FAA Powerplant Written Practice Test

For float-type carburetors equipped with economizers, how are they normally set?

1. For a rich mixture delivery

2. For the leanest practical mixture delivery at cruising speeds

3. For a mixture suitable for takeoff

4. For the most enriched setting at low speeds

The correct answer is: For the leanest practical mixture delivery at cruising speeds

The correct approach for setting float-type carburetors equipped with economizers is to configure them for the leanest practical mixture delivery at cruising speeds. This setting helps to optimize fuel economy and engine performance during cruising by ensuring that the engine runs efficiently without wasting fuel. At cruising speeds, the engine requires a mixture that is not overly rich, as excessive fuel can lead to incomplete combustion, which can result in lower performance and increased emissions. The economizer circuit is designed to enhance fuel economy and engine efficiency by leaning the mixture under cruise conditions. A rich mixture delivery would typically be more suitable for takeoff or other high-power settings, where additional fuel is necessary to support higher power outputs. Ensuring an optimal balance between fuel and air allows the engine to operate effectively, particularly in cruise mode, where efficiency is paramount.