Boat handstart gone wrong, because of an automatic emergency motor stop

[Flyingboy]

I launched my drone as many other times from a slow moving boat making sure it moved forward and I stood at the back of the boat so the drone drifts away from the boat as it holds its GPS position. But this time it lifted normaly out of my hands holded altituted and then all of the sudden it shut of its motors and sank in the sea. Could maybe someone help me to understand what could have caused this? Do I have to change some settings. Could it be that it somehow it triggered a crash detection and activated its emergency stop?
Unfortunately with the normal phantomlog viewer I couldn't find anything abnormal, just that it made a desecent even thoug i gave it full throttle.
Can someone shine some light on what might have happend? Thanks a lot!

DJI Flight Log Viewer - PhantomHelp.com

 

[RodPad]

Welcome to the forum!
Have you looked at the results of that link you shared?

My impression there is something I'm missing.
I will stay watching, waiting, for the flight data members!

Rod ..

 

[Meta4]

But this time it lifted normally out of my hands held altitude and then all of the sudden it shut of its motors and sank in the sea.

As I see the data, it shows the drone hardly lifting at all.
There is seven seconds of data before you pushed the left stick forward to launch.
In that time it's showing the forward speed of 1.3 - 2.7 metres/sec (the speed of the boat in the water).
IMU height is varying from 0 - 0.25 metres (the boat rising and falling on the water).

You pushed the left stick full forward at 7.2 seconds when the IMU height was showing 0.25 metres.
The IMU height never increased after that as it should have with the left stick pushed fully forward.

The VPS height should be accurately showing the drone's height above whatever is below it.
While you were holding the drone for launch, it shows 0 metres, which is expected.
After you launch and release, it continues to show 0 metres when it would be expected to show a change of 1 metre or more after the drone has left your hand.

The data shows the drone touching the water at 8.4 seconds when the pitch angle has changed from 16° to 71° and the forward speed drops from2.6 m/s to 0.9 m/s.

There's no indication in the data that the motors stopped.
Are you sure that the motors stopped?

The data doesn't show any decrease of height to indicate a fall into the water or descent.
It appears to show the drone failing to climb.

How high was the drone above the water after launching?
If you could post data from a normal takeoff from the boat for comparison, that might be helpful.

 

[RodPad]

@Meta4 Wow!

I didn't even think it was the correct flight log.

Rod ..

 

[msinger]

The last row of your flight log shows the motors stopped due to a "Takeoff exception". I've never seen that error before, but others reported it in these DJI forum threads:

DJI mini 3 pro crashed while taking off

Hello all, last weekend my drone crashed while taking off from my hand with a strange behavior. I will try to recap what I did, maybe some of you can help me understand if I did something wrong. So, after a successfully active tracking of few minutes, I switched of the drone and kept on my...

forum.dji.com

Air 2 Fall: Log Analysis Help

Hello Last week I lost my first ever drone - Air 2 (only 2 weeks and ~6 flights after I bought it second hand) and I am trying to understand why it happened and verify if it was my fault, or not. (I am rather new here, so sorry for possibly newbie questions) Story: I was starting the drone...

forum.dji.com

 

[JAW]

Take-off Exception
A "take-off exception" on a DJI drone refers to an error condition that prevents the drone from taking off normally, usually triggered by a safety check detecting an issue with the environment, the drone itself, or the pilot's input, which could include things like low battery, GPS signal loss, obstacles detected, incorrect gimbal position, or exceeding flight limits.

Key points about take-off exceptions:

• Safety feature:
  This is a safety mechanism designed to prevent potential accidents by stopping the drone from taking off if a potentially hazardous situation is detected.
  
  
• Alert on the app:
  When a take-off exception occurs, the DJI Fly app will display a message indicating the specific issue preventing takeoff, allowing the pilot to address it before attempting flight again.
  
  • Environmental factors: Strong winds, low visibility, extreme temperatures, magnetic interference
  • Drone issues: Low battery, faulty sensors, gimbal malfunction, damaged propellers
    
    
  • Pilot error: Incorrect settings, exceeding flight limits, not properly calibrating the drone

 

[msinger]

Take-off Exception
A "take-off exception" on a DJI drone refers to an error condition that prevents the drone from taking off normally, usually triggered by a safety check detecting an issue with the environment, the drone itself, or the pilot's input, which could include things like low battery, GPS signal loss, obstacles detected, incorrect gimbal position, or exceeding flight limits.

Key points about take-off exceptions:

• Safety feature:
  This is a safety mechanism designed to prevent potential accidents by stopping the drone from taking off if a potentially hazardous situation is detected.
  
  
• Alert on the app:
  When a take-off exception occurs, the DJI Fly app will display a message indicating the specific issue preventing takeoff, allowing the pilot to address it before attempting flight again.
  • Environmental factors: Strong winds, low visibility, extreme temperatures, magnetic interference
  • Drone issues: Low battery, faulty sensors, gimbal malfunction, damaged propellers
    
    
  • Pilot error: Incorrect settings, exceeding flight limits, not properly calibrating the drone

Was that generated with AI?

 

[Flyingboy]

Wow perfect thanks a lot for the answers!
The height of the VPS makes sense that it reads zero since i used a grab stick mounted to the drone which blocked the downward facing sonars.
Do you know how I could prevent that error from happening when I try to launch again from a boat?

PS: This is a flight log from the previous day, were everything worked perfectly.

 

[Capt KO]

Interesting post. I fly over water a lot, even from boats with the usual problems most encounter. Waiting to hear from others to solve your drones demise. Unlike some here, I believe that drones don't like flying over water and tend to decend uncontrolled, especially when unobserved. I've kept spares just in case but (knock on wood) so far never needed. Keep on flying, you're not alone.

 

[RodPad]

Wow perfect thanks a lot for the answers!
The height of the VPS makes sense that it reads zero since i used a grab stick mounted to the drone which blocked the downward facing sonars.
Do you know how I could prevent that error from happening when I try to launch again from a boat?

PS: This is a flight log from the previous day, were everything worked perfectly.

"PS: This is a flight log from the previous day, were everything worked perfectly."

I'm I missing a second flight log?

Rod ..

 

[jmrmavic2]

Sorry for your loss, had the same problem with auto take-off from slow moving ship,... Answer from Dji support was, Manual "Flight Environment Requirements"-7: DO NOT take off from moving objects such as cars and ships.

 

[Kilrah]

since i used a grab stick mounted to the drone which blocked the downward facing sonars.
Do you know how I could prevent that error from happening when I try to launch again from a boat?

Most likely "don't do that".
VPS sensors will be the first thing that confirm successful ascent, if you block them then it'll have to rely on the slow feedback from other sensors.

My guess is it's the combination of not having a working downward sensor and long time between motor start / takeoff attempt that triggered the "failed to take off".

So either don't block the sensors and/or "go for it" with a fast climb without waiting after starting the motors, ideally both.

 

[JAW]

Was that generated with AI?

I did a google search for dji what is a "take-off exception"
The reply was AI generated.

 

[msinger]

@Flyingboy did you trying reaching out to DJI support for help?

If they determine the problem is due to a defect, they might replace your drone or help cover the cost of a new one.

 

[MS Coast]

Take-off Exception
A "take-off exception" on a DJI drone refers to an error condition that prevents the drone from taking off normally, usually triggered by a safety check detecting an issue with the environment, the drone itself, or the pilot's input, which could include things like low battery, GPS signal loss, obstacles detected, incorrect gimbal position, or exceeding flight limits.

Key points about take-off exceptions:

• Safety feature:
  This is a safety mechanism designed to prevent potential accidents by stopping the drone from taking off if a potentially hazardous situation is detected.
  
  
• Alert on the app:
  When a take-off exception occurs, the DJI Fly app will display a message indicating the specific issue preventing takeoff, allowing the pilot to address it before attempting flight again.
  • Environmental factors: Strong winds, low visibility, extreme temperatures, magnetic interference
  • Drone issues: Low battery, faulty sensors, gimbal malfunction, damaged propellers
    
    
  • Pilot error: Incorrect settings, exceeding flight limits, not properly calibrating the drone

AI-generated search results typically use relevant words, are nicely formatted, and seem to be authoritative. But there's often a lot of nonsense.

• We're told that the pilot might have been in error by exceeding flight limits prior to the drone taking off.
• We're told that the app might issue an alert prior to takeoff for strong winds or low visibility, despite the fact that the drone has no capability to measure wind or visibility. Can DJI drones measure ambient temperature, or only battery temperature?
• What settings can be set incorrectly so that takeoff is not permitted?
• ...

 

[Flyingboy]

@Flyingboy did you trying reaching out to DJI support for help?

If they determine the problem is due to a defect, they might replace your drone or help cover the cost of a new one.

Yes I first reached out to the DJI Support, but first they didn't do anything since the drone is out of it's warranty but only by 2 months. They wanted to charge me 50 Bucks to analyze the flight log.
I got them then to look at the flight log after pressing them a bit that I will only buy another DJI drone when I know what happend, since I don't know what I did wrong or how I could prevent this from happening again.

They then just said this:
1) the aircraft was indeed started from a boat, which is directly connected to pilot error as our user manual clearly instructs pilots NOT to take off from ships, boats and other moving platforms.

2) we could not see any error message displayed. If you would like, you can send us a screenshot of that in order for us to check.

So they could not even figure out the Takeoff exception message you found in the flight logs. So there I really have to say that I am a bit disappointed from their support. The only upside is that they offered me a 15% discount if I want to buy a new mini 3 pro. But since I don't need a drone in the next few months I will wait maybe a bit until a new mini comes out and will hope that the price of the mavic 3 pro will drop a bit more.

Flight log of normal flight the day before the crash:

DJI Flight Log Viewer - PhantomHelp.com

 

[msinger]

So they could not even figure out the Takeoff exception message you found in the flight logs. So there I really have to say that I am a bit disappointed from their support.

To be fair, there isn't enough data in the TXT flight log to diagnose the issue. DJI would likely need access to additional flight data stored on the drone to determine what happened.