Question

[Aerospace Engineering]

1. Aerodynamics :

(a) how to find zero lift line of a wing and airfoil?

(b) how do we relate this with climb angle(gamma), pitch angle(theta), angle of incidence, and Angle of Attack(Alpha)

(c) why during climb Theta is not considered as Angle of attack since the aircraft moves with respect to x-axis? or is that with respect to thrust direction?

(d) then can we classify Angle of Attack to be similar with Angle of Incidence if the aircraft flies along the direction of thrust?

2. Flight Mechanics :

a) what is the differences between stick-fixed and stick-free? (including explanation on each)

b) consider that the aircraft flies in autopilot mode, is that considered as stick-fixed,free, or neither?

c) Consider Horizontal stabiliser on conventional aircraft, how to find these variables? given

C_LT = 2*phi*Alpha_Teffective + a2(eta) +a3(beta), ; C_LT is known, Aileron hinge location x1/c = 0.65 and Trim Tab hinge at x2/c = 0.8

C_H = b1*Alpha_Teffective + b2(eta) + a2(beta), ;beta = Trim tab deflection angle; eta = Elevator deflection angle

 

Answer 1

1(a) The main difference between the wing and the airfoil in aerodynamics is the " airfoil " is a 2-D shape of the wing where as the "wing" is 3-D in shape as follows.

The lift depends on body's inclination to the flow of the air. when the body moves parallel to the flow of or the negative angle made by chord line of airfoil to the axis shows zero lift. chord line is a straight line crawn between the trailing edge point and leading edge point.

In symmetric airfoil the chord line can be consider as a zero lift line when it is parallel to the flow of air but in assymetric airfoil the zero lift line depends on the reynolds number. Usually their is no any zero lift line just it is an zero lift angle.