Two Types of Drag That Can Affect an Aircraft

B. The Saga of Skin Friction Drag

The second type of drag we’ll talk about is ‘skin friction drag’ or ‘viscous drag’. This is all about the friction between the aeroplane’s surface and the air sliding over it.

Defining Skin Friction Drag

Imagine running your hand over a smooth sheet of silk versus a rough piece of sandpaper. It’s much easier to glide over the silk, right? This is the concept behind skin friction drag. It’s the resistance created when air molecules rub against the aeroplane’s surface.

What Influences Skin Friction Drag?

The smoother the aeroplane’s surface, the lower the skin friction drag. Conversely, a rough surface creates more friction as the air struggles to flow smoothly over it. Other factors, like air temperature, humidity, and altitude (which affect air viscosity), also come into play.

Understanding Skin Friction Drag with Examples

To better understand skin friction drag, consider two aeroplanes. One has a smooth, polished surface, while the other has a rough surface. The aeroplane with a rough surface would experience higher skin friction drag, as the air molecules grapple with the rough surface and create more friction.