Head shake on 4.0?

[smwht]

I have a SK540 clear on a goblin 500, updated it to 4.05 today (was on 3.43). I set heli size (to 500) and checked over the rest of the settings, everything looked fine (though I did miss at least one thing - more on that in a sec)

I took it out to the park and spooled up for a hover (after normal preflight checking all responses etc. - all fine) and went into a hover. After about 5 seconds it started shaking badly and getting worse (head going back and forth like a cyclic input) I'm not sure if it was ail+elev or just ail - only hovered tail-in. I hit TH, landed, tried again, same thing, so I plugged in the SK-LCD and started checking settings. I had cyclic and tail gain both locked to 50% on bank 1 (only bank available) so I dropped cyclic to 40% and tried again. Did the same thing. Then I checked the "Pilot Inputs" screen and saw tail gain was on bank 2 at 100%! I have not paid for the bank switching upgrade on this unit, so this confused me quite a bit. I flipped switches until it toggled to bank 1 (was on the aux/gov switch on my dx8) and it showed 50% as it should. However, it still got the shakes when I hovered it. I finally dropped cyclic gain to 25% and tail to 40%, but I still got shaking (and it doesn't look like it got any better)

The shakes get worse faster at higher headspeed (IU2). IU1 is ~ 2500rpm and IU2 is ~ 2700rpm (18T pinion, 75% / 80% gov store on a yep 120, quantum 4120-1200 motor)

I don't think I had logging enabled, but if that'll help diagnose it I can go turn it on and hover in the driveway.

I guess the question is, why is it shaking so badly, and why did the SK-LCD think it was in bank 2 for the tail?

Edit: forgot to mention, on 3.43 it did not have this issue, and I did notice the battery was pretty loose on its tray - was pretty easy to wiggle side to side. Tightening down the battery a bit also had no impact on the wobble, though.

[omerco]

Guys please we have asked that like 1000 times:
POST YOUR FLIGHT LOG.

There was a gain change from 3.4x to 4.x and your problem is gain related, but still it could be starting with your setup or something else - both we can see in the log.

[smwht]

Sorry

Was hoping there'd be a "magic toggle" of some sort. Here's the flight log and setup. Flight was: Turn on heli, check orientation, flip switch to go to bank 1 (still not sure why it does this, setup software shows the same thing) then flip out of TH and hover for a few seconds until it started shaking, then TH and land.

[omerco]

Looking at the log:


What i can see is before you takeoff gyro switches to bank 2, and just as you land it switches to bank 1.

From the setup i can see your bank 1 gain is "locked" on 20 (very low by the way), but you are flying on bank 2 - which is set to Tx.

What is your Tx value for that bank? if its default its 100...when it should be around 40 (if i remember correctly from the last gob i have set).
Also - are you switching to bank2? or is your Tx set in a wrong way? because it looks like it is connected to your Throttle command.

one more thing - in the control tab you probably need 0.5 dead bands as a minimum for elevator/aileron. you need to check in the live data that Tx's "noise is not above that, and if it is increase even more.

[smwht]

This is a 540 clear, there shouldn't be any bank switching. I found the tail thing by accident. I'll check I don't have anything mapped weird on that, though. The software won't let me adjust the other banks it appears to be defaulting to in flight.

I'll set the dead bands, missed those were 0.

[omerco]

I re-read your description especially about the lcd showing you are on bank2. apparently there is a bug here allowing you to use the second bank although you don't have access to it. your values there are default (210/240 rate for cyclics), and now I'm 99% certain you were using 100% gain.

So if you are already locking the gain in the software on cyclic bank1 you can cancel the bank selection in the control tab that way there will be no gremlins there - and test again with your old gain, or maybe a little less, locked in the software.

One more thing i forgot about your setup - you have self tune bell gains which threw your bells to high numbers. i would cancel the self tune and punch the bells manually.

[smwht]

Got a chance to test hover with the bank switching explicitly disabled in setup, seems solid. Thanks

I still have to go back through all the tuning stuff but that'll take more than a hover in my driveway in the dark so it'll have to wait for the weekend.