2nd Hex Crash :(

[Huddo]

Hi Folks.

I've just had my second hex crash and would like some guidance if anyone knows whats the best steps to take.

The symptoms in both crashes :

• Hovers fine at low altitude.. its very very stable in both GPS and Atti modes.
• As soon as flying higher altitude - about 15-20m or so, after a few seconds it seems one motor cuts out.
• Flys at great speed in the direction of the motor which cut out - at which point I kill the throttle and watch it plummet

Luckily this second crash was in soft dried up sea weed - no damage

I'm not sure if it was the same ESC/Motor combo in each crash.

Replace ESC's ?

Regards
Huddo (Greg)

 

[mbsteed]

I have a similar problem with my little quad. It is usually into the second flight of the day (this not with DJI - Gaui 344). In my case, I suspect an overheating problem with one of the electronic components but short of swapping one ESC out at a time, and then swapping out the FC, I am not sure what to do. I wonder if your problem is similar - electrical overheating once the system is stressed a bit by getting some altitude.

I feel your pain and frustration.

 

[Huddo]

I have a similar problem with my little quad. It is usually into the second flight of the day (this not with DJI - Gaui 344). In my case, I suspect an overheating problem with one of the electronic components but short of swapping one ESC out at a time, and then swapping out the FC, I am not sure what to do. I wonder if your problem is similar - electrical overheating once the system is stressed a bit by getting some altitude.

I feel your pain and frustration.

Pain and frustration... very fitting words

Thanks for your reply!

One thing I did check was the heat of the ESC's - and they were not warm to touch... just ambient temperature, same with the motors. It was a nice morning yesterday when it crashed... only about 24 degrees.

I also have a WKM on a quad also (flamewheel) with the same motor and esc combos (40a Plush and AXI 2814/22) and its rock solid - took it for a flight after the crash just to settle my nerves

 

[GGoodrum]

I too just had a crash of a WK-M - equipped XA hexa. I think in my case I just stung by this 10% throttle cut issue. Were you also descending at the time?

I was doing a test flight, trying to get the gains sorted out, and it ended up cutting power and dropping like a rock from about 50-60 feet. I was flying in the ATTI mode, so that the gimbal outputs would work properly, and it was working off a full set of batteries. Two minutes in, I was trying to bring it down, and it was wobbling quite a bit. I was just about to reach for the gain knob, to try to get rid of the wobble, and I think I went below the 10% throttle level, because for no apparent reason, it simply cutoff the motors, all of them, and the result was that it went down in the rough brush area that is part of the golf coarse behind our place. It took my son awhile to find it. The carnage picture is attached. Two broken plastic arms, broked supports for the electronics platform, a busted WK-M GPS mast, plus only one good prop. It's only about $30 of damage, but it is going to take many hours to get this back where I was.

You can clearly hear that motor power is cut, but not system power because you can still hear the gimbal servos, all the way up until my son shuts it off.


Anyway, another big +1 for having DJI fix this fatal flaw in logic. :censored:


-- Gary

 

[Huddo]

Hi Gary.

I was just hovering at the time. I had a GoPro onboard and my wife was also filming it with another camera... she had to run just in case it was coming towards her !

I know about the 10% throttle issue, but i was just hovering at 50% throttle at the time the motor cut out. It was only 1 motor which cut out, and you can hear the other motors trying to compensate for its loss - which causes it to speed up

 

[GGoodrum]

I had a similar problem before, with a loose battery connection, due to using regular Deans, and the so-called Cheans copies. This one cut all power. If yours was just one motor, I'd look at the motor wires. Are you using small bullet plugs, by chance? These have a history of working loose.

-- Gary

 

[Huddo]

Hi Gary.

I thought it might be my Deans connector, but then dis-counted that when all the other motors were fine as you say.

I am also using bullet's, I will check them over and check my wiring harness to ensure its still connected.

Will report back with results

 

[Bartman]

what is the 10% throttle issue? i'm not a DJI guy just yet but I'm curious
thanks,
Bart

 

[Huddo]

what is the 10% throttle issue? i'm not a DJI guy just yet but I'm curious
thanks,
Bart

If you drop below 10%, motors cut out.

Just the same as when you spool up on the ground after arming the motors, you need to increase to above 10% to keep them spinning.

 

[Bartman]

is there a way around this or does everyone live with it?

 

[Huddo]

Well in GPS and Atti mode, 50% is hover. Below 50% is descend, and above is ascend.

I've got used to slow descents without going below 10%.

I'm not sure if this is different in Manual mode though.

 

[david pritchard]

Its been fixed in a firmware update, check the "Intelligent mode" box

 

[mbsteed]

I don't understand the logic behind the 10% cut off. Please explain. ...or is it gone with the update? I am just in the midst of setting up a DJI-M system.

 

[DennyR]

There are several ways around it. One is to use the trim and the other is to set the throttle curve so that you can descend without going near the 10%. But if you open the throttle again within 5 sec the motors will restart instantly. A bit like the discuss throw launch.

There are options in the set-up for starting and stopping motors. I use the classic right rudder and Ail. like MK. for starting and instant shut down on close.

Why do you want to close the throttle anyway? It is important to have an instant motor cut if you tip it over on landing or take-off, or you will damage your motors.

But what I think is happening in this case is that the ESC is going into low battery mode so you need to set Nixx on the low battery setting of the ESC. Then let the DJI handle the battery. What you describe is exactly what happens if you turn off the protection switch.

Also check that the Motor timing suits you motor. Make a few instant throttle moves to see if if accelerates cleanly. If it starts to run rough or squeal then you are on the wrong setting.

 

[Huddo]

But what I think is happening in this case is that the ESC is going into low battery mode so you need to set Nixx on the low battery setting of the ESC. Then let the DJI handle the battery. What you describe is exactly what happens if you turn off the protection switch.

Thank you so much for the reply!

Oooh I was so hoping this was the case when I read it! Ive plugged my programming card in... and all are set to Ni-xx

To go over my ESC settings :

Brake : Off
Battery Type : Ni-xx
Cut Off Type : Soft-Cut
Cut Off Voltage : Low
Start Mode : Normal
Timing Mode : Low
Governor Mode : Off

Should I be changing my Timing Mode to Middle? Would that cause a Motor to stop?

 

[Droider]

Sounds like a bad joint somewhere.. check all bullets and power to that motors for cold joints and bullet connectivity.. better still if the bullts are cheap ones dump um and go for soldered joint.

Dave

 

[Sebas600]

is there a way around this or does everyone live with it?

Yes it's possible with the arming mode, when closing throttle full the motors will keep going. the sad fact is this can go wrong as well when you really want the motors to stop.... (when tipping over or something)

 

[Sebas600]

Thank you so much for the reply!

Oooh I was so hoping this was the case when I read it! Ive plugged my programming card in... and all are set to Ni-xx

To go over my ESC settings :

Brake : Off
Battery Type : Ni-xx
Cut Off Type : Soft-Cut
Cut Off Voltage : Low
Start Mode : Normal
Timing Mode : Low
Governor Mode : Off

Should I be changing my Timing Mode to Middle? Would that cause a Motor to stop?

timing should be high, they will heat up more but response will be much better. will not fix the problem dough

check all the soldering and connectors. are ESC's well vented? maybe some pics of your setup?

and maybe test it, just weigh it down and test is that way.

 

[swisser]

The latest firmware (release 27th Dec, version 4.26) changes the way the 10% thing works. With this firmware, the motors will NOT cut even if the throttle is less than 10% in any mode during normal flight. The only time it will cut out when the throttle is less than 10% is in the following conditions:

1) You're in GPS or ATTI mode and you've landed and left the throttle below 10% for 3 seconds.
2) You're in GPS or ATTI mode and the bank angle is over 70 degrees.
3) You're in GPS or ATTI mode, you've just started up, and you've not increased the throttle above 10% within 3 seconds.
4) You're idling and you execute the Command stick move (pushing both sticks to a lower corner position).

In manual mode the only way to stop the motors is a command stick move.

 

[GGoodrum]

I've done some more checking/theorizing on my issue, and it looks like what happened to me is that I lost the front-right motor (#1) power, which caused it to tilt over that direction. I couldn't see this from the ground as the sun was in my eyes just prior to that, but you can see this in the onboard video. When it hit the 70 degree "bank" angle, power to all motors was cut, and it then dropped from about 50 feet up. I checked and I have mine set to the Intelligent mode, so power was not cut because of the 10% issue, which only happens in the Immediate mode.

Not sure what happened to the motor or ESC, but I suspect a bad connection. I remember something similar happening on takeoff before, where that same motor never powered up above idle, and it flipped over on the grass, in that direction. It started right up, after that, and flew normally. This was right after "upgrading" to 4.26. I figured that maybe I didn't give it enough throttle. It now would appear that I simply have had some sort of connection issue all along. I've checked the connections, however, and they all seem quite solid. Maybe a faulty ESC? Just to be sure, I will replace it when I do the rebuild.

-- Gary