What happens to the stall speed as altitude increases if weight remains the same?

Stall speed is primarily influenced by the characteristics of the aircraft's airfoil and the weight of the aircraft. When altitude increases, the air density decreases, but the critical factors determining stall speed—namely the weight and aerodynamic properties of the aircraft—do not change.

Stall speed is calculated using the equation:

[ V_s = \sqrt{\frac{2W}{\rho S C_L_{max}}} ]

Where:

• ( V_s ) is the stall speed,

• ( W ) is the weight of the aircraft,

• ( \rho ) is the air density,

• ( S ) is the wing area,

• ( C_L_{max} ) is the maximum coefficient of lift.

If the weight of the aircraft remains constant while climbing to a higher altitude where the air density decreases, the stall speed does not decrease or increase significantly; it remains the same. Although the aircraft is interacting with less dense air at higher altitudes, the stall characteristics remain defined by the same forces acting on the aircraft under those specific conditions.

Therefore, the stall speed remains unchanged as altitude increases with weight held constant. This relationship emphasizes the importance of understanding how aerodynamic principles apply consistently across different operating conditions.