Out-of-Control Flight
Aerodynamic Principles
STATIC DIRECTIONAL STABILITY
The tendency of the aircraft to return to steady-state flight after a disturbance in the horizontal plane. Direc-
tional stability can be positive, neutral, or negative. The three types of directional stability are illustrated in
Figure 4.
POSITIVE STATIC STABILITY
NEUTRAL STATIC STABILITY
NEGATIVE STATIC STABILITY
Tendency to Return
Equilibrium Encountered
Tendency to Continue
to Equilibrium
at Any Point of Displacement
in Displacement Direction
Equilibrium
Equilibrium
Force Tends to Restore
No Restoring Force
Force Causes Divergence
Figure 4: DIRECTIONAL STABILITY STATES
(9-98) Original
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