I am working my way through Perkins & Hage chapter 5, Static Longitudinal Stability and Control, Stick-Fixed. The method presented is to add up the dC_m/dC_L contributions of the wing, tail, and fuselage. This sum should be negative for stability, and the equation (5-32) can be rewritten to determine the neutral point (eq. 5-35) and thus to find the static margin for any c.g. position.
I have worked my way up to equation 5-32:
But the fuselage term (dC_m/dC_L)_fus is giving me trouble. For this, we turn back to equation 5-30:
Here, (dM/dα)_fus, S_w, c, and a_w are known. But what value of q should be used?
In all of the other terms of eq. 5-32 (i.e. wing and tail contribution), q drops out when we convert moments to moment coefficients, but not for the fuselage contribution. So how do we calculate (dC_m/dC_L)_fus if q is unknown? Please help me understand what I am missing here.
I have worked my way up to equation 5-32:
But the fuselage term (dC_m/dC_L)_fus is giving me trouble. For this, we turn back to equation 5-30:
Here, (dM/dα)_fus, S_w, c, and a_w are known. But what value of q should be used?
In all of the other terms of eq. 5-32 (i.e. wing and tail contribution), q drops out when we convert moments to moment coefficients, but not for the fuselage contribution. So how do we calculate (dC_m/dC_L)_fus if q is unknown? Please help me understand what I am missing here.
