Private Pilot Private Exam

The formation of thermals primarily depends on what factor?

1. The wind speed at altitude.

2. Solar heating.

3. Aerodynamic lift techniques.

4. Altitude of the land.

The correct answer is: Solar heating.

The formation of thermals primarily depends on solar heating. Thermals are upward moving columns of warm air that form when the sun heats the Earth's surface unevenly. This heating causes pockets of air to become warmer than the surrounding air, resulting in the less dense warm air rising. As the ground absorbs sunlight, certain areas will heat up more quickly than others due to variations in surface materials and colors, creating these rising columns. Understanding this concept is crucial for pilots, especially when soaring or flying in gliders, as thermals can provide the lift needed to ascend without power. The other factors listed, while they can influence the conditions and strength of thermals, are not the primary drivers of their formation. Wind speed, for instance, can disrupt or cause thermals to break apart, while the altitude of the land may affect the stability of the air but does not directly cause the thermals to form. Aerodynamic lift techniques are more related to the mechanics of flight itself rather than the specific atmospheric phenomenon of thermals.