Please answer this question asap .. Its from stability and control course .. Aer
ID: 802231 • Letter: P
Question
Please answer this question asap .. Its from stability and control course .. Aerospace engineering The pitching moment characteristics of a general aviation airplane with the landing gear and flaps in their retracted position are given in Figure P2.7. 0.4 0.2 0.0 -0.2 -0.4 0.25c 5 ft S 150 ft2 -0.6 0.4 0.8 1.2 1.6 0.0 CL FIGURE P2.7 Pitching moment characteristics of a general aviation airplane. (a) Where is the stick fixed neutral point located? 0.002378 slug/ft', what is the elevator angle required for trim? (e) Discuss what happens to the pitching moment curve when the landing gear is deployed? How does the deflection of the high lift flaps affect the stability of the airplane?Explanation / Answer
a. The stick fixed neutral point is that point at which the static stability of aircraft is neutral or the slope of dCL/dCM is zero and the elevator is allowed to float. To determine the stick fixed neutral the aircraft is flied at a particular location with different speeds or CL and then the corresponding elevator angle to trim is measured. This procedure is repeated for different Cg positions. The slope of SeCL curves are plotted with respect to Xcg. The intersection of this curve with the Cg axis give the stick fixed neutral point. The intersection of line at which the delta e=0 and cmcg is zero represents the stick fixed neutral point.
b. If the net moment and forces acting on the aircraft is zero it is said to be trimmed. The value of elevator deflection can be given by the equation delta etrim= delta eo( d deltae/ d Lctrim)/CLtrim
c. The pitching moment from landing gears is usually small and act opposite to it. The gear will block the flaps and also reduce the nose down pitching moment. The landing gear affect the aerodynamics by adding an element of drag and also modify in lift by causing change in airflow across the wings. It increases the lift slightly.
high lift flaps are used to increase the lift of the wings of the aircraft at a particular speed. They are usually placed on the wings of the aircraft. Their purpose is to decrease the minimum speed at which air craft can be safely landed or increase in angle of descent. They increase the drag effect. Higher the flab greater is the drag.