I was hoping some folks out there would shed some light on why my 78" Extra tucks during knife-edge flight. The airplane flies very well in all other regimes of flight, but tucks strongly towards the belly during knife-edge flight. I hold alot of UP elevator during knife-edge. I believe too much.
My Staudacher has the same vice. It does no matter the throttle setting or airplane attitude. I've been told (rumor alert) that the problem is the way the air spills over the cowl on these when it gets sideways. Changing engines helped a buddy with his (going from 4 to 2 stroke), and if you look at trimming charts it tells you to change the wing incidence. My elevator is dead flat in level flight, and doesn't take any noticeable down elevator to keep it level inverted. I moved the second battery pack 4 inches forward to cure it, and it had no effect.
So, solution was to live with it for me. I tried putting in elevator mix to cancel it, and left the mixing switch on for a crosswind landing. Thank God I had some excess speed when I put in some rudder and it ballooned on me. Haven't used the mix since.
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