FAA Ground School Practice Test

What is the typical indicator of a properly adjusted fuel/air mixture during flight?

1. Steady RPM and optimal engine temperature

2. Intermittent RPM fluctuations

3. Continuous engine stall

4. Constant increase in fuel flow

The correct answer is: Steady RPM and optimal engine temperature

A properly adjusted fuel/air mixture during flight is indicated by steady RPM and optimal engine temperature. When the fuel/air mixture is set correctly, the engine operates efficiently, allowing it to maintain consistent RPM levels. This also contributes to the engine running at the desired temperature, as an optimal mixture helps in achieving balanced combustion, thereby avoiding overly rich or lean conditions that could cause overheating or other performance issues. In contrast, intermittent RPM fluctuations would suggest that the mixture is not stable, potentially indicating too lean or too rich conditions. A continuous engine stall showcases a much more severe issue, indicating a critical problem with either the mixture or another essential system. Meanwhile, a constant increase in fuel flow without a corresponding need could suggest an overly rich mixture, which does not reflect a properly adjusted system. Thus, steady RPM and optimal engine temperature serve as clear indicators of an engine performing well with a well-adjusted fuel/air mixture.