INCIDENCE settings

[Ron Van Putte]

On Sep 30, 2005, at 11:53 AM, Pat Hewitt wrote:

> I would like to learn more about incidence settings on our wings. I 
> have a
> chance to buy a plane that has preset settings such as O, .25, .50, or 
> .75 but
> how do I make the correct choice. I am sure the best is to have an 
> just able
> system but please lets not go there I just want to understand how you 
> pick the
> correct one.

Being an engineer, I will respond to this question as I would to 
similar questions.  My answer is, "It depends".  Sorry.

The dependency involves many factors, including the thrust  line angle, 
horizontal stabilizer incidence, location of the center of gravity, 
longitudinal and vertical distance between the wing and horizontal 
stabilizer and the fuselage design.  There are so many different 
factors which are interdependent, that it is impossible to give a 
direct answer to the question.  The best answer is from those who have 
flown a nearly identical configuration.  Empirical answers are usually 
best in our hobby.

This discussion also tapped into one of my pet peeves:  Guy sees an 
airplane flying around with the tail low and announces, "That airplane 
is tail heavy".  Probably wrong.  The incidence relationship between 
the wing and the horizontal tail is probably incorrect.  The CG has an 
effect, but the condition is usually caused by a bad trim setup.  Now I 
feel better.

Ron Van Putte

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