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Do horizontal stabilizer of ga planes e.g cessna 172(or ultralights e.g lazair) have cambered airfoils inverted to provide the tail downward force or do they have symmetrical airfoils at negative aoi to provide the downward tailforce during flight.

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  • $\begingroup$ I would think this answer will vary depending on if you are asking about stabilators or elevators both of which appear on small GA planes. You may want to specify which one you are asking about. $\endgroup$ – Dave May 30 '18 at 17:10
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    $\begingroup$ I think the design may vary for each manufacturer, and even for each model. You may restrict your question to specific aircrafts $\endgroup$ – Manu H May 30 '18 at 18:11
  • $\begingroup$ @ManuH How is the OP going to know this without knowing the answer to this question? I'm sure generalisations can be made and if not, that's an answer too! $\endgroup$ – Sanchises May 30 '18 at 19:05
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Generally they are either symmetrical airfoils (like NACA 0012) or flat plates (especially on fabric airplanes). The horizontal tail doesn't have to work as hard, or operate over as wide an AOA range, as the main wing in generating downforce, so you can get away with what amounts to, on most fabric airplanes, a slightly streamlined sheet of plywood.

There are some specialty exceptions. The Zenith 701 family of homebuilt STOL aircraft are unusual in having a heavily cambered flat bottom airfoil for the tail (actually, flat topped, since it lifts downward and is installed "upside down"). They did this to get as much down force as possible at very low speed and since the airplane is a bit of a slug anyway, the draggy tail airfoil wasn't so much of a penalty.

A homebuilt I had started on but never got anywhere with, called the Pegazair, had something similar, having ripped off a few of the 701's design elements.

Also, it was a practice at DeHavilland Canada to use tail airfoils with a bit of negative camber to improve down force at low speed on their STOL designs. I'm sure there are others.

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