for the situation. For future reference:

  • Flying over water at low altitude with VPS enabled can lead to trouble.
  • Taking off from a boat should always be done with a hand launch and hand catch.
  • Don't use auto-takeoff when on a boat.
During auto-takeoff, the VPS system is used to determine that the drone has risen to the proper altitude and is holding stable in position prior to the pilot taking control. Notice in the logs that it must have gotten completely confused by the platform moving away and the water beneath it. The VPS altitude shows a nearly constant 0.1; it should be increasing to around 3 to 4 feet during auto-takeoff. Notice that speed is a non-zero value; it should be close to zero during an auto-launch because the drone should be going straight up. Notice that the pitch and roll values are also non-zero values; unless you have a windy launch point these values should also be close to zero. So all of that does reflect issues that do seem to correlate with the situation of auto-launch from a moving platform and over water. I am afraid this is totally pilot error.
 
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Ashtojr

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Thanks for your input.
The manual launch thing is an interesting idea - in manual do all the auto systems not get involved (like VPS)?
The speed at launch is due to it being on the boat and moving forward; and I ‘think’ that the large roll/pitch commands may have been after it was already in the water!
I’m not sure that hand launch would have helped - except perhaps that I might have had more time to react with a higher launch;
I ‘think’ I also suspect the VPS as the culprit - perhaps as the boat moved away the sudden change in perceived altitude by the ultrasonic sensor caused it to descend (trying to re-acquire the correct height) and then the water below gave a rubbish enough signal that it never found the ground till it hit the water?!?
Lessons only get learnt the hard way I guess (and I didn’t even have video running to get a crash video)
 

BigAl07

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First off welcome to the forum and sorry you lost your aircraft.

Doing an Auto-Takeoff, from a moving platform (yacht), and over water is not really what I would call a good combination. I would (And do) always do a manual takeoff (me at the controls) just in case. You've just added so many variables to a complicated situation and hoping/expecting the processor to be able to cope with extremely varied input from the environment.

With a Manual TakeOff you, the operator, start the motors and initiate the takeoff and resultant climb-out (if any). All sensors etc are still in play but you're making the decisions and needed input corrections and hopefully you do better than the Auto-Takeoff did.
 
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Fat Bastard

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So sorry for your loss! As mentioned by others, when flying from and hand catching on a ship, moving or not, turn off all sensors, use the hand launch/recovery method and manually launch and return the drone. I've flown from ships hundreds of times now and only recently tried a few auto launches with success, however the vps was off.
 

Ashtojr

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Cheers and cheers folks!!

Sounds like I put a bit too much faith in tech and paid the price!
Lesson learnt and I’ll be a little more careful with the new one “Son of Mavic”
Got some great pics/video before it tanked in mind - so not completely wastedAF95CE2D-BFC0-4FF7-9091-0B77B24EFDCF.jpeg
 
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