AIR CRAFT STABILITY AND CONTROL

    

Stability of an aircraft means its ability to return to some particular condition of flight (after having been slightly disturbed from that condition) without any efforts on the part of the pilot.

 

               01. STATIC STABILITY

 

An aircraft is in a state of equilibrium when the sum of all the forces acting on the aircraft and all the moments is equal to zero. An aircraft in equilibrium experiences no accelerations, and the aircraft con­tinues in a steady condition of flight. A gust of wind or a deflection of the controls disturbs the equilibrium, and the aircraft experiences accelera­tion due to the unbalance of moment or force.

02.  DYNAMIC STABILITY

 

While static stability deals with the tendency of a displaced body to return to equilibrium, dynamic stability deals with the resulting motion with time. If an object is disturbed from equilibrium, the time history of the resulting motion defines the dynamic stability of the object. In general, an object demon­strates positive dynamic stability if the amplitude of motion decreases with time. If the amplitude of motion increases with time, the object is said to possess dynamic instability.

03.LONGITUDINAL STABILITY

 If the aircraft is stable about the lateral axis, (along the longitudinal axis) it is said to be longitudinally stable.

04.LATERAL STABILITY

Stability is the aircraft about its longitudinal axis (from rolling) is known as lateral stability.