What happens to the fuel/air mixture as altitude increases if adjustments are not made?

As altitude increases, the atmospheric pressure decreases, which in turn affects the density of the air. If adjustments to the fuel/air mixture are not made, the mixture becomes leaner. This leaner mixture occurs because the reduction in air density results in less oxygen available for combustion in the engine.

In a normally aspirated engine, as altitude increases, the air entering the engine is less dense, and consequently, if the fuel flow remains constant while the amount of air decreases, the fuel/air mixture becomes leaner, leading to a higher fuel-to-air ratio. This can cause engine performance issues if not corrected, as a lean mixture can lead to overheating and potential engine damage.

Therefore, understanding the need to enrich the mixture at higher altitudes is crucial for optimal engine performance and operation, as failing to do so can negatively impact both the efficiency and safety of flight operations.