crazy crash, need help analysing log

[RiazP]

hi all,

after over 135 event free flights i had what appears to be a radio signal loss, except i have two receivers my tx battery was fully charged and i was flying straight and level about 10m high and 5m away from me on a clear day!

i have failsafe set so the default behavior is to set blades at -3 and motor to idle so it floated down to the ground and broke a boom, landing gear and bent a blade grip. not catastrophic but i cant help wondering if return to home on signal loss would have been a good feature to have on CP Heli.

regardless of that i was wanting to ask georgi, omerco or one of the other guru's if the could please have a look and see if they could see a problem in my log?

i am rebuilding the heli and would like to know if there is anything that i can do better this time to avoid the issue i just had.

[dogbreath]

I see some possible brownouts on the servo buss voltage. Your line when zoomed in shows some drops to near 5 volts. But I don't know if that's the main problem. Dan

[dogbreath]

I remembered to check the event log:

Event at -19.9 seconds: SK720 initialized in Cyclic 2 and Tail 2

Warning at 230.4 seconds (3:50): Lost radio reception at Satellite Rx port A

Warning at 230.5 seconds (3:50): Lost radio reception at Satellite Rx port B

Error at 231.1 seconds (3:51): SK720 Entered fail-safe mode due to lost radio reception.

Number of missing receiver data frames from Sat Rx A: 543
Number of missing receiver data frames from Sat Rx B: 542

Both sats gone, looks like. Okay experts, are the brownouts enough to kill the sats? Dan

[dogbreath]

I'm fairly new at this, so when I look at the ail/ele/rud channels, I see no inputs starting at 230.4 when the sats were lost. Could that mean the xmtr stopped transmitting or is that the sats not receiving? There is pitch channel, but could that be fail-safe which started at 231.1? Dan

[RiazP]

Hi DogB

I noted the same, but was not able to correlate the failure to the data...

[dogbreath]

Look into those ESC/BEC voltage dips, though. Can you send pictures of your antenna mountings? Those with sats can tell if there's something to latch onto there. Seems that all the smart folks are taking a break. There's no thanksgiving weekend in Great Britain! Dan

[rickn816]

Generally, the servos are the cause for loss of signal. If a servo "fails", it draws tons of current which causes the Rx or Sats to fail.

I would look at the servos first, including any potential linkage binding.

Rick

[dogbreath]

There's a buss voltage drop at 224.3, then not another one until 237.9. LOS at 230.4. There's another thread about sat cables getting old, something else to check.

Dan

[CZorzella]

RiazP

I took some time to analyze your log file and it is showing that the elevator servo is causing most (if not all) of the voltage dips; This could either be related to a mechanical/electrical fatigue of the servo or simply that the linkage joints aren't running as smooth as it should be; If the servo isn't bad, then I'd consider lubing all the moving parts with appropriate lube.

Concerning the possible causes for loss of signal, I noticed that the place where you're flying is almost desert nearby the Pretoria area (at least it was desert when Google' photographies were taken); it's hard to tell, but that place doesn't seems to have lots of RF interference. Which radio are you using? which satellites you have? Are you absolutely certain that these aren't counterfeit? Which BEC are you using? Please send pictures of your antenna mountings.

As a side note, if telemetry readings are correct, it shows that you flew your bird at 85 meters high; What size is your helicopter?

Carlos

[RiazP]

Hi CZ,

thanx for the insight, i remember reading that transient voltage drops are not of concern in the logs as this is a logging glitch, but i am most definitely going to look at the servo on the elevator.

i fly at the PRF (Pretoria Radio Flyers) club east of pretoria central, we are lucky as we have separate flight lines for planks and helis, with an abundance of space! it also borders a private game farm so on the drive to the field you can spy some semi wild game!

the google pics are pretty recent, the area is really light savanna, with the current heat wave it could actually pass as desert! i thought that some one may have been jamming me as there isnt much in the way of rf interference but due to the secluded location i thought that improbable.

i am using the JR 11 X ZERO on dsmj and my sats are jr branded dsmj, i am pretty sure theyre OEM as i purchased them from a reputable JR dealer locally, the sat cables were out of the box when installed, specktrum however, the bec is a jeti mezom 135 opto, and i have a gryphon 7075 bec for good measure.

the heli is stripped for rebuild at the moment so no pics unfortunately, but i had the two mounted in opposite orientations, one underneath the landing gear and one on the back of the gyro mount to ensure that one sat was always unobstructed in any orientation.

this bird is a KSM Dune 600, running futaba bls 157 and 256 hv servos, mezon 135 esc, gryphon 7075 bec, pyro 700-52l hand wound for about 540kv and gens 4000 and 4400 mah batty and it has full telemetry via the jeti box pro.

i like really big air flying, it is very possible that i reached that altitude before diving into a speed run or while doing climbing cuban 8's.

[rickn816]

My two cents -

I find it unlikely that both sats would fail almost simultaneously.

It probably was electrical - and as pointed out earlier, a bad servo.

Rick

[RiazP]

Hi All,

i am in the process of setting up the electronics on my bird, and have noted that one of the sats are bad, i thought that having two sats would mitigate the failure of one.

i read in one of the stickys that a member had a single sat failure that he suspected caused his bird to crash, and at face value it seems as though the same may have happened to me!

i am going to strip a sat from one of my 5 other birds and going to do some bench testing, as suggested in the same sticky, as i cant aford to crash this bird again due to the very strong dollar!

@ Omer or Georgie,

i would really like your opinion on this matter if possible, maybe a quick peek at the log attached at the beginning of this post to see if i am reading too much into something that could just be fatigue related wear and tear?

regards,

[CZorzella]

RiazP, for all small cables (including the ones that goes to satellites and telemetry sensors) apply Plasti Dip to the ends of the cable at the connector to keep the wires and connectors from working loose during flight and to act as strain relief while installing and working on cables in cramped locations inside the model.

Carlos

[omerco]

I will take a look at this when back home - but in the mean time I would be happy to see another older log if you have one (which I guess you don't...). it could show if a sat problem was there before.

Sat are a very good setup but only if set correctly and checked from time to time that they don't blink and the connectors are fine.

[RiazP]

Hi Omerco

no problem, and thanx for the support!

i have included the previous flight of the day, and can supply a lot more if needed...

[RiazP]

Hi CZ

i have some shoe goo, and i used to use it on the servo wires coming out of one of my 720 blues on a 450, i will add it to the to do list for this rebuild, along with maybe soldering the BEC output directly to the skp-pb power input rather than the EC3 i currently have

[omerco]

OK seen the logs.
Your previous log is clean and the problem occurs on both sats at the same time. this makes me think about your Tx!

Please do some range checks. try to shake it a little to see if you can reproduce.

There is no voltage dip at the time of event which explains that, also your dips are to around 6V which is far from being a problem (but your battery does look weak).

[RiazP]

Hi Omerco,

thanx for the validation on some of my theories, i was leaning towards the RX, but i need to do some range tests and jiggle the TX as there could very well be an issue there. the TX has been around since 2009 i believe, while i purchased it about thee years ago.

regarding the voltage drops, this is a concern as i run the BEC off one of my flight packs and into the power bus, this is however connected via EC3, perhaps the connection and the soldering are presenting too much resistance under load.

ideally i would like to see a more consistent voltage profile in the logs, but i am going to focus on the TX RX first, try to replicate the condition at the bench, then tackle the power anomaly.

[jsbach#1]

Originally Posted by RiazP

******************** this is however connected via EC3, perhaps the connection and the soldering are presenting too much resistance under load ********************

Please inspect the EC3 very very very very carefully. I can't stress this enough.

If you go to the Bavarian Demon subforum you will see I started a thread there a while ago investigating a problem my friends 700 was having. He ran 2s lipo connected to his flight controller using EC3 as well flying JR DSMX with 2 satellites.

It start when we were flying with him saying I think my tail servo is going. We replaced his tail servo. Later it developed into,,, dude something is very wrong I am losing and regaining control during my flights and with a 700 that is very scary. So we grounded the bird were eventually able to visually see the satellies flickering on the bench and eventually you could see the 3SX flight controller would reset.

We tried and tried and tried and tried to pinpoint the problem. The quick response was get rid of satellites go to full rx and problems be gone. But he has 7 other birds setup the same way and they're ok ! And how many people in our club ok and how many thousands running 2 satellites.

So anyways, long story short. My friend said one day to me excited I think I figured it out it has to do with the main packs. When he would plug in the main pack and unplug it he could make the satellite flicker. I realized her knuckles were brushing the ec3 connector at a certain angle. And sure enough we were able to finally duplicate it on the bench (even after trying a thousand other times it did not ooccur) were if you wiggled the ec3 connection just the right way it was having a loss of contact/poor contact.

Now he is on rc pro plus and all is good again : )

So I'm wondering if you might have the same suspect. I'm telling you without exaggeration. We spent HOURS on the bench investigating this and wiggling connects and it never once glitched on the bench. Then days later and misdiagnosed replaced satellites replaced satellite wires it finally revealed itself as the ec3 connector at just the right angle and at just the right friction (how hard you push the connection) the male pins are free to rotate on that connector, the male pin has like a bushing style construction the spring loaded part that presses in the female rotates, maybe in a certain position they are losing connection.

All I know is its fixed and we're not using those anymore.

[A VIKING]

Great info jbach!

I also run 2 cell FBL batt and 2 sats DSMX and after nearly 1000 flights have never had a problem.

So the EC3 plug to the FBL was intermittent if I am understanding correctly?