What causes a change to the indicated airspeed (IAS) of a stall?

Indicated airspeed (IAS) is the speed that an aircraft's airspeed indicator shows, and it is critical for determining stall conditions. Stall occurs when an aircraft exceeds its critical angle of attack, leading to a loss of lift. The necessary lift for level flight is influenced by various factors, and any change in these factors can result in a change to the indicated airspeed at which a stall occurs.

For instance, if the aircraft weight increases, more lift is required to maintain level flight. This means that the pilot must fly at a higher airspeed to achieve the necessary lift, thus increasing the indicated airspeed at which the stall occurs. Similarly, changes in the aircraft's configuration (like deploying flaps) can alter the lift characteristics, affecting the stall speed.

Factors such as changes in air density could also be considered, as they impact the lift generated at a given airspeed. Therefore, any factor that alters the conditions under which the required lift is generated is indeed a valid reason for the indicated airspeed at stall to change.