Question

An aircraft with wing aft tail configuration has tail efficiency of 0.95 and tail volume ratio of horizontal tail is 0.7. Determine pitching moment coefficient slope for the tail. Given lift curve slope of tail is 4.2 per rad. Consider downwash derivative as 0.6.

(a) -1.1172 per rad

(b) 2.45

(c) 234.67 per degree

(d) 12.788

I have been asked this question in quiz.

I would like to ask this question from Longitudinal Static Stability and Control-1 in portion Stability, Control, and Handling Qualities of Aircraft Design

Answer 1

Correct option is (a) -1.1172 per rad

For explanation: Given, tail efficiency e = 0.95, tail volume ratio of horizontal tail v = 0.7, lift curve slope of tail c = 4.2 per rad, downwash derivative d = 0.6

Pitching moment coefficient slope for the tail = -e*v*c*(1-d)

= -0.95*0.7*4.2*(1-0.6) = -1.1172 per rad.