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Need help with terrible flying airplane

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Old 08-14-2010, 04:07 PM
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spitfire66
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Default Need help with terrible flying airplane

Hello,

I have recently purchased a super decathlon by phoenix models and the airplane was messed up from the get go. First thing I noticed was that the ailerons were terribly warped and was not flyable. Towerhobbies sent me a replacement wing and I thought that this would resolve the issue. It did not. The airplane wants to roll violently to the left in all phases of flight. I noticed that the rudder was warped, so I sent the airplane in to towerhobbies and they denied the claim. I ordered new tailfeathers and replaced that on the plane and thought I would be ready to go. The same thing happens again, wanting to roll hard left. I believe that towerhobbies should back there products, but I have already spend $85 on this p.o.s. and do not want to put a dime more into it. I believe that towerhobbies should refund/replace the airplane without me spending another dime. Do I sound out of line or do I have a legitimate claim? Now the only thing I can do is to try to straighten the wing with a heat gun and some force. Maybe I can finally get some flying in without fighting the plane.

My other question is what do I do with a plane that cannot fly normally?

Thanks for the help.

Shannon
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Old 08-14-2010, 04:15 PM
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mirwin
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Default RE: Need help with terrible flying airplane

Shannon,

Do I understand correctly that it wants to roll violently even when it's suppose to be flying straight & level?

Mike
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Old 08-14-2010, 04:18 PM
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spitfire66
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Default RE: Need help with terrible flying airplane

Correct. I have all surfaces in correct neutral position, and the radio and setup at zero with no mixing. I have been flying rc airplanes for 5 years and I am a professional pilot so I have some good understanding of aerodynamics. That being said I am really looking for help or suggestions on what to do. I am at a total loss right now []
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Old 08-14-2010, 04:52 PM
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mirwin
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Default RE: Need help with terrible flying airplane

Shannon,

Well, that eliminates an adverse yaw situation, doesn't it. If the plane isn't out of balance (laterally too), then there must be something wrong with the way the airframe or wing is built. I had a 109" Christen Husky that acted similarly. Nobody at both clubs where I fly could find anything wrong with it. I finally put it on my burn pile.

Maybe somebody else will have ideas but it sounds to me that you got a lemon with wings.


Mike
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Old 08-14-2010, 05:26 PM
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Default RE: Need help with terrible flying airplane

Sounds like you need to do a complete alignment and incidence check. Planes dont fly bad for no reason.

1. Align the wing and horizontal stab to a level condition in pitch, if you can.

2. Start measuring everything, the wings from fuse out to the tips both LE and TE, the fuse for warps, the Horz and Vert stabs for alignment, firewall incidence and thrust angles.

3. Measure again. I am thinking you will find some problems that are causing your flight characteristics.

Vince
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Old 08-14-2010, 09:17 PM
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Default RE: Need help with terrible flying airplane

ORIGINAL: vpresley

Sounds like you need to do a complete alignment and incidence check. Planes dont fly bad for no reason.

1. Align the wing and horizontal stab to a level condition in pitch, if you can.

Vince
What 'cha mean by "to a level condition in pitch"?

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Old 08-14-2010, 10:52 PM
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Edwin
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Default RE: Need help with terrible flying airplane

Decathalons can be a handfull in general. I have the GP. Like was said earlier, do a complete alignment check. I would start with a bubble level on the stab and center it. Then use an incedence meter on the wing. I dont know the Phoenix, but GP has about +2 deg incendence in the wing. Not real practical for a model, in my opinion. I would modify the wing seat for 0deg incedence. Use the incedence meter to check the wing at various stations out to the wing tip to check for warps. Warped wings in arfs isnt really that unusual. I've had to help a few students with bad flying planes that turned out to be warped wings this year. Tower replaced them and we were good the second time. Kit build or arf assembly, incedences need to be checked. This problem is showing up more than it should in arfs now. Lots of threads on this subject.
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Old 08-14-2010, 11:20 PM
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Default RE: Need help with terrible flying airplane

Thanks Edwin I will definetly take a look at that tomorro when I have some time. This is my second phoenix decathlon, 3rd phoenix model, and this is the first time I have ever had a problem. I wish I was around people that built from kits and not arf's. I believe a lot of knowledge is getting left on the wayside and more about just getting the thing in the air. I will have to buy an incidence meter and check that. Thanks.
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Old 08-14-2010, 11:21 PM
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Default RE: Need help with terrible flying airplane

I think the mistake was assembling the plane with warped parts; Tower can say you found them acceptable to put together or you would have sent them in before putting it together. Most would give an attempt to unwarp before glueing together to see if there is going to be a problem. Some ARFs require more work than others in that way.
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Old 08-15-2010, 10:51 AM
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Default RE: Need help with terrible flying airplane

What engine and prop are you running on it?
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Old 08-15-2010, 07:33 PM
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Default RE: Need help with terrible flying airplane

ORIGINAL: spitfire66

I will have to buy an incidence meter and check that.
This link shows how to align without any meter:

http://www.angelfire.com/indie/aerostuff/incidence.htm
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Old 08-15-2010, 08:14 PM
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Default RE: Need help with terrible flying airplane

Look for an experienced flyer who knows how to eyeball an airplane for "straightness".

He will sight from the rear and look for twists and wiggles. He will also give you some hints on how to straighten what isn't right. It's almost always fairly easy to do. Using an iron to straighten out warps is easier than you think, and the Decathlons I've had all needed some of that.

He'll also look for unbalanced surface deflections. And engine thrust problems.
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Old 08-15-2010, 10:04 PM
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Default RE: Need help with terrible flying airplane

Hello All! I had great success last night and today with the Decathlon. I was able to get the warp out of the wing after lots of measurements and eyeballing and the airplane now flies the way that it should. The wing had some bad warping going on that I was able to get out with a blow dryer and an iron. Today at the flying field I was able to use a little trim and had desireable results. Thanks to everyone who posted!

Shannon
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