Zephyr ZII - Highs and Lows…..

[mjc1970]

Sunday morning started out great, perfect weather with a little breeze which would be perfect for some ZII flying!  :D

Other than a couple of failed launches (one of which resulted in a torque roll and the ZII flying back into a hawthorne bush!) I had a couple of great flights with the ZII. See following video of one of these flights:

http://youtu.be/xjOIhRbDmT0

I'd calibrated the FY31AP during an earlier flight and on landing clicked the No4 dip switch down to save the stabilisation settings. On testing the stabilisation mode however the fun was about to begin as you'll see from the following video:  :'(

http://youtu.be/r_sC9Nqtyls

No problems with the take-off and having levelled out at a reasonable altitude my flying buddy activated the flight stabilisation mode setting for me. From the ground it looked like it was making little corrections, but from the flight video it was evident there was a fair amount of rocking up and down. Going into a turn, I started to lose altitude and pulled in a fair amount of up elevator to try and level out the ZII without much impact. She wasn't having any of it (from the flight video you'll see it was very unstable at this stage).  By now from a LOS view point, I was worried about the ZII descending too much and going into a tree so with that disabled the flight stabilisation mode (ABM on the OSD). The result was that the ZII pitched up very violently and in doing so, ejected one of the flight lipo batteries from it's wing batterybay! The result was a very unstable ZII and the corn field below beckoned!    Having recorded the OSD footage, this enabled us to pin-point the ZII within about 5 minutes. Luckily, other than losing one of the batteries and prop the ZII came off relatively unscathed other than a slight dent in one of the wings which shouldn't be too hard to sort out. The corn field must have softened the impact somewhat. Phew!

The only explanation is that the FY31AP must have been suffering from excess vibration, although this didn't show on the ground with motor test runs.  Further testing before I try again I think, but having enjoyed some really smooth flights earlier in the day; I'm  now questioning the use of the stabilisation function however the RTL is a major attraction however (not that I intend to fly too far away).

The first FPV flight will have to wait a little longer.

[6lennn]

Bummer

havent flown my for a while as waiting for lipos

however when i tested mine stab mode, i too thought it was losing altitude, I want fpv so dont know if Mine was doing same as yours, going to be a bit more careful when im next out, thanks fornheads up

[Coyote]

Glad to see you got it back ok. I see two things that stick out in that video.

First the ZII was not trimmed properly, it was gaining altitude all the time

Second was your artificial horizon showed no sign of the banked turn the plane was in. It should have been at the same angle of the horizon but wasn't.

What was a shame was the screen display choice, the horribly cluttered screen will show you your vibration reading so you know if that was it. But to me, your FY believed it was flying level when it was in a banked turn which lead to the rest

[dogzilla]

Cant watch it due to blocked music :) Might need to re-upload mate with a different sound track.

[pk-surfing]

Like Coyote says.... turn up the OSD to full data and you will see a whole line of zeros very top left, these should stay zero all the time, if they start showing numbers at all then it means the FY is picking up vibration that is effecting it's sensors.

The oscillation is either your elevator gain is set too high on the FY adjustment potentiometer
or
looking at how the oscillation built up it would be handy to see a photo of how you have the FY mounted in the Z2, if its on the soft sprung mount then too high gain linked in with maybe the various servo wires connected to the FY starting to tug it out of level due to inertia as the oscillation starts would cause this.

PK

[Coyote]

Top left not right AER0000

[mjc1970]

Thanks for the feedback guys. I will take your suggestions on board for future flights.

I'd run out of down trim on the elevator Coyote, hence why it was climbing slightly. I've now altered the elevator mechanically to allow more down. I have found that I've had to put in a fair bit of up elevator to get the thing away at launch.   I'll check out the OSD, still learning what all the readings are.

PK, if you have a look on my blog http://mjc70.blogspot.co.uk/ , you will see how the FY31AP is positioned. It's in the front battery bay behind the cameras and is mounted using some thickish double sided cushioned tape. It's not strictly on the CoG which maybe would also help too?

[Coyote]

Thanks for the feedback guys. I will take your suggestions on board for future flights.

I'd run out of down trim on the elevator Coyote, hence why it was climbing slightly.

There is one of the pieces of the puzzle found. There is no point in setting up FY if the plane can not fly straight and true by itself. You must trim it so its perfect first before DIP 4 up and Stab on for >2 seconds. With the plane not being able to sustain level flight because its not got the throws it needs its constantly fighting itself and the wing and it can not win.

It's in the front battery bay behind the cameras and is mounted using some thickish double sided cushioned tape. It's not strictly on the CoG which maybe would also help too?

And here is the second and third piece of the puzzle and prob the main reason of the problem.

Double sided cushioned tape is no good, I tried with velcro but although it works I still get readings on my X8, On my walker though I used double sides sticky pads, I stuck two together to double thickness and on my Walker I get 0000 all the time.

Also positioning the FY on the CG is highly recommended, although Gyro`s can be away from CG and work just the same, accelerometers are greatly affected by being away from the CG.

How far off the CG is the FY positioned Matt ?

Fix the issues above and I think you will have it sorted for the next flight

[Coyote]

Oh I forgot to add, which is THE most important point.............

Your artificial horizon to me is the biggest issue, it did not show your plane banking at all. So stabilization settings don`t come into it untill that`s resolved, there is something very wrong there

Have you updated to 1.2 firmware ?

[mjc1970]

Yeah, I updated to firmware 1.20 yesterday morning prior to flying.  The update was successful and I've confirmed it's at V1.20.

In the flight where we calibrated level flight, she appeared to be flying straight and level although we were doing judging it from a LOS perspective. Maybe doing it from a FPV perspective is better thinking about it.

Having just measured how far the FY31AP is from the CoG, I would say 3.5 inches forward of the CoG. Probably not ideal I know, but space issues don't really allow it to be positioned elsewhere.

Thanks again for the feedback.

[Coyote]

No problem, always trying to help :)

Yes do it using the Hornet display, the altitude will show you if your sinking or climbing. Once its sits level you know you are trimmed true. LOS wise you really have no idea of climb / sink because depth perception looking up is pretty impossible. Take your video, the altitude always shows the plane climbing in RC and ABM mode ( because you ran out of trim )

If you cant get it any closer ( CG ) then you will just have to live with that.

After flying my X8 on it, I would recommend setting aileron and elevator gains to half as a good starting point as too not over correct on both axis ( assuming that you have enough but not far too much throws )

[mjc1970]

Thanks Coyote. We'll get there I'm sure!  I'll keep you posted.

Cheers.

[Coyote]

You can do the above and improve thing no end ( if the systems working ) but I am really concerned that your FY does not recognize the plane is turning, even if setup totally wrong, the artificial horizon should still show correctly even if it cant react properly

[Coyote]

Ive watched again, you give trim during ABM mode, this does not work, because you plane can not level ( because of not enough endpoint ) you give it trim, you should not trim in ABM mode, if it cant hold in that mode then either - plane is not trimmed properly or not enough throws to let AP level it

But because your AP is showing it "believes" its level it wont be trying too, then when you feed trim in, because it believes its level it tries to flight your trim, the more trim you dial in the more it fights, hense its wobble gets worse and worse and worse

[Coyote]

Another thing I noticed, your artificial horizon sometimes does not react to a banked turn, on my videos from the other week, mines not either ???? Sometimes iit does, sometimes its not