It’s a beautiful summer day with temperatures in the high 80′s to low 90′s. The sky is clear as bell and the winds are calm. This is a perfect day for flying! You call up your CFI and beg him or her to find a slot for you to go up and get some more flight time. Fortunately, they fit you in and you start the countdown to being airborne again. Once you get up into this “perfect flying weather” you start getting bounced around like crazy. It’s like you’re flying through very windy conditions, but you know the winds are under 5 knots. What gives?
New flight students are often surprised to learn about thermals and how they can move your plane around more than you thought. The first time I experienced this, I was holding on to the controls for dear life hoping I could keep that plane in a straight and level flight. Little did I know this was normal and nothing to be worried about. Today when I fly and we hit a thermal, it will get my attention but it doesn’t freak me out. I just calmly adjust the plane back to a level state and keep on moving forward.
But, what causes these thermals and how come you can’t see them. If you could see them, you could fly around them. That would be wonderful! But it’s not going to happen. So, the best thing to do is get used to flying with thermals or move to Alaska (but, I bet they even get them in the middle of summer).
The best way to describe thermals is to think of them as the air starting to “boil”. If you’ve ever watched a pot of water come to a boil, you’ll see how it starts with little bubbles forming on the bottom and then slowly rising up to the surface when they disperse. The exact same thing happens to the air around your aircraft. In effect, you’re flying through boiling air.
In the middle of the day, the sun can heat the temperature of the ground quite a bit. The warm ground will then start to heat the air closest to it and create “thermals”. This is the same thing that happens in our pot of water when the heat from the stove warms the water. So, just think of them as little boiling bubbles of air. Nothing to worry about, but definitely something to keep you on your toes.