Equilibrium of the Glider (3-D Incompressible Flow) Glider Effective Aspect Ratio

As a glider (engine off), the glider has the following lift and moment coefficients in terms of the geometric angle of attack a (rd) and tail setting angle tt (rd):

Подпись: r(0 2UbA, Fig. 15.2 Distribution of circulation

Cl (a, tt) — 5.3a + 1.56 + 0.5tt
Cm, o (a, tt) — —1.7a — 0.43 — 0.45tt

The effective aspect ratio AR of the glider (wing+tail), assuming ideal loading is given by the lift slope

Подпись: dCL d a Подпись: 2n 1 + -21 + AR

Подпись: Solving for AR gives Equilibrium of the Glider (3-D Incompressible Flow) Подпись: 10.8.

— 5.3 Equilibrium Angle of Attack

The equilibrium of the moment corresponds to


CM, o(aeq, tt) + 7—- CL (aeq, tt) — 0


Equilibrium of the Glider (3-D Incompressible Flow)

When the lift and moment coefficients functions are replaced in the above equa­tion, taking into account ^ — 0.29, the solution for aeq(tt) reads

Plugging this result in the lift coefficient gives

Cl (tt) — 5.3(0.137 — 1.87tt) + 1.56 + 0.5tt — 2.286 — 9.411tt

which for CL — 1.9 results in tt — 0.041 rd — 2.35°.

The corresponding angle of attack is aeq — 0.06 rd — 3.46°. Landing Speed

Подпись: ueq — Подпись: 2mg pAref (CL ) max Подпись: 13.8 m/s

At sea level, p — 1.2kg/m3, g — 9.81 ms—2, given that the total mass m — 15kg, the maximum lift coefficient (CL)max — 1.9 corresponding to the reference area Aref — 0.68 m2, the landing speed corresponds to the equilibrium equation for the force in the direction normal to the trajectory. i. e.

15.2 Solution to Problem 2

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