ZYX - static causing intermittent pitch pump?

[majorlemond]

Hey guys,

I have a belt drive tarot 450 with dfc head, rjx servos all round on a bec (6v) and recently
I've noticed after running a high headspeed for 4 mins or so, on some flights towards the end of my flight, I'll get a very abrupt collective pitch reversal (goes negative) which only lasts a fraction of a second but is very scary and has put the heli into the ground from a 2 foot hover twice now. It's also happened at altitude, however I've been able to recover in time - it seems to happen once every 2 packs or so.

After reading about static issues, I tried the following:


- Running a carbon boom, earthed via a tail shaft bearing and and 2 stainless screws at each end of the boom and then to the negative of the flight pack (4s)

- I changed to an aluminium boom, earthed to the flight pack

However the problem persists with either method, and I'm a little bit stumped, as the gyro doesn't have any 'hard over' tendency which seems to be the norm for static discharges. Could this possibly be associated with a momentary bank switching?


Any help is most appreciated!

[Nihilistic]

You say you're running a separate BEC to power the servos and RX and ZYX? Sure it's providing enough amps? You could be having a brownout toward the end of your flight.

I'm running a 40A YEP ESC that has a 5.5V 5A SBEC to power my hungry KST215MG's, and I've never had a brownout so far.

People have reported an issue with the ZYX sometimes spontaneously switching between Condition 1 and Condition 2. So, it's best to be sure that everything is the same on both conditions. Go through the setup on condition 2 and make sure your collective pitch polarity isn't reversed.

I use condition 1 on my ZYX-S, but always make the same changes to condition 2 whenever I do any tweaking, and then put it back to condition 1 and save to a file.

[majorlemond]

Thanks mate, I`ll have a good look at the setup and hopefully I can get to the bottom of it, as the ZYX flies my 450 like it`s on rails and I don`t want to have to change it out!

Thanks again for your help

[Dr. M]

This doesn't sound like static to me. Also, probably not conditions switching either. The uncommanded condition switching happens during initialization (i.e. when you first power the gyro), I've never heard anyone reporting this in flight.

As Nihilistic suggested above, this could be a power issue (brownout). Or you could have a loose wire/connector somewhere - check the collective signal cable from the Rx to ZYX. It could also be a cold solder joint on the contact pins of the ZYX board, which I've seen before (this can be fixed by reflowing those solder points).

In any case, I recommend you do some bench testing and try to replicate the problem. Remove the blades and spool up your heli. Then wiggle the sticks, wiggle the wires, shake the whole frame and see if you can get it to glitch.

[majorlemond]

Ok so it seems I've discovered the problem. I tried using another FBL system, which had the exact same problem! That ruled out a defective ZYX.

I'm pretty sure it was the Frsky receiver I was using, which had been flawless on every model except my 450 - I had it mounted on the side frame where the boom is clamped, and I think as the aerials ran close to the boom, despite the boom being grounded the receiver was still being affected to some degree and causing the glitch.

Since moving the receiver to the front of the heli I haven't had a single glitch in probably 20 flights or so.

Thanks to everyone for your help

[Alexatu]

Thanks for posting your result, glad for you having solved that out.