Question

A wing alone arrangement has wing lift curve slope of 2.65 per rad. Find slope of pitching moment coefficient. Given Xcg = 0.3.

(a) 0.025 per degree

(b) 0.03 per rad

(c) 45 per rad

(d) 0.0035 per degree

I have been asked this question in an interview for job.

My question comes from Longitudinal Static Stability and Control-1 topic in chapter Stability, Control, and Handling Qualities of Aircraft Design

Answer 1

Right option is (a) 0.025 per degree

For explanation I would say: Considering ideal location of aerodynamic centre i.e. Xac = 0.25

Slope of pitching moment curve = (wing lift curve slope*[Xcg-Xac])

= (2.56[0.3-0.25])

= 0.1325 per rad = 0.00253 per degree.