FAA Powerplant Written Practice Test

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Prepare for the FAA Powerplant Written Test. Study with flashcards and multiple choice questions, each featuring hints and explanations. Ace your exam with confidence!

Practice this question and more.

What does the term "reach" refer to in spark plug design?

Distance from the spark plug electrode to the combustion chamber
Linear distance from the shell gasket seat to the end of the threads on the shell skirt
Depth of the spark plug hole in the cylinder head
Diameter of the spark plug thread

The correct answer is: Linear distance from the shell gasket seat to the end of the threads on the shell skirt

In spark plug design, "reach" specifically refers to the linear distance from the shell gasket seat to the end of the threads on the shell skirt. This measurement is critical because it determines how far the spark plug extends into the combustion chamber. The correct reach ensures that the spark plug is appropriately positioned within the combustion chamber for optimal ignition of the air-fuel mixture. An incorrect reach can lead to various performance issues, including pre-ignition or engine knock, as the spark plug may sit too far in or not far enough into the combustion chamber. Additionally, it affects the heat range of the spark plug, impacting spark plug temperature and performance.