DISASTER! Anyone in Hants area?

[Richlizard]

Unless I was seeing things around 1.37 but wasn';t that a very close proximity to some HV wires.... Maybe not a physical contact but you may have had some EMF interference as the descent followed quickly after? 

This may well be the case, but I lost any control or contact at around the 40s mark.

[Richlizard]

Did you get a good home lock before you took off?  It looks for all the world like a textbook RTH, descent wise anyhow, only the wrong home.  I don';t think it';s the power lines, that';s my thoughts.  For a minute I thought you were going to tell us your deceased great great Grandad used to own that plot!  Spooky.

Haha!

As for the good homelock, I always do the double 5 clicks before take-off, even after being given the course and home lock confirmation. Just routine now without thinking.

[Biffa]

That looks like a low voltage decent to me, hampered by the highish wind perhaps?

[n506]

Without even getting to the gimbal doing weird angles, the most unusual bit of this for me is the seemingly relatively sudden clockwise spin just after you reckoned you lost control around the 40-50 second mark. I';m just throwing out ideas here, but could you have a sparking connection on one of the ESCs that started to heat perhaps, or an ESC issue. Some iffy behaviour on one corner would cause the craft to rotate in the relevant direction, thereby requiring the flight controller to attempt to balance the craft by reducing overall power to match the weak link. Combined with heavy winds, you could easily get the battery being low in voltage and the increased resistance with heating would run the battery down a touch quicker than you might ever expect. You might also start to get intermittent surging across the bad connection which could possibly cause issues if the gimbal is running off the same lipo.

Other possibility on the same line is that sparking (or something else) caused a very significant drop in voltage across the receiver and caused the naza to go into RTH or low voltage safe mode. Now if I';m not mistaken, a naza fc will also give up on RTH if it doesn';t seem to be able to fight the wind and battery levels are getting critical? It will then just do a straight descent? I';m afraid I don';t know a whole lot about how the naza works because I purely use it as a smoother version of a kk2.0 without any gps etc. and all the low voltage options off. No doubt there are others might know it better than me!

What I would say is that it appeared to do a textbook naza descent, so the question is what caused it to do it. Before trusting it, I';d check all your power lines and connections for any signs of sparking just to be on the safe side.

Even if it isn';t a fault beyond low voltage, one very important thing to remember is that over around 35-40 feet (I regularly work on cherry pickers so I know well the effect as I come up to this level), you start to get significantly more wind than you see at ground level, especially in open areas like that. That little quad was working pretty hard there to stay in the one place, and that drains your batteries a lot quicker than hovering about in calm weather. So it';s conceivable you banked on having more minutes than you really had.

As for the EMF from the high tension lines, I don';t really think that';d be that big an issue to you, although some folk anecdotally say they are a problem. For the big pilons like that, they run them at very high voltages and lower current, so the magnetic field around them is always lower than people think. Also, the net magnetic field will be lower by the time you count the different phases if my high school physics memory serves me well. I';d have thought that you were well clear of them at the time that you were having issues. It was just by chance as the quad descended that it came so close.

My gut feeling is that something glitched around 40-50 secs when it did that sudden spin around (assuming that wasn';t your control inputs), and the rest was naza doing damage limitation for what was wrong (or it thought was wrong).

My only other last thought was where you were at the time? There were quite a lot of trees there at some points, so I';m just wondering whether you could have lost your transmitter signal too...

So many options that you may never know what it was that did it, but I';d suggest a fine tooth comb over connections and ESCs just to be on the safe side!

[Richlizard]

Thx for the detailed reply.

If only I knew how to do all that testing. My limit for testing electrics in is plug it in and see if it works. I just sent it up and all seemed to work as good as it ever did, although it is not really windy at the moment.

As for timings, I had already set my timer second alarm at 6 minutes. Looking at the image times, it had been up for 3 minutes maximum although I would stab at 2 minutes.

I have attached an image of the locations...

If anyone wants to explain how to test for sparking and other problems, I will give it a go. I have had a voltmeter for about 20yrs that I know will be of use one day!

Cheers
Rich

[guest325]

When you say you last saw your model is it possible that it went out of sight below the factories? If so it could be that radio contact was lost, that amount of buildings between you and your model could just be a possible explanation.

[Richlizard]

Well I suppose it is possible. But I was looking direct at it when I decided to bring it home. I glanced down for a split second to change my switch from slow move back to normal and looked back up and there it was... gone! 

[n506]

I think you';re a bit confused on positions when I compare the video to the map you';ve given. You followed the tree line and Churchill Way down past the Twining building. Based on where you were, you';d have seen the quad at all times to the right of the high part of the Twinings building. You were roughly above the mark where you say "Found Around Here" when it glitched at 40-50 secs. If your last visual was where you said it was, you were seeing something that wasn';t your quad!

I';m starting to wonder what happened when you went to change mode. Perhaps you looked down and looked up, and got disorientated, thinking it was in a different place? And let the power down a little as you searched the sky, causing the quad to duck further out of sight? When it then drifted down enough, I';m almost certain you';d lose radio contact with around 200-300m range through buildings and trees, and it';d go into failsafe. If it had lost GPS contact for any reason, then I can only assume it would drop vertically, which accounting for some wind (and given the tilting of the quad, I reckon the wind was coming from the direction of the Twining building - from North East), it would start to drift South West towards Admirals Way. As it came down though, the wind would be less, so it would start to come down in a more vertical descent, thereby landing in the allotments where you found it.

Don';t like to blame the pilot, but it';s seeming like a distinct possibility. I hadn';t realised you were on the other side of the industrial units (had assumed you were in the roadway of the Twining building somewhere) where you';d have had a more unrestricted view. I';m also aware that when it drifted across the road, you were heading more towards the direction of the sun, and therefore quite possibly partially blinded to its location.

To study the video in more detail, I';m guessing you were looking between the two industrial buildings at 0:39 to see it, but as we see, the quad starts to move west quite quickly up to around 0:43, thereby quite possibly becoming hard or impossible to see against the bright sky around the sun, which is when the unusual behaviour starts (possibly panic control inputs as you';ve lost sight of it?). Somewhere around the 1:00-1:25 range where the quad has been sitting about but drifting a little, these inputs I think became the naza doing its own thing as it decides to land. Most probably because the large building in front of you, plus whatever else, caused you to lose radio contact.

I still don';t like to rule out technical problems, but identifying where you were flying from has raised alternative possibilities for me.

[Richlizard]

lol, gimme a break n506  ::)

I take full responsibility as pilot for what happened and presume it was just too much wind for it. I have now purchased an anenometer or whatever it';s called.

Someone asked me for a rough idea of positions and I gave them just that... a rough idea. I was watching the quad all the way along it';s North path, over the highest point of Twining and to the other side when I realised there was nothing good to look at and that is when I last saw it.

As a fully qualified pilot who once tried to land on a disused racing track thinking it was my intended target airfield, I know very much how different things look from the ground and air.

I am sure I can give a more accurate placing if I knew there was going to be a CSI investigation!

ps I mean no offence 

[Richlizard]

pps everything else you say was almost spot on.

Wind was coming more North-west rather than North-east.

I had deliberately located myself so that I did not look into the sun which was on the South of this map. Finding the best place to film from is priority as you probably know. I was on a bridge at one point!



Someone did mention that there are accurate post event wind checks which might suggest the actual wind was greater than the forecasts I had with me. No idea if this is available.

But either way, I definitely had visual until I erm lost visual. But it wasn';t due to it being too low.  ::)
Always a chance I guess that a freak gust blew up from the valley and sucked it down a little as I glanced at my switch?

[n506]

Well, it was just my assessment of your video showed that you were nowhere near (around 150m out) where you had marked your last sighting assuming the video has no significant gaps in it (which didn';t seem to be the case at all). It';s funny when you try to remember situations how easily you trick yourself into thinking things were in different places. Being under pressure doesn';t always provide the best opportunity for being a good witness (to keep the CSI theme going)

I know well myself how easy it is to become disorientated or lose sight of quads at that kind of distance when flying LOS. Might be worth sticking FPV gear on it running out to a small monitor on a tripod. Even if you';re flying LOS, it gives a valuable resource to check what direction you';re pointing or if you lose sight, you may still be able to see where the quad is from the screen.

I certainly wasn';t out to offend in any way. Just interesting to analyse the time lapse video, and what I could see is that where you reckon you lose sight of it, it behaves a touch abnormally, but basically drops down within 50m (across the ground) or so of where it was hovering at that point. To me that doesn';t represent pilot error (beyond perhaps losing sight of the quad), but rather the quad deciding to land for whatever reason, and the wind pushing it a touch in the given direction. Essentially a straight drop accounting for wind - why it didn';t RTH on gps is then the question. If it had travelled the 150+ metres indicated on your map, it would have been more of a question of how it tried to RTH, but got it so spectacularly wrong as to where the home position is.

Sorry if I come across as a pain in the bum, but I always like to analyse everything when I have a crash (thankfully never had a flyaway), or analyse other folk';s problems, because it gives valuable information that I can use myself (as well as perhaps others) to make sure I don';t have the same problems myself if possible. If you don';t know what can go wrong, you might not know how to avoid it happening!

EDIT: Apologies, I had a flash of recollection about your original post and when checked, I see you mentioned you already had a monitor, but it had gone blank after you lost sight of the quad! So that wouldn';t have helped either in this case!

[Richlizard]

It';s funny when you try to remember situations how easily you trick yourself into thinking things were in different places. Being under pressure doesn';t always provide the best opportunity for being a good witness (to keep the CSI theme going)

Hence me trying to land on a racetrack! Wondered why there were no other aircraft on the ground! 

[Hands0n]

Memory is utterly unreliable in stressful circumstances. It often prompts us to take completely wrong actions during the period of stress. Worse still, it misleads afterwards when trying to understand what exactly happened.  The curse is that we do not truly remember, we reconstruct the memory.  And that is where it all breaks down.

[Michael Kheng]

Kept the landing on a disused racetrack quiet Rich! have you flow the quad since?

[Opto-Mystic]

Memory is utterly unreliable in stressful circumstances. It often prompts us to take completely wrong actions during the period of stress. Worse still, it misleads afterwards when trying to understand what exactly happened.  The curse is that we do not truly remember, we reconstruct the memory.  And that is where it all breaks down.

My memory is like that even without the stresses!

[XH558]

As a fully qualified pilot who once tried to land on a disused racing track thinking it was my intended target airfield, I know very much how different things look from the ground and air.

Not as bad as this bloke .... a C17 Globemaster FFS... that';s some mistake   

C17 Lands At Wrong Airport
C-17 Lands at small commuter airport by accident

[Michael Kheng]

 That was Rich!

[Hands0n]

Oh wow!    I was watching the landing in the first video and thinking "How the heck is he going to get out of there?"    The second video clip was even more impressive, the pilot performing that liftoff certainly has got a bit of backbone. 

I';d have hated being the pilot who flew it in. I guess the rest of his day didn';t go quite so well ::)

[n506]

I believe from memory of reading about the incident at the time that they stripped out everything non-essential into trucks till they got it down to a weight they reckoned could get off in that distance. That probably included taking the fuel weight down enough that they were able to circle into the other relatively nearby military airport, but didn';t have a huge amount to spare.

[Richlizard]

Kept the landing on a disused racetrack quiet Rich! have you flow the quad since?

That was in a REAL plane!

Yes, put the quad back in the air a few times since. Apart from gimbal leaning to the left which I think/hope/pray I have corrected, all seems to be in order.

[Toledodave]

Wow...im shocked it didnt go poof! Almost tangling I. The high tension power lines! That was close!   In my experiences near powerlines I watch my copters rt motors spool up out of nowhere and cart wheeled across the field untill the booms snapped off and stopped. Still have no explanation and never flying over there again lol.  Not taking the chance untill I can explain my errors :)

[Richlizard]

Wow...im shocked it didnt go poof! Almost tangling I. The high tension power lines! That was close!   In my experiences near powerlines I watch my copters rt motors spool up out of nowhere and cart wheeled across the field untill the booms snapped off and stopped. Still have no explanation and never flying over there again lol.  Not taking the chance untill I can explain my errors :)

I lost contact long before that. Guess I should consider myself lucky!