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  1. #1

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    Piper rolls right when up elevator is full

    I have a Flyzone http://www.hobbico.com/airplanes/hcaa2500.html 3' Piper Cub that I can't seem to get going very well. I've only tried it 3-4 times and have now converted to BL power.

    Here's what I realised today it is doing:

    It will fly all day if you are not aggressive with the elevator. It trimmed out well and was overpowered , but flew very well until the elevator is pulled back more than about half way. It doesn't have a lot of throw or speed from the stock servo. When the elevator is pulled to full it rolls right very sharply. It is very consistent.

    Fly all over the place , but yank back on the stick and it'll roll right very quickly , maybe more quickly than when using full ailerons. I tried to see if the ailerons or rudder were moving while flying , but I had to keep it too far away to avoid crashing.

    I know on the bench without the motor running it doesn't do anything funny when puling the right stick back all the way. I also now know that it did this with the stock brushed motor too.

    I'm using a 9x Turnigy TX that I use on many models. I'm also using the HK or Flysky 6 channel RX (same type I use in many models) I haven't changed any servos or RX yet.

    Some ideas I had that I don't think are the problem:

    I'm pulling the stick over when I'm pulling it back.
    The ailerons are moving when stick is pulled back all way.
    The RX is sending signal to ch 1 by mistake.
    The elevator isn't the strongest thing I've seen and does flex just a bit , compared to many of my models is normal. I have tried 2 different ones , servo horn is on the bottom left.

    Any common ideas to check out? Thanks.
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  2. #2
    hugger-4641's Avatar
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    RE: Piper rolls right when up elevator is full

    When you pull the stick full back, do both halves of the elevator deflect evenly?
    Jerry
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  3. #3

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    RE: Piper rolls right when up elevator is full

    No, it has a little bit of flex , and since the horn is on the lower left it gets "pushed" toward the rear. It makes the left portion a bit higher than the right (when using full elevator) of course. Wouldn't this cause a roll toward the left though?
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    RE: Piper rolls right when up elevator is full

    That would cause it to roll left...

    Are you at a high enough airspeed when getting aggressive? If not, it could be tip stalling to the right which is pretty dangerous.
    Flying is the art of throwing yourself at the ground... and missing.

  5. #5

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    RE: Piper rolls right when up elevator is full

    It happens at any airspeed.
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  6. #6
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    RE: Piper rolls right when up elevator is full

    I don't have the Fly zone cub, but I have several Parkzone and Hobbyzone cubs. When one of them does this it is usually either the vertical stab flexing, the entire tail section flexing, or the elevator flexing. I have had a warped wing on the Parkzone J-3 cause this. I also had a loose strut on the Hobbyzone cause this once, but in this case it was a very gentle roll. I would look closer at that tail section.
    Jerry
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  7. #7

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    RE: Piper rolls right when up elevator is full

    Checking the tails and the struts now. Thanks.

    The struts are a bit hokey , they are bowed in opposite directions (one up and one down) but they have about the same amount of slop in them when wing is pulled up.
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  8. #8

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    RE: Piper rolls right when up elevator is full

    The tails all look ok to me, a bit on the weak side compared to some of my other planes. Here's some pics and I might just flip the rear stab over so the horn is on the right instead. I'll move the rudder horn onto the left and swap servos inside. I'm not sure what that'll tell me if it changes , but if it does change the behavior then I know I am onto something. The rear of the plane is very strong anf the fuse has no noticeable flex. The rear stab does "steer" right and left a bit of slop in it.
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  9. #9
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    RE: Piper rolls right when up elevator is full

    Sorry, late to the party as usual but some thoughts.

    Easy enough to check if you are dumb thumbing the stick. Plane on a table where you can watch the control surfaces as you operate the tx. See if in fact you or the tx itself are moving the ailerons when pulling elevator.


    But probably most likely is your repower in action. It's now faster. It will require less control throw to operate it. Simple physics, slow speed will require a large throw to get a quick response.
    At high speed it take very little to get a response. It may be that you are just adding too much throw now then the plane needs.

    Also a very common problem when say attempting a loop, is to use too much elevator. It will cause a plane to snap/roll out of the loop. Simply easing off the elevator will eliminate this.
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  10. #10

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    RE: Piper rolls right when up elevator is full

    The stick has very light tension on it and it is easy to do if I don't pay attention, but I do use this TX for 4 other models ok.

    It sounds like you may be saying that this is somewhat "normal". I've checked things over once again and still can't see anything obvious to my inexperienced eye. I'll fly it some more and pay special attention to the symptoms. I'm interested to see at what point in elevator travel I get the sharp roll. I haven't even made it to a loop yet on this , it doesn't get that far. A nice steep climb will cause the roll to right.

    I appreciate all the ideas , even if they aren't what's going on with this particular problem I can learn from them. I wish I could get a video. Hey, I just might have to get some real live help on this one. I'm always by myself.
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  11. #11

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    RE: Piper rolls right when up elevator is full

    I had some time to goof around with this yesterday in the snow.

    I took it up and rolled it left (not holding it in) and then used elevator to do some very tight level circles (laps) I don't know what to call it , but it is counterclockwise circles looking from above. I was able to use full elevator travel with no problem and no loss or gain of altitude (very predictable)

    When I did this with rolling to the right (not holding the aileron in) and using elevator to maintain a tight circle , as soon as I got to a certain point with elevator it immediately spiraled down sharply to the right even more (as if I had applied right aileron again)

    I also figured out that it really doesn't do it all the time either. I can make a tight loop once in a while with full elevator. Also when looking at the plane fly it kinda appears as it's flying with a heavy tail especially at slow speeds. I don't think I can get it inverted.


    I took out 40% of the elevator with a D/R switch to try next time and then if I can fly it without ailerons I'll remove the ailerons all together and hopefully I could fly it with my left stick and rudder only just to test it. I guess if the problem goes away at least that points me to an aileron problem?

    Believe it or not, this is a little bit fun for me. A good way to learn. Of course I'd be bummed if this was my only plane.
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  12. #12

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    RE: Piper rolls right when up elevator is full

    I had to use up some batery so I used a elevator D/R swith set at 60% and guess what? At 60% elevator the problem is completey gone. Easy to toggle between 60 and 100% so I am sure that the trouble is occurring at some level OVER 60%

    I needed a bit more to land though. Anyways, I don't quite know what to conclude about this let alone how to "fix" it since I'm not even sure whether it's a "problem"

    While I was up I did many tight loops and many very tight circular laps both directions and all seemed well (except for needing a bit more elevator for landing) I forgot to turn the DR switcgh back to 100%. I'm curious to see how it acts when coming at me during slow landing when using 100% elevator.
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  13. #13
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    RE: Piper rolls right when up elevator is full

    As another poster suggested, sounds like she maybe tip stalling. Its possible to stall a wingtip even at higher airspeed if the angle of attack gets too large. Wondering if your wing is warped somewhat (those wonky spars look kinda scary). If the wing is strait then maybe she's favoring a right roll when she stalls due to prop torque *shrug*. Lastly you may want to mess with the CG. See if that helps any.

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    RE: Piper rolls right when up elevator is full

    I have currently moved the CG forward with a smaller batery and will test it soon. Thanks.
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    RE: Piper rolls right when up elevator is full

    I flew it today and was able to lock out the ailerons. It still acts up big time with a lot of elevator throw. I think I'll just adjust the throw to the point where it gives me trouble and then back off slightly. This will allow me to put lots of flights and time on it. The CG didn't seem to change anything. I will keep posted with results. I did get inverted a lot and notice that it takes lots of elevator to fly level when inverted.
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  16. #16

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    RE: Piper rolls right when up elevator is full

    A more forward CG with limited elevator travel fixed this problem. I don't fly it much , but it does ok now.

    Thanks to all who helped and gave me ideas. It wasn't my stick control, or a RX or TX problem or even any deflection or strut or wing problem. I think it was just too much elevator UP travel.

    Adjusting TX to a more permanent setting so I can put some good 15 minute flights on it.
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  17. #17
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    RE: Piper rolls right when up elevator is full

    Glad to hear you got that sorted out, even if it is still somewhat of a mystery. I guess its like the old saying... patient says: "Doc, it hurts when I do this", doctor says: "Well don't do that then".


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