FAA Powerplant Written Practice Test

Which is the consequence of using a spark plug with incorrect torque specifications?

1. It may crack under pressure

2. It will operate at a lower temperature

3. It will have increased efficiency

4. It can affect engine balance

The correct answer is: It may crack under pressure

Using a spark plug with incorrect torque specifications can lead to it cracking under pressure due to excessive stress on the ceramic insulator and the metal shell. When a spark plug is over-torqued, it can create high localized stresses that exceed the design limits of the materials, potentially causing cracks. This condition can lead to serious operational issues, including misfiring or loss of ignition, which in turn can affect engine performance and reliability. Proper torque is essential for ensuring that the spark plug is securely fitted while maintaining the integrity of the plug's materials under the operational conditions of the engine. The other options, such as a lower operating temperature, increased efficiency, or affecting engine balance, do not directly relate to the consequences of improper torque on spark plugs. A spark plug that is not torqued correctly is more likely to fail or produce unreliable ignition rather than demonstrate improved efficiency or optimal temperature management.