Chapter 6: stability and control


Figure 6.9 Aircraft Longitudinal Static Stability



Download 2.68 Mb.
Page7/25
Date28.05.2018
Size2.68 Mb.
#50510
1   2   3   4   5   6   7   8   9   10   ...   25

Figure 6.9 Aircraft Longitudinal Static Stability

Static Stability Criterion

The above discussion of stable responses to disturbances leads to a criterion for positive longitudinal stability. This stability criterion is a condition which must be satisfied in order for an aircraft to be stable. Since, for positive static longitudinal stability, pitching moment must decrease with increasing angle of attack, and increase with decreasing angle of attack, the partial derivative of the coefficient of pitching moment about the center of gravity, CMcg = Mcg / q S c, with respect to angle of attack must satisfy:


(6.3)
Equation (6.3) is the longitudinal static stability criterion.

Trim Diagram

A plot of pitching moment coefficient vs angle of attack or lift coefficient reveals the relationship between static stability and trim, and is usually called a trim diagram. It is convenient to plot the variation of CM cg with respect to absolute angle of attack, a = L = 0 , because a = 0 when CL = 0. Figure 6.10 illustrates a typical trim diagram for an aircraft with positive static longitudinal stability.





Download 2.68 Mb.

Share with your friends:
1   2   3   4   5   6   7   8   9   10   ...   25




The database is protected by copyright ©ininet.org 2024
send message

    Main page