Turbine trainer tail config?

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13 years 9 months

Posts: 151

I've noticed that on the Pilatus PC-21 & PC-6/7, as well as the Super Tucano's, the vertical stabilizers seem to be well forward of the horizontal stabilizer. Is there a particular reason for that? I thought I'd read what the advantage was but I can't seem to locate the material. The PC-21 looks like an absolutely awesome aircraft. 1600shp with an aerobatic weight of 3,100kg puts it in the class of the top WW2 fighter planes.
Original post

Member for

7 years 10 months

Posts: 5,831

Vortice. Horizontal surfaces tend to be inverted airfoils (pushing downward). Trailing stream hence is bent upward and vortices might induce a disturbed airflow around the rudder tip (and flutter). By positioning frwd the vertical surface you cancel the problem. However, frwd positioning means a bigger surface (less moment arm and less rudder (hence bigger tail)), hence more drag and less moment to counter a spin. Those two points are balanced by : - in a spin the frwd postionned vertical surface is less masked by the horizontal tail surface - Mach rise drag is reduced thanks to more balanced reduction of wet surface at the end of the aircraft (if the plane has to fly fast obviously). As you can see, there is not one single awnser in aircraft design without specifying clearly the problem. However, in a trainer, the need to impart a solid resistance to spin departure and exit direct our awnser toward the unshielded rudder ;). Many general purpose aircraft see their vertical moving frwd b/w early design and final test.

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7 years 10 months

Posts: 5,831

did I anwser your question?

Member for

13 years 9 months

Posts: 151

Absolutely you did. Thank you so much for being clear and concise.

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7 years 10 months

Posts: 5,831

You are welcomed. :)