Stop press! Droidworx CX4 in spectacular crash disaster!!

[flybywire]

So, it was a day that started windy, and ended windy, it';s the bit in the middle that I shall regale you good folk with.
I had recently been invited up to one of our local clubs (geographically about 5 miles hence) so tiring of my prevarications, today was the day that finally saw me making contact with a bunch of like minded guys (and indeed gals).  It all began well, a tour of the clubs grounds, and they are certainly expansive, I';m told roughly about 40 acres of plush Leics farmland, complete with tenant farmers who';s sheep graze the green fields.  As we toured around, the wind ripped at my clothing, and once or twice I was reaching for something solid to steady my self, windy it was!  In the background I could hear the whine of a lecci heli, being put through it';s 3D paces, and the guy sure could fly, put it this way, if I were a mushroom in the neighbourhood, I';d fear for my existence.  ::)

Anyways, cut to the chase, I';d virtually written off the day, as being mere show and tell, but all of a sudden, I got an urge to fly (driven on by another club members flying with a 450 (fpv) so I cut loose and went for it.  It';s a decent club, and as it goes with clubs, there are protocols.  I was shown the flight deck, and John (club sec) offered to carry mt model out to the beyond (a ritual that I am very unfamiliar with) so, I had to check everything, then have the model walked out to the mown grass.  I know this is mainly for heli';s as they can kill, but my quad?  So there it was, I had given her 2 mins, although I got a lock in about 25 secs (wookong m) I gave the csc command, but it appeared as nothing was happening!  Now if this had been one of my solo events, I would have given it the once over.  I checked the Spektrum model, yep, CX4, all fine.  I gave it the csc again, this time I could see a prop or two start to spin, so far so good.  (Please Bear in mind I had another quad flying just above me by this time, so was a little distracted).
I raised the throttle stick, and she lifted off, very smoothly, without even bothering with the gale force wind at all!
All was good, so I pulled down my goggles, to masses of interference, the other guy was on same 5.8 channel!!  He was not using his goggles, so he landed, which was sporting of him I thought.
I had a few guys around me, I think quite admiring her, especially the way she penetrated the wind, didn';t seem to bother one bit.  About 2 mins in, she started shaking, so I let the stix go so that she could settle herself, which she did, I moved her down the field, and executed a fast bank, that';s when it all went wrong!  A second or two later at about 60 ft, she shook uncontrollably, sending the craft forward and down, then on it';s back, turtle like!  I gave a commentary, to the guys, and declared that she was not responding at all, and it was all I could do not to turn my back, as £2000 or more';s worth of airspace grade carbon & electronic gizzardry plummeted into the soft earth. 

Ho hum, I wasn';t sure what I feared most, losing all that kit, or being watched when it happened!  If any of you are golfers, you';ll know what that moment feels like when you top your first tee 20 ft up the fairway, in the rough! 

We made our way over to the stricken craft, I was too baffled by the occurrence to even think of the £££ consequences.  Well, the gimbal rubbers had sprung, so the H2-3D lay lifeless and sadly detached upon the deck, with it';s brand spanking new unused GPH 3 Black  besmirched by mother earth!!! *********.
Other than that, she had a bit of a rattle apparent from inside, and mud in one of the motor ';pods';, but hey, nothing actually broken!!!  A 60 ft plunge, upside down, and the GPS dome was still intact.  There is an RC God after all. 

TBH I was more than a little peeved, but actually, now I sit here writting this account, I have had a little time to reflect, and there seems to be £0 damage, yes 0£, not even a bust prop.  So, the £600 the frame cost, may just have justified itself?  What was the cause?  That';s the $64,000 question of course, I suspected my (brand new) Zippy compact 4 cell 4000 mAh lipo, but another lad checked it with a meter, and it showed all cells good, with 60% left, so my attention then turned to under the lid.  The centre plate, held on with 3 or 4mm bolts and a standoff arrangement had sheared, which obviously happened in the crash, but I';m wondering if something hadn';t worked loose, the way the craft shook in the sky, just looked like controller failure, it simply got itself into a mother of all tizzies, which it ultimately could not resolve.
I have to get to the bottom of this, as it';s my main camera platform now, so I';m a bit lost without it, but I have to get to the bottom of it somehow.

Any of you guys got any theories?  Have you had a similar experience?  What was the resolution?
I know this craft has on occasion had some wobbles, I was explaining to the guys whilst flying that early firmware was not too good in high wind, and indeed a fware release did make a difference, but as I say, now and then, but nothing like today, man, it just went mental!  Of course, I hadn';t started my GpPro video, what with all the goings on of the protocol etc, which is annoying, otherwise you guys would';ve been in for a treat.

Oh well, at least I';ve popped my aerobatic cherry, as I';m sure it rolled at least twice on the way down!

Have fun 

Andy

Nil desperandum:

[Pauluk]

Thats unlucky,could have been something worked its way loose.

Did you really pay £600 for a quad frame

[flybywire]

Thats unlucky,could have been something worked its way loose.

Did you really pay £600 for a quad frame

Yep! 

[Jimbodiddly]

Geez that is a bit of a bugger to say the least, Andy apart from the broken frame parts is anything else loose like motor mounts or the bolts that go through the booms? i';m guessing the only way is to strip it down and see ? It almost sounds like the fc was trying to over correct itself and maybe the wind literally flipped it over during ovrt correction,  but apart from the wind what else would cause this massive flip, the only things I ';m trying to rule out are esc failure or motor fault?

Just my pennies worth.


Jim

[BadgerG]

Is it possible that the wind was just right to cause resonance in one or more of your motor pods. That vibration would cause the FC to lose gyro stabilization. That would cause a flip. Just theorizing. I have had that happen on a frame that I have, that has bolt on motor mounts. The motor mounts actual resonate so bad that the mounts actually turn left or right. Needless to say I scrapped that frame.

[Biffa]

Yep! 

I don';t know how you guys do it, I felt gutted the other day watching my mini H fall 3 feet to the deck in my garden when testing

[flybywire]

I don';t know how you guys do it, I felt gutted the other day watching my mini H fall 3 feet to the deck in my garden when testing

Lol Biffa!

No crash is good, thing I hate most is the uncertainty that it throws up. 

Jimbo: yes, that was my first thought, well actually I was cursin'; the new Zippy whilst it was doin'; it';s ';dance of death';, but it checked out ok.  There is actually no real damage to speak of, 4 x 3mm bolts that attach the main IMU plate & power board have sheared on impact, the gopro, gimbal and lipo were all thrown well clear, and seen none the worse, the GPS dome is intact and all sundry wiring has held. 

Badger, I';m working on vibes, and as you say, windy conditions setting up resonance, but I think the body itself does resonate, that';s bad news as you say for FC';s of any kind.
Motor';s esc';s?  Well, if you saw it you would kind of realise that it was trying to do stuff, albeit totally out of control, I think if it was an esc or motor, it would have just dropped out of the sky.
The guy next to me asked me if I dropped the throttle and cut the motor, truth is I';m not sure I did or didn';t!  It all happened so quick, I thought I';d l;ost radio at first, or been shot down, but then I realised it was the FC doing something bad, or reacting to vibes badly, leading to an effective los of control, as basically ones stick inputs are simply transferred via the FC to the ESC';s of course, so there is no direct connection between you and the mtor control, in that sense.  Once I realised the game was up, I did obviously lower the throttle, but whether or not I cut it off by mistake, I will never know.

Ah well, just a pain of a rebuild that I don';t need at present, as I';m in the middle of my XuGong 10 build, so could do without this post mortem business.

NB: in hindsight, I should';ve monitored the LED indicator, as it would have likely been flashing red, indicating IMU failure, but will never really know now. 

[guest325]

I don';t know how you guys do it, I felt gutted the other day watching my mini H fall 3 feet to the deck in my garden when testing

Yes, I';m just the same doesn';t matter whether it cost a few quid or mega bucks still don';t like the thought of them going in!
But have to say I was taught to fly by a bloke who';s been flying for 30 odd years and he has always told me not to fly anything I couldn';t afford to be a bin bag job - reckon he has a very good point!

[flybywire]

Well, he';s right there, I think it was ';Finless Bob'; who said ';the less $$ you throw up in the air, the more fun you';ll have!';

[BadgerG]

I don';t know how you guys do it, I felt gutted the other day watching my mini H fall 3 feet to the deck in my garden when testing

Biffa, wait till you have a fly away, and loose your entire quad   Had that happen a few weeks ago. I was flying at a nearby park and lost orientation and was sending it further away, till it lost radio link and came down. I never found it. $200+ bucks flew off never to be seen again. Talk about feeling gutted! I was ****** for a couple of weeks. And thing was I knew the approximate area were it came down and still couldn';t find it. All my quads from now on will have GPS with RTL capabilities. GPS is not fool proof, but it';s better than not having it.

[Biffa]

The guy next to me asked me if I dropped the throttle and cut the motor, truth is I';m not sure I did or didn';t!

That';s probably a valid point. It may just have been a subliminal thing where you see a model going tits up and without thinking or registering you may have (as we all do from time to time) drop the throttle.

If you did perhaps that saved you from a lot more damage rather than ploughing into the deck under steam, although if you did reduce throttle did that prevent the FC from powering itself out of trouble?

Someone give this man a call...

[Biffa]

Well, he';s right there, I think it was ';Finless Bob'; who said ';the less $$ you throw up in the air, the more fun you';ll have!';

Good ole Bob

[flybywire]

Well, I';ve wasted no time in the ';rebuild';:








L-o-w ri-der...




So yes, I';ve decided to go low rider, I have a feeling that the body may contribute to magnify/amplify the vibes, which are most severe in windy conditions.  I must add here, that I don';t normally fly in such conditions, but I guess I thought that if you can';t fly it in ';average c**p UK weather, then it';s certainly not worth the money I paid for it.  It was a little like taking a Dalek to bits, (do Haynes do a manual for a Dalek?)

Anyhow, I can';t find any obvious damage, all cables are intact, soldered joints/bullets all ok (although I will re-seat all the bullets, as they may oxidise over long periods of time maybe?

Hey, actually I think it looks damn cool now without the pie tin lid, why hide all that M-R bling?  Ok, it gives it protection in a crash, but hey! if it causes the crash in the first place??

Cheers

Andy

[flybywire]

That';s probably a valid point. It may just have been a subliminal thing where you see a model going tits up and without thinking or registering you may have (as we all do from time to time) drop the throttle.

If you did perhaps that saved you from a lot more damage rather than ploughing into the deck under steam, although if you did reduce throttle did that prevent the FC from powering itself out of trouble?

Someone give this man a call...

Yeah, jury';s out on that Biffa, chicken & egg etc?  I gave it a good chance, maybe 8 seconds or so trying to bring her down gentle (wobbling) but it was dead un-responsive to ele/yaw/aeil, but probably responded to throttle, maybe I cut the motors by mistake, really can';t say, but as you rightly commented, probably saved it';s life really, although at the time you do wonder!!

I think it does hold up my theory that the most resilient quad/hex  frames are simple 17 mm carbon tube & 2mm centre plates

[Jimbodiddly]

Andy,

Just a thought it looks like from your pictures your using the same cross shaped bit of cf/fg ';as I have on my dw y6.'; to mount your fc on, when I';ve look at the qav frames that have a top deck mounted on high quality rubber bobbins if that would be beneficial instead on the nylon standoffs. in reducing vibs etc that could resonate to the fc in strong winds?

Just a thought

Jim

[andythilo]

In terms of resonance, get some dynamat. Most car audio places sell it, might even give a piece for free.

Sent from my Z30 using Tapatalk

[flybywire]

Well, that';s the centre board/IMU/power board back on, plus the gimbal & gopro.

[flybywire]

Andy,

Just a thought it looks like from your pictures your using the same cross shaped bit of cf/fg ';as I have on my dw y6.'; to mount your fc on, when I';ve look at the qav frames that have a top deck mounted on high quality rubber bobbins if that would be beneficial instead on the nylon standoffs. in reducing vibs etc that could resonate to the fc in strong winds?

Just a thought

Jim

By-eck, must be telepathy!  I';ve just replaced them with 4 rubberised ones, that I had in the kit box!  Spooky.  Thanks for the comments tho Jim, they are appreciated.

[flybywire]

In terms of resonance, get some dynamat. Most car audio places sell it, might even give a piece for free.

Sent from my Z30 using Tapatalk

Thanks Andy, never thought of that!  I';m gonna try the new low rider style, sans lid, if anything it';ll stop the esc';s etc from getting too hot in summer, as it used to get to over 30 degrees! (SPektrum TM1000 telem module data)

[Biffa]

It was a little like taking a Dalek to bits, (do Haynes do a manual for a Dalek?)

As a matter of fact Andy...

[Hands0n]

Blimey Andy! I go out for a day and you take over my top spot for disaster in windy weather! ::) 

I';l really glad you got it all back in one piece and sorted so quickly. My brain can';t even contemplate the thought of circa £2,000 up in the air with only a radio link. But then again, the air frame took the hit amazingly well.  Had that been a DJI/clone it would have ended up in a lot of pieces. 

Thinking on the what may have happened - given my own experiences this past week with Naza M Lite I am forming doubts as to the capability of that FC in such strong winds. Not feeling the trust right now.  But of course, it could have been absolutely anything.  The sheared bolts on the flight controller board are an area for suspicion, did it happen as a result of the crash or was it the cause? Impossible to tell really.  If that was an APM/Pixhawk the flight data logging would offer clues.

Did you dump the throttle?  Possibly, although with your experience and skill it is unlikely.  I';d think you';d have the instinct and muscle memory to know not to do that.  But then panic/alarm can cause the bod to do the wrong thing (fight or flight).

All';s well that ends well mate. 

[flybywire]

Cheers mate, sounds like u had a better day than me!  I shot that footage over the trees with that quad a couple of weeks ago, it was sweet as a nut, very well behaved, that';s what';s so puzzeling.  Also a bummer that it happened in front of 20 people!  Still, that';s par for the course in a club environment, part of the ';sport'; i guess!

I';ll lick my wounds and come out fighting, hopefully with a better airframe to boot.   

To cap it all, some joker just weasled out of an ebay bid, grrr, sucks!

Knew i should';ve stayed in bed today 

[flybywire]

Back at work today, after the disastrous weekend that was.  Some time to think more clearly about what happened.  Obviously I will need to check all of the electric/electronics out ';on the bench'; so to speak, but I have to say, I';m 90% certain it wasn';t electrical failure in any sense.  I';ve never had a motor or ESC failure to date, but I';m guessing that the symptoms (in extreme failure) would be a drop from the sky, or dipping down on one side if a partial fail.  My quad didn';t do this, it just went ';crazy';, oscillating wildly in all planes, and finally flipping as I reduced the throttle. 

I';ve thought about it, and it is definitely ';oscillating';, and it has had this issue on occasions from day one.  I';ve not been able to nail it, as it only seems to manifest in strong gusty wind conditions.  I think I can also rule out a physical structure failure, as the sheared plastic bolts were a design feature, and did their job on impact.

So that leaves the gains.  It may be as simple as looking at the setup again, going back to basic gains and increasing them one by one.

I must say, I prefer it without the body, it looks more multi-rotor, less flying beetle! 
Just getting it back to bare bones reminded me of just how light this thing is, all that aerospace grade carbon!   ::)

[Hands0n]

I';m with you on the Gains and Wind thoughts, echoing my own doubts.  Last week was the first time I';ve flown my Naza M Lite in strong wind.  The only other change was that I had tweaked the gains upwards, from the default 100% to 135%/125% for Basic and Atti respectively.  So that is supposed to make the quad more responsive to its Acc/Gyro and pilot stick inputs. But what if that also sets up the Naza to enter some software state of hysteresis that it cannot recover from?  Unpredictable behaviour such as a high power fly away or uncontrollable wobble might ensue.

The trouble is, it can only be guesswork in the absence of any empirical data. Time to go APM/Pixhawk? ::)

[Cloudbuster]

Yep! 

as i keep saying !!! you gets what u pays for ... testament to a well made frame !!! i have had similar expieriences with only minor injuries... 

[Cloudbuster]

I';m with you on the Gains and Wind thoughts, echoing my own doubts.  Last week was the first time I';ve flown my Naza M Lite in strong wind.  The only other change was that I had tweaked the gains upwards, from the default 100% to 135%/125% for Basic and Atti respectively.  So that is supposed to make the quad more responsive to its Acc/Gyro and pilot stick inputs. But what if that also sets up the Naza to enter some software state of hysteresis that it cannot recover from?  Unpredictable behaviour such as a high power fly away or uncontrollable wobble might ensue.

The trouble is, it can only be guesswork in the absence of any empirical data. Time to go APM/Pixhawk? ::)

hi danny ... i too had a very unwealdy quad yesterday in very gusty conditions, a quad that flew absolutely rock steady last weekend turned into a real bag of twitchy nerves in the gusty conditions, mine is also a naza lite with GPS, wind was gusting up to 30mph and to be honest was out of limits really !! but a very weird very twitchy quad that was so benign last week !!!

regards rob

[flybywire]

I';m with you on the Gains and Wind thoughts, echoing my own doubts.  Last week was the first time I';ve flown my Naza M Lite in strong wind.  The only other change was that I had tweaked the gains upwards, from the default 100% to 135%/125% for Basic and Atti respectively.  So that is supposed to make the quad more responsive to its Acc/Gyro and pilot stick inputs. But what if that also sets up the Naza to enter some software state of hysteresis that it cannot recover from?  Unpredictable behaviour such as a high power fly away or uncontrollable wobble might ensue.

The trouble is, it can only be guesswork in the absence of any empirical data. Time to go APM/Pixhawk? ::)

LOL Danny, you';d make a fair salesman!!    Thing is, barring one or two ';glitches'; in 3 years or so, my DJI controlled multi';s are very reliable.  THe CX4/WKM does have an issue with gains maybe, but now I';ve been forced to address it, square on as it were, before, TBH I couldn';t be asked tweaking, I just ';flew it';, (and put up with odd wobble moment in winds) ultimately until it crashed, which I guess is really my own fault.

Saying this, I may very well buy the excellent Naze 32 (full) at a later stage, but at the mo, my eggs are in the DJI basket. 
I';m desperate to get my camera back in the air, but ATM there';s probably no need to rush as the weather is so bl**dy windy 

[Hands0n]

I reckon I';d stake a bit of trust on the Naze32 - we';ve yet to see it reach its potential, I';m really encouraged by the tech.  I got on really well with MultiWii and the new Baseflight and the Chrome integration is superb. Plus no more compiling code in Arduino, it is all plug in and configure on that FC.

However, Arducopter (APM and Pixhawk) seem to be the only FCs that support on-board data logging and the ability to perform forensic analysis of a failure is short on fantastic. Just as long as you recover the aircraft.  I';m not sure that any of the other FCs do this - even by telemetry that may be recorded at the ground control station.  I';d love to see the Naze32 start to do that (either way).

Naza? I';m so wary at the moment - and that Facebook self-help page isn';t helping the confidence ::)  I';m almost expecting the thing to attempt another fly away.  Seriously considering lowering the Gains back to what they were, 100% all round and simply never, ever, attempt to fly it in windy weather!  Which brings me all the way back to APM/Pixhawk, strategically.