Certified Flight Instructor - Flight Instructor Airplane Practice Exam

What should a pilot do to ensure the engine is receiving the correct mixture at altitude?

1. Richen the mixture to increase power

2. Lean the mixture to adjust for altitude

3. Adjust the mixture as needed based on temperature

4. Leave the mixture settings unchanged

The correct answer is: Lean the mixture to adjust for altitude

To ensure the engine is receiving the correct mixture at altitude, a pilot should lean the mixture to adjust for altitude. As altitude increases, the air becomes less dense, which means there is less oxygen available for combustion. In order to maintain an optimal fuel-to-air ratio, the pilot needs to decrease the amount of fuel entering the engine by leaning the mixture. This adjustment prevents the engine from running too rich, which can lead to a variety of issues, including fouled spark plugs, reduced engine efficiency, and potential engine roughness. Leaning the mixture allows the engine to operate more efficiently by providing just enough fuel to match the reduced oxygen levels, thereby maintaining power and engine performance. This adjustment is particularly important in aircraft with fixed-pitch propellers and less sophisticated fuel metering systems, as these engines rely on the pilot to manually adjust the mixture for changing altitudes and atmospheric conditions.