Wind Drift
The three keys of understanding "drift" from a pilots point of view are:
- Air is a soup
- Motion is relative
- You are "in" the air
Air is a soup.
In physics there exist three states of matter. A solid, a liquid and a gas. Air is a gas. It is composed of a number of different molecules that have mass and take up space. It is like an invisible fluid that flows. Wind is air in motion.
Motion is relative.
A moving stream is like moving air or ''wind." If you are floating downstream in an enclosed boat without windows you don't have a sensation of actually moving. You can move about in the boat easily. If you ignore all the noise outside the boat you don't have any sensation that you are moving. You really are in a moving mass of soup. Steady flow of air is wind. As long as the flow of water is steady you feel like there is no motion at all. If you walk to one end of the boat and return to where you started you are, in fact, moving in the boat while the boat has continued to float downstream.The fact that motion downstream is taking place is real. Frame of reference is important. Which side of facts you choose to disregard. Do you judge your position by reference to the boat or by the boats position to the shore outside? Try climbing a down escalator in a store. Its a matter of relativity of motion. On the ground you don't have trouble with the "familiar." In flying it suddenly matters.
Your "in" the air.
An airplane that flies in moving air is like, in the example above, when you walked back and forth in a boat. Your plane is "contained" ,once in flight, by the surrounding air. The difference, when we fly, is the air is invisible as it surrounds the plane and the boat surrounds you in the stream.
The airplane, like the boat, has two motions both at the same time. It has motion through the air mass, like walking in the boat, and it has motion with the air called "drift." In the boat you were "drifting" downstream (one motion) and walking in the boat. (the other motion)
You, as the pilot, can fix your attention on one type of motion or on the other as you choose. After you feel comfortable in the air, you can watch both motions at the same time and not become confused.
