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Parkzone ArtiZan - strange loop behaviour

Old 05-08-2015, 04:58 PM
  #1  
Swiss Flyer
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Default Parkzone ArtiZan - strange loop behaviour

Hi guys,

I cannot figure out what is going on here.

My Parkzone Artizan flies beautifully, trimmed out for level flight at half throttle and climbs, dives and rolls as expected. However as soon as I pull a loop (full throttle with a dive going in) the plane seems to dip a wing and almost wobble at the apex of the loop (i.e. when inverted). Initially I thought that something was loose is the fuselage, but I've checked the battery, ESC etc.. and all of them are tied down. In addition all control linkages are fine with no slop.

Its very consistent and I've now experienced it on two different days (calm and 5 km/h wind). I'm pretty sure its not a stall as the plane is going into the loop with lots of speed and power. I've even created a new model on my DX6 in case there is some rogue mixing going on with that particular model memory.

Any ideas?
Thanks in advance
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Old 05-08-2015, 05:44 PM
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Yakfishingfool
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Does this one have the safe or asx 3 technology? Could the inversion be playing games with the auto stabilization software?
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Old 05-08-2015, 05:49 PM
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The Artizan doesn't have SAFE.. it has AS3X but that wouldn't cause anything like this.

Sounds to me like you are may be trying to pull the loop to tight and stalling. Remember a stall can happen at any airspeed. Try using less up elevator and make the loop bigger.
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Old 05-08-2015, 05:50 PM
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Check wing flex... I bet its uneven.
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Old 05-08-2015, 06:10 PM
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Likely too much elevator throw and it is snapping/stalling.

Mike
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Old 05-08-2015, 06:57 PM
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Thanks for all the help folks

Originally Posted by Yakfishingfool View Post
Does this one have the safe or asx 3 technology? Could the inversion be playing games with the auto stabilization software?
No, mine is a PNP running a non-ASX3 (AR610) receiver.

Originally Posted by JetPlaneFlyer View Post
Sounds to me like you are may be trying to pull the loop to tight and stalling. Remember a stall can happen at any airspeed. Try using less up elevator and make the loop bigger.
I've got dual rates set up on the toggle switch (70% and 25% expo) and its the same on both settings. However I will try to do bigger loops with more altitude.

Originally Posted by fhhuber View Post
Check wing flex... I bet its uneven.
A silly question, but how? Both wings look straight and true on the bench, however I am not sure how they would look when pulling some Gs.

Originally Posted by rcers View Post
Likely too much elevator throw and it is snapping/stalling.
I will reduce rate to 60% on the elevator and see what happens.

Cheers
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Old 05-08-2015, 07:38 PM
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They are certainly capable of doing perfectly nice loops without wing flex, and a lot more far advanced aerobatics.

I found this video on youtube that shows a nice loop with no 'funny business' .. see one minute into video:

Try to emulate that size of loop...

I take it that you havent added anything that will make the model heavy, like a bigger battery or such like?
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Old 05-08-2015, 07:53 PM
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Uneven flex can be caused by the spar not being glued in correctly. Found that on a few foamies.

Hold the model by the wingtips canopy toward your chest and pull the wingtips back. You don't have to apply a lot of force you just want to flex the wing a bit. Anything in the wing that isn't glued right will show very fast.

Its one of the checks to do any time a plane is acting strange and you can't figure it out. You can find cracked spars in a wood structure plane this way.

*************

Another thing that will give strange results is the trim covering coming loose. I had that happen in a manner that made the plane act like the right aileron had gone to 90 deg up deflection any speed above 1/3 throttle. Getting that one down intact was not fun. (but it taught me to do the harrier...)
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Old 05-08-2015, 08:06 PM
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Originally Posted by rcers View Post
Likely too much elevator throw and it is snapping/stalling.

Mike
There's your answer. Let us know how it works out when you reduce the elevator throw.

TP
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Old 05-09-2015, 03:44 AM
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question about the artizan i don't get any power til about half throttle what could cause that.
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Old 05-09-2015, 03:53 AM
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Originally Posted by cj2563 View Post
question about the artizan i don't get any power til about half throttle what could cause that.

ESC auto-detect of throttle range. Check the manual for making it detect how much range your throttle channel has.

I have one ESC where that function is broken. ESC won't arm without 150% ATV range low end and then the prop doesn't move until stick is centered with high end at 100% ATV
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Old 05-09-2015, 04:05 AM
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Ok i will check it out what receiver and tx setup do you use
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Old 05-09-2015, 04:25 AM
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I use DX-18... Forgot what RX is in the Dynam Tiger Moth with the flaky ESC. Some day I'll quit being lazy and swap that out. I only have about 30 ESCs sitting around.
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Old 05-09-2015, 09:08 AM
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Originally Posted by cj2563 View Post
question about the artizan i don't get any power til about half throttle what could cause that.
First check that the throttle trim is centred. Having the throttle trim closed will cause that problem.
If the throttle trim is centred and if it still has the problem then the ESC throttle range needs to be calibrated

ESC's vary but the most common way to calibrate the throttle range is:
  1. Take off prop or secure plane so it's safe if motor accidentally starts
  2. Turn on Tx and put throttle stick to wide open
  3. Plug in battery on the plane
  4. ESC should beep (but it wont start). When it beeps fully close the throttle on the Tx.
The ESC should now play it's usual series of beeps that indicate it's armed. Throttle should now be calibrated.
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Old 05-09-2015, 04:30 PM
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Can you fly it inverted?
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Old 05-09-2015, 04:38 PM
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When you do a loop you are not really 'flying inverted' as such because the plane is pulling positive g all the time.

Having said that, the Artizan is a fully aerobatic model with a symmetrical airfoil wing, so it will fly inverted just as well as it will fly the right way up.
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Old 05-09-2015, 05:36 PM
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Completely agree with jet flyer , and I think the most likely cause of the problem is snapping the airplane . But since the Swiss flyer hasn't figured out the problem yet, I just thought his feedback on inverted flight would give everyone helpful data for the diagnosis
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Old 05-11-2015, 12:08 AM
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Hey guys,

By means of an update, I took her up again with the rate set at 60% on the elevator and she looped nice and straight with no problem. Switched to 70% and the same problem I noted before so it would seem that I had too much throw on the elevator.

Thanks again
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Old 05-11-2015, 06:45 AM
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Good to hear
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Old 05-16-2015, 02:26 AM
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cj2563
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the elevator doesnt move much at all on mine what could cause that or should it be like that?
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Old 05-16-2015, 02:40 AM
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Several reasons possible.

Linkage adjustments. Connecting the push-rod close to the servo arm center of rotation and/or far out on the control horn will give low throw.

ATV/endpoints/dual rate programming of the TX

Programmable servo set for reduced rotation.

How much throw you actually want is partly a matter of pilot's taste.... partly what is necessary to be able to properly control the model.
10 deg +/- from centered is enough to fly almost any model doing no aerobatics, just racetrack laps around the field.
You might need 45 deg +/- from center for some advanced maneuvers, especially the low airspeed "3D" stuff. (all flying occurs in 3D....)

More than appx 45 deg +/- you are adding more drag than actual control effect. You may actually roll slower with extreme aileron throw than with something in the range of 25 deg to 45 deg. There is a point where more deflection just does no good at all.
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Old 05-16-2015, 09:31 AM
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Originally Posted by fhhuber View Post
Several reasons possible.

Linkage adjustments. Connecting the push-rod close to the servo arm center of rotation and/or far out on the control horn will give low throw.

ATV/endpoints/dual rate programming of the TX

Programmable servo set for reduced rotation.

How much throw you actually want is partly a matter of pilot's taste.... partly what is necessary to be able to properly control the model.
10 deg +/- from centered is enough to fly almost any model doing no aerobatics, just racetrack laps around the field.
You might need 45 deg +/- from center for some advanced maneuvers, especially the low airspeed "3D" stuff. (all flying occurs in 3D....)

More than appx 45 deg +/- you are adding more drag than actual control effect. You may actually roll slower with extreme aileron throw than with something in the range of 25 deg to 45 deg. There is a point where more deflection just does no good at all.
Based on this advice I've just added a deflection measuring device to my tool box I actually thought that barn door style deflection was good for aerobatics but as I saw it crossed over from useful control to drag/stall like behaviour.
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Old 05-16-2015, 09:55 AM
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Originally Posted by Swiss Flyer View Post
Hey guys,

By means of an update, I took her up again with the rate set at 60% on the elevator and she looped nice and straight with no problem. Switched to 70% and the same problem I noted before so it would seem that I had too much throw on the elevator.

Thanks again
mmmmmmm forgive my comment - but stick movement is proportional and really all you need to do is not bang the stick to limits !

Its actually a matter I used to drum into people I taught to fly years ago .... learn to move the stick enough but not more. So many times you'd see a new guy get up there and pull tight small loops. If you say to them ---- now try that but with only half stick - the look of fear on their face ! Its a common fault.

I would suggest putting the elevator back to its previous setting and then go out and fly using amount of stick instead of making Tx do it for you.

Another factor that screws a model out at top - is too late closing throttle. At top of loop, the model is at its most vulnerable in terms of thrust lines, inbalance and torque. Being slow at that point - if motor is kept full on just a second or so too long - she skews out. How to determine if this applies? Shut throttle little earlier than usual - see what she does.

Just adding to the ideas pot ! But my money was always on too tight a loop !

Nigel
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Old 05-16-2015, 11:46 AM
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You can get a combination where moderate deflection at speed can G load the aircraft and force an effective AOA > where the wing will stall.
Referred to as an "accelerated stall".

You can stall at ANY airspeed, which is why "stall speed" is a bad term. Its actually minimum airspeed for sustained level flight. Any slower and the wing will be unable to provide the lift needed to keep the aircraft in the air.
(You might be hanging on the prop at a lower speed... but the wing isn't holding the airplane up.)

Since your loop behavior turned out to be excess elevator at speed you might want the higher deflection available for lower airspeed.

You can deal with this by moderating your stick movement... or use of dual rates.
I prefer moderating stick movement.

My TX I can assign different expo values on the "dual rate" (I can have 5 "flight modes" using 2 switches) switch and thus have different expos all with the same max deflection... or with different max deflections. (I never use different max deflections. 100% always available.)
For low speed I find I generally don't want as much expo as at high speed.

Example flight modes might be:
Takeoff... low expo, wheels down, flaps up
Cruise.. moderate expo, wheels up, flaps up
High speed... high expo, wheels up, flaps up
Landing approach... moderate expo, wheels down, flaps 20%
Final... low expo, wheels down, flaps full.

(note more modes than I can have all at once)

Nice to be able to do all that with 2 switches.
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Old 05-17-2015, 04:28 AM
  #25  
cj2563
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Another question why would anybody need 18 channels not trying to be rude but i cant think of enought things for 18 channels
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