Roll And Yaw Stability of Airplane

amadali · January 14, 2025, 11:55

Hi, What is the necessary condition for roll and yaw stability of Airplane. Plz Enlist conditions with appropriate reasonings. Explain in simple terms.

Marc_462 · January 15, 2025, 03:35

CMα < 0, CLβ < 0, CNβ > 0
The first inequality tells us that the pitching moment must behave inversely to α (angle of attack). As the angle of attack increases, the aircraft will generate a pitching moment in the opposite direction, bringing it back to its equilibrium point. This point is the trim angle, αtrim. To meet the criterion for longitudinal stability, the center of gravity, xCdG, must be located ahead of the neutral point, xNP. The other two equations describe that at any roll angle β, the roll moment must be restorative, and the yaw moment must counteract disturbances during turns.

IMPORTANT: this is not a CFD question!!!

January 14, 2025, 11:55	Roll And Yaw Stability of Airplane	#1
amadali New Member amad Join Date: Jan 2020 Posts: 2 Rep Power: 0	Hi, What is the necessary condition for roll and yaw stability of Airplane. Plz Enlist conditions with appropriate reasonings. Explain in simple terms.

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January 15, 2025, 03:35		#2
Marc_462 Member Marc Aragó Cebolla Join Date: Oct 2021 Location: Spain Posts: 41 Rep Power: 5	CMα < 0, CLβ < 0, CNβ > 0 The first inequality tells us that the pitching moment must behave inversely to α (angle of attack). As the angle of attack increases, the aircraft will generate a pitching moment in the opposite direction, bringing it back to its equilibrium point. This point is the trim angle, αtrim. To meet the criterion for longitudinal stability, the center of gravity, xCdG, must be located ahead of the neutral point, xNP. The other two equations describe that at any roll angle β, the roll moment must be restorative, and the yaw moment must counteract disturbances during turns. IMPORTANT: this is not a CFD question!!!