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I can attest to the lack of coupling in the full scale model 12 Ti-12. In our test flights, the airplane was rigged for hands and feet free flight level and high cruise speed, say 190 mph. Knife edge flight left or right wing down had zero pitch coupling. It did not want to go to the canopy or to the wheels in level knife edge or in a knife edge climb. Wings level same speed hands off the stick and input full left or right rudder made a flat skidding turn, no roll, no pitch deviation. From 230mph 5 g pull to vertical, hands and feet off controls on the vertical line, the airplane continues straight up until stops and simply flops over pointing vertical down and did not deviate off the vertical downline as it gained speed. Pilot reported he felt it would drive straight in if he did not make control inputs.
So, this is an example of an airplane that has a high stab and some of the arrangement issues pointed out above to allow pesky humans to ride in it that has near zero coupling. This shows that some full size airplanes can fly like a model and do not count on the pilot to "correct" the coupling issues.
Some other notes on this airframe is that the wings and stab are all +2 deg incidence while the engine is zero down and 2 deg left thrust (russian backwards rotation engine). CG at about 27% MAC. |
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Very cool! That's a pretty amazing set of accomplishments for any airplane, but especially so for a biplane. Great work!
The Sukhoi I fly, OTOH, has coupling galore with its high stab and low wing. Oh well, still suits me.
Scott