For directional stability, the following condition must be satisfied:

The pitching moment coefficient (Cm) is given by:

The directional stability derivative (Cnβ) is given by:

Substituting the given values, we get:

Altitude Sensor → Controller → Actuator → Aircraft → Altitude Sensor

Therefore, the aircraft is directionally unstable.

∂l / ∂β < 0

Cnβ = ∂n / ∂β

The autopilot system can be tuned by adjusting the controller gains to achieve stable and accurate altitude control.