FAA Powerplant Written Practice Test

What is the primary function of an altitude mixture control?

1. To increase engine power

2. To regulate the engine temperature

3. To regulate the richness of the fuel/air charge

4. To maintain constant RPM

The correct answer is: To regulate the richness of the fuel/air charge

The primary function of an altitude mixture control is to regulate the richness of the fuel/air charge. As an aircraft ascends to higher altitudes, the air density decreases, which affects the engine's performance if the fuel mixture is not adjusted accordingly. The altitude mixture control helps to ensure that the fuel-air mixture remains optimal for combustion, allowing the engine to run efficiently and effectively under varying atmospheric conditions. By adjusting the richness of the mixture, it helps prevent issues such as engine roughness, misfiring, and power loss, which can occur if the mixture is too rich or too lean at higher altitudes. Proper management of this mixture is crucial for maintaining engine performance during flight operations at different altitudes.