Tower Kaos, was Right Thrust?

I've been following the Right Thrust thread for a while, and I wonder why my Tower Kaos (the kit, not the ARF), has a significant amount of both right and down thrust. I've noticed the plane tracks beautifully in inside loops, but outside loops, unless corrected, turn into corkscrews. The Kaos design has been around for ages and has been used in many successful pattern planes. As was said in the above-mentioned thread, pattern planes are supposed to be neutral, with the thrust line going straight down the middle. Why did Tower put right and down thrust in what's supposed to be a pattern design?

-- Morris Lee

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Morris Lee
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The thrust line and the engine line are not one and the same. The engine produces torque which generally tries to pull the plane to the left and up. Each engine and prop combination produces a different amount of torque. The engine line must be set so that the thrust line of the plane is neutral, not so that the engine line is neutral. Very simplified, but it works for me.

Trimming a plane correctly starts with a plane that is built correctly. See this trim chart to learn how to trim your plane:

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. Be sure to read the stuff at the top of the chart.

In all probability, you have too much downgoing elevator and you are stalling the plane during the outside loops, thus causing the corkscrews. While flying, flip the plane inverted and do your outside. If it corkscrews, try again applying less elevator. If this fixes the problem, then you need to adjust the throws on the plane so that in inside loops and outside loops are the same size. If it does not fix the problem, you probably have a building error in the plane, i.e. a slightly warped wing or one of about 100 other things.


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For a plane to be absolutely neutral, you have a symmetric airfoil, the wing and the engine set at zero! incidence and thrust, and the same amount of fin/fuselage area above and below the thrust line, which must co-incide with the plane's centerline. In fact the plane must be symmetrical in side view and in top view. Such a plane would need just the right amount of aft CG location to keep the nose up, in order to provide the needed angle of attack for the wing to just support the weight of the airplane in flight. This would work at one speed only. It climbs at lower speeds, and dives (tucks under) at high speeds.

The Kaos is a long shot from that, It probably has normal CG, and the wing probably set at one (1) degree incidence, the engine has down thrust, and right thrust to compensate for prop wash, torque and incidence; so you need to compromise towards trimming out one error, and increasing an other error.

Life's supposed to be easy, but kit builders messed op good to humor the mean sports flier.

Reply to
Pé Reivers

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