Flintlock28

When people talk about "incidence" is this the difference between the bottom of the wing and the horizontal stabilizer in reference to a level fuselage? For example if the fuselage is leveled front to back the wing will have a little bit of angle of attack, is the horizontal stabilizer than usually planed out lower than the bottom of the wing?? Anybody please help me with this one......Thanks.

DMcQuinn

My Feedback: (13)

The term "incidence" generally refers to the difference in the angle of the wing relative to the horizontal stabilizer. Draw a line through the middle of the wing, and the middle of the tail. The difference in these lines is incidence. For a flat bottom wing, the bottom of the wing would be OK. For a symmetric wing, the line is straight through the chord of the wing.
Quite often the airplane designer will also show an arbitrary line down the fuselage and show various angles of "incidence" from that line. For example, the engine thrust may have negative and/or right incidence as compared to that line. Usually the horizontal stab is parallel to that line, and the wing may have a few degrees of "positive incidence", meaning that the wing angle of attack is higher than the horizontal stab

Flintlock28

Thanks for the info. I would assume in most aircraft that the hor. stab. is generally lower than the wing bottom (or chord). Are there cases of the hor. stab. being directly in line with the wing, or is there some kind of problem with putting the hor. stab. in line with the wing?

DMcQuinn

My Feedback: (13)

The horizontal stab can be below, above or directly in line with the wing. In full scale planes there can be an issue where byt he turbulence of the air behind the wing affects the tail surfaces. Moving the tail higher or lower lets the tail fly thru cleaner air.

Flintlock28

Thanks again...