Certified Flight Instructor - Flight Instructor Airplane Practice Exam

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Prepare to excel in your Certified Flight Instructor exam with engaging flashcards and multiple choice questions, each featuring hints and explanations. Master the knowledge you need for success and achieve your certification with confidence!

Practice this question and more.

What is an effect of using fuel with a lower grade than specified?

Increased efficiency.
Detonation.
Lower operating temperatures.
Increased horsepower.

The correct answer is: Detonation.

Using fuel with a lower grade than specified can lead to detonation. Detonation is an abnormal combustion process that occurs when the air-fuel mixture ignites prematurely, creating shock waves within the cylinder. This can cause an uncontrolled explosion instead of a smooth, controlled burn. Higher-octane fuels are formulated to withstand more compression before igniting, which is important in high-performance engines that operate under higher temperatures and pressures. When lower-grade fuel is used in such engines, it is more likely to ignite prematurely, leading to potential engine damage, reduced performance, and increased wear and tear. This abnormal combustion can cause knocking or pinging sounds and may result in long-term damage if not addressed. Therefore, using the specified fuel grade is critical for maintaining engine efficiency and overall performance.