Hi,

I was just wondering how you would go about sizing a tailplane for positive longitudinal stability (particularly static stability).

Basically, as i understand it, longitudinal stability is all to do with the location of the CG relative to the neutral point (the aerodynamic centre of the whole aircraft). So long as the CG is forward of the NP then the aircaft should be stable in pitch. The distance between the CG and the NP is the staic margin.

Cambered wings generate a nose down pitching moment, and so the role of the tailplane is to produce anb equal and opposite nose up pitching moment to counter it. The tailplane also produces a restoring pitching moment should the angle of attack be changed by a gust for example.

Ok, thats what i know! What i'd like to know is how you decide on the surface area for a tailplane to achieve stability. Tailplane volume coefficient is an important factor, as is the moment arm of the tailpane etc.... so much to figure out!

I don't expect pages of equations(!) but i was wondering if anyone out there could shed any light on how to solve such a problem - i.e. i need first to calculate this, then go on to determine this and so on...! The methodology if you will.

Sorry for all the waffle! Any help is much apprieciated.

m