FAA Powerplant Written Practice Test

What type of engines do most small, in-line, light sport aircraft use?

1. Four cycle engines

2. Two cycle engines

3. Rotary engines

4. Diesel engines

The correct answer is: Two cycle engines

Small, in-line, light sport aircraft predominantly utilize two-cycle engines due to their favorable power-to-weight ratio and simpler design compared to four-cycle engines. Two-cycle engines deliver power on every revolution of the crankshaft, which allows for more efficient use of engine displacement and contributes to lighter overall weight—an essential factor in light sport aircraft design where performance and efficiency are crucial. Moreover, two-cycle engines tend to have fewer moving parts, which can simplify maintenance and reduce costs, making them appealing for light sport applications. The simplicity of these engines also makes them easier to operate and can provide reliable performance, which is critical for the recreational flying experience. While four-cycle engines are also common in larger aircraft due to their efficiency and better fuel consumption at cruising speeds, they typically weigh more and have more complex designs than two-cycle engines. Rotary engines and diesel engines, while they have their own benefits, are less commonly found in the category of small, light sport aircraft and are generally more specialized.