FAA Powerplant Written Practice Test

What determines which cylinder should be monitored for cylinder head temperature?

1. The cylinder with the largest displacement

2. The cylinder that is easiest to access

3. The cylinder seen as the hottest during previous tests

4. The cylinder located first in the firing order

The correct answer is: The cylinder seen as the hottest during previous tests

Monitoring cylinder head temperature is crucial for engine performance and reliability, as it helps to prevent potential issues such as overheating. The correct answer focuses on choosing the cylinder that has shown signs of running the hottest during previous tests. This approach is based on empirical data collected from engine operation, which reveals temperature variations among cylinders. Engines can experience uneven temperature distributions due to factors like fuel distribution, intake efficiency, or variations in combustion characteristics from one cylinder to another. If a particular cylinder has consistently shown a higher temperature, it can indicate issues such as lean running conditions, poor airflow, or potential mechanical problems. By monitoring this cylinder specifically, technicians can keep a closer watch on its performance and take corrective action if necessary to prevent engine failure or damage. The other options, while they may seem practical, do not prioritize the actual thermal performance of the cylinders. The cylinder with the largest displacement may not necessarily indicate higher temperatures, as temperature is affected by many operational factors rather than just the size of the cylinder. Accessibility is also not a reliable criterion for monitoring temperature; the focus should be on engine performance data rather than convenience. Lastly, the firing order does not determine temperature; it's more about how evenly the load and combustion processes are distributed among the cylinders during operation.