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Old Apr 08, 2010, 04:17 PM
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Yak 54 Landing Issue?

Hey Guys need a bit of direction! I have a Modeltech Yak 54 with a 26cc gasser in it. Not quite a giant but figured you guys would be the ones to ask on this. The plane flyes great and is slightly nose heavy ( tried moving the CG back slightly and it seemed to become pretty unstable) So everything is great till I try to land, I will set up the approach like the rest of my planes but when I drop the throttle to let it glide and flair in the plane wants to climb! If I add some throttle it levels back out. So what would make it climb with no throttle/ at idle. Because of this I am having some really fast landings which are sketchy! Any advise would be great!
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Old Apr 08, 2010, 09:02 PM
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Egg Harbor City, New Jersey
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Too much engine down thrust could cause it.
With power on it is pulling the plane slightly down, when chopping the throttle it balloons.
Your trim to fly level with power on is fighting down thrust ( some up trim ).
When at idle the engine isn't pulling down and the trim makes the plane rise.

I would check down thrust and / or your CG.
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Old Apr 08, 2010, 09:06 PM
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Thanks for th reply, I will check the downthrust, if it was the CG is it a nose or tail heavy characteristic?
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Old Apr 08, 2010, 09:08 PM
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Thanks for the reply, I will check the downthrust, if it is a CG issue is it a nose or tail heavy characteristic?
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Old Apr 08, 2010, 09:37 PM
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Tail heavy.
A nose heavy CG you would have a hard time slowing it down it would want to land hot.
A nose heavy CG you would have a hard making it flare for touchdown.
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Old Apr 08, 2010, 09:48 PM
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Quote:
Originally Posted by 2robinhood View Post
Tail heavy.
A nose heavy CG you would have a hard time slowing it down it would want to land hot.
A nose heavy CG you would have a hard making it flare for touchdown.
Well thats the issue I am having It is coming in real hot! I cant get it to slow down for landing so I am guessing Nose Heavy which would also explain the up elevator at normal flight, but the nose wanting to come up when I let off the throttle has me baffled!
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Old Apr 08, 2010, 10:04 PM
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Quote:
Originally Posted by bri6672 View Post
, but the nose wanting to come up when I let off the throttle has me baffled!
Engine down trust.
Try shimming a little less down thrust and see what happens.
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Old Apr 11, 2010, 09:02 PM
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You Nailed it!!!! I took out the down thrust (putting the motor at dead center) and the issue is gone! landings are back to normal! Thanks so much for the help! For others that have this issue it basically came down to this: The engine down thrust (factory spec) was forcing me to have to trim about 4-5 clicks of up elevator for level flight under power, when I removed power to flair in for a landing the up elevator trim was making the plane rise and I had to give it down elevator to get it to drop, this also created some fast sketchy landings. With the engine at zero down thrust I no longer needed the up trim for level flight (about 2 clicks) and now she flairs in nice and slow and no issues!
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Old Apr 11, 2010, 10:03 PM
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Glad to hear, good luck, and good flying.
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