Pitching moment and lift coefficient

[xzibition8612]

Consider a proposed airplane design shape in a wind tunnel. The forces and moments are measured at the proposed center of gravity location. At zero angle of attack, pitching moment is zero and lift is 10N. At 5 degrees angle of attack, pitching moment is -5Nm and lift is 60N. The chord of the wing is 1 meter.
(a) What is dM/dL (sensitivity of pitching moment to lift coefficient)?
(b) What is dCm/dCL (sensitivity of pitching moment coefficient to lift coefficient)?
(c) Is this design longitudinally statically stable?


I have no idea how to do this. The formula for pitching moment coefficient is Cm=Cmwing+(h-hwing)Clwing-(Vh)(Cltail). I honestly don't think this equation applies in this problem, because there is no h, tail dimensions...etc. So I guess I'm supposed to figure out the pitching moment from the given data. But I need the line equation to do that? How do I find that? Am I even going on the right track?

Thanks a lot

[viscousflow]

You're forgetting that C_M = \frac{M}{qS} and C_L = \frac{L}{qS}

[njardus]

You're forgetting that C_M = \frac{M}{qS} and C_L = \frac{L}{qS}

You're forgetting the c in C_M = \frac{M}{qSc} :wink:

[xzibition8612]

Ah ha, so I plug it in and that's the answer right? Thanks a lot.