where m is the pitching moment and α is the angle of attack.
∂n / ∂β > 0
Design an autopilot system to control an aircraft's altitude. Flight Stability And Automatic Control Nelson Solutions
∂l / ∂β < 0
-0.05 < 0
Altitude Sensor → Controller → Actuator → Aircraft → Altitude Sensor
Cnβ = ∂n / ∂β
∂m / ∂α < 0
For longitudinal stability, the following condition must be satisfied: where m is the pitching moment and α is the angle of attack