RC Airplane Design

How Aspect Ratio (AR) affects the stall angle of attack (AoA) of RC Airplane


Let us now consider the effect of Aspect ratio on the Stall Angle of Attack of RC Airplanes. Consider the graph below, on the x-axis is Wing Angle of Attack in degrees and on the y-axis is the Wing Lift Coefficient (CL). Lift curve of different RC Airplanes Wings are drawn with increasing Aspect ratio. Note, that the maximum Lift coefficient is considered the same for all the RC Airplanes Wings with different Aspect Ratio. From the graph, we can see that an RC Airplane with small Aspect Ratio stalls at a higher Angle of Attack. On the other hand we can see that when the Aspect Ratio of the RC Airplane Wing is increased the wing stalls at a lower Angle of Attack.

So, in conclusion we can say that a wing with a smaller value of Aspect ratio stalls at a higher Angle of Attack and a wing with a higher Aspect Ratio stalls at a lower value of angle of attack. Now, we know that Aspect Ratio is defined as, (Wing Span*Wing Span) / Wing Area or b2/S. When the value of Aspect Ratio is higher, the wing reaches the maximum lift coefficient at a smaller angle of attack. Further, increase of the angle of attack will cause the flow separation and the wing will stall. When the aspect ratio is smaller, higher values of angle of attack are required to achieve the maximum lift coefficient and thus the wing stalls at a higher value of Angle of Attack.