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Old Jan 26, 2013, 02:41 PM
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Joined Aug 2012
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question on my 50cc ultimate

When i fly the ultimate its flies perfectly fine and when i go vertically up the airplane pulls to the wheels does it have to do with the engine angle giving it a down thrust vertically??? and when i knife edge it pulls to the wheels allot. PLZ help
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Old Jan 26, 2013, 02:54 PM
team sleprock
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United States, WA, Port Angeles
Joined Dec 2009
3,490 Posts
it's normal for it to pull towards the gear in knife edge! heck I can do a perfect canopener, with just rudder!

hafta let someone else help you out on the vertical pull! only thing I can suggest is to make shure you don't have too much down thrust!

I asume you are talking about a well trimed airplane, like as in hands off in level flight! if thats the case then you might be nose heavy, as in the tail is working overtime keeping the plane level in flight, then when vet. there is no nose weight! so it would pull too the gear! so check CoG!
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Old Jan 26, 2013, 02:56 PM
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United States, WA, Port Angeles
Joined Dec 2009
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oops I might be backwards on that but you get the idea of where I am coming from!
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Old Jan 27, 2013, 11:01 AM
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Ty il try that
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Old Jan 27, 2013, 04:45 PM
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winston mo
Joined Oct 2006
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fine tuning an airplane takes a bit. Trying little things at a time like adding a bit of up thrust to the motor.
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Old Jan 27, 2013, 10:08 PM
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Hi 3DNOOBS,

Unfortunately, bipes can be a pain to get trimmed correctly. This is mainly because the wings (and often the stab) are nowhere close to being on the engine's thrust line.

There are several things you can test that should help you diagnose and resolve the problem.

First, confirm that your plane is setup correctly. If you have the plans (or manual) verify that the thrust line, wing & tail incidence, aileron reflex, and CG all are within the designer's specs. The rudder and elevator also need to be zeroed out.

As you mentioned, there may be too much engine down thrust. To test this, fly straight and level slightly above stall speed, then slam the throttle wide open. If the plane pitches down, you will probably need to add some up thrust.

The Ulti may also be tail heavy. To find out, fly straight and level at half throttle and roll inverted. If your plane climbs, slowly move the CG forward until it holds altitude or slowly descends.

If the thrust line and CG check out and it still pitches to the belly, you might try vertically balancing it. To do this, hang the plane in the KE position by the prop shaft and at a point near the tail along the thrust line. If the plane rolls to the belly you can rearrange the internal components / add weight, as needed, to keep the wings straight up and down.

If all else fails, you can reflex the ailerons up a little and re-trim the plane. This should be a last resort, though, because it will likely introduce other handling issues.
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Last edited by modestmagi; Jan 27, 2013 at 10:20 PM.
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