Drone Pilot Practice Exam

How does humidity affect density altitude?

1. It decreases density altitude

2. It has no effect

3. It increases density altitude

4. It always stabilizes density altitude

The correct answer is: It increases density altitude

Humidity has a significant impact on density altitude, primarily because it influences the overall density of the air. As humidity increases, the amount of water vapor in the air rises. Water vapor is less dense than the nitrogen and oxygen that make up the majority of the atmosphere. Therefore, as the humidity increases, the overall density of the air decreases, leading to a rise in density altitude. When density altitude is higher, aircraft performance can be adversely affected. A higher density altitude means that the aircraft's wings generate less lift, engines perform less efficiently, and propellers produce less thrust. This is crucial information for pilots as it underscores the importance of environmental conditions on flight performance. As for the statement about other options, the notion that humidity has no effect or that it stabilizes density altitude is not accurate, as humidity inherently alters air density. Additionally, while it can be a bit counterintuitive, the correlation between increased humidity leading to increased density altitude is widely accepted in aerodynamics.