XAircraft SuperX crash... what happened?!

[neavissa]

Hi,

Some of you might have seen this before?! I also send an email to Drew and Xaircraft in China. That was 3 days ago. Haven't heard from anyone yet.

BB of the crash: http://log.xaircraft.com/#2014_08_04_143054.500_57.2.03.40

Onboard video of the crash: https://www.youtube.com/watch?v=irO4znGcMho

Video of maiden flight: https://www.youtube.com/watch?v=LiTXIq6CV2M

OK, here we go. I try to make it as brief as possible...

I flew this Aircraft before, without the Gimbal and the Battery was mounted on top of the I/O unit, on top of the Aircraft. It was on a calm day, the Aircraft was balanced perfectly and everything went very smooth... On the attached picture, you can see how I pretty much flew today. The only difference was, that I moved the GPS forward, behind the gimbal, and the battery further back...

- I went to the soccer field, turned my radio on, plugged the battery in for my Video RX/screen and plugged my flight pack in.

- Turned GoPro on to record.

- On the first take off, the aircraft tipped over. I remember throttling down as soon I saw it tip over, so I believe there was no harm done to the esc's or motors. I am actually pretty sure they were fine, as I learned to throttle down when something is not right from flying helicopter...

- Second take of was better, but not perfect. I hate this "thing" the SuperX does, when trying to take off. Others had the same problem. More about that, later.

- Once in the air, it looked OK. Not too stable though, a bit on the wobbly side. Kinda like stable, little wobble, back to stable. It was pretty windy though. Not too windy to not be flying though!!!

- I hovered and moved around a little bit, trying to see how the aircraft is doing. After a few wobbles, I tried some gains, briefly, but I felt it made it worse.

- After a relatively "unstable" flight, I decided to test the RTH feature.

- I hit the fail safe switch on the radio and watch the aircraft climb. I was surprised how how it went. I had forgotten that it was set at 50m, ha ha. Anyhow...

- Aircraft got to 50m and set there for a little bit, probably thinking about what to do next. That seems normal, as it did this before on other test flights.

- The next part is, where it all went down the hill, or should I say - from the sky?!?!?

- The aircraft started to decent. During the decent, it started to wobble.

- As the Aircraft started to wobble more and more, I switch Fail safe off, hoping it will stop the decent and stabilize itself.

- By the time I really knew what is going on though, it shook itself apart - IN THE AIR. That is probably where the battery got disconnected?!

Anyhow, the aircraft fell from the sky like a stone and hit the ground. Luckily it was on grass and no one got hurt. (There was no one around anyway).

I am not happy with what happened, but before I start my b*tch fest, I would like other to chime in and tell me what they think...

thanks,

G

 

[kloner]

man, something really let loose there, went into safe mode then all hell broke loose, 100% throttle, alot of vibration at the end, alot of full-0 throttle. looks like what made it come down at the very end is low voltage from all that full throttle

 

[dazzab]

First of all, I'm so sorry this happened. I hate reading posts like this.

I watched your flight record and looked at the report. The only thing that stood out to me was that the GPS accuracy was extremely poor and you didn't have that many satellites. If the GPS graph in SuperX is recording the DHop value then yours was way too high indicating that there really wasn't a clear enough signal to support flying in GPS. I check my SuperX graphs quite often and I've never seen the GPS accuracy that poor. If I"m correct anything over 2.0 is bad. DHop is a measure of the accuracy I believe. Someone here will know more than me but I think it's actually a measure of granularity or how far apart GPS reading are. I hope someone will clear that up for me/us.

The other thing that looks odd in comparison to my graphs is the Remote control, Attitude and Gyro Angle. Unless you weren't moving it around at all shouldn't they be more separate? I've just never seen those graphs so flat in my flights. Again, hopefully someone who knows more will clarify that.

It concerns me you haven't heard back yet. I've had absolutely amazing support from Drew at XAircraft and even from China in one instance. They promote their attention to support so if it's not happening that is a real worry.

Overall I think Kloner said it best. It looks like something went catastrophically wrong mechanically. You did mention it was doing odd things on take off.

Sure wish I could be more help. I'll be very interested to read the outcome of this and hope you get the support and information you need soon.

 

[neavissa]

man, something really let loose there, went into safe mode then all hell broke loose, 100% throttle, alot of vibration at the end, alot of full-0 throttle. looks like what made it come down at the very end is low voltage from all that full throttle

Well, it actually did not go into safe mode by itself, if you mean that?! I was just flying around, very smoothly because the wind was kinda strong, when I decided to test the RTH feature. I used it before with this FC, in a different frame though and it worked fine. Anyhow, when switching RTH on, it started to climb. Once it got to 50m it just set there for a minute or so. Instead of then coming first the take off spot, staying at 50m, it started to descend?! That is when it started to shake itself to "death". I had a NAZA V1 before, and I remember it correctly, it used to wobble as well on descend, when the gains were not right?! I have seen others describe the "wobble on descend" problem before, so I think it not only the SuperX that is prone to that?!

thanks,

G

 

[neavissa]

I am no expert at this and know nothing about GPS Dhop's, ha ha. All I know is, that I let the Aircraft sit there for a minute or so, before taking off, waiting for a GPS signal. I did not get the double green lights. I decided to take of in Atti mode. After I did that, I got a double green like right away. The weather was over cast, if I remember correctly, but it wasn't that bad at all...

I am not sure what you mean when you say "The other thing that looks odd in comparison to my graphs is the Remote control, Attitude and Gyro Angle"?! I did not move the sticks at all, from what I remember, as I had switch to Fail Safe thinking the SuperX will do the rest for me, ha ha.

Well, today is Tuesday. I did send it over the weekend, and maybe they simply did not get to it. On the other hand, I am being a little bit treated as the Black Sheep, over at the RCG thread, as I have publicly bitched about Xaircraft not doing anything to improve, update or what not, the SuperX. You know that goes... Its a Forum, LOL.

thanks,

G

 

[Webheadfred]

I'm a HoverFly veteran and in the process of converting to Xaircraft. I'm no expert but it definitely looks as if you had a catastrophic failure of some sort. Very smooth and then some sort of snap and all hell broke loose. Maybe a partially broken prop or loose motor mount? So smooth and then that. Sorry to see this but I've been there. Almost always the mechanics of it all.

 

[jfro]

After you moved the gps unit, did you recalibrate your quad, ie. do the dance on 3 axis counterclockwise 3 turns each? Not sure if that would have anything to do with your problem, but I always recalibrate when I go to a new location or move parts around. I get made fun of a lot, but seems a good practice....

 

[jfro]

I'm a HoverFly veteran and in the process of converting to Xaircraft. I'm no expert but it definitely looks as if you had a catastrophic failure of some sort. Very smooth and then some sort of snap and all hell broke loose. Maybe a partially broken prop or loose motor mount? So smooth and then that. Sorry to see this but I've been there. Almost always the mechanics of it all.

You putting it on an X8. If so, I'd be interested in hearing how it goes. I didn't have a lot of success so my xaircraft is now on a low kv motor quad. Like it a lot better.

 

[Webheadfred]

You putting it on an X8. If so, I'd be interested in hearing how it goes.

Initially on a quad or my Hex. I did like the way the X8 flew in the wind though. Still getting back up to speed.

 

[JoeBob]

On the video it seems as if something let go on top and got into one of your props.

I know it will be hard to tell after impact damage. Did the rubber band on your battery break? Did the GPS puck come loose?

 

[neavissa]

After you moved the gps unit, did you recalibrate your quad, ie. do the dance on 3 axis counterclockwise 3 turns each? Not sure if that would have anything to do with your problem, but I always recalibrate when I go to a new location or move parts around. I get made fun of a lot, but seems a good practice....

Yes, I did the calibration after I moved it.

thanks,

G

 

[neavissa]

You putting it on an X8. If so, I'd be interested in hearing how it goes. I didn't have a lot of success so my xaircraft is now on a low kv motor quad. Like it a lot better.

Irrelevant to this thread...

 

[neavissa]

Initially on a quad or my Hex. I did like the way the X8 flew in the wind though. Still getting back up to speed.

Irrelevant to this thread...

 

[neavissa]

On the video it seems as if something let go on top and got into one of your props.

I know it will be hard to tell after impact damage. Did the rubber band on your battery break? Did the GPS puck come loose?

Interesting... I am going to have to watch the video again. The rubber band was intact. Like I said, it started to wobble when it started to descend?! I thought that when you use the wrong gains, the Multicopter can start to wobble on descend, no matter what controller you have?! Is that wrong?!

thanks,

G

 

[dazzab]

Multicopter can start to wobble on descend, no matter what controller you have?! Is that wrong?!

Not wrong but shouldn't be nearly enough to cause a crash, let alone what happened to you. Apparently it's caused by coming down through the propwash. You can avoid it simply by moving along the X or Y axis a bit as you descend. Give it a try. Makes for a much nicer landing.

 

[neavissa]

Not wrong but shouldn't be nearly enough to cause a crash, let alone what happened to you. Apparently it's caused by coming down through the propwash. You can avoid it simply by moving along the X or Y axis a bit as you descend. Give it a try. Makes for a much nicer landing.

I understand. The only problem was, I did not descend manually. I had switched to fail safe and by the time I could take over, it was too late! If I would have flown it in atti, I would have recognized the problem...

 

[Webheadfred]

All single plane multi rotors (octo, hex, quad) will waffle as they descend through their own prop wash regardless of the flight controller. Obviously, the slower you descend the less movement. Coaxial multi rotors such as X8 or Y6's (my irrelevant post as you so politely pointed out) mitigate this as the bottom rotors counter the upper rotors and smoothes the air, allowing a much more stable descent.

 

[neavissa]

All single plane multi rotors (octo, hex, quad) will waffle as they descend through their own prop wash regardless of the flight controller. Obviously, the slower you descend the less movement. Coaxial multi rotors such as X8 or Y6's (my irrelevant post as you so politely pointed out) mitigate this as the bottom rotors counter the upper rotors and smoothes the air, allowing a much more stable descent.

Good to know. What bugs me though is, that the manufacturer should know this as well and the FC should have stopped descending, once it realizes that the aircraft is wobbling more and more...

Thanks,

G

P.s. hey, please don't take any offense. You know how fast a thread get off topic... [emoji6]

 

[stevemaller]

I took a look at the photo of your copter, and I am amazed that you could fly it at all with a rubber band holding the LiPo in place. It's easy to imagine that the battery was bouncing around a little on its booms, causing some serious movement being translated to the flight controller, which in turn would cause it to try and correct, which could create a feedback loop. If the rubber bands holding the battery were, in fact, still intact, I'd be shocked. But if that was the case, I'd still vote for that being a serious contender for your smoking gun.

My other concern is the length of CF boom holding your camera gimbal. That can also introduce vibrations and oscillations back to the centre hub which can cause problems for the flight control.

Lastly, what is holding the SuperX flight controller onto the frame?

 

[neavissa]

I took a look at the photo of your copter, and I am amazed that you could fly it at all with a rubber band holding the LiPo in place. It's easy to imagine that the battery was bouncing around a little on its booms, causing some serious movement being translated to the flight controller, which in turn would cause it to try and correct, which could create a feedback loop. If the rubber bands holding the battery were, in fact, still intact, I'd be shocked. But if that was the case, I'd still vote for that being a serious contender for your smoking gun.

My other concern is the length of CF boom holding your camera gimbal. That can also introduce vibrations and oscillations back to the centre hub which can cause problems for the flight control.

Lastly, what is holding the SuperX flight controller onto the frame?

I flew it in the garage fine. The vibrations were very low. The Log of the SuperX, also confirms that the vibes were very low. I also fly planes and we use those rubber bands, to secure the wing to the frame. At least we did back in the days, ha ha. Anyhow, I have also seen other have the gimbal on a boom like that. Maybe not that far out. What I should have done is, wait till the proper battery mount is here, which it is now, and do a "real" flight outside and not just hove in the garage. Lesson learned on many levels! The SuperX was mounted underneath the bottom frame plate with Servo Gel Tape...

thanks for the input.

G

https://www.youtube.com/watch?v=LiTXIq6CV2M