Help!! My hexacopter crashed and I have no idea why!

L

lucab1

Member
Hi Everyone,

I was flying my DJI f550 Naza-M hexacopter and the motors turned off mid flight in GPS mode and my copter crashed to the ground. I don't have a video of the actual crash, but I do have one of a few minutes before when the same thing happened, except in this case the motors turned back on shortly after turning off.

http://www.youtube.com/watch?v=w2bL3SQ7Pbg

The helicopter is in intelligent mode so it couldn't have shut off from the throttle being lowered too quickly. I was about 100 yards away from my hexacopter when the motors stopped and it crashed. Could it be that there is something wrong with my Tx and the signal wasn't strong enough at that distance? The other thing I considered was possible interference somewhere nearby that interfered with my transmitter and caused my copter to shut down.

I'm really stumped by this one and can't figure it out through traditional research on the forums. Any help on why this crash happened would be awesome!
 

E

Electro 2

Member
Highly unlikely it's a radio issue. In the video the ESCs don't reboot, so it's no a cessation of DC power issue. Rules out batteries/PDB/wiring. And all 6 motors stop and start syncronously, so its not a motor specifc issue. Leaves the possibility FC chopping the motor dirve as the only possible thing. Since you don't say what FC you're using we're at a loss to TS it further. I will ask what in the world you're doing flying at altitude in high-wind conditions with an unproven bird, though? No more than a few feet for the first 20 or so flights is a good rule.
 

L

lucab1

Member
Hi Electro 2 thanks for the quick response. Excuse this possibly stupid question, but whats an FC? I'd like to say the copter isn't unproven though (despite the fact the video evidence says otherwise). I've have probably flown it more than a couple dozen times almost without incident and certainly nothing close to this ever happened.
 


OneStopRC

OneStopRC

Dirty Little Hucker
That certainly was nothing to do with radio signal, if it was I would not expect something like this... which brings me to a question. Did you set up failsafes for radio loss?.

I did not at any point hear the ESC boot either, so that was not the problem as mentioned above. I would check your solder joints on the BEC wires, make sure your connections are tight and you have not damaged any wires between the BEC wire and the FC.

I would suspect you lost power to the FC only, and you probably would have seen this on the LED on the BEC if close enough. I would not attempt to fly again until you resolve this issue, it is dangerous for you, anyone nearby and might cost you quite a bit.

Hope you figure it out soon...
 

L

lucab1

Member
No I can't remember why I didn't set up the fail safes for radio loss, but I just never did it. Thanks for the advice deanot, I'll be sure to make sure i fix it before I fly again!
 

BorisS

BorisS

Drone Enthusiast
To tell the truth i am not too sure that this wasn't a radio issue or the wiring to the RX ! Nothing like you guys mentioned rebooted the ESCs didnt and the NAZA didnt. If the Naza would have restarted it would have caused a crash, since arming of the copter would have been necessary again. Power loss of the RX should have caused depending on which rx is used traditional PPM or S-bus either direct failsafe ( in case of PPM and SBUS not matter if set or not ) or something similar as we have seen here.

I would check the power supply of the RX and the wiring to the NAZA. Possibility also is that if you have a single wiring for each channel that the throttle wiring has an issue. Best take of the props turn on the motors on some low speed and start some wiggling of the cables, especially those RX related !

Dont spin up the motors all the way without the props not good for them, but you probably know that anyways !

Boris
 
Last edited by a moderator:

BorisS

BorisS

Drone Enthusiast
lucab1 said:
No I can't remember why I didn't set up the fail safes for radio loss, but I just never did it. Thanks for the advice deanot, I'll be sure to make sure i fix it before I fly again!
Click to expand...

Lucab what RX are you using ? SBUS, single cable per channel or PPM ?

Boris
 

L

lucab1

Member
I use the Spektrum DX7 for a Tx with the Spektrum AR8000 and I use just put one cable for each channel from the FC to the reciever
 

BorisS

BorisS

Drone Enthusiast
In this case it can be a failasfe issue. Having throttle set to zero in case of signal loss and you not setting the flight mode channel to go to failsafe if case of a signal loss ! Still it can also be the cables from the naza to you RX check those !

Cheers

Brois
 


D

Dewster

Member
What batteries are you using and what rating? You may have experienced a brown out. Not a complete loss of power, but a drop in power due to demands or running your battery to the hilt. The power loss was enough for your batteries to catch their breath and supply enough power to keep your bird in the air. (Am I talking crazy??).
 

L

lucab1

Member
At the time I was using a Turnigy 4s 58000mah, I figured that this battery would be fine, but I really don't know. And I had switched the battery after the incedent in the video and that is when the the same thing happened again except the copter didn't regain control and it crashed.
 

BorisS

BorisS

Drone Enthusiast
lucab1 said:
Alright, I will be sure to check them. Thanks for the help BorisS!
Click to expand...

Its simple, hook up your bird without props to the lipo and connect it to the assitant. Go to the tab were you see the RX sliders. Switch off you radio and see what happens to the sliders ! If the throttle goes to zero than you when the radio is off you more or less have your answer !

Boris
 

BorisS

BorisS

Drone Enthusiast
lucab1 said:
At the time I was using a Turnigy 4s 58000mah, I figured that this battery would be fine, but I really don't know. And I had switched the battery after the incedent in the video and that is when the the same thing happened again except the copter didn't regain control and it crashed.
Click to expand...

Important would have been to know the c rating of the lipo. But since its a f550 and your are running a 5800 mah which is a variable to the actual A that can be drawn, i dont believe its the lipo ! Considering that you always treated it well.

Boris
 

L

lucab1

Member
BorisS said:
Important would have been to know the c rating of the lipo. But since its a f550 and your are running a 5800 mah which is a variable to the actual A that can be drawn, i dont believe its the lipo ! Considering that you always treated it well
Click to expand...

Yeah its a brand new Lipo, I literally bought this one a couple weeks ago and it had worked just fine so that definitely makes sense.
 


sim_io

sim_io

Member
The problem is you didn't set the fail-safe. Once the signal from the tx is lost the DJI software doesn't know where fail-safe is so it will just shut down the motors, its how its designed. What I see in the video is that you momentarily lost link, the naza didn't know which mode to be in because no FS setting thus shutting down, link is established again in GPS mode and it recovers barely in time.

The problem with the Naza is that it needs a solid link, 2.4Ghz is prone for multipathing the signal if the battery/motors/frame is in the way. People put satellites on their receivers to counteract this issue.
 

You must log in or register to reply here.
Top