Certified Flight Instructor - Flight Instructor Airplane Practice Exam

What is the effect of leaving the carburetor heat on during takeoff?

1. Leans the mixture for more power on takeoff

2. Decreases the takeoff distance

3. Increases the ground roll

4. Improves climb performance

The correct answer is: Increases the ground roll

Leaving the carburetor heat on during takeoff generally leads to an increase in the ground roll. When carburetor heat is applied, it introduces warmer air into the carburetor. While this is beneficial in preventing carburetor icing, it also reduces the air density entering the engine, which can result in a richer fuel mixture. A richer mixture means that the engine produces less power compared to a leaner mixture, which actually could cause a decrease in engine performance. As a result, during takoff, if the carburetor heat is left on, the aircraft may experience a reduction in thrust and acceleration, leading to an increase in the distance required to reach takeoff speed. Hence, the ground roll is longer than it would be if the carberator heat were turned off. Understanding this concept is crucial for pilots to ensure optimal engine performance and to achieve the desired takeoff characteristics.