stab placement

[Woodward James R Civ 412 TW/DRP (Test Ops)]

Hi All,

 

I was having a conversation about stab placements with someone and wanted to
gather some opinions.  Imagine the following setup:  Main wing is 2.5" below
thrust line and at 0.25 degree positive incidence.  Stab is placed 0.5 -
0.75" or so above main wing, and at zero degrees incidence.  Engine down and
side thrust are 2 and 2.5 degrees respectively.  Knife edge flight requires
10% up-elevator mix to rudder.  CG is set so that when flying inverted, it
requires just a little touch of down elevator (not tail heavy, Inverted 45
degree uplines do fall to earth ever so gently).  Plane has 4% aileron to
rudder mix, so that adverse roll couple is removed when flying knife-edge.  

 

"In - General" - if the stab was lowered to being 0.25-0.5" above the wing
CL, would the mix require for K.E. flight be reduced?  If the stab is
lowered, would this impact the adverse roll-couple at all?  Or, would
raising the wing effectively reduce the pitch and adverse roll couple?

 

Thanks,

Jim

 

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